Angular quantization and the density matrix renormalization group

Path integral techniques for the density matrix of a one-dimensional statistical system near a boundary previously employed in black-hole physics are applied to providing a new interpretation of the density matrix renormalization group: its efficacy is due to the concentration of quantum states near the boundary.Comment: 8 pages, 3 figures, to appear in Mod. Phys. Lett.

Effects of Administrator Implemented Homogeneous and Heterogeneous Grouping on Reading Achievement of Selected Sixth-Grade Students

Problem. A Nation at Risk reported that the average achievement score of high-school students on most standardized tests is lower now than it was a quarter of a century ago, and the majority of the brightest students fail to achieve according to their ability. A salient problem in educating pupils is that of attaining reading comprehension achievement scores comparable to their intellectual potential. This study examines the effects of administrator implemented homogeneous and heterogeneous grouping on the reading achievement of selected sixth-grade students. Method. This was a quasi-experimental study using parametric techniques. The tests for hypotheses were analysis of variance, analysis of covariance, and multiple linear regression. This study compares the reading comprehension achievement of an experimental group and a control group. It also compares the interaction of gender as a factor in reading achievement due to instructional grouping techniques. There were 113 sixth-grade students in the experimental group and 59 students in the control group. Results. Nine hypotheses were tested for three reading group levels: (1) high ability, (2) average ability, and (3) low ability. Reading achievement was not affected to a statistically significant degree at alpha = .05 by either instructional approach--homogeneous or heterogeneous--regardless of reading group ability level. Hypotheses applicable to both high-ability and average-ability students exposed to homogeneous instruction found no significant differences related to gender. However, low-ability female students scored significantly higher than low-ability male students. Hypotheses applicable to both high-ability and low-ability students exposed to heterogeneous instruction found no significant differences related to gender. However, average-ability male students scored significantly better than average-ability female students. Conclusions. Academic performance, as measured by sixth-grade reading scores, was not affected to a statistically significant degree by the instructional approach--homogeneous or heterogeneous--regardless of reading group ability level. Although there was a degree of inconsistency in regard to gender, average-ability male students tended to perform better in reading classes when exposed to heterogeneous instruction and low-ability female students tended to perform better in reading classes when exposed to homogeneous instruction

Lymphocyte Populations and Antibody Production in Vaccinated and Non-vaccinated Pigs Challenged with Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae (M. hyo), the cause of enzootic pneumonia in swine, is a worldwide problem. Despite the developmental vaccines that have been commercially available for several years, M. hyo-induced pneumonia is still a major concern to swine producers. The pathologic lesions observed with enzootic pneumonia consist primarily of a lymphoid cell infiltration of the lungs. Four groups of pigs consisting of challenge control, vaccinated and challenged, vaccinated only, and nonvaccinated and non-challenged were used in this study. Lymphocytes from the peripheral blood, lung, and bronchial lymph nodes were analyzed by flow cytometry (FACs) to determine the populations of cells activated by M. hyo. No significant difference in percentages of B or T lymphocytes was found between the vaccinated and nonvaccinated groups. An ELISPOT assay was used to evaluate the isotype of antibodies secreted by B lymphocytes from the same tissues. Total secreted immunoglobulin and mycoplasmal membrane specific immunoglobulin secretion were measured. A significant increase in secretion of total IgG by lymphocytes in the lungs of pigs only challenged with M. hyo, and vaccinated/challenged was observed. No mycoplasma-specific stimulation was observed. The mycoplasmal membrane preparation induced a non-specific stimulation by IgM secreting cells in all groups. Again, no mycoplasma-specific response was observed. These results suggest that although IgGsecreting lymphocytes are stimulated to secrete antibodies in infected pigs, the lymphocyte response observed in enzootic pneumonia may not be to the M. hyo membrane antigen. At this time, it is unknown whether the immune response to M. hyo is predominately an antibody- or cellmediated immune response, and how these immune responses contribute to protection from enzootic pneumonia

Effect of PRRSV Infection on MHC Expression by Macrophages and Monocytes

Porcine reproductive and respiratory syndrome virus (PRRSV) is a recent and widespread pathogen in the U.S. swine population. PRRSV infects cells of the macrophage/ monocyte/dendritic lineages which are important antigen presenting cells (APCs) of the immune system. Using flow cytometric (FACs) analysis, we demonstrated that PRRSV infection decreases the expression of the major histocompatibility complex (MHC) glycoproteins on the cell surface of infected macrophages. This decrease in MHC protein expression may reduce the ability of the macrophages to present viral antigens to the appropriate lymphocytes. The potential lack of viral antigen presentation may play a crucial role in the persistent viremia observed in PRRSV-infected pigs

A study of the subsurface stratigraphy of the upper Cambrian in Western Missouri

Megascopic examination of diamond-drill cores supplemented by insoluble residue data provides a usable means of studying the lithologic characteristic of Upper Cambrian strata in the subsurface of western Missouri. The stratigraphic relationships within each Cambrian formation and the relationships of each Cambrian unit to formations above and below are discussed. The relationship of Upper Cambrian strata to the Precambrian surface in western Missouri and easternmost Kansas is illustrated. The Lamotte Sandstone is overlapped by the Reagan Sandstone against Precambrian topographic highs and the Bonneterre and lower Davis are replaced by sandstones similar to the Reagan in southwest Missouri and southeast Kansas. Northward, in western Missouri, from Jasper County to Bates County the Bonneterre and lower Davis (?) is absent and in easternmost Kansas the Lamotte, Bonneterre, and Davis Formations have been overlapped by the Derby-Doerun Dolomite. All Upper Cambrian formations thin westward, away from the St. Francois Mountains, across the study area. However, pre-Derby-Doerun units thin more rapidly than do the Derby-Doerun, Potosi, or Eminence Formations. The areal extent of the Sullivan Siltstone and the Whetstone Creek Members of the Bonneterre Formation in the central and western portions of southern Missouri has been determined and the westward extent of the Whetstone Creek Member is believed to represent an erosional surface on the top of the Bonneterre. The green clay residue facies and the spongy chert residue facies occur by facies substitution with more typical, chert-bearing Potosi and Eminence Dolomites. Although the reasons for these residue facies in the Potosi and Eminence are not fully known at this time, the areal distribution of these units in the study area have been determined --Abstract, pages ii-iii

The Influence of Passive Immunity on Serological Responses to Mycoplasma hyopneumoniae Vaccination

Vaccine induced serum antibody levels were significantly less in pigs with passive immunity to Mycoplasma hyopneumoniae compared to pigs without passive immunity. Age at vaccination did not influence antibody responses to vaccination. The presence of passive antibodies at the time of vaccination may provide an explanation for vaccination failure under field conditions

What is the Health Impact of Day Care Attendance on Infants and Preschoolers?

The impact of various child care arrangements on the health of infants and preschool children is not known in any systematic way, yet by 1990 more than 10 million of these children may be receiving their care in day care facilities (1). Concerns over the health of these children and health practices within day care facilities have already led some States to place regulation of day care facilities under the jurisdiction of the department of health (2,3), and others are presently considering such legislation. In addition, the American Academy of Pediatrics has recently published Health in Day Care, a manual for health professionals who are being increasingly called upon for advice concerning health issues related to children in day care facilities (4)