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The GLH proteins belong to a family of four germline RNA helicases in Caenorhabditis elegans. These putative ATP-dependent enzymes localize to the P granules, which are nonmembranous complexes of protein and RNA exclusively found in the cytoplasm of all C. elegans germ cells and germ cell precursors. To determine what proteins the GLHs bind, C. elegans cDNA libraries were screened by the yeast two-hybrid method, using GLHs as bait. Three interacting proteins, CSN-5, KGB-1, and ZYX-1, were identified and further characterized. GST pull-down assays independently established that these proteins bind GLHs. CSN-5 is closely related to the subunit 5 protein of COP9 signalosomes, conserved multiprotein complexes of plants and animals. RNA interference (RNAi) with csn-5 results in sterile worms with small gonads and no oocytes, a defect essentially identical to that produced by RNAi with a combination of glh-1 and glh-4. KGB-1 is a putative JNK MAP kinase that GLHs bind. A kgb-1 deletion strain has a temperature-sensitive, sterile phenotype characterized by the absence of mature oocytes and the presence of trapped, immature oocytes that have undergone endoreplication. ZYX-1 is a LIM domain protein most like vertebrate Zyxin, a cytoskeletal adaptor protein. In C. elegans, while zyx-1 appears to be a single copy gene, neither RNAi depletion nor a zyx-1 deletion strain results in an obvious phenotype. These three conserved proteins are the first members in each of their families reported to associate with germline helicases. Similar to the loss of GLH-1 and GLH-4, loss of either CSN-5 or KGB-1 causes oogenesis to cease, but does not affect the initial assembly of P granules. Key Words: germline; RNA helicase; two-hybrid screen; GST pull-downs; COP9 signalosome; RNAi; MAP kinase; JNK kinase; Zyxin; LIM domain.

The circular dichroism in a series of 5-alkyl- and 5-alkoxy-substituted butenolides has been investigated. The results showed that the absolute configuration at C(5) is correlated to the sign of the Cotton effects of the n-pi* (235-250 nm) and pi-pi* (200-220 nm) transitions. This has been observed regardless of an additional chiral center on the substituent R and is also applicable for butenolides bearing additional methyl groups attached to the C=C bond.

Four germline-specific RNA helicases, GLHs, have been identified in the free-living soil nematode Caenorhabditis elegans. This family of putative ATP-dependent enzymes is localized to the P granules, which are nonmembranous, cytoplasmic complexes of protein and RNA. P granules are potential determinants of germline development, segregating with the germline precursor lineage from the first embryonic cell division. The GLH proteins are similar to the Drosophila melanogaster germline RNA helicase VASA; however, the GLHs differ in having multiple CCHC zinc fingers as well as multiple N-terminal, noncharged phenylalanine/ glycine-rich repeats. GLH-3 is unique among the GLHs because it does not contain FGG repeats. Essentially complete sterility results when GLH-1 and GLH-4 are eliminated by RNA interference (RNAi) (Kuznicki et al., Development, 2000, 127, 2907). To study the relationships of the GLHs with other proteins, two libraries were screened by the yeast two-hybrid method, using GLHs as bait. Three C. elegans proteins have been identified; along with two-hybrid interactions, these proteins bind GLHs in GST pulldown assays. Ongoing tests consider their function in P granules and in germline development. The GLH binding partners include: (1) KGB-1, a novel putative kinase that GLHs bind, most closely related to the serine/threonine JNK (Jun N-terminal kinase) MAP kinase family. We generated a KGB-1 deletion strain; it has a temperature-sensitive sterile phenotype. (2) ZYX-1, a LIM domain-containing protein most related to vertebrate zyxin. Antibodies reveal that ZYX-1 is a component of P granules. (3) COP-9/JAB-1, closely related to subunit 5 of the cell's signalosome complex, conserved in plants and animals. COP-9 RNAi results in worms with small gonads and no oocytes, similar to those produced with GLH-1/4 RNAi.

We report that four putative germline RNA helicases, GLHs are components of the germline-specific P granules in the nematode Caenorhabditis elegans. GLH-3 and GLH-4 are newly discovered and belong to a multi-gene glh family; each of the four GLHs contain multiple CCHC zinc fingers. The GLHs are homologous to Drosophila VASA, a polar granule component necessary for oogenesis and embryonic pattern formation. RNA-mediated interference (RNAi) reveals that the GLHs, like VASA are critical for oogenesis. At permissive temperatures (20o), loss of GLH-1 and GLH-4 results in 97% sterility in the glh-1/4(RNAi) animals, the offspring of injected hermaphrodites, glh-1/4(RNAi) germlines are underproliferated and are without oocytes. Spermatogenesis is also delayed in glh-1/4(RNAi) animals; progeny lacking these GLH proteins produce defective sperm. P granules are still present in glh-1/4(RNAi)sterile worms as revealed with antibodies against the remaining GLH-2 and GLH-3 proteins. These studies indicate that C. elegans can use GLH-1 or GLH-4 to promote germline development.

