Modular Forms and the Cosmological Constant

The vacuum amplitude of the heterotic string in a flat background vanishes for the first twenty orders of string perturbation theory. The proof relies on the algebraic geometry of modular forms

Method and apparatus for determining time, direction, and composition of impacting space particles

A space particle collector for recording the time specific particles are captured, and its direction at the time of capture, utilizes an array of targets, each comprised of an MOS capacitor on a chip charged from an external source and discharged upon impact by a particle through a tab on the chip that serves as a fuse. Any impacting particle creates a crater, but only the first will cause a discharge of the capacitor. A substantial part of the metal film around the first crater is burned off by the discharge current. The time of the impulse which burns the tab, and the identification of the target, is recorded together with data from flight instruments. The metal film is partitioned into pie sections to provide a plurality of targets on each of an array of silicon wafers, thus increasing the total number of identified particles that can be collected. It is thus certain which particles were captured at what specific times

Long Duration Exposure Facility (LDEF) attitude measurements of the Interplanetary Dust Experiment

Analysis of the data from the Long Duration Exposure Facility (LDEF) Interplanetary Dust Experiment (IDE) sun sensors has allowed a confirmation of the attitude of LDEF during its first year in orbit. Eight observations of the yaw angle at specific times were made and are tabulated in this paper. These values range from 4.3 to 12.4 deg with maximum uncertainty of plus or minus 2.0 deg and an average of 7.9 deg. No specific measurements of pitch or roll were made but the data indicates that LDEF had an average pitch down attitude of less than 0.7 deg

Influence of local fullerene orientation on the electronic properties of A3C60 compounds

We have investigated sodium containing fullerene superconductors Na2AC60, A = Cs, Rb, and K, by Na-23 nuclear magnetic resonance (NMR) spectroscopy at 7.5 T in the temperature range of 10 to 400 K. Despite the structural differences from the Rb3C60 class of fullerene superconductors, in these compounds the NMR line of the tetrahedrally coordinated alkali nuclei also splits into two lines (T and T') at low temperature. In Na2CsC60 the splitting occurs at 170 K; in the quenched cubic phase of Na2RbC60 and Na2KC60 we observe split lines at 80 K. Detailed investigations of the spectrum, spin-spin and spin-lattice relaxation as well as spin-echo double resonance (SEDOR) in Na2CsC60 we show that these two different tetrahedral sites are mixed on a microscopic scale. The T and T' sites differ in the orientation of first-neighbor C60 molecules. We present evidence that the orientations of neighboring molecules are uncorrelated. Thermally activated molecular reorientations cause an exchange between the T and T' sites and motional narrowing at high temperature. We infer the same activation energy, 3300 K, in the temperature range 125 to 300 K. The spin lattice relaxation rate is the same for T and T' down to 125 K but different below. Both the spin-lattice relaxation rate and Knight shift are strongly temperature dependent in the whole range investigated. We interpret this temperature variation by the effect of phonon excitations involving the rigid librational motion of the C60 molecules. By extending the understanding of the structure and molecular dynamics of C60 superconductors, these results may help in clarifying the effects of the structure on the superconducting properties.Comment: 13 pages, 10 figures, submitted to PR

Health, Nutrition and Healthcare Availability (Survey 2, Report 2)

With support and collaboration from the W.K. Kellogg Foundation through the America Healing initiative, researchers at the University of Michigan are leading the National Voices Project (NVP) from 2011-2015. The central goals of the NVP are to examine the sources of racial/ethnic inequity and other disparities for children in the United States today, identify interventions that address disparities effectively, and inform the public dialogue about racial healing and racial equality. The NVP offers a fresh perspective on community-level opportunities for children throughout the country, in the domains of health and nutrition, education, and economic security -- through the eyes of adults whose work and volunteer efforts affect such opportunities. In other words, the NVP reflects the perceptions of individuals throughout the United States who are in a position to improve children's opportunities in the future. The questionnaire for NVP Survey 2 was developed by the National Voices Project team at the University of Michigan, with input from WKKF collaborators. We examined how individuals who work or volunteer with children view opportunities for education, health and healthcare, and economic well-being related to children and adolescents. Many of the questions were identical to questions fielded for NVP Survey 1 in 2011, to facilitate comparisons of responses across these different samples and over time. New questions in NVP Survey 2 centered on respondents' perceptions of segregation and inequities in the communities they know best, and on respondents' awareness about efforts to bridge racial/ethnic inequities in those communities

Education and Learning Opportunities (Survey 2, Report 3)

