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ABSTRACT: The number and size of urban settlements are increasing in all the continents of the world at a rapid pace. Urban sprawl is associated not only with changes in landcover and area, but also ecological, climate and social transformations. Mapping the growth and spread of urban areas is important. Remote sensing has long been used to map human settlements. Today the availability of a large number of satellites and sensors, determining the appropriate image to map urban area is a research area itself. This study compares two satellite images: Landsat Enhanced Thematic Mapper data and Defence Meteorological Satellite Program, Operational Linescan System image to map the urban footprint of the city of Hyderabad, India. Landsat ETM data is captured during the daytime and gives spectral reflectance values while the DMSP-OLS data captures artificial lights from human settlements at night and produces brightness information. The results show an accuracy of more than 90% in the classification and delineation of urban, suburban and rural landcover types. This study shows that in addition to spectral reflectance captured by satellites from different features on the earth surface during the daytime, differences in the degree of brightness of the lights emitted from urban areas at night is also an effective indicator in delineating landcover types.
Urban Remote Sensing Event (JURSE), 2011 Joint; 05/2011
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ABSTRACT: Monitoring hepatitis C virus (HCV) infection among injecting drug users (IDUs) in the community is complicated by difficulties in obtaining biological specimens and biases in recruitment and follow-up. This study examined the utility of dried blood spot (DBS) specimens from IDUs recruited using respondent-driven sampling (RDS). Active IDUs underwent a computer-assisted interview and provided a DBS sample, tested for HCV antibody (anti-HCV) and HCV-RNA. HCV incidence was estimated from the proportion of anti-HCV-negative subjects found HCV-RNA-positive and estimates of the duration of this state. Results were adjusted according to RDS derived sample weights. HCV-RNA testing was performed on 288 DBS samples; 173 were anti-HCV-positive (54% weighted), of which 70 (42%, 95%CI 34-50% weighted) were RNA-negative indicating cleared infection. Among the 115 anti-HCV-negatives, 14 were RNA-positive suggesting an incidence of 38-47 per 100pyrs. Incident infections were younger than anti-HCV-negative and prevalent infections: 25 vs. 29 and 34, respectively. Incidence was highest among individuals with poor needle exchange coverage. One hundred and fourteen were genotyped (60 1a, 46 3a): a cluster of 14 had homology of >98.5% including 10 incident infections. Public health surveillance of HCV among IDUs could be enhanced through the collection of DBS samples with appropriate recruitment approaches. DBS allow differentiation between individuals with cleared infections, ongoing infection and those recently infected. They also enable virus characterization at genotype and nucleotide level. This would allow surveillance to inform development of harm reduction interventions, and the international evidence base for these.
Journal of Viral Hepatitis 04/2010; 18(4):262-70. · 4.09 Impact Factor
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ABSTRACT: Urbanization, that is the movement of population from rural to urban locations, is a process that has been occurring for hundreds of years, but is increasingly prevalent in today's world. In 2008 most of the global population was resident in urban areas. It has been predicted that in the coming years, an increasing number of people will be living in cities; especially in the developing countries within in Asia and Latin America. This study considers the case of India, the second most populated country in the world, with a present total population exceeding 1 billion. It focuses on the state of Maharashtra (including the mega-city of Mumbai and its surrounds - the largest in India with a population of approximately 18.1 million). The Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) is a spaceborne system that detects visible light and thermal emissions of the earth at night. The data is collected nightly, on a global basis. The aim of this paper is to correlate the values obtained from the radiance calibrated DMSP/OLS night-time images of 2001 with population data. The spatial resolution of DMSP/OLS images is approximately 1 Km. This paper asks the question over what range of spatial scales does DMSP/OLS have utility in retrieving metrics of urbanization.
Urban Remote Sensing Event, 2009 Joint; 06/2009
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ABSTRACT: We sought to corroborate geographical differences in hepatitis C virus (HCV) prevalence and assess whether these can be explained by differences in injecting risk behaviour. A community recruited interview survey of 1058 injecting drug users (IDU) - including a blood spot specimen for antibody testing - was undertaken in seven cities in England. HCV prevalence varied from 27% to 74% across sites (chi(2)(6) = 115.3, P < 0.001). There was a significant variation in crack-injection, prison history, injecting frequency, homelessness, groin injecting, syringe reuse and sharing between the sites. Adjustment for clustering by site and other covariates attenuated the odds ratios (OR) for most variables: e.g. crack injection changed from an unadjusted OR of >2 to an adjusted OR of 1.4 (95% CI 0.9-2.0). Remaining significant covariates included: homelessness (OR 2.2; 1.4-3.6); ever imprisonment (OR 1.7; 1.2-2.5); syringe sharing >18 months ago (OR 2.0; 1.3-3.0); injecting duration and age. Introducing site as a second level variable did not reach significance (P = 0.10). HCV prevalence among IDU reporting 'never sharing' was 48%. Geographical variation in HCV prevalence remains poorly explained, but should be the key focus of our surveillance effort. Measures of sharing and their interpretation require greater scrutiny.
