A linked risk group model for investigating the spread of HIV

This paper describes a model that simulates the spread of HIV and progression to AIDS. The model is based on classical models of disease transmission. It consists of six linked risk groups and tracks the numbers of infectives, AIDS cases, AIDS related deaths, and other deaths of infected persons in each risk group. Parametric functions are used to represent risk-group-specific and time-dependent average contact rates. Contacts are needle sharing, sexual contacts, or blood product transfers.

An important feature of the model is that the contact rate parameters are estimated by minimizing differences between AIDS incidence and reported AIDS cases adjusted for undercounting biases. This feature results in an HIV epidemic curve that is analogous to one estimated by backcalculation models but whose dynamics are determined by simulating disease transmission. The model exhibits characteristics of both the disease transmission and the backcalculation approaches, i.e., the model:

• reconstructs the historical behavior patterns of the different risk groups,

• includes separate effects of treatment and changes in average contact rates,

• accounts for other mortality risks for persons infected with HIV,

• calculates short-term projections of AIDS incidence, HIV incidence, and HIV prevalence,

• calculates cumulative HIV infections (the quantity calculated by backcalculation approaches) and HIV prevalence (the quantity measured by seroprevalence and sentinel surveys). This latter feature permits the validation of the estimates generated by two distinct approaches.

We demonstrate the use of the model with an application to U.S. AIDS data through 1991.     

Gain-assisted optical switching in plasmonic nanocavities

A plasmonic cavity filled with active material is proposed to explain optical switching. Optical properties, including transmission, response time, and field distribution of on/off state, are numerically investigated. We demonstrate that such a gain-assisted plasmonic structure can achieve optical switching in the nan- odomain and shorten the switching time to the subpicosecond level. Our results indicate the potential application of the proposed structure in optical communication and photonic integrated circuits.     

BK7玻璃保护层掺钕磷酸盐玻璃波导特性

实验研究了基于KNO3稀释AgNO3混合熔盐离子交换法制备的镀有BK7玻璃保护层的N31型掺钕磷酸玻璃平面波导。采用棱镜耦合技术测试了其波导的有效折射率,应用IWBK方法拟合了其折射率分布。实验结果表明:在一定的扩散时间(5～7h)和交换温度(360～380℃)范围内,KNO3与AgNO3混合熔盐比对波导制备的影响起主导作用,引起的表面折射率的变化可达到0.025;BK7玻璃保护层对热离子交换掺钕磷酸盐玻璃表面起到了很好的保护作用,获得了良好的导模传输特性,其光传输损耗约为0.9dB/cm。     

Calculation of charring rate and char depth of spruce and pine wood from mass loss

Journal of Thermal Analysis and Calorimetry - A charring rate is a key parameter for the calculation of fire resistance of timber structures and for fire investigation. Charring rates are...