Supercluster states and phase transitions in aggregation-fragmentation processes

We study the evolution of aggregates triggered by collisions with monomers that either lead to the attachment of monomers or the break-up of aggregates into constituting monomers. Depending on parameters quantifying addition and break-up rates, the system falls into a jammed or a steady state. Supercluster states (SCSs) are very peculiar non-extensive jammed states that also arise in some models. Fluctuations underlie the formation of the SCSs. Conventional tools, such as the van Kampen expansion, apply to small fluctuations. We go beyond the van Kampen expansion and determine a set of critical exponents quantifying SCSs. We observe continuous and discontinuous phase transitions between the states. Our theoretical predictions are in good agreement with numerical results.Comment: 19 pages, 15 figure

Rational homotopy type of the component of inclusion in the nthspace of continuous mappings from Gr (k, n) to Gr(k, n + 1)

Paper presented at the 4th Strathmore International Mathematics Conference (SIMC 2017), 19 - 23 June 2017, Strathmore University, Nairobi, Kenya.A complex manifold can be embedded in some complex projective space CP (N ), in particular, the Grassmann manifold Gr(n, k) of k dimensional subspaces in Cn can bembedded in some complex projective space CP (N ).Moreover G(k, n) ‹→ G(k, n + 1). For k = 1, we get a one dimensional vector space which is the complex projective plane and is an embedding of CP (n)in CP (n + 1).The Grassmanian admits a CW structure and any CW structure on a space provides a filtration relative to the empty space. To a simply connected topo-logical space, Sullivan associates a commutative differential graded algebra(∧V, d) which encodes the rational homotopy type of X. This is called aSullivan model of X. Given that H∗(CP (n), Q) is the truncated polynomialalgebra ∧x/(xn+1), one gets a a Sullivan model of the form () ∧ (x, y), d)where |x| = 2, |y| = 2n + 1 and dx = 0, dy = xn+1. For k ≥ 1, one might usethe homeomorphism G(k, n) = U (n)/(U (k) × U (n − k)) to find a Sullivanmodel. In this paper, we use a Sullivan model of the inclusion Gr(k, n) −→ Gr(k, n+1) to compute the rational homotopy type of the component of the inclusionin the space of mappings from Gr(k, n) to Gr(k, n + 1)

Direct simulation Monte Carlo for new regimes in aggregation-fragmentation kinetics

We revisit two basic Direct Simulation Monte Carlo Methods to model aggregation kinetics and extend them for aggregation processes with collisional fragmentation (shattering). We test the performance and accuracy of the extended methods and compare their performance with efficient deterministic finite-difference method applied to the same model. We validate the stochastic methods on the test problems and apply them to verify the existence of oscillating regimes in the aggregation-fragmentation kinetics recently detected in deterministic simulations. We confirm the emergence of steady oscillations of densities in such systems and prove the stability of the oscillations with respect to fluctuations and noise.Comment: 19 pages, 2 figures, 4 table

Refining a questionnaire to assess breast cancer knowledge and barriers to screening in Kenya: Psychometric assessment of the BCAM

Background Our study objective was to determine the validity and reliability of the breast module of a cancer awareness measure (BCAM) among adult women in western Kenya. Methods The study was conducted between October and November 2012, following three breast cancer screening events. Purposive and systematic random sampling methods were used to identity 48 women for cognitive focus group discussions, and 1061 (594 who attended vs. 467 who did not attend screening events) for surveys, respectively. Face and psychometric validity of the BCAM survey was assessed using cognitive testing, factor analysis of survey data, and correlations. Internal reliability was assessed using Cronbach’s alpha. Results Among survey participants, the overall median age was 34 (IQR: 26–44) years. Compared to those women who did not attend the screening events, women attendees were older (median: 35 vs. 32 years, p = 0.001) more often married (79% vs. 72%, p = 0.006), more educated (52% vs. 46% with more than an elementary level of education, p = 0.001), more unemployed (59% vs. 11%, p = 0.001), more likely to report doing breast self-examination (56% vs. 40%, p = 0.001) and more likely to report having felt a breast lump (16% vs. 7%, p = 0.001). For domain 1 on knowledge of breast cancer symptoms, one factor (three items) with Eigen value of 1.76 emerged for the group that did not attend screening, and 1.50 for the group that attended screening. For both groups two factors (factor 1 “internal influences” and factor 2 “external influences”) emerged among domain 4 on barriers to screening, with varied item loadings and Eigen values. There were no statistically significant differences in the factor scores between attendees and non-attendees. There were significant associations between factor scores and other attributes of the surveyed population, including associations with occupation, transportation type, and training for and practice of breast self-examination. Cronbach’s alpha showed an acceptable internal consistency. Conclusion Certain subpopulations are less likely than others to attend breast screening in Kenya. A survey measure of breast cancer knowledge and perceived barriers to screening shows promise for use in Kenya for characterizing clinical and community population beliefs, but needs adaptation for setting, language and culture

