Light propagation in a Penrose unilluminable room.

Using the finite-difference time-domain method, propagation of light waves is studied in a Penrose unilluminable room. Such a room always has dark (unilluminated) regions, regardless of the position of a point source in it. However, in contrast to the predictions of ray dynamical simulations, a small amount of light propagates into the unilluminated regions via diffraction. We conjecture that this diffraction effect becomes more prominent as the size of the room decreases.

Crossover from capacitive to inductive electromagnetic responses in near self-complementary metallic checkerboard patterns.

Transmission spectra of near-self-complementary metallic checkerboard patterns (MCPs) exhibit a drastic change when the metal squares are brought into contact with each other from a noncontact state. Transmission spectra of near-self-complementary samples, which are fabricated by printing technology, show rather gradual systematic change with changing the nominal metal square size while keeping the period because of randomness naturally introduced by the limited accuracy of the printer. The spectra have transmission-invariant frequencies, which means that the spectra are a superposition of two types of spectra, the ratio of which depends on the nominal square size. The correlation seen in the real and imaginary parts of the complex amplitude spectra can be interpreted based on the Kramers-Kronig relation. As an application of the sensitiveness of the transmission spectrum of the MCPs to connectivity of the metal squares, the revealing of an optically hidden pattern by a terahertz beam is demonstrated.

Lasing of TM modes in a two-dimensional GaAs microlaser.

We fabricated and tested an unstrained GaAs single-quantum-well microlaser which has a two-dimensional cavity shape known as the Penrose unilluminable room. The cavity exhibits quasi-one-dimensional modes, namely axial, diamond-shaped, and V-shaped modes. In contrast to previous observations of TE-polarized emission in GaAs microlasers, we observed TM-polarized emission. We explain this observation as being the result of lasing of the diamond-shaped modes whose incident angle at the cavity interface is very close to the Brewster angle.

A case of mucosa-associated lymphoid tissue lymphoma of the gastrointestinal tract showing extensive plasma cell differentiation with prominent Russell bodies.

A 73-year-old Japanese woman was hospitalized for detailed examination of nausea, diarrhea and loss of appetite. Atypical erosion in the ileum was found on endoscopy. Biopsy of this erosion showed proliferation of cells containing numerous Russell bodies. Differential diagnoses considered were Russell body enteritis, crystal-storing histiocytosis, Mott cell tumor, immunoproliferative small intestinal disease (IPSID) and mucosa-associated lymphoid tissue (MALT) lymphoma. The cells containing prominent Russell bodies showed diffuse positivity for CD79a and CD138, but negative results for CD20, CD3, UCHL-1, CD38 and CD68. Russell bodies were diffusely positive for lambda light chain, but negative for kappa light chain, and immunoglobulin (Ig) G, IgA and IgM. Based on these findings, Russell body enteritis, crystal-storing histiocytosis and IPSID were ruled out. As the tumor formed no mass lesions and was restricted to the gastrointestinal tract, MALT lymphoma with extensive plasma cell differentiation was finally diagnosed. The patient showed an unexpectedly aggressive clinical course. The number of atypical lymphocytes in peripheral blood gradually increased and T-prolymphocytic leukemia (T-PLL) emerged. The patient died of T-PLL 7 mo after admission. Autopsy was not permitted.

Selective excitation of lowest-order transverse ring modes in a quasi-stadium laser diode.

For a two-dimensional quasi-stadium laser diode, we demonstrate stable excitation of the lowest-order transverse ring modes by optimally designing the confocal end mirrors of the laser cavity based on extended Fox-Li mode calculations. We observe kink-free light output versus injection current characteristics and highly directional single-peak emissions corresponding to the diamond-shaped trajectory in the cavity. These results provide convincing evidence for selective excitation of the lowest-order transverse modes.

Lowest-order axial and ring mode lasing in confocal quasi-stadium laser diodes.

We investigated the lasing modes of quasi-stadium laser diodes that have confocal cavity geometries, with stripe electrode contacts formed either along the cavity axis or a diamond-shaped trajectory. It was clearly demonstrated that by using narrow electrode contact patterns of 2 µm width, the lowest-order axial and ring modes were excited selectively. On the other hand, the second-lowest-order axial and ring modes were excited by using broad electrode patterns of 14 µm width. Experimentally obtained far-field patterns for lasers with broad and narrow electrode contact patterns agree very well with the simulation results obtained using an extended Fox-Li mode calculation method.

