Charge-Induced Force Noise on Free-Falling Test Masses: Results from LISA Pathfinder.

We report on electrostatic measurements made on board the European Space Agency mission LISA Pathfinder. Detailed measurements of the charge-induced electrostatic forces exerted on free-falling test masses (TMs) inside the capacitive gravitational reference sensor are the first made in a relevant environment for a space-based gravitational wave detector. Employing a combination of charge control and electric-field compensation, we show that the level of charge-induced acceleration noise on a single TM can be maintained at a level close to 1.0 fm s^{-2} Hz^{-1/2} across the 0.1-100 mHz frequency band that is crucial to an observatory such as the Laser Interferometer Space Antenna (LISA). Using dedicated measurements that detect these effects in the differential acceleration between the two test masses, we resolve the stochastic nature of the TM charge buildup due to interplanetary cosmic rays and the TM charge-to-force coupling through stray electric fields in the sensor. All our measurements are in good agreement with predictions based on a relatively simple electrostatic model of the LISA Pathfinder instrument.

Sub-Femto-g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results.

We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2±0.1 fm s^{-2}/sqrt[Hz], or (0.54±0.01)×10^{-15} g/sqrt[Hz], with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8±0.3) fm/sqrt[Hz], about 2 orders of magnitude better than requirements. At f≤0.5 mHz we observe a low-frequency tail that stays below 12 fm s^{-2}/sqrt[Hz] down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.

Parity and hypertension.

Among the many physiological factors which have been hypothesized as associated with elevated blood pressure levels and increased incidence of hypertension, the possible effect of pregnancy in the production of these conditions has proven to be among the more elusive to quantitate and evaluate. At the same time, the possible association is among the more interesting from an epidemiological standpoint, not only because of the importance of the primal question of whether or not pregnancy is a factor in the etiology of hypertension, but also because of the component parts represented by those pregnancies complicated by preeclampsia. Age is considered by many observers to be an important factor in the production of residual hypertension, and the statistical association of age with increased blood pressure levels is probably the most pronounced and easily demonstrated phenomenon observable in any study population. A moderate decline in average diastolic blood pressure among the general population after age 55 is an exception to this, and is less frequently evaluated. Body measurements, race, and several other variables may be cited as also being correlated with blood pressure levels, however, their effect is much less significant than that observable for age.

Sample design and estimation procedures for a national health examination survey of children.

The Health Examination Survey is one of the major survey programs employed by the National Center for Health Statistics to obtain information about the health status of the U.S. population. It is a part of the National Health Survey, authorized in 1956 by the 84th Congress as a continuing Public Health Service activity. The National Health Survey employs three different survey programs to accomplish its objectives. One of these is the Health Interview Survey in which persons are asked to give in-formation related to their health or to the health of other household members. The second program, Health Resources, obtains health data and health resource and utilization information through surveys of hospitals, nursing homes, and other resident institutions and through the entire range of personnel in the health occupations. The third major program is the Health Examination Survey (HES), The Health Examination Survey collects data from samples of the civilian, noninstitutional population of the United States and, by means of medical and dental examinations and various tests and measurements, undertakes to characterize the population under study. This is the most accurate way to obtain diagnostic data on the prevalence of certain medically defined illnesses. It is the only way to obtain information on unrecognized and undiagnosed conditions-in some cases, even nonsymptomatic conditions. It is also the only way presently available to obtain distributions of the population by a variety of physical, physiological, and psychological measurements. Although the sample is designed primarily to estimate the prevalence of specified health and health-related conditions in the population, the design also makes possible the study of relationships of the examination findings to one another and to certain demographic and socioeconomic factors.

Parent ratings of behavioral patterns of children, United States.

This report contains information from parents' ratings of the behavioral patterns of their children 6-11 years of age in the noninstitutional population of the United States as obtained in the Health Examination Survey of 1963-65. Only age and sex differentials are considered in this first of a series of reports on various aspects of the behavior of children as rated by parents and teachers. These findings provide more definite baseline data on the behavior of American children of this age than have been available previously. The Health Examination Survey is one of the major programs within the National Center for Health Statistics which carries out the National Health Survey as authorized in 1956 by the 84th Congress.