Plant microfossil record of the terminal Cretaceous event in the western United States and Canada

Plant microfossils, principally pollen grains and spores produced by land plants, provide an excellent record of the terminal Cretaceous event in nonmarine environments. The record indicates regional devastation of the latest Cretaceous vegetation with the extinction of many groups, followed by a recolonization of the earliest Tertiary land surface, and development of a permanently changed land flora. The regional variations in depositional environments, plant communities, and paleoclimates provide insight into the nature and effects of the event, which were short-lived but profound. The plant microfossil data support the hypothesis that an abruptly initiated, major ecological crisis occurred at the end of the Cretaceous. Disruption of the Late Cretaceous flora ultimately contributred to the rise of modern vegetation. The plant microfossils together with geochemical and mineralogical data are consistent with an extraterrestrial impact having been the cause of the terminal Cretaceous event

School and Sector Switching in Milwaukee

In this report we analyze the movement of students to and from the Milwaukee Parental Choice Program (MPCP) and Milwaukee Public Schools (MPS). We also analyze student mobility between schools within each sector. The analysis rests on two separate sets of data: the administrative records we have collected as part of our separate analysis of academic achievement in MPCP (Witte , Wolf, Cowen, Fleming, & Lucas-McLean, 2010), and the results of an extensive set of surveys collected from parents of private and public school students

Student Attainment and the Milwaukee Parental Choice Program

In this report we examine high school completion and postsecondary enrollment (a.k.a. “educational attainment”) of the cohort of 9th grade students who were in the Milwaukee Parental Choice Program (MPCP) at the beginning of our state-mandated evaluation of the MPCP in 2006. After tracking the MPCP 9th graders following the 2006-07 year and comparing them to a carefully matched sample of 9th graders who were in Milwaukee Public Schools (MPS) during the 2006-07 year, we use a combination of parent surveys and administrative (school) records to estimate attainment

The Preparation of Pure Di-Isobutyl

The preparation of pure 2, 5 dimethyl hexane by means of the Wurtz reaction has been studied and the results show a number of interesting things. One is that the presence of solvent slows down the time of reaction so much as to produce practically none of the desired substance. In the second place, it has been shown that the iso-butyl bromide can be mixed directly with sodium under conditions which will permit of refluxing. In a short time as indicated by the reflux temperature, the reaction is practically complete and yields nearly quantitative are obtained. There is a loss of either bromide or product through the open end of the system in the vapor phase. A study of the velocity factors of this reaction has been made

Residual risk of transmission of HIV through blood transfusion in South Africa

Despite the ongoing review of donor recruitment criteria by local blood transfusion services and the developmnt of highly sensitive and specific testing for the presence of antibodies to HIV in blood and blood products, there remains a residue of HIV in donated blood. This is because of donors who are in the 'window period' between acquisition of HIV and seroconversion, human errors and limits to the sensitivity and specificity of current tests. Data available from a national survey of HIV seroprevalence in South African blood donors allowed for the estimation of the number of units screened negative but likely to be infected with HIV. Assuming window periods of 4,8 and 14 weeks, a test sensitivity of 99,9%, a specificity of 98,5% and a human error rate of 0,1%, the likely rate of HIV-infected blood in the South African blood transfusion supply ranges from 1,1 to 3,9/ 100 000 units, with a likely estimate of 2,2/100 000 units. In the current South African blood transfusion setting, between 8,1 and 28,2 units of blood per annum. will be HIV-positive with a likely estimate of 15,9 units. This corresponds to an odds ratio of between 1:90 909 and 1:25 641 units infected with HIV. These data are comparable with the risk in developed countries. The expected increase in the incidence and prevalence of HIV infection in all adult South African populations necessitates additional measures to ensure a blood supply which is as safe as possible. Some of these measures have already been taken by local blood transfusion services

The MPCP Longitudinal Educational Growth Study Third Year Report

This is the third-year report in a five-year evaluation of the Milwaukee Parental Choice Program (MPCP). The MPCP, which began in 1990, provides government-funded vouchers for low-income children to attend private schools in the City of Milwaukee. The maximum voucher amount in 2008-09 was $6,607, and approximately 20,000 children used a voucher to attend either secular or religious private schools. The MPCP is the oldest and largest urban school voucher program in the United States. This evaluation was authorized by Wisconsin Act 125 enacted in 2005

The Effect of Resistivity on the Nonlinear Stage of the Magnetorotational Instability in Accretion Disks

We present three-dimensional magnetohydrodynamic simulations of the nonlinear evolution of the magnetorotational instability (MRI) with a non-zero Ohmic resistivity. The properties of the saturated state depend on the initial magnetic field configuration. In simulations with an initial uniform vertical field, the MRI is able to support angular momentum transport even for large resistivities through the quasi-periodic generation of axisymmetric radial channel solutions rather than through the maintenance of anisotropic turbulence. Simulations with zero net flux show that the angular momentum transport and the amplitude of magnetic energy after saturation are significantly reduced by finite resistivity, even at levels where the linear modes are only slightly affected. This occurs at magnetic Reynolds numbers expected in low, cool states of dwarf novae, these results suggest that finite resistivity may account for the low and high angular momentum transport rates inferred for these systems.Comment: 8 figures, accepted for publication in Ap

The evidence for automated grading in diabetic retinopathy screening

Peer reviewedPostprin

Imaging analysis of LDEF craters

Two small craters in Al from the Long Duration Exposure Facility (LDEF) experiment tray A11E00F (no. 74, 119 micron diameter and no. 31, 158 micron diameter) were analyzed using Auger electron spectroscopy (AES), time-of-flight secondary ion mass spectroscopy (TOF-SIMS), low voltage scanning electron microscopy (LVSEM), and SEM energy dispersive spectroscopy (EDS). High resolution images and sensitive elemental and molecular analysis were obtained with this combined approach. The result of these analyses are presented