Showing papers by "San Diego State University published in 1997"

Fluorescent indicators for Ca2+based on green fluorescent proteins and calmodulin

Abstract: Important Ca2+ signals in the cytosol and organelles are often extremely localized and hard to measure. To overcome this problem we have constructed new fluorescent indicators for Ca2+ that are genetically encoded without cofactors and are targetable to specific intracellular locations. We have dubbed these fluorescent indicators 'cameleons'. They consist of tandem fusions of a blue- or cyan-emitting mutant of the green fluorescent protein (GFP), calmodulin, the calmodulin-binding peptide M13, and an enhanced green- or yellow-emitting GFP. Binding of Ca2+ makes calmodulin wrap around the M13 domain, increasing the fluorescence resonance energy transfer (FRET) between the flanking GFPs. Calmodulin mutations can tune the Ca2+ affinities to measure free Ca2+ concentrations in the range 10(-8) to 10(-2) M. We have visualized free Ca2+ dynamics in the cytosol, nucleus and endoplasmic reticulum of single HeLa cells transfected with complementary DNAs encoding chimaeras bearing appropriate localization signals. Ca2+ concentration in the endoplasmic reticulum of individual cells ranged from 60 to 400 microM at rest, and 1 to 50 microM after Ca2+ mobilization. FRET is also an indicator of the reversible intermolecular association of cyan-GFP-labelled calmodulin with yellow-GFP-labelled M13. Thus FRET between GFP mutants can monitor localized Ca2+ signals and protein heterodimerization in individual live cells.

The effects of a 2-year physical education program (SPARK) on physical activity and fitness in elementary school students. Sports, Play and Active Recreation for Kids.

Abstract: OBJECTIVES: This study evaluated a health-related physical education program for fourth- and fifth-grade students designed to increase physical activity during physical education classes and outside of school. METHODS: Seven schools were assigned to three conditions in a quasi-experimental design. Health-related physical education was taught by physical education specialists or trained classroom teachers. Students from these classes were compared with those in control classes. Analyses were conducted on 955 students with complete data. RESULTS: Students spent more minutes per week being physically active in specialist-led (40 min) and teacher-led (33 min) physical education classes than in control classes (18 min; P < .001). After 2 years, girls in the specialist-led condition were superior to girls in the control condition on abdominal strength and endurance (P < .001) and cardiorespiratory endurance (P < .001). There were no effects on physical activity outside of school. CONCLUSIONS: A health-related p...

Text, Role and Context: Developing Academic Literacies

Abstract: 1. Literacy and pedagogy: three views 2. Genre knowledge and socioliteracies: what readers and writers may share 3. Genres and social forces: homely and academic texts 4. Discourse communities/communities of practice: membership, conflict and diversity 5. Our special roles: literacy practitioners as campus mediators and researchers 6. Students as researchers: investigating texts, processes and contexts 7. The socioliterate classroom: basic tenets and goals 8. Putting tenets and goals into practice: using portfolios in literacy classrooms 9. Conclusion.

Assessing Perceived Physical Environmental Variables that May Influence Physical Activity

Abstract: The present study evaluated a measure of perceived physical environments that may influence physical activity. Forty-three self-report items were used to assess environmental variables at homes, in neighborhoods, or on frequently traveled routes. The presence of facilitators of (e.g., equipment, programs, attractive surroundings) and barriers to (e.g., high crime) physical activity was assessed. In 110 college students, test-retest reliabilities were .89 for the home equipment scale, .68 for the neighborhood scale, and .80 for the convenient facilities scale. Home equipment and convenient facilities scales were correlated with self-reported physical activity. In multiple regression analyses, the only significant association, after adjusting for neighborhood socioeconomic status, was home equipment with strength exercise. Further research is needed to identify other environmental characteristics that may influence physical activity.

