Transmission-Line Class-E Power Amplifier With Extended Maximum Operating Frequency

A novel Class-E power amplifier (PA) topology with transmission-line load network is presented in this brief. When compared with the classic Class-E topology, the new circuit can increase the maximum operating frequency up to 50% higher without trading the other Class-E figures of merit. Neither quarterwave line/massive radio-frequency choke for collector/drain biasing nor additional fundamental-frequency output matching circuit are needed in the proposed PA, thus resulting in a compact design. Closed-form formulations are derived and verified by simulations with practical design limitations carefully taken into consideration and good agreement achieved.

Transmission characteristics of a vaginally-worn UHF radio telemeter

A vaginally-worn temperature telemeter may be used by women to chart their basal body temperature for ovulation detection. The telemeter uses a temperature to pulse width converter to key a Colpitts oscillator which is controlled in frequency by a 418 MHz SAW resonator. The circuit’s tank inductor acts as a compact, multi-turn loop antenna with a radiated power in isolation of around 1 uW. The transmission characteristics of the system are affected by the proximity of the human body, which acts as an electrically-large lossy dielectric. The RF link-budget must allow for the reduction in total emitted power, directional body-induced fading, and polarization effects. The polar power patterns of the telemeter were measured for both isolated and in-situ cases, using horizontal and vertical polarization. The power patterns were numerically integrated to determine relative emitted power, and a reference dipole used to determine the emitted power for the isolated device. In isolation the telemeter radiation is vertically polarized and isotropic in nature. With the telemeter in-situ, total body absorption was found to be over 20 dB, with directional fades of up to 40 dB; there was extensive cross-polarization, with up to 60% of radiated power horizontally polarized. With limited radiated power and directional fading, the operating range for the telemeter is limited to single room operation (less than 10m). The majority of RF radiation is absorbed by the body, but the radiation hazard is negligible due to the low power level of the device. The high level of cross-polarization suggests that either horizontal or vertically polarized base-station antennas may be used.

Deformed wing virus and drone mating flights in the honey bee (Apis mellifera): implications for sexual transmission of a major honey bee virus

Deformed wing virus (DWV) represents an ideal model to study the interaction between mode of transmission and virulence in honey bees since it exhibits both horizontal and vertical transmissions. However, it is not yet clear if venereal-vertical transmission represents a regular mode of transmission for this virus in natural honey bee populations. Here, we provide clear evidence for the occurrence of high DWV titres in the endophallus of sexually mature drones collected from drone congregation areas (DCAs). Furthermore, the endophallus DWV titres of drones collected at their maternal hives were no different from drones collected at nearby DCAs, suggesting that high-titre DWV infection of the endophallus does not hinder the ability of drones to reach the mating area. The results are discussed within the context of the dispersal of DWV between colonies and the definition of DWV virulence with respect to the transmission route and the types of tissues infected.

Infection-control strategies for preventing the transmission of meticillin-resistant Staphylococcus aureus (MRSA) in nursing homes for older people (Review)

Background: Nursing homes for older people provide an environment likely to promote the acquisition and spread of meticillin-resistant Staphylococcus aureus (MRSA), putting residents at increased risk of colonisation and infection. It is recognised that infection control strategies are important in preventing and controlling MRSA transmission.

Objectives: The objective of this review was to determine the effects of infection control strategies for preventing the transmission of MRSA in nursing homes for older people.

Search strategy: We searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library 2009, Issue 2), the Cochrane Wounds Group Specialised Register (searched May 29th, 2009). We also searched MEDLINE (from 1950 to May Week 4 2009), Ovid EMBASE (1980 to 2009 Week 21), EBSCO CINAHL (1982 to May Week 4 2009), British Nursing Index (1985 to May 2009), DARE (1992 to May 2009), Web of Science (1981 to May 2009), and the Health Technology Assessment (HTA) website (1988 to May 2009). Research in progress was sought through Current Clinical Trials (www.controlled-trials.com), Medical Research Council Research portfolio, and HSRPRoj (current USA projects). SIGLE was also searched in order to identify atypical material which was not accessible through more conventional sources.

Selection criteria: All randomised and controlled clinical trials, controlled before and after studies and interrupted time series studies of infection control interventions in nursing homes for older people were eligible for inclusion.

Data collection and analysis: Two authors independently reviewed the results of the searches.

Main results: Since no studies met the selection criteria, neither a meta-analysis nor a narrative description of studies was possible.

Authors' conclusions: The lack of studies in this field is surprising. Nursing homes for older people provide an environment likely to promote the acquisition and spread of infection, with observational studies repeatedly reporting that being a resident of a nursing home increases the risk of MRSA colonisation. Much of the evidence for recently-issued United Kingdom guidelines for the control and prevention of MRSA in health care facilities was generated in the acute care setting. It may not be possible to transfer such strategies directly to the nursing home environment, which serves as both a healthcare setting and a resident's home. Rigorous studies should be conducted in nursing homes, to test interventions that have been specifically designed for this unique environment.

FASCIOLA-HEPATICA - DISRUPTION OF SPERMATOGENESIS BY THE MICROFILAMENT INHIBITOR CYTOCHALASIN-B

The distribution of actin filaments in the spermatogenic cells of Fasciola hepatica was determined using a fluorescent derivative of phalloidin. Actin was localised primarily in the region of separation of a secondary spermatogonium from a primary spermatogonium, in the inner faces at the centre of four-cell clusters of tertiary spermatogonia and in the cytophore region of spermatocyte and spermatid rosettes. The effect of the microfilament inhibitor cytochalasin B (100-mu-g/ml) on the ultrastructure of the spermatogenic cells was determined in vitro by transmission electron microscopy using tissue-slice material. Cytochalasin B treatment led to the formation of bi- and multinucleate cells, whose frequency increased with progressively longer incubation periods. Few typical rosettes of spermatocyte and spermatid cells were evident from 6 h onwards, being replaced by syncytial masses of cells. Spermatozoon formation became abnormal in the longer treatment periods, the spermatozoa containing variable numbers of axonemes and an altered distribution of cortical microtubules. Multiple axonemes were observed in the cytoplasm of spermatid cells. The results are discussed in relation to the established role of actin in the cytokinesis phase of cell division and to the effects of cytochalasin B on other tissues and organ systems within the fluke.

Cryptic plasmid pKA22 isolated from the naphthalene degrading derivative of Rhodococcus rhodochrous NCIMB13064

Cryptic plasmids were found in Rhodococcus rhodochrous NCIMB13064 derivatives which had lost the ability to utilize short-chain 1-chloroalkanes (chain length C-3-C-10) and had acquired the ability to degrade naphthalene. The reversions of these derivatives to the original phenotype were accompanied by the loss of the cryptic plasmids. The 4969-bp pKA22 plasmid was cloned in Escherichia coli and sequenced. This plasmid encodes a putative 33,200-Da protein which contains motifs typical of theta replicase proteins and shows a high degree of similarity to a putative theta replicase from Brevibacterium linens plasmid pRBL1 and to a putative protein encoded by ORF1 of the plasmid pAL5000 from Mycobacterium fortuitum. Two sets of long direct repeats were found in pKA22 which may be involved in the replication of the plasmid and recombination processes. (C) 1997 Academic Press.