Imaging Carrier Inhomogeneities in Ambipolar Tellurene Field Effect Transistors

Developing van der Waals (vdW) homojunction devices requires materials with narrow bandgaps and simultaneously high hole and electron mobilities for bipolar transport, as well as methods to image and study spatial variations in carrier type and associated conductivity with nanometer spatial resolution. Here we demonstrate the general capability of near-field scanning microwave microscopy (SMM) to image and study the local carrier type and associated conductivity in operando by studying ambiploar field effect transistors (FETs) of the 1D vdW material tellurium in 2D form. To quantitatively understand electronic variations across the device, we produce nanometer resolved maps of the local carrier equivalence backgate voltage. We show that the global device conductivity minimum determined from transport measurements does not arise from uniform carrier neutrality, but rather from the continued coexistence of p-type regions at the device edge and n-type regions in the interior of our micron-scale devices. This work both underscores and addresses the need to image and understand spatial variations in the electronic properties of nanoscale devices.Comment: 15 pages, 4 figure

Soil microorganisms behave like macroscopic organisms: patterns in the global distribution of soil euglyphid testate amoeba

Aim: Patterns of α- and β-diversity of soil protist communities and the factors that shape them remain largely unknown. We undertook a world-wide survey of forest litter to investigate the patterns of diversity in a group of testate amoebae. We aimed to assess: (1) whether there is a latitudinal gradient in α-diversity, and (2) whether β-diversity was correlated solely with environmental factors commonly used in soil biology research or if it was also independently explained by geographical barriers. Location: World-wide. Methods: We studied the diversity of Euglyphida, a common group of testate amoebae, in 35 samples of forest litter and moss samples from a global survey, using small subunit rRNA gene sequences. We assessed the relationship between sample α-diversity and latitude using generalized additive models (GAM). Furthermore, we determined the relationships between community composition and geographical models (distance-based Moran's Eigenvector Maps – db-MEM) using Generalized UniFrac distances (GUniFrac). We also investigated the relationship between individual measured soil parameters, WorldClim data and diversity (alpha plus beta) using both raw data and synthetic variables obtained through principal components analysis. Results: We recorded 245 phylotypes belonging to 6 out of 7 known Euglyphida families, plus four novel deep clades. Euglyphid α-diversity was positively correlated with temperature and negatively with latitude and litter C/N ratio. Euglyphida community structure was correlated with the spatial eigenvector Db-MEM31, independently of all measured environmental variables. Db-MEM31 corresponds to a natural barrier constituted by the Northern Hemisphere desert belt. Beta diversity was correlated with other environmental variables, such as pH, isothermality and temperature in the coldest month of the year. Main conclusions: Soil euglyphid α-diversity displays a latitudinal gradient, and β-diversity is not only correlated with climatic and physicochemical parameters but also with geographical barriers. Such patterns of diversity were until recently believed to be characteristic only for macroscopic organisms

Vertical zonation of testate amoebae in the Elatia Mires, northern Greece : palaeoecological evidence for a wetland response to recent climate change or autogenic processes?

The Elatia Mires of northern Greece are unique ecosystems of high conservation value. The mires are climatically marginal and may be sensitive to changing hydroclimate, while northern Greece has experienced a significant increase in aridity since the late twentieth century. To investigate the impact of recent climatic change on the hydrology of the mires, the palaeoecological record was investigated from three near-surface monoliths extracted from two sites. Testate amoebae were analysed as sensitive indicators of hydrology. Results were interpreted using transfer function models to provide quantitative reconstructions of changing water table depth and pH. AMS radiocarbon dates and 210Pb suggest the peats were deposited within the last c. 50 years, but do not allow a secure chronology to be established. Results from all three profiles show a distinct shift towards a more xerophilic community particularly noted by increases in Euglypha species. Transfer function results infer a distinct lowering of water tables in this period. A hydrological response to recent climate change is a tenable hypothesis to explain this change; however other possible explanations include selective test decay, vertical zonation of living amoebae, ombrotrophication and local hydrological change. It is suggested that a peatland response to climatic change is the most probable hypothesis, showing the sensitivity of marginal peatlands to recent climatic change

