Processes for the 3D Printing of Hydrodynamic Flow-Focusing Devices.

Flow focusing is an important hydrodynamic technique for cytometric analysis, enabling the rapid study of cellular samples to identify a variety of biological processes. To date, the majority of flow-focusing devices are fabricated using conventional photolithography or flame processing of glass capillaries. This article presents a suite of low-cost, millifluidic, flow-focusing devices that were fabricated using a desktop sterolithgraphy (SLA) 3D printer. The suite of SLA printing strategies consists of a monolithic SLA method and a hybrid molding process. In the monolithic SLA approach, 1.3 mm square millifluidic channels were printed as a single piece. The printed device does not require any post processing, such as bonding or surface polishing for optical access. The hybrid molding approach consists of printing a mold using the SLA 3D printer. The mold is treated to an extended UV exposure and oven baked before using PDMS as the molding material for the channel. To demonstrate the viability of these channels, we performed a series of experiments using several flow-rate ratios to show the range of focusing widths that can be achieved in these devices. The experiments are validated using a numerical model developed in ANSYS.

Nitrogen-Induced Hysteresis in Grassland Biodiversity: A Theoretical Test of Litter-Mediated Mechanisms.

AbstractThe global rise in anthropogenic reactive nitrogen and the negative impacts of N deposition on terrestrial plant diversity are well documented. The R* theory of resource competition predicts reversible decreases in plant diversity in response to N loading. However, empirical evidence for the reversibility of N-induced biodiversity loss is mixed. In a long-term N-enrichment experiment in Minnesota, a low-diversity state that emerged during N addition has persisted for decades after additions ceased. Hypothesized mechanisms preventing recovery of biodiversity include nutrient recycling, insufficient external seed supply, and litter inhibition of plant growth. Here, we present an ordinary differential equation model that unifies these mechanisms, produces bistability at intermediate N inputs, and qualitatively matches the observed hysteresis at Cedar Creek. Key features of the model, including native species' growth advantage in low-N conditions and limitation by litter accumulation, generalize from Cedar Creek to North American grasslands. Our results suggest that effective biodiversity restoration in these systems may require management beyond reducing N inputs, such as burning, grazing, haying, and seed additions. By coupling resource competition with an additional interspecific inhibitory process, the model also illustrates a general mechanism for bistability and hysteresis that may occur in multiple ecosystem types.

Understanding the Sexual and Reproductive Health Experiences of Refugee and Host Community Adolescents and Youth in Rwanda During COVID-19: Needs, Barriers, and Opportunities.

Background: COVID-19 has exacerbated the sexual and reproductive health (SRH) needs of those affected by humanitarian emergencies, particularly affecting adolescents and youth, whose needs are often neglected during crises. In Rwanda, the situation for refugees in Mahama Refugee Camp has worsened, as COVID-19 lockdown measures have increased needs while restricting access to basic services. Few assessments have been conducted on the SRH needs of refugees in Mahama camp, including adolescents and youth, since COVID-19. To address this gap, Save the Children (SC) undertook research utilizing SenseMaker to collect data on the SRH needs of adolescents and youth in Mahama camp, as well as in the surrounding host community. Methodology: SC used SenseMaker to collect 745 data entries from adolescents and youth in Mahama camp and the surrounding host community. The application was pretested with adolescents and youth in Mahama camp before initiating the research. SenseMaker asks participants to share their stories in response to a prompt; our prompt asked participants to describe their experience seeking help with their health during COVID-19. The research team analyzed the data using simultaneous coding to examine key themes. The results were discussed with SC staff to validate the coding analysis results before conducting four focus group discussions to further clarify results and propose action steps in response to the findings. Results: Many adolescents and youth reported significant difficulties accessing SRH information and services, including stigmatization among service providers. Provider biases and negative attitudes were repeatedly cited as barriers. Stories collected during COVID-19 show how these biases and judgmental attitudes continue to adversely affect access and use of SRH services for young people. Coercive, non-consensual, and transactional sexual incidents were reported from adolescents and youth. They cited reduced time in education spaces as a source of distress as well as increasing their level of sexual activity and associated risks. Limited data exists for SRH needs among adolescents and youth during COVID-19 in humanitarian settings. This study adds to the evidence, making the case for increased SRH prioritization for adolescents and youth in humanitarian settings, particularly when facing overlapping crises like during the COVID-19 pandemic.

Hepatitis C virus testing perspectives among primary care physicians in four large primary care settings.

