Comparison of Langmuir probe and optical emission spectroscopy on a volume-cusp filament ion source using helium

D-Pace has a Penning ion source that runs with helium for studies of α-particle production. We want to study its plasma properties as a function of varying operational parameters, which results in varied output ion beam characteristics. In order to diagnose the ion source plasma, a collisional-radiative code for helium to be used with optical emission spectroscopy measurements is developed. This has the advantage of being non-invasive, which allows for measurements using the emitted light from the plasma. This collisional-radiative code is shown to compare well with the Yacora on the Web model developed at IPP-Garching, and improves upon it with the addition of radiation trapping. Furthermore, the sensitivity of this model to the inclusion of additional excited state populations and non-Maxwellian electron energy distribution functions is investigated. It is shown that non-Maxwellian distributions can significantly affect spectroscopy measurements. This diagnostic is benchmarked to Langmuir probe measurements on the TRIUMF-licensed volume-cusp ion source to determine whether it can replicate the measured electron density and electron temperature as a function of varied operational parameters. The operational parameters are helium gas flow (10-40 SCCM), arc voltage (100-200 V), and arc current (1-5 A). The measured plasma properties, while different in absolute value, have similar trends for each operational parameter except when varying arc voltage. It is shown that this mismatch as a function of arc voltage is likely due to high energy non-Maxwellian electrons from the cathode sheath, which are not included within the collisional-radiative model.

ISIS Penning source extraction studies reveal the 3-dimensional Child-Langmuir effect

The standard 1X ISIS negative Penning surface plasma source has reliably produced an H^- beam for ISIS operations for 35 years. In order to meet the 60 mA, 2 ms, and 50 Hz beam current and duty cycle required for the front end test stand (Letchford et al., in Proceedings of IPAC2015, Richmond, VA, USA, 2015), a 2X scaled source has been developed [Faircloth et al., AIP Conf. Proc. 2052, 050004 (2018)]. The 2X source has a plasma chamber twice the linear dimensions of the 1X source. This paper investigates the comparison between different emission areas (plasma electrode aperture dimensions) for both the 1X and 2X sources. Slit and circular extraction schemes are studied. A 3D Child-Langmuir relationship is observed where the space charge limited current density depends on the aspect ratio of the extraction aperture.

Association between prenatal care and small for gestational age birth: an ecological study in Quebec, Canada

BACKGROUND

In Quebec, women living on low income receive a number of additional prenatal care visits, determined by their area of residence, of both multi-component and food supplementation programs. We investigated whether increasing the number of visits reduces the odds of the main outcome of small for gestational age (SGA) birth (weight < 10th percentile on the Canadian scale).

METHODS

In this ecological study, births were identified from Quebec's registry of demographic events between 2006 and 2008 (n = 156 404; 134 areas). Individual characteristics were extracted from the registry, and portraits of the general population were deduced from data on multi-component and food supplement interventions, the Canadian census and the Canadian Community Health Survey. Mothers without a high school diploma were eligible for the programs. Multilevel logistic regression models were fitted using generalized estimating equations to account for the correlation between individuals on the same territory. Potential confounders included sedentary behaviour and cigarette smoking. The odds ratios (ORs) were adjusted for mother's age, marital status, parity, program coverage and mean income in the area.

RESULTS

Mothers eligible for the programs remain at a higher odds of SGA than non-eligible mothers (OR = 1.40; 95% confidence interval [CI]: 1.30-1.51). Further, areas that provide more visits to eligible mothers (4-6 food supplementation visits) seem more successful at reducing the frequency of SGA birth than those that provide 1-2 or 3 visits (OR = 0.86; 95% CI: 0.75-0.99).

CONCLUSION

Further studies that validate whether an increase in the number of prenatal care interventions reduces the odds of SGA birth in different populations and evaluate other potential benefits for the children should be done.

Impact of individual and ecological characteristics on small for gestational age births: an observational study in Quebec

INTRODUCTION

We evaluated associations between ecological variables and the risk of very small for gestational age (VSGA) birth in Quebec in 2000-2008.

METHODS

Ecological variables came from the Canadian Community Health Survey, the Canadian census and Quebec's birth registry; individual variables also came from Quebec's birth registry. Odds ratios (ORs) adjusted for mother's age, academic qualification, parity, marital status and country of birth were estimated using multilevel logistic regression (generalized estimating equations method).

RESULTS

Births in neighbourhoods with a high proportion of people leading a sedentary lifestyle (OR: 1.07, 95% confidence interval [CI]: 1.01-1.11) and those with a high/middle proportion of residents with food insecurity (OR: 1.09, 95% CI: 1.05-1.15; OR: 1.05, 95% CI: 1.01-1.11) had higher odds of VSGA birth. Those with middle proportion of married residents had lower odds of VSGA birth (OR: 0.94, 95% CI: 0.90-0.98).