The genome of the free-living soil nematode Caenorhabditis elegans contains four germline RNA helicase (glh) genes. The GLH proteins are localized to germline specific P granules. All organisms, including humans, have similar RNA-binding helicases in their primordial germ cells. The role of these helicases in germline development is unknown, although RNA interference (RNAi) studies with glh-1 and glh-4 imply both have a function during mitotic proliferation and oogenesis (see Kuznicki et al.). To determine the role of the glhs, we have isolated two glh null strains from mutagenized libraries. To create a library, L4 larval worms are treated with 4,5,8-trimethylpsoralen (TMP), a mutagen that induces DNA deletions upon UV exposure. Over 500,000 progeny of the mutagenized worms are screened in each library by polymerase chain reactions (PCRs) with nested glh-specific primers to amplify wildtype and, if present, mutant glh genes. Deletion bands smaller than the wildtype band are observed by gel electrophoresis. The deletion mutant progeny are isolated from the library by progressive platings, sibling selection, and eventually narrowing to plates started by a single worm. In this study, glh-2-/- and glh-3-/- strains were identified, isolated, and confirmed. The DNA sequence of each deletion was determined and compared to the wildtype gene with 2.8 kb, including the start codon, being absent in the glh-2 gene, and 1.7 kb missing in the glh-3 gene. Therefore both mutant strains are predicted to produce no GLH protein and to be genetic nulls. The isolated strains were made homozygous, backcrossed to eliminate extraneous mutations, and are currently being characterized for sterility phenotypes. NSF REU student.

An analysis of tetraorganothallium ate complexes proved that they provide a novel synthetic transformation through their capacity to react selectively with enones in the presence of ketones. Enhancements in the selectivity of the mechanism accompany declines in the inherent reactivity of the carbonyl function and a rise in the conjugation of the substrate. Exclusive preference for the conjugated ketone results when the aromatic ring is substituted by an electron withdrawing group.

A wideband 90° hybrid coupler has been presented and implemented in planar microstrip circuit. With similar structure of conversional 2-section branch-line coupler, the proposed coupler consists of a lumped high-pass network but not the quarter wavelength transmission at the center. The values of all lumped elements were optimized to replace a quarter-wavelength transmission line with a phase inverter. To demonstrate the proposed concept, a 1-GHz prototype was fabricated and tested. It achieves 90% impedance bandwidth with magnitude of S11 less than -10 dB. Within this bandwidth, more than 13 dB port-toport isolation, less than 5.0 degree phase imbalance, and less than 4.5 dB magnitude imbalance are achieved, simultaneously. The proposed coupler not only achievesmuch wider bandwidth but also occupies less circuit area than that of the conversional 2-section branch-line coupler. [ABSTRACT FROM AUTHOR]

A parallel-strip phase inverter with a pair of simple impedance matching networks is designed. The phase inverter introduces the almost frequency independent 180º phase shift and was employed in the wideband parallel-strip balun. The balun was designed and measured with the maximum magnitude imbalance of 0.5 dB and the maximum phase imbalance of 6.0º. The proposed balun is used as input network for the wideband balanced frequency doubler. The proposed frequency doubler achieves significant conversion gain from 0.1GHz to 1.7GHz. The frequency doubler achieves 7.4 dB conversion gain and 23 dB fundamental signal suppression at 1GHz. [ABSTRACT FROM AUTHOR]

This paper presents a class of wideband 180º hybrid (rat race) couplers implemented by parallel-strip line. By replacing the 270º arm of a conventional 180º hybrid coupler by a 90º arm with phase inverter, the bandwidth of the coupler is greatly enhanced and the total circuit size is reduced by almost half. Simple design formulas relating the characteristic impedance of the arms and power division ration are derived. To demonstrate the concept, four couplers with different power division ratios of 1, 2, 4, and 8 were designed, fabricated, and tested. S-parameters of the coupler are simulated and measured with good agreement. All working prototypes operate more than 112% impedance bandwidth with more than 25 dB port-to-port isolation and less than 5º absolute phase imbalance. The proposed 180º hybrid couplers can be employed as a wideband in-phase/differential power divider/combiner, which are essential for many RF and microwave subsystem designs. [ABSTRACT FROM AUTHOR]

