4,959 research outputs found
GCM simulations of the Indian Ocean dipole influence on East African rainfall: present and future.
No full textSix coupled GCMs are assessed in terms of their ability to simulate observed characteristics of East African rainfall, the Indian Ocean dipole and their temporal correlation. Model results are then used to analyze the future behaviour of rainfall and the DMI. All models simulate reasonably well the spatial distribution and variability of annual and seasonal rainfall over the 1961–1990 period. Model simulation of observed DMI characteristics is less consistent with observations, however, five models reproduce similar correlations to those observed between the DMI and East African short rains (SON). In the future, there are no clear inter-model patterns of rainfall or DMI behaviour. In this sample of models four (two) out of six simulate modest increases (decreases) in annual rainfall by the 2080s. For SON, three of the six models indicate a trend towards increasingly positive phase of the DMI, two indicate a decrease and one shows no substantial change
A 39 W Fully Digital Wideband Inverted Doherty Transmitter
No full textA high-power fully-digital Doherty transmitter (DDTX) is proposed. It features two segmented LDMOS output switch banks implemented in a custom V T -down-shifted LDMOS technology. A 40 nm CMOS controller digitally activates the individual LDMOS gate segments of the output stage at RF speed. An inverted Doherty power combiner is proposed that features non-short circuited 2 nd harmonic conditions for the main and peak switch banks to boost the RF bandwidth. To guarantee smooth output power and efficiency vs. frequency, a 2 nd harmonic trap is introduced in the power combiner, yielding an RF bandwidth of > 400 MHz. The realized demonstrator can achieve over 39 W peak output power. Its highest drain and system efficiencies, respectively 60 % and 57 %, were found at 34.2 W of output power, while in power back-off its peak drain and system efficiencies are 52 % and 48 % respectively. Over a 25 dB output range, the system efficiency is within 4 percent points of the drain efficiency.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
Letter from George D. Johnston, Saltillo, Mississippi, to Captain T. B. Roy, July 13, 1862
No full textLetter from George D. Johnston, Knoxville, Tennessee, to Captain T. B. Roy, October 26, 1862
No full textOutput Bandwidth Limitations of Basestation Power Amplifier Design and Its Implementation Using Doherty Amplifier
No full textabstract: This thesis is a study of Bandwidth limitation of basestation power amplifier and its Doherty application. Fundamentally, bandwidth of a power amplifier (PA) is limited by both its input and output prematch networks and its Doherty architecture, specifically the impedance inverter between the main and auxiliary amplifier. In this study, only the output prematch network and the Doherty architecture follows are being investigated. A new proposed impedance inverter in the Doherty architecture exhibits an extended bandwidth compared to traditional quarterwave line.
Base on the loadline analysis, output impedance of the power amplifier can be represented by a loadline resistor and an output shunt capacitor. Base on this simple model, the maximum allowed bandwidth of the output impedance of the power amplifier can be estimated using the Bode-Fano method. However, since power amplifier is in fact nonlinear, harmonic balance simulation is used to loadpull the device across a broad range of frequencies. Base on the simulated large signal impedance at maximum power, the prematch circuitry can be designed. On a system level, the prematch power amplifier is used in Doherty amplifier. Two different prematch circuitries, T- section and shunt L methods are investigated along with their comparison in the Doherty architecture at both back off power and peak power condition. The last section of the thesis will be incorporating the proposed impedance inverter structure between the main and auxiliary amplifiers.
The simulated results showed the shunt L prematch topology has the least impedance dispersion across frequency. Along with the new impedance inverter structure, the 65% efficiency bandwidth improves by 50% compared to the original impedance inverter structure at back off power level.Dissertation/ThesisMasters Thesis Electrical Engineering 201
Features of metabolic disorder in late adolescence are negatively associated with testicular function aT 20 years of age; evidence from a birth cohort
No full textOral Presentation #O-065R. Hart, D. Doherty, L. Adams, R.C. Huang, T. Mori, N. Minae, R. MacLachlan, N. Skakkebaek, R. Norman, D. Handelsman, J. Olynyk, L. Beili
Effect of the HIV epidemic on infant feeding in South Africa: “When they see me coming with the tins they laugh at me”
No full text<p>Doherty T, Chopra M, Nkonki L, Jackson D, Greiner T. Effect of the HIV epidemic on infant feeding in South Africa: “When they see me coming with the tins they laugh at me”. WHO Bulletin 2006;84(2):90-96.This qualittive study examined the issue of stigma, only one of the downsides of the earlier UN and later South African government policy of giving free formula to HIV-infected women. Both have since changed their policies. </p
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
Okudrilus nyosensis Csuzdi & Sherlock & Kouete & Doherty-Bone 2015, sp. n.