With support and collaboration from the W.K. Kellogg Foundation through the America Healing initiative, researchers at the University of Michigan are leading the National Voices Project (NVP) from 2011-2016. The central goals of the NVP are to examine the sources of racial/ethnic inequity and other disparities for children in the United States today, identify interventions that address disparities effectively, and inform the public dialogue about racial healing and racial equality.The NVP offers a fresh perspective on community-level opportunities for children throughout the country, in the domains of health and nutrition, education, and economic security – through the eyes of adults whose work and volunteer efforts affect such opportunities. In other words, the NVP reflects the perceptions of individuals throughout the United States who are in a position to improve children?s opportunities in the future.NVP Survey 1 was conducted in November-December 2011. NVP Survey 2 was fielded in August-September 2012. NVP Survey 2 differed from NVP Survey 1 in two key respects: 1) NVP Survey 2 included an oversample in communities included in the "Place Matters" initiative led by the Joint Center for Political and Economic Studies, a fellow grantee of the W.K. Kellogg Foundation. The oversample included sufficient numbers of responses to permit the NVP team to analyze differences across 6 specific "Place Matters" counties, and 2) Questions were asked in greater depth about efforts at community levels about bridging efforts to address racial/ethnic inequities.

Opportunities and Barriers Related to Income (Survey 2, Report 4)

Led by researchers at the University of Michigan, the National Voices Project is an effort to bring the perspectives of thousands of people in communities across the United States to the national dialogue about opportunities and barriers for children related to race/ethnicity. The National Voices Project conducts major national surveys twice each yearamong adults who work and volunteer on behalf of children. These surveys focus on racial/ethnic disparities at the community level that affect children?s health, education, and economic security.NVP Survey 1 was conducted in November-December 2011. NVP Survey 2 was fielded in August-September 2012.The final eligible sample for NVP Survey 2 included 2,311 adults from 48 states and D.C. NVP Survey 2 differed from NVP Survey 1 in two key respects: 1) NVP Survey 2 included an oversample in communities included in the "Place Matters" initiative led by the Joint Center for Political and Economic Studies, a fellow grantee of the W.K. Kellogg Foundation. The oversample included sufficient numbers of responses to permit the NVP team to analyze differences across 6 specific "Place Matters" counties, and 2) Questions were asked in greater depth about efforts at community levels about bridging efforts to address racial/ethnic inequities.

Opportunities and Barriers Related to Income (NVP 2013, Report 4)

With support and collaboration from the W.K. Kellogg Foundation through the America Healing initiative, researchers at the University of Michigan are leading the National Voices Project (NVP) from 2011-2016. The central goals of the NVP are to examine the sources of racial/ethnic inequity and other disparities for children in the United States today and identify interventions that address disparities effectively.The NVP offers an unprecedented perspective on community-level opportunities for children throughout the country, in the domains of health and nutrition, education and learning, and economic security – through the eyes of adults whoseoccupations and volunteer work affect such opportunities. In other words, the NVP reflects the perceptions of individuals throughout the United States who are in a position to improve children's opportunities in the future. We generally use the word "children" throughout the report to describe young children from age 0-8 years, and "teens" for children ages 13-18 years old.Report #4 for NVP 2013 focuses chiefly on findings on children's and teens' health, education and learning, andeconomic opportunities related to income

Education and Learning Opportunities (NVP 2013, Report 3)

With support and collaboration from the W.K. Kellogg Foundation through the America Healing initiative,  researchers at the University of Michigan are leading the National Voices Project (NVP) from 2011-2016. The central goals of the NVP are to examine the sources of racial/ethnic inequity and other disparities for children in the United States today and identify interventions that address disparities effectively.The NVP offers an unprecedented perspective on community-level opportunities for children throughout the country, in the domains of health and nutrition, education and learning, and economic security – through the eyes of adults whose occupations and volunteer work affect such opportunities. In other words, the NVP reflects the perceptions of individuals throughout the United States who are in a position to improve children's opportunities in the future. We generally use the word ?children? throughout the report to describe children from age 0-18 years, unless otherwise noted.Report #3 for NVP 2013 focuses on findings related to children's education and learning

Performance of Installed Cooking Exhaust Devices

The performance metrics of airflow, sound, and combustion product capture efficiency (CE) were measured for a convenience sample of fifteen cooking exhaust devices, as installed in residences. Results were analyzed to quantify the impact of various device- and installation-dependent parameters on CE. Measured maximum airflows were 70% or lower than values noted on product literature for 10 of the devices. Above-the-cooktop devices with flat bottom surfaces (no capture hood) – including exhaust fan/microwave combination appliances – were found to have much lower CE at similar flow rates, compared to devices with capture hoods. For almost all exhaust devices and especially for rear-mounted downdraft exhaust and microwaves, CE was substantially higher for back compared with front burner use. Flow rate, and the extent to which the exhaust device extends over the burners that are in use, also had a large effect on CE. A flow rate of 95 liters per second (200 cubic feet per minute) was necessary, but not sufficient, to attain capture efficiency in excess of 75% for the front burners. A-weighted sound levels in kitchens exceeded 57 dB when operating at the highest fan setting for all 14 devices evaluated for sound performance