A Tilted Subgrid for Two Dimensional FDTD

Although the Finite Difference Time Domain (FDTD) method is well established for addressing a wide variety problems including the characterization of antenna arrays, a long standing challenge is to reduce discretization errors whileavoiding the use of impractically large numbers of cells, particularly when the structure is large and contains regions of fine detail. One solution is to use subgrids. In most published work, Cartesian subgrids are proposed which are in the same orientation as the main grid. However there is considerable benefit to allowing for the subgrid to be tilted. In this work, a method for introducing a tilted subgrid into the 2D FDTD mesh is presented and its effectiveness, accuracy and stability is demonstrated using examples. The method is readily extendable to a full 3D implementation

The analysis of reactively loaded microstrip antennas by finite difference time domain modelling

In recent years, much interest has been shown in the use of printed circuit antennas in mobile satellite and communications terminals at microwave frequencies. Although such antennas have many advantages in weight and profile size over more conventional reflector/horn configurations, they do, however, suffer from an inherently narrow bandwidth. A way of optimizing the bandwidth of such antennas by an electronic tuning technique using a loaded probe mounted within the antenna structure is examined, and the resulting far-field radiation patterns are shown. Simulation results from a 2D finite difference time domain (FDTD) model for a rectangular microstrip antenna loaded with shorting pins are given and compared to results obtained with an actual antenna. It is hoped that this work will result in a design package for the analysis of microstrip patch antenna elements

How children access antiretroviral treatment at Kgapane District Hospital, Limpopo, South Africa

Background: At Kgapane Hospital, Limpopo Province, only 20% of eligible children initiated antiretroviral treatment (ART) in 2007. The aim of this study was to improve the ART programme by assessing how children were accessing ART, and to explore the factors that facilitate or obstruct this access.Method: Mixed methods were used in a descriptive study of human immunodeficiency virus (HIV)-infected children admitted to the hospital over a seven-month period and their caregivers. Children’s subsequent attendance for ART was tracked and caregivers were interviewed about factors influencing access and attendance.Results: Of 132 children initially admitted, 14 (10.6%) subsequently died and 13 (9.8%) relocated. Sixty of the remaining 105 (57.1%) returned within one month to the antiretroviral clinic, three (2.9%) attended later and 42 (40.0%) did not return at all. Quantitative data associated with poor attendance were younger age, higher CD4 count, maternal caregiver, no income and participation in the prevention of mother-to-child transmission program. Qualitative factors included a lack of money for transport, poor social support, and mothers who struggled to accept their diagnosis, had poor understanding of HIV and strong traditional beliefs. Primary care providers delayed HIV testing and referral, displayed poor attitudes, and were insufficient in number. Quantitative factors significantly associated with good attendance were prior knowledge of the child/mother’s HIV status, mother’s ART treatment and referral to the dietician.Conclusion: There are serious deficiencies in the prevention, diagnosis and treatment of HIV in children. Factors were identified to improve health services and these highlight the need for broader strategies aimed at addressing poverty, stigma and education

Reply to Justin D’Arms

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43371/1/11098_2005_Article_2319.pd

Cross-sectional study of the provision of interventional oncology services in the UK

Objective: To map out the current provision of interventional oncology (IO) services in the UK. Design: Cross-sectional multicentre study. Setting: All National Health Service (NHS) trusts in England and Scottish, Welsh and Northern Ireland health boards. Participants: Interventional radiology (IR) departments in all NHS trusts/health boards in the UK. Results: A total of 179 NHS trusts/health boards were contacted. We received a 100% response rate. Only 19 (11%) institutions had an IO lead. 144 trusts (80%) provided IO services or had a formal pathway of referral in place for patients to a recipient trust. 21 trusts (12%) had plans to provide an IO service or formal referral pathway in the next 12 months only. 14 trusts (8%) did not have a pathway of referral and no plans to implement one. 70 trusts (39%) offered supportive and disease-modifying procedures. One trust had a formal referral pathway for supportive procedures. 73 trusts (41%) provided only supportive procedures (diagnostic or therapeutic). Of these, 43 (59%) had a referral pathway for disease-modifying IO procedures, either from a regional cancer network or through IR networks and 30 trusts (41%) did not have a referral pathway for disease-modifying procedures. Conclusion: The provision of IO services in the UK is promising; however, collaborative networks are necessary to ensure disease-modifying IO procedures are made accessible to all patients and to facilitate larger registry data for research with commissioning of new services

Rotated Subgrids in the FDTD Method

Although the Finite Difference Time Domain (FDTD) method is well established for addressing a wide variety problems, a long standing challenge is to reduce discretization errors while avoiding the use of impractically large numbers of cells, particularly when the structure is large and contains regions of fine detail. One solution is to use sub-grids but in most published work, Cartesian sub-grids are proposed which are constrained to have the same orientation as the main grid. However there is considerable benefit to allowing for the sub-grid to be rotated. In this work, a method for introducing a rotated sub-grid into the FDTD mesh is presented and its effectiveness, accuracy and stability is demonstrated by means of some simple examples