No full textOkudrilus nyosensis Csuzdi & Sherlock sp. n. Figs 7, 8 Etymology: From the type locality, adjacent to Lake Nyos where the holotype was collected. Diagnosis: L: 82 mm, D: 3 mm. Colour red-violet, paler on ventrum. Head epilobous, setae closely paired. Clitellum annular on ½14–17. Prostatic pores postsetal in 17 a–a, spermathecal pores 12 between a–a, female pores on 14 close to 14/ 15 in d. Gizzard in 6, calciferous glands in 12, chylus-sacs in 10, 11. Testes in 11, vesicles in 12 long running back to 22. Ovo-spermathecal apparatus aired, spermathecal ampulla elongated tube, laterally continues in an ovo-spermathecal duct communicating with the ovarian capsule. The right and left ovarian duct interconnected by a small channel. Prostates without copulatory sacs. Simple penial setae 7 mm in length and 0.02 mm in diameter. Description: External characters: Holotype: Preserved length 82 mm diameter after clitellum 3 mm. Segment number: 168. Colour: Preserved reddish-brown, paler on ventrum. Head: Epilobous, ¾ closed. Dorsal pores: Lacking. Setae: Closely paired, setal ratio aa:ab:bc:cd:dd = 6:1.2:4:1:20. Nephridial pores: Begin on segment 2, somewhat dorsal to setal line d. Clitellum: Annular on segments ½ 14–17. Prostatic pores: Postsetal on 17 situated on a pair of slightly elevated papilla. The prostatic pores on both sides are connected by a straight seminal groove with small porophores on 18 in setal line a–a. Female pores: Small dots on 14, close to the intersegmental furrow 14/15 just below setal line d. Spermathecal pores: Paired on a small glandular elevation in 12 between setae a–a (Fig. 7). Glandular swellings: One pair on 11 around setae ab connected with the spermathecal pore on both sides by slightly curved grooves. Internal characters: Muscular gizzard: Large in 6. Septa: 7/8 slightly thickened, 8/9–11/12 moderately strengthened. Calciferous glands: paired in 12, large curved, chylus-sacs in 10, 11. Dorsal blood vessel: Simple throughout. Hearts: In 9–11, moniliform. Testes and sperm funnels: In 11 enclosed in an oval sperm-reservoir. Seminal vesicles: Long, running alongside the intestine from 12 to 22. Ovo-spermathecal apparatus: Ovaries in 13 enclosed in an ovarian capsule pendant from septum 12/13. The ovarian capsule laterally continuing in an ovarian duct becoming undulating before joining the fertilisation chamber bearing a pendant ovisac. From the fertilisation chamber a straight oviduct leads to the female pore. The ovarian capsule medially communicates with an ovo-spermathecal duct joining laterally the elongated and muscular spermathecal ampulla. The spermathecal ampulla bears ectally a spherical dilatation which continues in a long spermathecal duct opening into the spermathecal pore. The left and right ovospermathecal ducts communicate by a small interconnecting channel (Fig. 8). Prostates: Long simple tubes without bursa copulatrix or bursa propulsoria. Penial setae: Simple, smooth, c. 7 mm long and 0.02mm in diameter. Holotype: CAMEROON: North-West Region, Lake Nyos 1041 m, 28.v.2012, M. T. Kouete & T. DohertyBone (NHM 2013.443) Remarks: The new species differs from the other two Okudrilus species in the position of the spermathecal pores located in segment 12 (12/ 13 in O. monticolus, 11 in O. sulcatus) and furthermore in the structure of the ovo-spermathecal apparatus. The habitat where this species was collected was in subsistence agriculture, with a canopy cover estimated ~ 60 and 80 % and largely cOnsisting Of aVOcadO, guaVa and raffia trees. There were also cocoyam, yam and ground nuts.Published as part of Csuzdi, Cs., Sherlock, E., Kouete, M. Talla & Doherty-Bone, T. M., 2015, Four new earthworm species from the highlands of Cameroon with description of a new genus Okudrilus gen. n. (Oligochaeta: Eudrilidae & Acanthodrilidae), pp. 25-38 in African Invertebrates 56 (1) on pages 30-32, DOI: 10.5733/afin.056.0103, http://zenodo.org/record/767041
- …
