The 2001 National Household Travel Survey: a look into the travel patterns of older Americans

INTRODUCTION: The main objective of this paper is to highlight travel patterns of older adults living in the United States as depicted in the 2001 National Household Travel Survey (NHTS). The NHTS is a national data collection program sponsored by the Bureau of Transportation Statistics and the Federal Highway Administration. It is the first national comprehensive household survey of both daily and long-distance travel, allowing for analysis of the full continuum of personal travel by Americans. To better understand the transportation needs of older Americans, it is useful to examine how travel patterns differ across age groups. The intent is to present basic travel characteristics of older adults (age 65+) and allow for comparisons with younger adults (ages 19-64). Travel-related characteristics of older adults in the United States: Results of the 2001 survey showed that older Americans travel extensively and rely on personal vehicles as heavily as their younger counterparts. Older Americans conduct 89% of their travel in personal vehicles. CHARACTERISTICS OF DAILY TRIPS TAKEN BY OLDER ADULTS: Older adults tend to be less mobile in that they take fewer trips, travel shorter distances, and have shorter travel times. This pattern is even more pronounced among older women. They are also more likely to suffer from self-reported medical conditions that further limit their travel. Characteristics of long-distance travel by older adults: Older men and women take long-distance trips at about the same rates and show a strong preference for using personal vehicles. And, while men and women take an equal percentage of their trips by air, older women show a strong preference for bus travel. CONCLUSIONS: Although older Americans travel extensively, they are less mobile than their younger counterparts. This pattern is more pronounced among older women and among those with self-reported medical conditions that affect their ability to travel outside their home. Older women consistently take the least number of trips per day, have the lowest driving rates, travel the shortest distances, and are more likely to report medical conditions that limit their travel. For men and women who have to give up driving, alternative means of transportation becomes a necessity. Yet, use of alternative transportation is relatively low; excluding personal vehicle and walking, all other means of transportation account for about 2% of daily travel. Further, of those with medical conditions that affect their travel, only about 12% use special transportation services such as dial-a-ride.     

Fetoscopy and fetal blood sampling in the management of a twin pregnancy with 45,X/46,XX amniotic fluid cell mosaicism and a suspected fluid sampling error

A 37 year-old woman with a twin pregnancy underwent amniocentesis to exclude fetal chromosome abnormality. The results indicated that both fetuses were mosaics, with 45,X and 46,XX, cell lines. Since it was suspected from the ultrasound scan that the twins were dizygotic, the result was questioned. Fetoscopy and fetal blood sampling were performed and karyotyping the fetal lymphocytes confirmed that one twin was indeed a mosaic, 45,X/ 46,XX, but the other had a normal male chromosome complement. The pregnancy resulted in the birth of a phenotypically normal girl, in whom the 45,X/46,XX mosaicism was confirmed, and a normal boy.     

Costing the countryside

The debate on valuing the environment moved to the fore in Britain in the late 1980s, principally as the result of the interaction of two factors: growing party political competition on the environment; and difficulties the Conservative Government were experiencing in defining a distinct neo‐liberal agenda for the environment. Despite its technocratic overtones, valuing the environment has thus become part of a broader political debate. Moreover, there are a number of radical implications for decision making and the role of conservation organizations which flow from an adoption of valuation practices and we seek to identify these as well.     

Variable-density groundwater flow and solute transport in heterogeneous porous media: approaches, resolutions and future challenges