BACKGROUND: In 1998, the Centers for Disease Control and Prevention (CDC) published Recommendations for Prevention and Control of Hepatitis C Virus (HCV) Infection and HCV-Related Chronic Disease, recommending HCV testing for populations most likely to be infected with HCV. However, the implementation of risk-based screening has not been widely adopted in health care settings, and 45% to 85% of infected U.S. adults remain unidentified. OBJECTIVES: To develop a better understanding of why CDC's 1998 recommendations have had limited success in identifying persons with HCV infection and provide information about how CDC's 2012 Recommendations for the Identification of Chronic Hepatitis C Virus Infection Among Persons Born During 1945-1965 may be implemented more effectively. DESIGN: Qualitative data were collected and analyzed from a multidisciplinary team as part of the Birth Cohort Evaluation to Advance Screening and Testing for Hepatitis C project. RESPONDENTS: Nineteen providers were asked open-ended questions to identify current perspectives, practices, facilitators, and barriers to HCV screening and testing. Providers were affiliated with Henry Ford Hospital, Mount Sinai Hospital, the University of Alabama, and the University of Texas Health Science Center. RESULTS: Respondents reported the complexity of the 1998 recommendations, and numerous indicated risk factors were major barriers to effective implementation. Other hindrances to hepatitis C testing included physician discomfort in asking questions about socially undesirable behaviors and physician uncertainty about patient insurance coverage. CONCLUSION: Implementation of the CDC's 2012 recommendations could be more successful than the 1998 recommendations due to their relative simplicity; however, effective strategies need to be used for dissemination and implementation for full success.

Interplay between structure-specific endonucleases for crossover control during Caenorhabditis elegans meiosis.

The number and distribution of crossover events are tightly regulated at prophase of meiosis I. The resolution of Holliday junctions by structure-specific endonucleases, including MUS-81, SLX-1, XPF-1 and GEN-1, is one of the main mechanisms proposed for crossover formation. However, how these nucleases coordinately resolve Holliday junctions is still unclear. Here we identify both the functional overlap and differences between these four nucleases regarding their roles in crossover formation and control in the Caenorhabditis elegans germline. We show that MUS-81, XPF-1 and SLX-1, but not GEN-1, can bind to HIM-18/SLX4, a key scaffold for nucleases. Analysis of synthetic mitotic defects revealed that MUS-81 and SLX-1, but not XPF-1 and GEN-1, have overlapping roles with the Bloom syndrome helicase ortholog, HIM-6, supporting their in vivo roles in processing recombination intermediates. Taking advantage of the ease of genetic analysis and high-resolution imaging afforded by C. elegans, we examined crossover designation, frequency, distribution and chromosomal morphology in single, double, triple and quadruple mutants of the structure-specific endonucleases. This revealed that XPF-1 functions redundantly with MUS-81 and SLX-1 in executing crossover formation during meiotic double-strand break repair. Analysis of crossover distribution revealed that SLX-1 is required for crossover suppression at the center region of the autosomes. Finally, analysis of chromosome morphology in oocytes at late meiosis I stages uncovered that SLX-1 and XPF-1 promote meiotic chromosomal stability by preventing formation of chromosomal abnormalities. We propose a model in which coordinate action between structure-specific nucleases at different chromosome domains, namely MUS-81, SLX-1 and XPF-1 at the arms and SLX-1 at the center region, exerts positive and negative regulatory roles, respectively, for crossover control during C. elegans meiosis.

Speed of kill efficacy and efficacy of flavored spinosad tablets administered orally to cats in a simulated home environment for the treatment and prevention of cat flea (Ctenocephalides felis) infestations.

The efficacy of spinosad against adult fleas (Ctenocephalides felis) on cats was evaluated in two separate controlled, blinded studies-one to determine flea knockdown and speed of flea kill (SOFK) on experimentally infested cats, another to assess the ability of spinosad to prevent flea infestations in a simulated home environment (SHE) study design. In each study, pre-treatment live flea counts were used as a blocking factor to randomize cats to treatment, and treated in the fed state, with flavored tablets containing either no active ingredient (control) or spinosad (50-100mg/kg in the SOFK study; 50-75 mg/kg body weight in the SHE study). In the SOFK study, 6 cats per group were infested with unfed adult fleas on Day -1. Groups 1-5 received control tablets; groups 6-10 received spinosad tablets. Flea counts were conducted at 0.5, 2, 4, 8 and 24h post-dosing. In the SHE study, 12 flea-free cats per group, treated on Days 0, 30 and 60, were maintained in solid-sided cages with solid carpeted floors. Each cat was infested on Days 1, 7 and 14 with 100 unfed adult fleas. Individual flea comb counts were performed on Days 3, 9, 16, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91 and 95. After each count, except Day 95, up to 300 live fleas were replaced on each cat. To augment flea challenge, the carpeted area in each cage was sprinkled weekly with larval flea growth media (dried blood, yeast). In the SOFK study, reductions in mean flea counts in the spinosad groups were observed at all post-treatment assessments, beginning at 0.5h post-infestation with significant differences (p<0.0001) from vehicle-treated cats from 2h post-treatment when efficacy was >90%, through the final flea counts 24h post-infestation when no fleas were found on spinosad treated cats. In the SHE study, GM post-treatment flea counts in the control group ranged between 38.9 and 107.0 (arithmetic means 58.8-118.1); no live fleas were combed from spinosad-treated cats (100% effectiveness) at any time point post-treatment. No adverse events that were attributable to the treatments were observed in either study. These studies demonstrated that spinosad administered orally to cats is safe and effective, providing >90% efficacy from 2h post-dosing and 100% knockdown at 24h, and preventing infestations over a 95 day study period from a flea-contaminated simulated home environment.