Prevalence of head lice infestation in Primary School children in Port Harcourt

Background: Head lice infestation affects mainly school-aged children and prevalence varies from region to region. Head lice infestation is of public health concern and screening is integrated into the School Health Programme.Objective: To determine the prevalence of head lice infestation in primary school – aged children in Port Harcourt, Nigeria.Design: Cross-sectional descriptive study.Subjects: A stratified multi-staged sampling technique was used to recruit pupils between six and 12 years of age, from thirteen primary schools located in three School Districts in the area. The heads of the pupils were inspected for head lice and nits with the aid of a battery operated Robi lice comb, magnifying glass and a torch as light source.Results: A total of 1350 pupils were studied, 743 (55%) females and 607 (45%) males giving a female to male ratio of 1.2:1. Ten (0.7%) of the pupils had head lice infestation while five (0.4%) had evidence of past head lice infestation. The number of infested pupils among the younger age group (six to nine years) was seven (0.8%) and is higher, though not statistically significant, than that in the older age group (ten to twelve years) which was three (0.6%) (p = 0.453). No male was found to be infested while ten (1.3%) females were infested and the observed gender difference was statistically significant (p = 0.002).Conclusion: Head lice infestation still exists in Primary School children in Nigeria, therefore, screening for head lice infestation should still remain a part of the School Health Programme

Childhood hypertension and family history of hypertension in primary school children in Port Harcourt

Objective: To determine the relationship between childhood hypertension and family history of hypertension in primary school children in Port Harcourt.Methods: A stratified multi-staged sampling technique was used torecruit pupils between 6-12 years of age, from thirteen primary schoolslocated in three school districts. Data was collected using a pretestedquestionnaire completed by parents / guardians. The average of three blood pressure measurements, weight and height were taken for each pupil, using standardized techniques. Hypertension was defined as average systolic and / or diastolic blood pressure greater than or equalto the 95th percentile for age, gender and height using the standard bloodpressure charts. Family history of hypertension was defined as eitherparent indicating on the submitted questionnaire that they were hypertensive (diagnosed by a physician and/or on antihypertensive drugs)or had a family history of hypertension.Results: A total of 1302 pupils with 717 (55.1%) females and 585(44.9%) males were studied, giving a female to male ratio of 1.2:1. Themean age of pupils studied was 8.82±1.91 years. Sixty one (4.7%)of the pupils examined had hypertension. Of the 1302 pupils, 316(24.3%) had a family history of hypertension. The mean systolic(p<0.001) and diastolic (p=0.220) blood pressures were higher in childrenwith a family history of hypertension than in those without. Ofthe pupils that had a family history of hypertension, 7.9% had  hypertension, while 3.7% of those that did not have a family history, werefound to be hypertensive (p=0.001).Conclusion: A family history of hypertension was associated with a higher prevalence of childhood hypertension than was seen in children without a family history of hypertension.Key words: Childhood Hypertension, Family history

Sociocultural issues and causes of cerebral palsy in Port Harcourt, Nigeria

Background: Cerebral palsy (CP) is a common neurological disorder of childhood with significant neurological complications and associated comorbidities. The aim of this study was to determine the socio- cultural characteristics and causes of CP in children who presented to the Paediatric neurology clinic in Port Harcourt, Nigeria. Method: Hospital records of 834 children with CP who presented between 1 June 2008 and 1 June .2010 were reviewed Demographic data were extracted and a validated socio-economic classification of parents was used. Data was analyzed using SPSS version 15 software. Results: of the 2,288 patients with neurological disorders seen. 834 had cerebral palsy giving a prevalence of 36.45%. Theirages ranged from 5 months to 13 years. Socio-economic stratification of the patients showed concentration in the lower socioeconomic groups IV (35.73%) andV(56.35%). Majority of the children 668 (80.09%) had spastic CP. Eighty seven (10.43%) had hypotonic and 57 (6.83%) extrapyramidal types, the mixed type 22 (2.64%) was the least common. Asphyxia (27.94%), kernicterus (26.26%) and Central Nerves System infections (15.95%) were the leading identified causes. Co-morbidities such as seizures, microcephaly and speech and auditory deficits were present in majority of the subjects. Seizures and microcephaly were commoner among CP cases associated with asphyxia than those associated with kernicterus. Conclusion: Cerebral palsy was commoner amongst those in low socio-economic status with perinatal problems. Improved perinatal care will reduce the burden of CP. Continuing training of health workers and traditional birth attendants are essential.Keywords: Cerebral palsy, Social cultural issues, Port Harcourt