A study of the association between characteristics of CLSCs and the risk of small for gestational age births among term and preterm births in Quebec, Canada

OBJECTIVES

The objective of this study was to describe whether the social environment of the territory of residence is associated with indicators of foetal growth retardation.

METHODS

All newborns (n = 667,254) from 143 Centres locaux de services communautaires (CLSC) territories of Quebec, Canada, 2000-2008 were included in this study. Small for gestational age (SGA), very small for gestational age (VSGA) and SGA-preterm births were identified. Social characteristics and access to medical services of the population in the CLSCs were obtained from the Canadian Community Health Survey. Data on material deprivation, racial diversity and social isolation were obtained from the 2001 and 2006 Canadian censuses. A compromise between two methods, stepwise and best subset, was used to select variables for multivariate logistic modelling. The model was fitted on each studied outcome: SGA, VSGA and SGA among preterm births.

RESULTS

When investigating material deprivation, racial diversity, social isolation, proportion of sedentary residents and proportion with fair or poor availability of health care services in the CLSC territories, material deprivation, racial diversity, social isolation and sedentary residents showed increased adjusted risk of SGA. Results of the model fit on VSGA birth and on SGA among preterm births were similar.

CONCLUSION

CLSC characteristics of material deprivation, racial diversity, social isolation as well as the contextual variable of sedentary lifestyle were associated with indicators of foetal growth retardation. Further work on features of the CLSCs could help understand how the outcome of SGA is associated with contextual factors and identify groups for intervention.

Promoter suppression in cultured mammalian cells can be blocked by the chicken beta-globin chromatin insulator 5'HS4 and matrix/scaffold attachment regions

Studies have indicated that two transcriptionally active units can repress one another when they lie adjacent in head-to-tail tandem on a chromosome. Repression of a downstream (3') unit by an upstream (5') unit is known as "transcriptional interference", whereas repression of a 5' unit by a 3' unit is termed "promoter suppression". These two processes can occur between head-to-tail tandem copies of a transgene, or between transgenes and adjacent chromosomal genes. Interference can be blocked by inserting a transcription terminator between adjacent units. Here, we report that "promoter suppression" could be blocked by the insulator 5' DNaseI hypersensitive site 4, or matrix/scaffold attachment regions (MAR/SARs), when these elements were interposed between adjacent units. Because intergenic spacers of many repeated eukaryotic genes contain MAR/SARs and insulators, our observations suggest that these elements have the ability to segregate repeated genes into domains that act independently of one another. Our observations also suggest strategies to design transgenes that can act as autonomous units of expression.

Defective herpes simplex virus type 1 vectors harboring gag, pol, and env genes can be used to rescue defective retrovirus vectors

A retroviral packaging transcription unit was constructed in which the Moloney murine leukemia virus (MoMLV) gag-pol and env genes are expressed under the control of herpesvirus regulatory sequences. This transcription unit, lacking long terminal repeats, primer binding sites, and most of the retrovirus packaging signal but retaining both retroviral donor and acceptor splice sites, was cloned into a herpes simplex virus type 1 (HSV-1) amplicon plasmid, and amplicon vectors (the gag-pol-env [GPE] vectors) were generated by using a defective HSV-1 vector as helper virus. The GPE vector population was used to infect human TE671 cells (ATCC CRL 8805), harboring a lacZ provirus (TE-lac2 cells), and supernatants of infected cells were collected and filtered at different times after infection. These supernatants were found to contain infectious ecotropic lacZ retroviral particles, as shown both by reverse transcription-PCR and by their ability to transduce a beta-galactosidase activity to murine NIH 3T3 cells but not to human TE671 cells. The titer of retroviral vectors released by GPE vector-infected TE-lac2 cells increased with the dose of infectious amplicon particles. Retrovirus vector production was inhibited by superinfection with helper virus, indicating that helper virus coinfection negatively interfered with retrovirus production. Induction of retrovirus vectors by GPE vectors was neutralized by anti-HSV-1 but not by anti-MoMLV antiserum, while transduction of beta-galactosidase activity to NIH 3T3 cells by supernatants of GPE vector-infected TE-lac2 cells was neutralized by anti-MoMLV antiserum. These results demonstrate that HSV-1 GPE amplicon vectors can rescue defective lacZ retrovirus vectors and suggest that they could be used as a sort of launching ramp to fire defective retrovirus vectors from within virtually any in vitro or in vivo cell type containing defective retroviral vectors.

[Caregivers and HIV]

An exploratory study conducted among 18 natural caregivers of persons with HIV revealed that extreme emotion was the results of the high cost of personal devotion.