Partition regularity without the columns property

A finite or infinite matrix A with rational entries is called partition regular if whenever the natural numbers are finitely coloured there is a monochromatic vector x with Ax=0. Many of the classical theorems of Ramsey Theory may naturally be interpreted as assertions that particular matrices are partition regular. In the finite case, Rado proved that a matrix is partition regular if and only it satisfies a computable condition known as the columns property. The first requirement of the columns property is that some set of columns sums to zero. In the infinite case, much less is known. There are many examples of matrices with the columns property that are not partition regular, but until now all known examples of partition regular matrices did have the columns property. Our main aim in this paper is to show that, perhaps surprisingly, there are infinite partition regular matrices without the columns property --- in fact, having no set of columns summing to zero. We also make a conjecture that if a partition regular matrix (say with integer coefficients) has bounded row sums then it must have the columns property, and prove a first step towards this.Comment: 13 page

Distinguishing subgroups of the rationals by their Ramsey properties

A system of linear equations with integer coefficients is partition regular over a subset S of the reals if, whenever S\{0} is finitely coloured, there is a solution to the system contained in one colour class. It has been known for some time that there is an infinite system of linear equations that is partition regular over R but not over Q, and it was recently shown (answering a long-standing open question) that one can also distinguish Q from Z in this way. Our aim is to show that the transition from Z to Q is not sharp: there is an infinite chain of subgroups of Q, each of which has a system that is partition regular over it but not over its predecessors. We actually prove something stronger: our main result is that if R and S are subrings of Q with R not contained in S, then there is a system that is partition regular over R but not over S. This implies, for example, that the chain above may be taken to be uncountable.Comment: 14 page

Almost disjoint large subsets of semigroups

AbstractThere are several notions of largeness in a semigroup S that originated in topological dynamics. Among these are thick, central, syndetic and piecewise syndetic. Of these, central sets are especially interesting because they are partition regular and are guaranteed to contain substantial combinatorial structure. It is known that in (N,+) any central set may be partitioned into infinitely many pairwise disjoint central sets. We extend this result to a large class of semigroups (including (N,+)) by showing that if S is a semigroup in this class which has cardinality κ then any central set can be partitioned into κ many pairwise disjoint central sets. We also show that for this same class of semigroups, if there exists a collection of μ almost disjoint subsets of any member S, then any central subset of S contains a collection of μ almost disjoint central sets. The same statement applies if “central” is replaced by “thick”; and in the case that the semigroup is left cancellative, “central” may be replaced by “piecewise syndetic”. The situation with respect to syndetic sets is much more restrictive. For example, there does not exist an uncountable collection of almost disjoint syndetic subsets of N. We investigate the extent to which syndetic sets can be split into disjoint syndetic sets

HIV infection and susceptibility to epidemic bacterial infections among Rwandan refugees

AbstractObjective: To study HIV prevalence and susceptibility to epidemic bacterial infections among Rwandan refugees treated at the Israeli military field hospital in Goma, Zaire, during a 2-week period of massive outbreaks of cholera, shigellosis, and meningitis in the summer of 1994.Methods: Anonymous testing was performed on serum samples obtained for laboratory analysis from patients who had had an intravenous line inserted at the hospital's emergency facility. The prevalence of HIV was compared among patients who presented at the emergency facility because of watery or bloody diarrhea, pneumonia, meningitis, or trauma.Results: Of the 1350 patients who were seen during the period, 127 were tested: 35 of 127 (27.5%) were HIV seropositive by enzyme-linked immunosorbent assay (ELISA) and Western blot. No statistical difference in the prevalence of HIV was found among the four categories.Conclusion: A high prevalence of HIV infection was observed among Rwandan refugees treated for severe cholera, shigellosis, pneumonia, meningitis, or trauma in a field hospital in Goma, Zaire in the summer of 1994. This rate was similar to that reported among the healthy Rwandan population. Although based on only a small sample of the sick refugees in the camps, this study suggests that HIV infection did not cause increased susceptibility to the epidemic bacterial infections seen during the 1994 refugee crisis in Rwanda

