Reactivity and chemical synthesis of L-pyrrolysine- the 22(nd) genetically encoded amino acid

L-pyrrolysine, the 22(nd) genetically encoded amino acid, was previously deduced to be (4R, 5R)-4-substituted-pyrroline-5-carboxylate attached to the epsilon-nitrogen of lysine based on the crystal structure of the M. barkeri monomethylamine methyltransferase (MtmB). To confirm L-pyrrolysine's identity, structures of MtmB have been determined following treatment with hydroxylamine, N-methylhydroxylamine, or dithionite. Analysis of these structures has provided additional support for the presence of the pyrroline ring and, together with previous mass spectroscopy data, has led us to assign the C(4)-substituent to a methyl group. Based on this assignment, synthetic L-pyrrolysine was prepared by chemical methods. Detailed study of this chemically synthesized L-pyrrolysine has allowed us to characterize its physical properties, to study its chemical stability, and to elucidate the role of its C(4) substituent. Future applications of this synthetic L-pyrrolysine include its in vivo incorporation into recombinant proteins.     

Two-photon microscopy of fura-2-loaded cardiac myocytes with an all-solid-state tunable and visible femtosecond laser source

We report a robust and reliable platform source for visible-wavelength multiphoton microscopy that is based on nonlinear optical methods. We demonstrate a synchronously pumped, singly resonant optical parametric oscillator with simultaneous intracavity third-order quasi-phase matching in a single crystal that generates continuously tunable, visible, and femtosecond-pulsed radiation. The application of the system is demonstrated by two-photon laser-scanning fluorescence microscopy of rabbit cardiac myocytes loaded with the fluorescent Ca2+ indicator fura-2.     

Ergodic dynamics in a natural threshold system

Numerical simulations suggest that certain driven, dissipative mean-field threshold systems, including earthquake models, can be characterized by statistical properties often associated with ergodic dynamics, in the same sense as stochastic Brownian motion. We applied a fluctuation metric proposed by Thirumalai and Mountain [Phys. Rev. E 47, 479 (1993)]] for statistically stationary systems and find that the natural earthquake fault system in California demonstrates similar ergodic dynamics.     

First search for the flavor changing neutral current decay D0-->gammagamma

Using 13.8 fb(-1) of data collected at or just below the Upsilon(4S) with the CLEO detector, we report the result of a search for the flavor changing neutral current process D0-->gammagamma. We observe no significant signal for this decay mode and determine 90% confidence level upper limits on the branching fractions B(D0-->gammagamma)/B(D0-->pi(0)pi(0))<0.033 and B(D0-->gammagamma)<2.9 x 10(-5).     

Characterization of the nonlinear refractive index of the laser crystal Yb:KGd(WO<Subscript>4</Subscript>)<Subscript>2</Subscript>

We present results of the characterization of the nonlinear refractive index of the laser crystal Yb:KGd(WO₄)₂ using a z-scan technique over the 800–1600 nm wavelength range. Based on our experimental and theoretical results we conclude that Yb:KGW crystal is a good candidate for efficient Kerr-lens mode locking. PACS 42.65.An; 42.65.Hw; 42.55.Rz; 42.65.Re     

Turboprop and rotary-wing aircraft flight parameter estimation using both narrow-band and broadband passive acoustic signal-processing methods

Flight parameter estimation methods for an airborne acoustic source can be divided into two categories, depending on whether the narrow-band lines or the broadband component of the received signal spectrum is processed to estimate the flight parameters. This paper provides a common framework for the formulation and test of two flight parameter estimation methods: one narrow band, the other broadband. The performances of the two methods are evaluated by applying them to the same acoustic data set, which is recorded by a planar array of passive acoustic sensors during multiple transits of a turboprop fixed-wing aircraft and two types of rotary-wing aircraft. The narrow-band method, which is based on a kinematic model that assumes the source travels in a straight line at constant speed and altitude, requires time-frequency analysis of the acoustic signal received by a single sensor during each aircraft transit. The broadband method is based on the same kinematic model, but requires observing the temporal variation of the differential time of arrival of the acoustic signal at each pair of sensors that comprises the planar array. Generalized cross correlation of each pair of sensor outputs using a cross-spectral phase transform prefilter provides instantaneous estimates of the differential times of arrival of the signal as the acoustic wavefront traverses the array.     

T-Ray Sensing and Imaging

T-ray wavelengths are long enough to pass through dry, nonpolar objects opaque at visible wavelengths, but short enough to be manipulated by optical components to form an image. Sensing in this band potentially provides advantages in a number of areas of interest to security and defense such as screening of personnel for hidden objects and the retection of chemical and biological agents. Several private companies are developing smaller, reliable cheaper systems allowing for commercialization and this motivates us to review a number of promising applications within this paper. While there are a number of challenges to be overcome there is little doubt that T-ray technology will play a significant role in the near future for advancement of security, public health, and defense.     

New insight into the role of the β3 subunit of the GABA<Subscript>A</Subscript>-R in development,behavior, body weight regulation,and anesthesia revealed by conditional gene knockout

Background  

The β3 subunit of the γ-aminobutyric acid type A receptor (GABA_A-R) has been reported to be important for palate formation, anesthetic action, and normal nervous system function. This subunit has also been implicated in the pathogenesis of Angelman syndrome and autism spectrum disorder. To further investigate involvement of this subunit, we previously produced mice with a global knockout of β3. However, developmental abnormalities, compensation, reduced viability, and numerous behavioral abnormalities limited the usefulness of that murine model. To overcome many of these limitations, a mouse line with a conditionally inactivated β3 gene was engineered.     

Psychophysically derived quantisation model for efficient DWT imagecoding

An efficient method for the optimum quantisation of the luminance and chrominance components for discrete wavelet transform (DWT) still image coding, based on current psychophysical evidence, is described. Its practical application to image compression is presented. This new approach is further supported by experimental work which compares perceived DWT image quality with conventional JPEG-encoding, that is block-based discrete cosine transform (DCT) coding, on the basis of quantisation distortion