SLX-1 is required for maintaining genomic integrity and promoting meiotic noncrossovers in the Caenorhabditis elegans germline.

Although the SLX4 complex, which includes structure-specific nucleases such as XPF, MUS81, and SLX1, plays important roles in the repair of several kinds of DNA damage, the function of SLX1 in the germline remains unknown. Here we characterized the endonuclease activities of the Caenorhabditis elegans SLX-1-HIM-18/SLX-4 complex co-purified from human 293T cells and determined SLX-1 germline function via analysis of slx-1(tm2644) mutants. SLX-1 shows a HIM-18/SLX-4-dependent endonuclease activity toward replication forks, 5'-flaps, and Holliday junctions. slx-1 mutants exhibit hypersensitivity to UV, nitrogen mustard, and camptothecin, but not gamma irradiation. Consistent with a role in DNA repair, recombination intermediates accumulate in both mitotic and meiotic germ cells in slx-1 mutants. Importantly, meiotic crossover distribution, but not crossover frequency, is altered on chromosomes in slx-1 mutants compared to wild type. This alteration is not due to changes in either the levels or distribution of double-strand breaks (DSBs) along chromosomes. We propose that SLX-1 is required for repair at stalled or collapsed replication forks, interstrand crosslink repair, and nucleotide excision repair during mitosis. Moreover, we hypothesize that SLX-1 regulates the crossover landscape during meiosis by acting as a noncrossover-promoting factor in a subset of DSBs.

A comparison of developmental social-pragmatic and naturalistic behavioral interventions on language use and social engagement in children with autism.

PURPOSE: Developmental social-pragmatic and naturalistic behavioral interventions share a number of features, but they differ in their use of facilitative strategies and direct elicitation of child language. In this study, the authors investigated whether these approaches produce different language and social outcomes in young children with autism. METHOD: The authors used an ABACAD design to compare the effects of a developmental social-pragmatic, naturalistic behavioral, and combined intervention on language type and function and social engagement in 5 children with autism. RESULTS: Milieu teaching and the combined intervention produced higher rates of language targets than did responsive interaction. An analysis of the type and function of language targets suggested that differences between conditions were driven primarily by prompted-and, to a lesser extent, spontaneous-requests. Social engagement ratings were higher during each intervention than at baseline, but differences between treatment conditions were not consistent across children. CONCLUSIONS: For children with autism, naturalistic interventions that use direct elicitation of child language lead to greater short-term gains in the use of expressive language targets-in particular, prompted requests-than interventions that use facilitative strategies only. All 3 naturalistic language interventions can promote social engagement. For some children, the combined use of direct elicitation and responsiveness-based strategies may enhance treatment response.

Increased rates of depressed mood in mothers of children with ASD associated with the presence of the broader autism phenotype.

This study examined the relationship between the broader autism phenotype (BAP) and depressed mood in mothers of children with and without autism spectrum disorders (ASD). One hundred and sixty-five mothers (71 with an ASD child and 94 with a non-ASD child) completed a survey of child autism severity (ASD mothers only), parenting stress, BAP, and depression. Mothers of children with ASD reported greater depressed mood, higher parenting stress, and more characteristics associated with the BAP than mothers of children without ASD. For mothers of children with ASD, the BAP uniquely predicted number of depressive symptoms after controlling for child autism severity and parenting stress. In the full sample, the relationship between group status and depressed mood was no longer significant after controlling for parenting stress and maternal BAP. These findings suggest that the higher rate of depression found in mothers of children with ASD may be attributed both to the increased stress of raising a child with ASD, as well as a greater number of autistic features in the mothers that may place them at higher risk for developing depression.

Chronic physical health conditions and disability among Canadian school-aged children: a national profile.

OBJECTIVE: The objective of this study was to provide a national health and disability profile of Canadian school-aged children based on the World Health Organization's definitions of health condition and disability that would facilitate international comparisons of child health data. METHODS: Data were used from the National Longitudinal Survey of Children and Youth, a 1994 - 95 population-based sample of 22 831 children. FINDINGS: An estimated total of 30.3% of Canadian children aged 6 to 11 had one or more chronic physical health conditions/impairments, while 3.6% had activity-limiting conditions/impairments. Children living with one parent were significantly more likely to have activity-limiting conditions/impairments than those living with two parents. Children with conditions/impairments, particularly those with activity limitations, were significantly more likely than children without health problems to have experienced mental health conditions and learning disabilities, missed school days, received special education, visited health professionals, been hospitalized, and used prescription medication. CONCLUSION: Important differences were found among children in a number of areas as a function of overall physical health status. The findings emphasize the importance of measuring activity limitations distinctly from chronic conditions and impairments, and, perhaps, of measuring impairments distinctly from chronic conditions, and of comparing children with such health problems to children without health problems in order to obtain a more accurate picture of the impact of health on children's lives. The World Health Organization's distinct definitions of health condition and disability facilitate a dimensional approach for describing child health that can serve to clarify this field of study and improve comparability of data across countries.