A gain-coefficient switched Alexandrite laser

We report on a gain-coefficient switched Alexandrite laser. An electro-optic modulator is used to switch between high and low gain states by making use of the polarization dependent gain of Alexandrite. In gain-coefficient switched mode, the laser produces 85 ns pulses with a pulse energy of 240 mJ at a repetition rate of 5 Hz.Comment: 8 pages, 5 figure

Mapping individual electromagnetic field components inside a photonic crystal

We present a method to map the absolute electromagnetic field strength inside photonic crystals. We apply the method to map the electric field component Ez of a two-dimensional photonic crystal slab at microwave frequencies. The slab is placed between two mirrors to select Bloch standing waves and a subwavelength spherical scatterer is scanned inside the resulting resonator. The resonant Bloch frequencies shift depending on the electric field at the position of the scatterer. To map the electric field component Ez we measure the frequency shift in the reflection and transmission spectrum of the slab versus the scatterer position. Very good agreement is found between measurements and calculations without any adjustable parameters.Comment: 12 pages, 7 figure

General weak segregation theory with an application to monodisperse semi-flexible diblock copolymers

A general theory has been developed for a polydisperse semi-flexible multi-block copolymer melt. Using the Bawendi-Freed approach to model semi-flexible chains, an expression for the Landau free energy is derived in the weak segregation regime, which includes density and orientation order-parameters. The orientation order-parameter is described in the smectic phase and in more complicated structures, such as the hexagonal phase. The Landau free energy contains contributions of two kinds of interactions. The first kind is the Flory-Huggins interaction, which describes the incompatibility of chemically different blocks and may induce microphase separation. The second kind is the Maier-Saupe interaction, which may induce nematic ordering. In the framework of the weak segregation limit, the Landau theory allows us to predict phase structures in the melt as a function of the composition, persistence length, and the strength of the Flory-Huggins and Maier-Saupe interaction. The general theory is applied to a simple system of monodisperse semi-flexible diblock copolymers. In several phase diagrams, a number of possible phase structures are predicted, such as the bcc, hexagonal, smectic-A, smectic-C, and nematic phase. The influence of the Maier-Saupe interaction on the microphase structure is thoroughly discussed.</p

Robust zero-energy modes in an electronic higher-order topological insulator: the dimerized Kagome lattice

Quantum simulators are an essential tool for understanding complex quantum materials. Platforms based on ultracold atoms in optical lattices and photonic devices led the field so far, but electronic quantum simulators are proving to be equally relevant. Simulating topological states of matter is one of the holy grails in the field. Here, we experimentally realize a higher-order electronic topological insulator (HOTI). Specifically, we create a dimerized Kagome lattice by manipulating carbon-monoxide (CO) molecules on a Cu(111) surface using a scanning tunneling microscope (STM). We engineer alternating weak and strong bonds to show that a topological state emerges at the corner of the non-trivial configuration, while it is absent in the trivial one. Contrarily to conventional topological insulators (TIs), the topological state has two dimensions less than the bulk, denoting a HOTI. The corner mode is protected by a generalized chiral symmetry, which leads to a particular robustness against perturbations. Our versatile approach to quantum simulation with artificial lattices holds promises of revealing unexpected quantum phases of matter

Vesicular Tubular Clusters between the ER and Golgi Mediate Concentration of Soluble Secretory Proteins by Exclusion from COPI-Coated Vesicles

AbstractWe have determined the concentrations of the secretory proteins amylase and chymotrypsinogen and the membrane proteins KDELr and rBet1 in COPII- and COPI-coated pre-Golgi compartments of pancreatic cells by quantitative immunoelectron microscopy. COPII was confined to ER membrane buds and adjacent vesicles. COPI occurred on vesicular tubular clusters (VTCs), Golgi cisternae, the trans-Golgi network, and immature secretory granules. Both secretory proteins exhibited a first, significant concentration step in noncoated segments of VTC tubules and were excluded from COPI-coated tips. By contrast, KDELr and rBet1 showed a first, significant concentration in COPII-coated ER buds and vesicles and were prominently present in COPI-coated tips of VTC tubules. These data suggest an important role of VTCs in soluble cargo concentration by exclusion from COPI-coated domains

Thrombin Stimulates Glucose Transport in Human Platelets via the Translocation of the Glucose Transporter GLUT-3 from α-Granules to the Cell Surface

Increased energy metabolism in the circulating blood platelet plays an essential role in platelet plug formation and clot retraction. This increased energy consumption is mainly due to enhanced anaerobic consumption of glucose via the glycolytic pathway. The aim of the present study was to determine the role of glucose transport as a potential rate-limiting step for human platelet glucose metabolism. We measured in isolated platelet preparations the effect of thrombin and ADP activation, on glucose transport (2-deoxyglucose uptake), and the cellular distribution of the platelet glucose transporter (GLUT), GLUT-3. Thrombin (0.5 U/ml) caused a pronounced shape change and secretion of most α-granules within 10 min. During that time glucose transport increased approximately threefold, concomitant with a similar increase in expression of GLUT-3 on the plasma membrane as observed by immunocytochemistry. A major shift in GLUT-3 labeling was observed from the α-granule membranes in resting platelets to the plasma membrane after thrombin treatment. ADP induced shape change but no significant α-granule secretion. Accordingly, ADP-treated platelets showed no increased glucose transport and no increased GLUT-3 labeling on the plasma membrane. These studies suggest that, in human blood platelets, increased energy metabolism may be precisely coupled to the platelet activation response by means of the translocation of GLUT-3 by regulated secretion of α-granules. Observations in megakaryocytes and platelets freshly fixed from blood confirmed the predominant GLUT-3 localization in α-granules in the isolated cells, except that even less GLUT-3 is present at the plasma membrane in the circulating cells (∼15%), indicating that glucose uptake may be upregulated five to six times during in vivo activation of platelets

Precisie rechtgeleiding werktuig met RTK GPS : een onderzoek naar verschillende stuursystemen op basis van nauwkeurige GPS systemen

Porojectnummer 325003150