Food web analysis of southern California coastal wetlands using multiple stable isotopes

Abstract: Carbon, nitrogen, and sulfur stable isotopes were used to characterize the food webs (i.e., sources of carbon and trophic status of consumers) in Tijuana Estuary and San Dieguito Lagoon. Producer groups were most clearly differentiated by carbon, then by sulfur, and least clearly by nitrogen isotope measurements. Consumer 15N isotopic enrichment suggested that there are four trophic levels in the Tijuana Estuary food web and three in San Dieguito Lagoon. A significant difference in multiple isotope ratio distributions of fishes between wetlands suggested that the food web of San Dieguito Lagoon is less complex than that of Tijuana Estuary. Associations among sources and consumers indicated that inputs from intertidal macroalgae, marsh microalgae, and Spartina foliosa provide the organic matter that supports invertebrates, fishes, and the light-footed clapper rail (Rallus longirostris levipes). These three producers occupy tidal channels, low salt marsh, and mid salt marsh habitats. The only consumer sampled that appears dependent upon primary productivity from high salt marsh habitat is the sora (Porzana carolina). Two- and three-source mixing models identified Spartina as the major organic matter source for fishes, and macroalgae for invertebrates and the light-footed clapper rail in Tijuana Estuary. In San Dieguito Lagoon, a system lacking Spartina, inputs of macroalgae and microalgae support fishes. Salicornia virginica, S. subterminalis, Monanthochloe littoralis, sewage- derived organic matter, and suspended particulate organic matter were deductively excluded as dominant, direct influences on the food web. The demonstration of a salt marsh-channel linkage in these systems affirms that these habitats should be managed as a single ecosystem and that the restoration of intertidal marshes for endangered birds and other biota is compatible with enhancement of coastal fish populations; heretofore, these have been considered to be competing objectives.

Overexpression of the rat sarcoplasmic reticulum Ca2+ ATPase gene in the heart of transgenic mice accelerates calcium transients and cardiac relaxation

Abstract: The Ca2+ ATPase of the sarcoplasmic reticulum (SERCA2) plays a dominant role in lowering cytoplasmic calcium levels during cardiac relaxation and reduction of its activity has been linked to delayed diastolic relaxation in hypothyroid and failing hearts. To determine the contractile alterations resulting from increased SERCA2 expression, we generated transgenic mice overexpressing a rat SERCA2 transgene. Characterization of a heterozygous transgenic mouse line (CJ5) showed that the amount of SERCA2 mRNA and protein increased 2. 6-fold and 1.2-fold, respectively, relative to control mice. Determination of the relative synthesis rate of SERCA2 protein showed an 82% increase. The mRNA levels of some of the other genes involved in calcium handling, such as the ryanodine receptor and calsequestrin, remained unchanged, but the mRNA levels of phospholamban and Na+/Ca2+ exchanger increased 1.4-fold and 1.8-fold, respectively. The increase in phospholamban or Na+/Ca2+ exchanger mRNAs did not, however, result in changes in protein levels. Functional analysis of calcium handling and contractile parameters in isolated cardiac myocytes indicated that the intracellular calcium decline (t1/2) and myocyte relengthening (t1/2) were accelerated by 23 and 22%, respectively. In addition, the rate of myocyte shortening was also significantly faster. In isolated papillary muscle from SERCA2 transgenic mice, the time to half maximum postrest potentiation was significantly shorter than in negative littermates. Furthermore, cardiac function measured in vivo, demonstrated significantly accelerated contraction and relaxation in SERCA2 transgenic mice that were further augmented in both groups with isoproterenol administration. Similar results were obtained for the contractile performance of myocytes isolated from a separate line (CJ2) of homozygous SERCA2 transgenic mice. Our findings suggest, for the first time, that increased SERCA2 expression is feasible in vivo and results in enhanced calcium transients, myocardial contractility, and relaxation that may have further therapeutic implications.

A role for the p38 mitogen-activated protein kinase pathway in myocardial cell growth, sarcomeric organization, and cardiac-specific gene expression.

