On the Radii of Close-in Giant Planets

The recent discovery that the close-in extrasolar giant planet HD 209458b transits its star has provided a first-of-its-kind measurement of the planet's radius and mass. In addition, there is a provocative detection of the light reflected off of the giant planet tau Bootis b. Including the effects of stellar irradiation, we estimate the general behavior of radius/age trajectories for such planets and interpret the large measured radii of HD 209458b and tau Boo b in that context. We find that HD 209458b must be a hydrogen-rich gas giant. Furthermore, the large radius of a close-in gas giant is not due to the thermal expansion of its atmosphere but to the high residual entropy that remains throughout its bulk by dint of its early proximity to a luminous primary. The large stellar flux does not inflate the planet but retards its otherwise inexorable contraction from a more extended configuration at birth. This implies either that such a planet was formed near its current orbital distance or that it migrated in from larger distances (>/=0.5 AU), no later than a few times 107 yr of birth.     

Geomasking sensitive health data and privacy protection: an evaluation using an E911 database

Geomasking is used to provide privacy protection for individual address information while maintaining spatial resolution for mapping purposes. Donut geomasking and other random perturbation geomasking algorithms rely on the assumption of a homogeneously distributed population to calculate displacement distances, leading to possible under-protection of individuals when this condition is not met. Using household data from 2007, we evaluated the performance of donut geomasking in Orange County, North Carolina. We calculated the estimated k-anonymity for every household based on the assumption of uniform household distribution. We then determined the actual k-anonymity by revealing household locations contained in the county E911 database. Census block groups in mixed-use areas with high population distribution heterogeneity were the most likely to have privacy protection below selected criteria. For heterogeneous populations, we suggest tripling the minimum displacement area in the donut to protect privacy with a less than 1% error rate.     

Conceptual models for carbonate aquifers. 1969

The very diverse types of ground‐water behavior in carbonate terrains can be classified by relating the flow type to a particular hydrogeologic environment each exhibiting a characteristic cave morphology. The ground water may move by diffuse flow, by retarded flow, or by free flow. Diffuse flow occurs in less soluble rocks such as extremely shaley limestones or crystalline dolomites. Integrated conduits are rare. Caves tend to be small, irregular, and often little more than solutionally widened joints. Retarded flows occur in artesian environments and in situations where unfavorable stratigraphy forces ground water to be confined to relatively thin beds. Network cave patterns are characteristic since hydrodynamic forces are damped by the external controls. Solution occurs along many available joints. Free flowing aquifers are those in which solution has developed a subsurface drainage system logically regarded as an underground extension of surface streams. These streams may have fully developed surface tributaries as well as recharge from sinkholes and general infiltration. Characteristic cave patterns are those of integrated conduit systems which are often truncated into linear, angulate, and branchwork caves. Free Flow aquifers may be further subdivided into Open aquifers lying beneath karst plains and Capped aquifers in which significant parts of the drainage net lie beneath an insoluble cap rock. Other geologic factors such as structure, detailed lithology, relief, and locations of major streams, control the details of cave morphology and orientation of the drainage network.     

Permeameter data verify new turbulence process for MODFLOW

A sample of Key Largo Limestone from southern Florida exhibited turbulent flow behavior along three orthogonal axes as reported in recently published permeameter experiments. The limestone sample was a cube measuring 0.2 m on edge. The published nonlinear relation between hydraulic gradient and discharge was simulated using the turbulent flow approximation applied in the Conduit Flow Process (CFP) for MODFLOW-2005 mode 2, CFPM2. The good agreement between the experimental data and the simulated results verifies the utility of the approach used to simulate the effects of turbulent flow on head distributions and flux in the CFPM2 module of MODFLOW-2005.     

寒冻条件下花岗岩小块体的风化模拟实验及其分析

５０ｍｍ×５０ｍｍ×５０ｍｍ的一些小花岗岩块体被单轴挤压使之表面出现裂隙，然后分别预处理成干燥、水饱和与硫酸钠溶液饱和的３组样品，使之经历不同温度变幅下的冻融过程。在冻融过程中，分别记录了样品表面、表面下１０ｍｍ及２５ｍｍ处的温度变化，同时在实验前后，对所有样品都进行了超声波传输速率测定和重量测定。实验结果表明，这些小的花岗岩块体表面与内部的温度变化没有明显差异，其温度变化随外界温度而变化，但在外界温度变幅整体低于０℃时，岩石温度逐渐趋于稳定。样品在实验前后的重量变化很小，但是仍能反映最大的变化发生在水饱和的一组样品中。所有样品在实验后的超声波传输速率都明显下降，特别是在垂直于微裂隙的方向，超声波传输速率下降大于平均下降幅度，表明冻融过程中岩石内部的孔隙可能增大而微裂隙具有明显的加剧作用。     

International refugees: a geographical perspective

In the modern era, the world's refugee problem has changed magnitude and location; it has expanded from a local to a continental, and now global, scale issue. About 90% of the world's 10 million refugees are from developing countries, and over 90% of these will stay there. Refugee generating and receiving countries are concentrated in 5 world regions: Central America, Southwest Asia, Southeast Asia, and Sub-Saharan Africa. Each concentration is unique and is associated with a particular set of regional conflicts. International efforts address short-term relief needs, whereas political instability and repression that generate refugees continue unabated. Refugees along sensitive border regions affect bilateral relations, large groups of refugees can pose political and security problems for the host country, and disputes over refugee policies and their implementation can complicate diplomatic ties. Some highlights of the data follow. 1) The 3 million cross-border refugees and 5.5 million internally displaced persons make the many governments in Sub-Saharan Africa increasingly dependent on Western assistance to solve their problems. Refugees are fleeing armed conflict, tribal violence, and drought, and often generate additional regional turmoil. 2) 3-4 million Afghans have fled their country since the 1978 Marxist coup; about 2.5 million have entered Pakistan. Most choose to remain in camps near the Afghanistan border where they are targets of cross-border attacks. 3) 1.2 million Salvadorans, Guatemalans, and Nicaraguans live outside their native countries. Official refugee and unofficial migrant populations are active in various rebel insurgencies, contribute to strained bilateral relations and tensions in border areas, and are the subject of heated political debate in host countries. 4) 90% of the 1.7 million Indochinese who fled from 1975-May 1986 have been resettled; 168,000 refugees remain in 1st-asylum camps, not including 240,000 Khmer without refugee status, in temporary camps in Thailand. Thailand's large refugee population is involved in factional strife, smuggling, and guerrilla activities. The Thai are particularly concerned about Hmong refugees, who are accused of opium cultivation and destruction of Thai forests through slash-and-burn cultivation. 5) Nearly 62% of the thousands of present Vietnamese refugees to Hong Kong have been in camps 3 years, and 17% 6 years. Many have turned to crime, alcohol, drugs, or prostitution.     

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