Impact of an Educational Intervention on Breast Cancer Knowledge in Western Kenya

Our objective was to assess the effectiveness of educational sessions that accompanied breast cancer screening events in three communities in western Kenya between October and November 2013. Five hundred and thirty-two women were recruited to complete a test of breast cancer-relevant knowledge and randomly allocated to ‘pre-test’ or ‘post-test’ groups that immediately preceded or followed participation in the educational sessions. The education was organized as a presentation by health professionals and focused mainly on causes of breast cancer, early and late cancer presentation signs, high-risk groups, screening methods to find early-stage breast cancer, self-breast exam procedures and treatment options for this disease. Participants were invited to ask questions and practice finding nodules in silicone breast models. The median age was 35 years (interquartile range: 28–45), and 86% had not undergone breast cancer screening previously. Many individual items in our test of knowledge showed statistically significant shifts to better-informed responses. When all items in the assessment questionnaire were scored as a ‘test’, on average there was a 2.80 point (95% CI: 2.38, 3.22) significant improvement in knowledge about breast cancer after the educational session. Our study provides evidence for the effectiveness of an educational strategy carefully tailored for women in these communities in Kenya

Screening and selection of lactic acid bacteria for EPS production

Poster presentationExopolysaccharides (EPS) synthesized by lactic acid bacteria (LAB) play an important role in stabilizing and enhancing the viscosity and water binding properties of fermented dairy products and also contribute to the mouth-feel, texture and taste perception of those products. Seventeen LAB strains grown in 10% (w/v) reconstituted skim milk were examined by Gram staining and capsule determination using India ink stain and laser confocal microscopy. Under microscopy, all strains showed capsular EPS, and Streptococcus …postprin

Qualitative exploration of perceived benefits of care and barriers influencing HIV care in trans Nzoia, Kenya

Background: Substantial efforts have been made to ensure people living with HIV (PLHIV) are linked to and retained in care but many challenges deter care utilization. We report perceived benefits of seeking HIV care and barriers to HIV care that were identified through a formative assessment conducted to advise the development of an alternative care model to deliver antiretroviral treatment therapy (ART) in Trans Nzoia County, Kenya. Methods: Data were collected in 2015 through key informant interviews (KIIs), in-depth interviews (IDIs), and focus group discussions (FGDs). The study involved 55 participants of whom 53% were female. Ten KIIs provided community contextual information and viewpoints on the HIV epidemic in Trans Nzoia County while 20 PLHIV (10 male and 10 female) participated in IDIs. Twenty-five individuals living with HIV participated in four FGDs - two groups for men and two for women. Key informants were purposively selected, while every third patient above 18 years at the Kitale HIV Clinic was invited to share their HIV care experience through IDIs or FGDs. Trained research assistants moderated all sessions and audio recordings were transcribed and analyzed thematically. Results: Findings showed that PLHIV in Trans Nzoia County used both conventional and complementary alternative care for HIV; however, public health facilities were preferred. Popular perceived benefits of adopting care were relief from symptoms and the chance to live longer. Benefits of care uptake included weight gain, renewed energy, and positive behavior change. Individual-level barriers to HIV care included lack of money and food, use of alternative care, negative side effects of ART, denial, and disclosure difficulties. At the community level, stigma, limited social support for conventional HIV treatment, and poor means of transport were reported. The health system barriers were limited supplies and staff, long distance to conventional HIV care, and unprofessional providers. Conclusions: Diverse individual, community and health system barriers continue to affect HIV care-seeking efforts in Kenya. Appreciation of context and lived experiences allows for development of realistic care models

Using molecular data for epidemiological inference: assessing the prevalence of Trypanosoma brucei rhodesiense in Tsetse in Serengeti, Tanzania