Abstract: Three hallmark features of the cardiac hypertrophic growth program are increases in cell size, sarcomeric organization, and the induction of certain cardiac-specific genes. All three features of hypertrophy are induced in cultured myocardial cells by α1- adrenergic receptor agonists, such as phenylephrine (PE) and other growth factors that activate mitogen- activated protein kinases (MAPKs). In this study the MAPK family members extracellular signal–regulated kinase (ERK), c-jun NH2-terminal kinase (JNK), and p38 were activated by transfecting cultured cardiac myocytes with constructs encoding the appropriate kinases possessing gain-of-function mutations. Transfected cells were then analyzed for changes in cell size, sarcomeric organization, and induction of the genes for the A- and B-type natriuretic peptides (NPs), as well as the α-skeletal actin (α-SkA) gene. While activation of JNK and/or ERK with MEKK1COOH or Raf-1 BXB, respectively, augmented cell size and effected relatively modest increases in NP and α-SkA promoter activities, neither upstream kinase conferred sarcomeric organization. However, transfection with MKK6 (Glu), which specifically activated p38, augmented cell size, induced NP and α-Ska promoter activities by up to 130-fold, and elicited sarcomeric organization in a manner similar to PE. Moreover, all three growth features induced by MKK6 (Glu) or PE were blocked with the p38-specific inhibitor, SB 203580. These results demonstrate novel and potentially central roles for MKK6 and p38 in the regulation of myocardial cell hypertrophy.

Influence of oxygen content on the structural, magnetotransport, and magnetic properties of LaMnO 3 + δ

Abstract: A systematic study of the effect of oxygen content on the structural, magnetotransport, and magnetic properties has been undertaken on a series of ${\mathrm{LaMnO}}_{3+\mathrm{\ensuremath{\delta}}}$ samples, with $\ensuremath{\delta}=0,$ 0.025, 0.07, 0.1, and 0.15. Measurements of the ac initial magnetic susceptibility, magnetization, magnetoresistance, and neutron diffraction, including small-angle neutron scattering (SANS), were performed in the temperature range 1--320 K using high magnetic fields up to 12 T. The antiferromagnetic order found in ${\mathrm{LaMnO}}_{3}$ evolves towards a ferromagnetic order as \ensuremath{\delta} increases. This behavior is accompanied by a drastic reduction of the static Jahn-Teller distortion of the ${\mathrm{MnO}}_{6}$ octahedra. The ferromagnetic coupling weakens for $\ensuremath{\delta}g~0.1.$ The magnetic behavior is interpreted by taking into account two effects caused by the increase in \ensuremath{\delta}: cation vacancies and ${\mathrm{Mn}}^{4+}{/\mathrm{M}\mathrm{n}}^{3+}$ ratio enhancement. The orthorhombic crystallographic structure becomes unstable at room temperature for $\ensuremath{\delta}g~0.1.$ The sample $\ensuremath{\delta}=0.1$ shows a structural transition from rhombohedral to orthorhombic below ${T}_{S}\ensuremath{\approx}300\mathrm{K}$ with a huge change in the cell volume. All the studied compounds were found to be insulating at low temperatures with no appreciable magnetoresistance, except for $\ensuremath{\delta}=0.15,$ in which we observed a large value for the magnetoresistance. The SANS results indicate that magnetic clustering effects are important below ${T}_{C}$ for $\ensuremath{\delta}g~0.07,$ which could explain the intriguing ferromagnetic insulator state. In the $\ensuremath{\delta}=0.07$ and $\ensuremath{\delta}=0.10$ samples we found at temperatures below ${T}_{C}$ magnetic and structural anomalies that are characteristic of charge ordering.

Restoration Biology: A Population Biology Perspective

Abstract: A major goal of population biologists involved in restoration work is to restore populations to a level that will allow them to persist over the long term within a dynamic landscape and include the ability to undergo adaptive evolutionary change. We discuss five research areas of particular importance to restoration biology that offer potentially unique opportunities to couple basic research with the practical needs of restorationists. The five research areas are: (1) the influence of numbers of individuals and genetic variation in the initial population on population colonization, establishment, growth, and evolutionary potential; (2) the role of local adaptation and life history traits in the success of restored populations; (3) the influence of the spatial arrangement of landscape elements on metapopulation dynamics and population processes such as migration; (4) the effects of genetic drift, gene flow, and selection on population persistence within an often accelerated, successional time frame; and (5) the influence of interspecific interactions on population dynamics and community development. We also provide a sample of practical problems faced by practitioners, each of which encompasses one or more of the research areas discussed, and that may be solved by addressing fundamental research questions.