This paper presents an alterative implementation of a shunt open-circuited stub for multilayer microwave circuit. With making use of the proposed implementation, a simple and compact bandstop filter with a district bandstop characteristics and a first spurious at the third harmonic is proposed. The proposed filter exhibits about 12.5% fractional bandwidth of -10 dB signal rejection at the center frequency of 2.04GHz and flat group delay at the pass bands. Besides, by cascading a number of the proposed bandstop filters designed at the different frequencies, multiband bandstop filters can be easily realized. A dual- (tri-) band design at the center frequencies of 2GHz and 3GHz (and 4GHz) is designed, realized, and measured. The proposed bandstop filter well suits the nowadays multilayer and compact radio frequency integrated circuit design. [ABSTRACT FROM AUTHOR]

This paper presents a new class of wideband 90° hybrid coupler with an arbitrary coupling level. The physical size of the proposed coupler is close to that of a conventional two-section branch-line coupler, but it has an additional phase inverter. The impedance bandwidth of the proposed coupler is close to that of a four-section branch-line coupler. The proposed coupler is a backward-wave coupler with a port assignment different from that of a conventional branch-line coupler. The design formulas of the proposed coupler are proved based on its even- and odd-mode half structures. We demonstrated three couplers at the center frequency of 2 GHz with different design parameters. [ABSTRACT FROM AUTHOR]

A 1-D four-element and 2-D eight-element phase-conjugated retrodirective arrays employing low conversion-loss resistive field-effect transistor mixers and stub-loaded patch elements are proposed. The mixer, systematically designed using a multi-harmonic loading technique, offers a low 5.2-dB conversion loss at a 4.5-dBm local oscillator power level. The stub-loaded patch element is a square patch with a capacitive open stub loaded at each of its four corners, leading to patch-size reduction, lower mutual coupling between adjacent elements, and broader beamwidth. With the same element spacing of half a free-space wavelength at 5.8 GHz, the mutual coupling is suppressed by 3.1 and 3.3 dB in the E- and H-planes, respectively, when compared to the conventional square patches. Within an angle of ±60° normal to the arrays, distinct linearly polarized retrodirectivities in terms of pattern deformations are experimentally confirmed for both the H-plane of the 1-D array and both E- and H-planes for the 2-D array. Additionally, circularly polarized retrodirectivity are also experimentally confirmed for 2-D arrays. [ABSTRACT FROM AUTHOR]

In this paper, a new power divider concept, which provides high flexibility of transmission line characteristic impedance and port impedance, is proposed. This power divider is implemented on a parallel-strip line, which is a balanced transmission line. By implementing the advantages and uniqueness of the parallel-strip line, the divider outperforms the conventional divider in terms of isolation bandwidths. A swap structure of the two lines of the parallel-strip line is employed in this design, which is critical for the isolation enhancements. A lumped-circuit model of the parallel-strip swap including all parasitic effects has been analyzed. An equal power divider with center frequency of 2 GHz was designed to demonstrate the idea. The experimental results show that the equal power divider has 96.5% - 19-dB impedance bandwidth with more than 25-dB isolation and less than 0.7-dB insertion loss. In order to generalize the concept with an arbitrary power ratio, we also realize unequal power dividers with the same isolation characteristics. The impedance bandwidth of the proposed power divider will increase with the dividing ratio, which is opposite to the conventional Wilkinson power divider. Unequal dividers with dividing ratios of 1 :2 and 1 : 12 are designed and measured. Additionally, a frequency independent 180° power divider has been realized with less than 2° phase errors. [ABSTRACT FROM AUTHOR]

The realization of a highly efficient linearized amplifier has emerged as a paramount issue in the design of advanced mobile handsets. In this paper, a new RF amplifier linearization scheme using a compensating transistor combination is proposed. The devised approach ably utilizes all terminals of an additional transistor that offers a unified pre-post-distortion and cubic distortion characteristic for performance improvement. Meticulous modeling along with a power-dependent Volterra series is performed to identify contributions on each mechanism under various power levels. An experimental four-tone test reveals a maximum 28-dB reduction for the intermodulation distortion at 1.95 GHz, which outperforms typical pre-distortions of 5–10 dB. A single-ended two-stage amplifier module demonstrates a state-of-the-art power efficiency of 55% with 27-dB transducer gain at 24-dBm output power. Meanwhile, the adjacent channel power ratio (ACPR1) is maintained with good margins of -35 dBc for a four-channel wideband code-division multiple-access signal under all output dynamics. Graceful degradations on modulation bandwidths, tone spacing, bias, and gain variations are also discussed, showing superb performance with virtually no dedicated retuning circuit parameters for multicarrier applications. By combining a bias control along with the proposed linearization technique, the average efficiency (12%) is 3× higher than that of the fixed bias (3.94%), demonstrating the potential utility on further prolonging battery lifetime in practical scenarios. [ABSTRACT FROM AUTHOR]