Background: Measuring the prevalence of transmissible Trypanosoma brucei rhodesiense in tsetse populations is essential for understanding transmission dynamics, assessing human disease risk and monitoring spatio-temporal trends and the impact of control interventions. Although an important epidemiological variable, identifying flies which carry transmissible infections is difficult, with challenges including low prevalence, presence of other trypanosome species in the same fly, and concurrent detection of immature non-transmissible infections. Diagnostic tests to measure the prevalence of T. b. rhodesiense in tsetse are applied and interpreted inconsistently, and discrepancies between studies suggest this value is not consistently estimated even to within an order of magnitude. Methodology/Principal Findings: Three approaches were used to estimate the prevalence of transmissible Trypanosoma brucei s.l. and T. b. rhodesiense in Glossina swynnertoni and G. pallidipes in Serengeti National Park, Tanzania: (i) dissection/microscopy; (ii) PCR on infected tsetse midguts; and (iii) inference from a mathematical model. Using dissection/microscopy the prevalence of transmissible T. brucei s.l. was 0% (95% CI 0–0.085) for G. swynnertoni and 0% (0–0.18) G. pallidipes; using PCR the prevalence of transmissible T. b. rhodesiense was 0.010% (0–0.054) and 0.0089% (0–0.059) respectively, and by model inference 0.0064% and 0.00085% respectively. Conclusions/Significance: The zero prevalence result by dissection/microscopy (likely really greater than zero given the results of other approaches) is not unusual by this technique, often ascribed to poor sensitivity. The application of additional techniques confirmed the very low prevalence of T. brucei suggesting the zero prevalence result was attributable to insufficient sample size (despite examination of 6000 tsetse). Given the prohibitively high sample sizes required to obtain meaningful results by dissection/microscopy, PCR-based approaches offer the current best option for assessing trypanosome prevalence in tsetse but inconsistencies in relating PCR results to transmissibility highlight the need for a consensus approach to generate meaningful and comparable data

Spatial-temporal distribution and sequence diversity of Group A human respiratory syncytial viruses in Kenya preceding the emergence of ON1 genotype

Background Human respiratory syncytial virus (HRSV) is a major cause of severe viral acute respiratory illness and contributes significantly to severe pneumonia cases in Africa. Little is known about its spatial–temporal distribution as defined by its genetic diversity. Methods A retrospective study conducted utilizing archived nasopharyngeal specimens from patients attending outpatient clinics in hospitals located in five demographically and climatically distinct regions of Kenya; Coast, Western, Highlands, Eastern and Nairobi. The viral total RNA was extracted and tested using multiplex real time RT-PCR (reverse transcriptase polymerase chain reaction). A segment of the G-gene was amplified using one-step RT-PCR and sequenced by Sanger di-deoxy method. Bayesian analysis of phylogeny was utilized and subsequently median joining methods for haplotype network reconstruction. Results Three genotypes of HRSVA were detected; GA5 (14.0%), GA2 (33.1%), and NA1 (52.9%). HRSVA prevalence varied by location from 33% to 13.2% in the Highlands and the Eastern regions respectively. The mean nucleotide diversity (Pi[π]) varied by genotype: highest of 0.018 for GA5 and lowest of 0.005 for NA1. A total of 58 haplotypes were identified (GA5 10; GA2 20; NA1 28). These haplotypes were introduced into the population locally by single haplotypes and additional subsidiary seeds amongst the GA2 and the NA1 haplotypes. Conclusions HRSVA was found across all the regions throughout the study period and comprised three genotypes; GA5, GA2, and NA1 genotypes. The genotypes were disproportionately distributed across the regions with GA5 gradually increasing toward the Western zones and decreasing toward the Eastern zones of the country

Caffeine for the care of preterm infants in sub-Saharan Africa: a missed opportunity?

In 2019, 2.4 million neonates (infants <28 days of age) died globally. Of these, over 80% were preterm infants (<37 weeks gestation), with the majority born in low-income and middle-income countries.1 Complications of preterm birth, largely from respiratory distress syndrome due to surfactant deficiency, pneumonia or apnoea of prematurity (AOP), are now the leading cause of under 5 mortality globally.1 These conditions are frequently fatal in the absence of effective ventilatory support which is commonplace in neonatal units across sub-Saharan Africa. Although the global neonatal mortality rate (NMR) has halved over the past three decades, significant regional disparities remain. These correlate with World Bank and International Monetary Fund estimates of the proportion of the population living on less than US$1.90 a day, with the majority of poorer countries being in sub-Saharan Africa.1 2 As the region with the highest NMR of 27 per 1000 live births, it is estimated that a baby born in in sub-Saharan Africa is 10 times more likely to die than one born in a high income country.1 Countries in sub-Saharan Africa are unlikely to meet the global target of no more than 12 newborn deaths per 1000 live births by 2030.3 In 2017, 75 countries (almost half from sub-Saharan Africa) signed up to the ‘Every Newborn Action Plan’ that has strategic global and national actions and milestones to address gaps in maternal and newborn care.4 This ambitious commitment requires evidence-based interventions5 and innovative strategies to improve neonatal survival and longer-term outcomes