Journal of Viral Hepatitis 09/2007; 14(9):645-52. · 4.09 Impact Factor
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A Judd,
S Hutchinson,
S Wadd,
M Hickman,
A Taylor, S Jones,
J V Parry,
S Cameron,
T Rhodes,
S Ahmed,
S Bird,
R Fox,
A Renton,
G V Stimson,
D Goldberg
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ABSTRACT: Our aim was to compare the prevalence of antibody to hepatitis C virus (anti-HCV) among recently initiated injecting drug users (IDUs) in London and Glasgow, and to identify risk factors which could explain differences in prevalence between the cities. Complementary studies of community recruited IDUs who had initiated injection drug use since 1996 were conducted during 2001-2002. Data on HCV risk behaviours were gathered using structured questionnaires with identical core questions and respondents were asked to provide an oral fluid specimen which was tested anonymously for anti-HCV but was linked to the questionnaire. Sensitivities of the anti-HCV assays for oral fluid were 92-96%. Prevalence of anti-HCV was 35% (122/354) in London and 57% (207/366) in Glasgow (P < 0.001). Multifactorially, factors significantly associated with raised odds of anti-HCV positivity were increasing length of injecting career, daily injection, polydrug use, having had a needlestick injury, and having served a prison sentence. In addition lower odds of anti-HCV positivity were associated with non-injection use of crack cocaine and recruitment from drug agencies. After adjustment for these factors, the increased odds of anti-HCV associated with being a Glasgow IDU were diminished but remained significant. HCV continues to be transmitted among the IDU population of both cities at high rates despite the availability of syringe exchange and methadone maintenance. Effectiveness of harm reduction interventions may be compromised by inadequate coverage and failure to reduce sufficiently the frequency of sharing different types of injecting equipment, as well as the high background prevalence of HCV, and its high infectivity. Comprehensive action is urgently required to reduce the incidence of HCV among injectors.
Journal of Viral Hepatitis 12/2005; 12(6):655-62. · 4.09 Impact Factor
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ABSTRACT: This study sought to establish the prevalence of hepatitis C antibodies (anti-HCV) and hepatitis B antibodies (anti-HBc) among injection drug users in England and Wales.
A voluntary cross-sectional survey collected oral fluid samples and behavioral information; 2203 injectors were recruited through drug agencies, and 758 were recruited in the community.
Prevalence was 30% for anti-HCV, 21% for anti-HBc, and 0.9% for HIV antibodies. Anti-HCV prevalence rates were significantly greater among those with longer injecting careers, those in older age groups, those residing in London, those recruited in drug agencies, those positive for anti-HBc, and those with a previous voluntary HIV test.
Anti-HCV prevalence rates among injectors in England and Wales, where comprehensive harm reduction programs exist, are lower than rates in other industrialized countries.
American Journal of Public Health 02/2001; 91(1):38-42. · 3.93 Impact Factor
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AIDS 11/2000; 14(15):2413-5. · 6.24 Impact Factor
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ABSTRACT: To measure risk behaviour among injecting drug users (IDUs) using the Injecting Risk Questionnaire (IRQ).
Data were analysed from the first multi-site survey of injecting risk behaviour among IDUs not in contact with drug services in England. A total of 1214 IDUs were recruited from community settings in seven sites.
Fifty-two per cent reported sharing injecting equipment in the previous 4 weeks in response to a single question on sharing. This rose to 78% when asked more detailed and multiple questions on injecting risk practices. Levels of injecting risk behaviour did not differ substantially by gender, age, length of injecting career, main drug of injection, previous treatment contact or geographical location. However, sharing partners were restricted to a median of two others.
These data raise questions concerning the extent to which levels of injecting risk behaviour have increased over recent years, or the extent to which previous monitoring systems underestimated levels of risk. None the less, the data confirm that the promotion of safer injecting continues to be an important public health issue with regard to reducing blood-borne infections.
Addiction 10/2000; 95(9):1351-61. · 4.31 Impact Factor
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ABSTRACT: To develop a short injecting risk questionnaire (IRQ) to measure sharing of injecting equipment.