A downconverting second harmonic self-oscillating mixer (SOM) is developed for low-cost wireless communications applications. Incorporating resonant cell in the SOM, we can provide suitable oscillation for generating LO and terminations to all major unwanted mixing products, leading to high conversion gain design. The proposed SOM was measured with 8.5 dB down conversion gain at the RF frequency of 8.2 GHz RF, LO frequency of 4.0 GHz, and IF frequency of 0.2 GHz. The proposed design achieves higher conversion gain than that of the SOM without resonant cell. [ABSTRACT FROM AUTHOR]

A compact nonresonating, dual-band bandstop filter is proposed. By connecting two transmission lines with proper characteristic impedances and phase delay (one is 90° and the other one is 450° in electrical length at center frequency), a dual stopband with two transmission zeros at each stopband is obtained. A prototype is demonstrated for 2.4/5.8-GHz applications. The measured results show the dual fractional stopband bandwidths with 20-dB signal attenuation are 25.2% and 12.4%. Also, the theoretical simulation, electromagnetic simulation, and the measured results show good agreement with this simple design. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2952–2954, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24753 [ABSTRACT FROM AUTHOR]

A new wideband parallel-strip bandpass filter using phase inverter with stubs is proposed. With the wideband phase inverter in the parallel-strip line structure, the measured fractional passband bandwidth is 123% with a flat group delay response. Also, over 90% impedance bandwidth is obtained for the return loss higher than 20 dB. The theoretical simulation, electromagnetic simulation, and measured results show good agreement with this proposed design. [ABSTRACT FROM PUBLISHER]

A new passive 2-D Van Atta array is introduced with star-shaped antenna elements. The star-shaped antenna is proposed for low mutual coupling in the array. A single antenna element designed at 5.8 GHz has two orthogonal feeding ports with 23 dB port return loss and 28 dB isolation between ports. The mutual coupling among the antenna elements is less than -15.5 dB, which is 5 dB better than the conventional square patch antenna. Experimental results show that this array keeps a constant retrodirective characteristic at arbitrary injection polarization and direction. A stable bistatic radar cross section (BRCS) within 120° angle can be achieved at 5.8 GHz. [ABSTRACT FROM AUTHOR]

A lumped quadrature coupler based on a ferromagnetic core is proposed for high-frequency (HF) application. The four terminals of the transformer are connected to the four ports, whereas two inductors and two capacitors are connected between two adjacent ports. The bandwidth is only limited by magnitude imbalance. A 13.56 MHz prototype is designed and tested. A 69% bandwidth is achieved with ±3 dB magnitude imbalance. Within the frequency band, the measured return loss is greater than 31.57 dB, port-to-port isolation is greater than 33.21 dB and the phase imbalance is <2°. [ABSTRACT FROM AUTHOR]

We report that four putative germline RNA helicases, GLHs, are components of the germline-specific P granules in Caenorhabditis elegans. GLH-3 and GLH-4, newly discovered, belong to a multi-gene glh family. Although GLHs are homologous to Drosophila VASA, a polar granule component necessary for oogenesis and embryonic pattern formation, the GLHs are distinguished by containing multiple CCHC zinc fingers. RNA-mediated interference (RNAi) reveals the GLHs are critical for oogenesis. By RNAi at 20 degrees C, when either loss of GLH-1 or GLH-4 alone has no effect, loss of both GLH-1 and GLH-4 results in 97% sterility in the glh-1/4(RNAi) offspring of injected hermaphrodites. glh-1/4(RNAi) germlines are under-proliferated and are without oocytes. glh-1/4(RNAi) animals produce sperm; however, spermatogenesis is delayed and the sperm are defective. P granules are still present in glh-1/4(RNAi) sterile worms as revealed with antibodies against the remaining GLH-2 and GLH-3 proteins, indicating the GLHs function independently in P granule assembly. These studies reveal that C.elegans can use GLH-1 or GLH-4 to promote germline development.