Biosynthesis of proteins containing modified lysines and fluorescent labels using non-natural amino acid mutagenesis.

The preparation of posttranslationally modified proteins is required to investigate the function and structure of modified proteins. However, homogeneously modified proteins are not easily isolated from natural sources or prepared using modification enzymes. Non-natural amino acid mutagenesis has enabled us to incorporate modified amino acids into specific positions of proteins in both cell-free and in-cell translation systems using tRNAs that are aminoacylated with modified amino acids. Here, we developed a method of double incorporation of modified amino acids and fluorescent non-natural amino acids in a quantitative, position-specific manner to obtain modified and fluorescently labeled proteins. To introduce methyllysine, dimethyllysine, trimethyllysine, and acetyllysine, frameshift and amber suppressor tRNAs aminoacylated with modified lysines were synthesized by chemical aminoacylation and supplied to an Escherichia coli cell-free translation system. The immunodetection of the translation products indicated that the modified lysines were incorporated into streptavidin and histone H3 in a quantitative, position-specific manner. Calmodulin derivatives containing a fluorescent non-natural amino acid at the N-terminal region and modified lysines at the Lys115 position were also synthesized, and their binding activity to a calmodulin-binding peptide was analyzed by fluorescence correlation spectroscopy. The results obtained here demonstrate that this method is useful in preparing and analyzing naturally occurring and non-natural modified proteins.

Optical transmission anomalies in a double-layered metallic slit array.

We theoretically predicted the existence of an anomalous optical transmittance dip, which must be observed for a metamaterial structure with two metallic slabs with cut-through slit arrays of a constant period d under a normal incident condition. By changing the relative lateral displacement l between the two slabs, the dip frequency varies across that of a so-called Rayleigh-Wood's (RW) anomaly frequency. The mechanism of this anomaly is quite different from that of the RW anomaly and interpreted in terms of the interference between the propagating and evanescent waves. For the present double-layered system, furthermore, it is suggested that the RW anomaly vanishes for l = 0 and d/2. In experiments in the terahertz region, we observe that the fundamental features agree with these theoretical predictions.

Efficient incorporation of a nonnatural amino acid into a protein in an insect cell-free translation system.

Recently, we have succeeded in incorporating various nonnatural amino acids into proteins by using four-base codon-anticodon pairs in Spodoptera frugiperda 21 (Sf21) insect cell-free protein synthesizing system. Here, the reaction was conducted under various conditions in order to optimize the incorporation efficiency. The optimal concentration of aminoacyl-tRNA, reaction temperature, and reaction time were 2 nM, 25 degrees C, and 1.5 hr, respectively.

Design of carrier tRNAs and selection of four-base codons for efficient incorporation of various nonnatural amino acids into proteins in Spodoptera frugiperda 21 (Sf21) insect cell-free translation system.

Spodoptera frugiperda 21 (Sf21) insect cell-free protein synthesizing system was expanded to include nonnatural amino acids. Orthogonal tRNAs that work as carriers of nonnatural amino acids in the insect system were explored. Four-base codons for assigning the positions of nonnatural amino acids were also selected. Mutated streptavidin mRNAs that contained different four-base codons were prepared and added to the insect cell-free system in the presence of various tRNAs possessing the corresponding four-base anticodons. The tRNAs were chemically aminoacylated with various types of nonnatural amino acids to examine their incorporation efficiencies. Using p-nitrophenylalanine as the nonnatural amino acid and streptavidin as the target protein, tRNA sequences and the types of four-base codons were optimized to maximize the yield of the nonnatural mutant and to minimize production of full-length proteins that do not contain the nonnatural amino acid. Among the tRNA sequences taken from a variety of tRNAs of nonstandard structures, the tRNA derived from Methanosarcina acetivorans tRNA(Pyl) was the most efficient and orthogonal tRNA. Of the CGGN-type four-base codons, CGGA and CGGG were the most efficient ones for assigning the positions of nonnatural amino acids. p-Nitrophenylalanine and 2-naphthylalanine were efficiently incorporated as in the case of Escherichia coli and rabbit reticulocyte cell-free systems. Much less efficient incorporation was observed, however, for other nonnatural amino acids, indicating that the insect system is less tolerant to the structural diversity of amino acids than the E. coli cell-free system.