Matrix design with quota assignment, designed to compare the questionnaire when used by interview and self-completion, in agency and community settings, by agency staff and fieldworkers, with different injectors (age < 26 vs. 26+; male vs. female, opiate vs stimulant injectors), and in different geographical areas.
Drug treatment and helping agencies, and community settings, in England.
Drug users who had injected in the last 4 weeks.
Questions measured different aspects of equipment sharing. Questionnaire performance assessed by question acceptability, test-retest (parallel forms) reliability, inter-rater reliability, inter-instrument reliability, internal reliability, construct validity and internal collateral validity. Statistical tests included product moment correlation, principal components analysis, and Cronbach's alpha.
The questionnaire was highly acceptable. Test-retest correlations were all high and significant, questions performed well in all conditions, with no differences by site (agency vs. out-of-contact), order (interview or self-completion first), administration (staff vs. fieldworker), elapsed time or subject characteristics. The questionnaire had high internal reliability (Cronbach's alpha > +0.86), and items measured a similar domain with all questions loading highly (> 0.32) on a single factor which accounted for > 42% of the variance. The complete IRQ elicited higher reports of equipment sharing (77%) than a single question (56%).
IRQ performs well in a variety of settings, when administered in different ways to different kinds of IDUs. A single question on 'sharing' elicits fewer positive responses than the use of multiple questions about different sharing practices.
Addiction 04/1998; 93(3):337-47. · 4.31 Impact Factor
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ABSTRACT: This paper considers the prevention of HIV in rural and urban areas among both opiate and non-opiate drug injectors. A 2-year study evaluated specialist and community based syringe-exchange provision in Wales. Numbers of clients and patterns of attendance at eight syringe-exchange schemes were monitored together with comparative cross-sectional studies of attenders (n = 152) and non-attenders (n = 176) from the population of drug injectors in 1990 and 1991. A total of 1171 clients made 7553 visits in the 2-year period, 110,000 syringes were issued and 80% of needles and syringes were returned. There were few demographic differences between attenders and non-attenders, but large and significant differences in HIV risk behaviour; only 9% of attenders had recently shared syringes in 1990 (10% in 1991) compared to 41% of non-attenders (39% in 1991). The catchment areas of specialised services were limited (5 miles or less) and insufficient in rural areas. Alternative community approaches to syringe distribution and exchange are examined.
Addiction 09/1993; 88(8):1063-70. · 4.31 Impact Factor
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ABSTRACT: The number and size of urban settlements are increasing in all the continents of the world at a rapid pace. Urban sprawl is associated not only with changes in landcover and area, but also ecological, climate and social transformations. Mapping the growth and spread of urban areas is important. Remote sensing has long been used to map human settlements. Today the availability of a large number of satellites and sensors, determining the appropriate image to map urban area is a research area itself. This study compares two satellite images: Landsat Enhanced Thematic Mapper data and Defence Meteorological Satellite Program, Operational Linescan System image to map the urban footprint of the city of Hyderabad, India. Landsat ETM data is captured during the daytime and gives spectral reflectance values while the DMSP-OLS data captures artificial lights from human settlements at night and produces brightness information. The results show an accuracy of more than 90% in the classification and delineation of urban, suburban and rural landcover types. This study shows that in addition to spectral reflectance captured by satellites from different features on the earth surface during the daytime, differences in the degree of brightness of the lights emitted from urban areas at night is also an effective indicator in delineating landcover types.
JURSE 2011;
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ABSTRACT: The study investigates and compares various methods that aim to diagnose Rossby wave trains with the help of Hovmöller diagrams. Three groups of methods are distinguished: The first group contains trough-and-ridge Hovmöller diagrams of the meridional wind; they provide full phase information, but differ in the method for latitudinal averaging or weighting. The second group aims to identify Rossby wave trains as a whole, discounting individual troughs and ridges. The third group contains diagnostics which focus on physical mechanisms during the different phases of a Rossby wave train life cycle; they include the analysis of eddy kinetic energy and methods for quantifying Rossby wave breaking.
The different methods are analysed and systematically compared with each other in the framework of a two-month period in fall 2008. Each method more or less serves its designed purpose, but they all have their own strengths and weaknesses. Notable differences between the individual methods render an objective identification of a Rossby wave train somewhat elusive. Nevertheless, the combination of several techniques provides a rather comprehensive picture of the Rossby wave train life cycle, being broadly consistent with the expected behaviour from previous theoretical analysis.
Tellus A - Dynamic Meteorology and Oceanography. 63(2011):991-1006.
