Sterile Neutrinos and Global Symmetries

We use an effective-field-theory approach to construct models with naturally light sterile neutrinos, due to either exact or accidental global symmetries. The most attractive models we find are based on gauge symmetries, either discrete or continuous. We give examples of simple models based on Z_N, U(1)', and SU(2)'.Comment: 8 pages. v2 (as in PRD): minor changes, typos corrected, two refs adde

Soil microbial communities in restored and unrestored coastal dune ecosystems in California

Most restoration projects involving invasive plant eradication tend to focus on plant removal with little consideration given to how these invasives change soil microbial communities. However, soil microorganisms can determine invasibility of habitats and, in turn, be altered by invasives once established, potentially inhibiting native plant establishment. We studied soil microbial communities in coastal dunes with varying invasion intensity and different restoration approaches (herbicide, mechanical excavation) at Point Reyes National Seashore. Overall, we found evidence of a strong link between bacterial and fungal soil communities and the presence of invasives and restoration approach. Heavily invaded sites were characterized by a lower abundance of putatively identified nitrifiers, fermentative bacteria, fungal parasites, and fungal dung saprotrophs and a higher abundance of cellulolytic bacteria and a class of arbuscular mycorrhizal fungi (Archaeosporomycetes). Changes in soil microbiota did not fully dissipate following removal of invasives using herbicide, with exception of reductions in cellulolytic bacteria and Archaeosporomycetes abundance. Mechanical restoration effectively removed both invasives and soil legacy effects by inverting or “flipping” rhizome-contaminated surface soils with soils from below and may have inadvertently induced other adverse effects on soils that impeded reestablishment of native dune plants. Land managers should consider additional measures to counteract lingering legacy effects and/or focus restoration efforts in areas where legacy effects are less pronounced

Social Work Ethics: Decision Making and Accountability

Book accompanies course that examines the interplay of social work, values, ethics, and decision-making processes. Through the use of practice scenarios, social workers will learn how to approach risk management and thorny ethical dilemmas that are common to many practice areas. The course discusses the role of laws and regulations in regard to ethics, highlights the importance of the distinction between legal and moral problems, and describes the National Association of Social Workers (NASW) Code of Ethics

Extent and Nature of Deer Damage to Commercial Nurseries in New York

We surveyed nursery producers in New York to determine the extent, nature and economic impact of deer damage to their operations, and to assess their attitudes towards deer. Seventy-three percent of the producers experienced deer damage to their crops in 1988. Average costs for replacement were nearly $6,000 per grower for those reporting damage estimates (and over$8,000 if 1 extreme value was included). Statewide damage estimates ranged from $500,000 to$1.2 million (depending on assumptions). Forty-six percent used damage control, which cost an average of about $2,000 per grower. More than 80% of the producers were classified as nonaccepting of deer damage and deer populations. We also reviewed several deer damage studies to compare economic and attitudinal impacts of deer damage to various agricultural constituencies. Nursery producers, orchardists, and Christmas tree growers appear to incur the greatest per capita deer damage costs. Of agriculturists, nursery producers and orchardists appear to be the least accepting of deer and deer damage. Deer managers and policy makers may need to consider the nursery producers in the same at risk category as orchardists

Naturalness and the Neutrino Matrix

The observed pattern of neutrino mass splittings and mixing angles indicates that their family structure is significantly different from that of the charged fermions. We investigate the implications of these data for the fermion mass matrices in grand unified theories with a type-I seesaw mechanism. We show that, with simple assumptions, naturalness leads to a strongly hierarchical Majorana mass matrix for heavy right-handed neutrinos and a partially cascade form for the Dirac neutrino matrix. We consider various model building scenarios which could alter this conclusion, and discuss their consequences for the construction of a natural model. We find that including partially lopsided matrices can aid us in generating a satisfying model.Comment: Discussion about neutrinoless double beta decay expanded; typos corrected; references added and update

Fire protection and recompression systems for a hypobaric research chamber Final report, Jul. - Dec. 1967

Fire detection-extinguishment and automatic rapid recompression systems for hypobaric spacecraft cabin simulator