精密CNC增压器转子加工提供更大的动力

Whipple Superchargers 公司更先进的转子加工工艺使它的功率加法器变得更强大.1987 年,前车队队长兼车主 Art Whipple在California的Fresno创办了这家公司,主要为赛车、赛艇选手以及所有希望提高发动机性能的人们生产双螺杆增压器.作为几种不同类型的功率加法器中的一种,增压...     

Analysis of the regulatory phosphorylation site in Acanthamoeba myosin IC by using site-directed mutagenesis

The actin-activated ATPase activity of Acanthamoeba myosin IC is stimulated 15- to 20-fold by phosphorylation of Ser-329 in the heavy chain. In most myosins, either glutamate or aspartate occupies this position, which lies within a surface loop that forms part of the actomyosin interface. To investigate the apparent need for a negative charge at this site, we mutated Ser-329 to alanine, asparagine, aspartate, or glutamate and coexpressed the Flag-tagged wild-type or mutant heavy chain and light chain in baculovirus-infected insect cells. Recombinant wild-type myosin IC was indistinguishable from myosin IC purified from Acanthamoeba as determined by (i) the dependence of its actin-activated ATPase activity on heavy-chain phosphorylation, (ii) the unusual triphasic dependence of its ATPase activity on the concentration of F-actin, (iii) its Km for ATP, and (iv) its ability to translocate actin filaments. The Ala and Asn mutants had the same low actin-activated ATPase activity as unphosphorylated wild-type myosin IC. The Glu mutant, like the phosphorylated wild-type protein, was 16-fold more active than unphosphorylated wild type, and the Asp mutant was 8-fold more active. The wild-type and mutant proteins had the same Km for ATP. Unphosphorylated wild-type protein and the Ala and Asn mutants were unable to translocate actin filaments, whereas the Glu mutant translocated filaments at the same velocity, and the Asp mutant at 50% the velocity, as phosphorylated wild-type proteins. These results demonstrate that an acidic amino acid can supply the negative charge in the surface loop required for the actin-dependent activities of Acanthamoeba myosin IC in vitro and indicate that the length of the side chain that delivers this charge is important.     

Binary PRCPM with differential phase detection and maximal ratiocombining diversity in fading channels

We derive a formula for the bit-error probability (BEP) of binary partial-response continuous-phase modulation (PRCPM) with N-bit differential phase detection (DPD) in a Rician fading channel subject to L-branch maximum ratio combining (MRC) diversity. We compute the BEP for minimum-shift keying (MSK), Gaussian MSK (GMSK), and 2 RC (2-b-duration raised cosine) frequency signals as a function of the energy-to-noise ratio per bit E_b/N₀ and other system and channel parameters [N=1 and 2 and L=1, 2, and 3, Rician factor K=-∞, 0, 6, 10, and ∝ dB, Doppler frequency shift f_DT=0, 0.01, and 0.02, Gaussian premodulation filter bandwidth B_gT=∞, 0.5, 0.25, and the presence or absence of a Doppler frequency tracking loop (DFTL) in the receiver]. In all cases, the BEP is significantly reduced by diversity