In certain hydrogeological situations, fluid density variations occur because of changes in the solute or colloidal concentration, temperature, and pressure of the groundwater. These include seawater intrusion, high-level radioactive waste disposal, groundwater contamination, and geothermal energy production. When the density of the invading fluid is greater than that of the ambient one, density-driven free convection can lead to transport of heat and solutes over larger spatial scales and significantly shorter time scales than compared with diffusion alone. Beginning with the work of Lord Rayleigh in 1916, thermal and solute instabilities in homogeneous media have been studied in detail for almost a century. Recently, these theoretical and experimental studies have been applied in the study of groundwater phenomena, where the assumptions of homogeneity and isotropy rarely, if ever, apply. The critical role that heterogeneity plays in the onset as well as the growth and/or decay of convective motion is discussed by way of a review of pertinent literature and numerical simulations performed using a variable-density flow and solute transport numerical code. Different styles of heterogeneity are considered and range from continuously "trending" heterogeneity (sinusoidal and stochastic permeability distributions) to discretely fractured geologic media. Results indicate that both the onset of instabilities and their subsequent growth and decay are intimately related to the structure and variance of the permeability field. While disordered heterogeneity tends to dissipate convection through dispersive mixing, an ordered heterogeneity (e.g., sets of vertical fractures) allows instabilities to propagate at modest combinations of fracture aperture and separation distances. Despite a clearer understanding of the processes that control the onset and propagation of instabilities, resultant plume patterns and their migration rates and pathways do not appear amenable to prediction at present. The classical Rayleigh number used to predict the occurrence of instabilities fails, in most cases, when heterogeneous conditions prevail. The incorporation of key characteristics of the heterogeneous permeability field into relevant stability criteria and numerical models remains a challenge for future research.     

Bound residues: environmental solution or future problem?

The paper examines the issue of bound residues from the viewpoint of the risk assessment procedures employed for environmental protection. It considers, on one hand, the evidence that such residues are so tightly bound to soil organic matter as to be essentially unavailable; and on the other, the perspective that we should not be loading up the environment with compounds whose future behaviour and release we cannot predict. Existing knowledge of the mechanisms by which residues bind to soil organic matter suggests that release will be closely dependent on soil organic matter breakdown. Simple models of organic matter turnover suggest that the release following single applications of individual compounds will be very slow; but the significance of releases following repeated application over many years of a number of compounds needs to be investigated further. Applying environmental risk assessment techniques is complicated by the difficulty in identifying parent molecules and potential metabolites in the bound residue fraction. The paper concludes that for single additions of individual compounds, bound residues probably do represent an environmental solution. But the long-term significance of bound residues formed from multiple additions of a number of compounds is less clear. The paper recommends that future work should emphasise the biological significance of such residues and their release.     

Debromination of 1,4-Dibromobenzene and 4,4′-Dibromobiphenyl: A Model for Cleansing of PCBs

The aim of this study is to develop a catalytic method which has advantages over current method to detoxify and degrade environmentally harmful polychlorinated biphenyls (PCBs). A variety of catalysts have been employed in a preliminary study on 1,4-dibromobenzene and 4,4-dibromobiphenyl which may be considered to represent simple analogues of PCBs. The most satisfactory catalysts are those involving [Pd(dppf)] [dppf = 1,1-bis(diphenylphosphino)ferrocene], generated in situ from PdCl2(dppf) or Pd(dppf)2. In the presence of the reducing reagent, namely NaBH4, debromination has been achieved at relative mild conditions with high product yields (> 70%). Thus, our results indicate the possibility of dechlorination of PCBs with such catalysts.     

In search of a recyclable sulphur dioxide sponge—a new look at an old system

The sulphur dioxide content and thermal stability of the quinol-SO₂ clathrate have been studied by thermogravimetric analysis (TG), its derivative (DTG) and differential scanning calorimetry (DSC). These analyses demonstrated the thermal recoverability of the quinol from the clathrate and hence its potential use as a sponge for SO₂ present in the environment as a pollutant. Similarly, Bu₄N⁺I^- was found to occlude NO₂ and SO₂ at 50°C in solution.     

Field Deaths in Plant Agriculture

We know that animals are harmed in plant production. Unfortunately, though, we know very little about the scale of the problem. This matters for two reasons. First, we can’t decide how many resources to devote to the problem without a better sense of its scope. Second, this information shortage throws a wrench in arguments for veganism, since it’s always possible that a diet that contains animal products is complicit in fewer deaths than a diet that avoids them. In this paper, then, we have two aims: first, we want to collect and analyze all the available information about animal death associated with plant agriculture; second, we try to show just how difficult it’s to come up with a plausible estimate of how many animals are killed by plant agriculture, and not just because of a lack of empirical information. Additionally, we show that there are significant philosophical questions associated with interpreting the available data—questions such that different answers generate dramatically different estimates of the scope of the problem. Finally, we document current trends in plant agriculture that cause little or no collateral harm to animals, trends which suggest that field animal deaths are a historically contingent problem that in future may be reduced or eliminated altogether.