Periodically-driven quantum systems: Effective Hamiltonians and engineered gauge fields

Driving a quantum system periodically in time can profoundly alter its long-time dynamics and trigger topological order. Such schemes are particularly promising for generating non-trivial energy bands and gauge structures in quantum-matter systems. Here, we develop a general formalism that captures the essential features ruling the dynamics: the effective Hamiltonian, but also the effects related to the initial phase of the modulation and the micro-motion. This framework allows for the identification of driving schemes, based on general N-step modulations, which lead to configurations relevant for quantum simulation. In particular, we explore methods to generate synthetic spin-orbit couplings and magnetic fields in cold-atom setups.Comment: 25 pages, 6 figures, includes Appendices (A-K). An erroneous factor of two has been corrected in the last term of Eq. C10 (Appendix C); this typo had no impact on the rest of the articl

Targeting L-type amino acid transporter 1 in innate and adaptive T cells efficiently controls skin inflammation

BACKGROUND: Psoriasis is a frequent inflammatory skin disease that is mainly mediated by IL-23, IL-1β, and IL-17 cytokines. Although psoriasis is a hyperproliferative skin disorder, the possible role of amino acid transporters has remained unexplored. OBJECTIVE: We sought to investigate the role of the essential amino acid transporter L-type amino acid transporter (LAT) 1 (SLC7A5) in psoriasis. METHODS: LAT1 floxed mice were crossed to Cre-expressing mouse strains under the control of keratin 5, CD4, and retinoic acid receptor-related orphan receptor γ. We produced models of skin inflammation induced by imiquimod (IMQ) and IL-23 and tested the effect of inhibiting LAT1 (JPH203) and mammalian target of rapamycin (mTOR [rapamycin]). RESULTS: LAT1 expression is increased in keratinocytes and skin-infiltrating lymphocytes of psoriatic lesions in human subjects and mice. LAT1 deletion in keratinocytes does not dampen the inflammatory response or their proliferation, which could be maintained by increased expression of the alternative amino acid transporters LAT2 and LAT3. Specific deletion of LAT1 in γδ and CD4 T cells controls the inflammatory response induced by IMQ. LAT1 deletion or inhibition blocks expansion of IL-17-secreting γ4+δ4+ and CD4 T cells and dampens the release of IL-1β, IL-17, and IL-22 in the IMQ-induced model. Moreover, inhibition of LAT1 blocks expansion of human γδ T cells and IL-17 secretion by human CD4 T cells. IL-23 and IL-1β stimulation upregulates LAT1 expression and induces mTOR activation in IL-17+ γδ and TH17 cells. Deletion or inhibition of LAT1 efficiently controls IL-23- and IL-1β-induced phosphatidylinositol 3-kinase/AKT/mTOR activation independent of T-cell receptor signaling. CONCLUSION: Targeting LAT1-mediated amino acid uptake is a potentially useful immunosuppressive strategy to control skin inflammation mediated by the IL-23/IL-1β/IL-17 axis.Funding This manuscript has been funded by grants SAF 2017-82886-R (FS-M) and SAF 2013-42850-R (MF) from the Spanish Ministry of Economy and Competitiveness; CAM (S2017/BMD-3671-INFLAMUNE-CM) from the Comunidad de Madrid (FS-M); CIBERCV, BIOIMID PIE13/041 from Instituto de Salud Carlos III and Fundación La Marató TV3 (20152330 31). The project leading to these results has also received funding from FUNDACIÓN BBVA A EQUIPOS DE INVESTIGACIÓN CIENTÍFICA 2018 and from “la Caixa” Banking Foundation under the project code HR17-00016 (FS-M), and from Agencia Estatal de Investigación, Fondo Europeo de Desarrollo Regional PI17/01972 (E.D).S

Likelihood Estimation for Block Cipher Keys

In this paper, we give a general framework for the analysis of block ciphers using the statistical technique of likelihood estimation. We show how various recent successful cryptanalyses of block ciphers can be regarded in this framework. By analysing the SAFER block cipher in this framework we expose a cryptographic weakness of that cipher

Coloring and constructing (hyper)graphs with restrictions

We consider questions regarding the existence of graphs and hypergraphs with certain coloring properties and other structural properties. In Chapter 2 we consider color-critical graphs that are nearly bipartite and have few edges. We prove a conjecture of Chen, Erdős, Gyárfás, and Schelp concerning the minimum number of edges in a “nearly bipartite” 4-critical graph. In Chapter 3 we consider coloring and list-coloring graphs and hypergraphs with few edges and no small cycles. We prove two main results. If a bipartite graph has maximum average degree at most 2(k−1), then it is colorable from lists of size k; we prove that this is sharp, even with an additional girth requirement. Using the same approach, we also provide a simple construction of graphs with arbitrarily large girth and chromatic number (first proved to exist by Erdős). In Chapter 4 we consider list-coloring the family of kth power graphs. Kostochka and Woodall conjectured that graph squares are chromatic-choosable, as a strengthening of the Total List Coloring Conjecture. Kim and Park disproved this stronger conjecture, and Zhu asked whether graph kth powers are chromatic-choosable for any k. We show that this is not true: we construct families of graphs based on affine planes whose choice number exceeds their chromatic number by a logarithmic factor. In Chapter 5 we consider the existence of uniform hypergraphs with prescribed degrees and codegrees. In Section 5.2, we show that a generalization of the graphic 2-switch is insufficient to connect realizations of a given degree sequence. In Section 5.3, we consider an operation on 3-graphs related to the octahedron that preserves codegrees; this leads to an inductive definition for 2-colorable triangulations of the sphere. In Section 5.4, we discuss the notion of fractional realizations of degree sequences, in particular noting the equivalence of the existence of a realization and the existence of a fractional realization in the graph and multihypergraph cases. In Chapter 6 we consider a question concerning poset dimension. Dorais asked for the maximum guaranteed size of a subposet with dimension at most d of an n-element poset. A lower bound of sqrt(dn) was observed by Goodwillie. We provide a sublinear upper bound

Probing unconventional vesicular trafficking with K63-polyubiquitin sensors

2019 Summer.Includes bibliographical references.For signaling purposes, the small protein ubiquitin (Ub) acts as a post-translational modification. Ub can polymerize with diverse Ub-Ub chain linkages which are involved in numerous cellular mechanisms. To investigate processes mediated by a particular Ub linkage, tools selective against specific forms of polyUb are useful. Vx3 is a previously developed sensor that specifically binds K63-linked polyUb with high affinity and acts as a competitive inhibitor by blocking K63-polyUb-dependent signaling. When expressed in cells, Vx3 forms stable cytoplasmic foci that co-localize with autophagy related protein 9A (ATG9A) and late endosomal/lysosomal markers. However, Vx3 foci only co-localize with the autophagy marker LC3 upon selective autophagy induction. Proteins associated with Vx3 were identified through Vx3 co-immunoprecipitation and mass spectrometry analysis. The most abundant were plasma membrane proteins including transferrin receptor (TfR) and major histocompatibility complex I (MHC-I), which co-localized into cytoplasmic foci with Vx3. Biochemical and confocal microscopy analyses revealed that TfR at Vx3 foci is K63-polyubiquitinated, originated from the ER, and bypassed the Golgi apparatus via a non-canonical trafficking pathway. In addition, Vx3 was modified to allow inducible release of bound K63-polyUb. By disabling Vx3, tracking of the ubiquitinated proteins to observe their downstream activities becomes possible. This thesis preliminarily identifies K63-polyUb as a signal for what is possibly a quality control pathway and offers tools for further investigation in context of Vx3