Conduct Disorder amongst Children in an Urban School in Nigeria

Background: Conduct disorder is a childhood behavioral disorder characterized by aggressive and destructive activities that cause disruptions in the child's natural environments such as home, school, church, or the neighbourhood. It is a source of concern to the clinicians as it is comorbid with other mental disorders, particularly anxiety, depression and learning disabilities. The aim of this research was to evaluate the prevalence of conduct disorder amongst secondary school children in urban schools in Port Harcourt.Method: A structured questionnaire based on Vanderbilt ADHD Diagnostic Teacher Rating Scale for oppositional defiant and conduct disorder symptoms was used. A list of signs taken from the Diagnostic and Statistical Manual text revision (American Psychiatric Association, 2000) that indicates a child may have Conduct Disorder was also used. A child must show a pattern of at least three of these behaviour groups for at least a year before the diagnosis was considered. The questionnaires administered to the students were filled with the assistance of the researchers and the classroom teachers. Direct verbal interview was conducted for those noted to have signs of conduct disorder.Result: There were 885 students studied and 140 were diagnosed with conduct disorder, giving a prevalence of 15.82%. The age range of the entire students ranged from 9-18 years with a modal age of 13 years. Sex distribution of those with the conduct disorder was 112 males and 28 females (male: female ratio of 4:1). The various behaviours exhibited included bullying and or threatening classmates and other students, poor school attendance, stealing, and poor academic performance.Conclusions: The prevalence of conduct disorder amongst school children is high. Poor academic performance and other associated comorbidities impair the quality of life of these children. Early identification and appropriate treatment will improve the course of this behavioral disorder.Keywords: Conduct disorder, urban schools, children

Long term neurological complications of bacterial meningitis in Nigerian children

Background: Neurological disorders in children are common occurrence in clinical practice. The disorder account for more than 170,000 deaths  worldwide each year and contributes to the world's disease burden withmajority of people affected living in Africa. When affected by such illnesses, a person's memory, motor and cognitive abilities, concentration,speech, and physique can be drastically altered. Many of these disorders are chronic, frustrating to caregivers and parents and require adequate understanding to cope with management. Bacterial meningitis contributessignificantly to this morbidity and mortality in sub-Saharan Africa, known as the “meningitis belt”.This study highlights the long term neurological complications of bacterial meningitis amongst children who were on follow up at the neurology unit at the University of Port Harcourt Teaching Hospital (UPTH), a tertiary hospitalin Southern Nigeria.Method: This is a three year follow up prospective study of children with meningitis at the Paediatric neurology unit of the University of Port Harcourt Teaching Hospital, Nigeria between January 1st 2010 and December, 31st 2012. Descriptive analysis was done using SPSS® version 17.Result and Conclusion: Out of 7,644 patients seen in the department,624 of them were diagnosed with meningitis given a prevalence of 8.16%.These patients were followed up at least one year in the neurological outpatient clinic to assess the outcome post admission.Those with neurological sequelae were 94 cases (given a prevalenceof 15.06%) comprising 58 males and 36 females which gave a ratio of 1:0.6. The most common complication was recurrent seizure disorder in 28(29.79%) of them and motor developmental delay in almost 20% of them. Others are focal neurologic deficits and neuropsychologic impairment. The impact and consequences of meningitis is grave, it is important to prevent the disease at all cost. Key words: Meningitis, children, Neurologic complications, longterm