Universal gestational age effects on cognitive and basic mathematic processing

Prematurity has adverse effects on basic mathematic processing following birth at all gestations <36 weeks and on IQ and mathematic attainment <34 weeks GA. The ability to predict IQ and mathematic processing scores from one cohort to another among children cared for in different eras and countries indicates that universal neurodevelopmental factors explain the effects of gestation at birth. In contrast, mathematic attainment may be improved by schooling

Learning disabilities among extremely preterm children without neurosensory impairment: Comorbidity, neuropsychological profiles and scholastic outcomes

Background: Children born extremely preterm are at high risk for intellectual impairment, learning disabilities, executive dysfunction and special educational needs, but little is understood about the comorbidity of intellectual and learning disorders in this population. Aims: This study explored comorbidity in intellectual disability (ID) and learning disabilities (LD) in children born extremely preterm (EP; <26+0 weeks’ gestation). Subjects and study design: A UK national cohort of 161 EP children and 153 term-born controls without neurosensory impairments was assessed at 11 years of age (the EPICure Study). Outcome measures: IQ, mathematics and reading attainment, executive function, visuospatial processing and sensorimotor skills were assessed using standardised tests, and curriculum-based attainment and special educational needs (SEN) using teacher reports. Results: Overall, 75 (47%) EP children and 7 (4.6%) controls had ID or LD (RR 10.12; 95% CI 4.81, 21.27). Comorbidity in ID/LD was more common among EP children than controls (24% vs. 0%). EP children with comorbid ID/LD had significantly poorer neuropsychological abilities and curriculum-based attainment than EP children with isolated or no disabilities. LD were associated with a 3 times increased risk for SEN. However, EP children with ID alone had poorer neuropsychological abilities and curriculum-based attainment than children with no disabilities, yet there was no increase in SEN provision among this group. Conclusions: EP children are at high risk for comorbid intellectual and learning disabilities. Education professionals should be aware of the complex nature of EP children’s difficulties and the need for multi-domain assessments to guide intervention

Izvještaji kotarskih i mjesnih komiteta s područja Slavonije (Daruvar, Osijek, Slavonski Brod) o radu u 1947. godini - 2.dio

Kotarski komitet KPH Našice Mjesni komitet KPH Slavonski Brod Kotarski komitet KPH Brod Mjesni komitet KPH Vinkovci Kotarski komitet KPH Vinkovci Kotarski komitet KPH Slavonska Požega Kotarski komitet KPH Nova Gradiška Kotarski komitet KPH Đakovo Kotarski komitet KPH Županj

Perception of soundscapes : an interdisciplinary approach

This paper takes an overall view of findings from the Positive Soundscape Project, a large inter-disciplinary soundscapes study. Qualitative fieldwork (soundwalks and focus groups) have found that soundscape perception is influenced by cognitive effects such as the meaning of a soundscape and its components, and how information is conveyed by a soundscape, for example on the behaviour of people within the soundscape. Three significant clusters were found in the language people use to describe soundscapes: sound sources, sound descriptors and soundscape descriptors. Results from listening tests and soundwalks have been integrated to show that the two principal dimensions of soundscape emotional response seem to be calmness and vibrancy. Further, vibrancy seems to have two aspects: organisation of sounds and changes over time. The possible application of the results to soundscape assessment and design are briefly discussed

The journey effect: how travel affects the experiences of mental health in-patient service-users and their families

The qualitative study presented in this paper explored the perspectives of service-users, family members and staff about the impact of travel issues on the lives of mental health in-patients and carers. This topic was chosen because it was prioritised by members of Xplore, a service-user and carer research group, and has received little research attention. Travel problems were a significant issue for many service-users and carers, bound-up with mental health issues and the recovery experience. Travel facilitation through the funding of taxis and the provision of guides was appreciated. A few service-users and carers positively valued distancing from their previous home environment. The meaning of travel issues could only be understood in the context of individuals’ wider lives and relationships. The significance of the findings is discussed in relation to the social model of disability