Validation of atmospheric correction over the oceans

Abstract: By validation of atmospheric correction, we mean quantification of the uncertainty expected to be associated with the retrieval of the water-leaving radiance from the measurement of the total radiance exiting the ocean-atmosphere system. This uncertainty includes that associated with the measurement or estimation of auxiliary data required for the retrieval process, for example, surface wind speed, surface atmospheric pressure, and total ozone concentration. For a definitive validation this quantification should be carried out over the full range of atmospheric types expected to be encountered. However, funding constraints require that the individual validation campaigns must be planned to address the individual components of the atmospheric correction algorithm believed to represent the greatest potential sources of error. In this paper we develop a strategy for validation of atmospheric correction over the oceans that is focused on EOS/MODIS. We also provide a description of the instrumentation and methods to be used in the implementation of the plan.

Physical Activity Levels and Prompts in Young Children at Recess: A Two-Year Study of a Bi-Ethnic Sample

Abstract: We investigated physical activity and encouragement for activity in a bi-ethnic cohort during recess. Activity and associated interactions of 287 children were recorded at preschool and again 2.2 years later. Children expended nearly twice as much energy at preschool recess than at elementary recess. Activity levels declined as recess time elapsed. At preschool, European-American children engaged in more moderate to vigorous activity than Mexican-Americans. As participants moved to elementary school, teachers' prompts to be active decreased and prompts from peers increased. Boys and girls received similar amounts of activity prompts at preschool, but prompts to boys increased over time. The findings suggest that school environments could be altered to promote healthful physical activity among young children.

Long-Term Effects of a Physical Education Curriculum and Staff Development Program: SPARK

Abstract: This 4-year study, conducted in seven elementary schools assigned to three conditions—Physical Education Specialists (PES), Trained Classroom Teachers (TT), and Controls (CO)—had two parts. The first investigated effects of a health-related physical education program on quantity and quality of lessons. Specialists produced the best outcomes, and TT were significantly better than nontrained peers. Part Two assessed maintenance effects approximately 1.5 years after intervention termination. Withdrawal of specialists significantly reduced the quantity and quality of physical education. TT maintained PES frequency but with a loss in lesson quality and a decline in student activity to 88% of intervention levels. Results support employing specialists and demonstrate the need for extensive professional development for classroom teachers responsible for physical education.

Cigarette smoking predicts development of depressive symptoms among U.S. adolescents.

Abstract: To examine whether adolescent cigarette smoking predicts the development of depressive symptoms, we used a longitudinal follow-up survey of 6,863 adolescents ages 12 to 18 in the U.S. who did not report notable depressive symptoms at baseline. This study used a self-report measure of six depressive symptoms experienced within the past twelve months at follow-up as the outcome of interest. Results indicated that 11.5% developed notable depressive symptoms at follow-up. There were marked gender differences with 15.3% of girls developing notable depressive symptoms compared to 8.1% of boys. Gender differences in depressive symptoms were consistent across all age groups and were apparent by the age of twelve. For both genders, smoking status was the most significant predictor of developing notable depressive symptoms. Several other risk factors including involvement in organized athletics, availability of social support, and personality characteristics were also found to be associated with development of depressive symptoms. Adolescent cigarette smoking may have marked health consequences in terms of depressive symptoms. The reduction of cigarette smoking among adolescents should be a focus of depression prevention interventions. In addition, the development of gender-specific components of prevention interventions may be warranted.

Using multimedia to overcome the problems with problem based learning

Abstract: Much of the literature on problem based learning (PBL) is concerned with efficacy or with guidelines on design or implementation. Relatively few articles focus on problems with problem based learning, and none that we could find provided suggestions as to how interactive multimedia might help alleviate those problems. In this article we begin with a review of problem based learning including a rationale for its use in the curriculum. Then we identify some of the problems inherent in designing and implementing problem based learning, and end the article with a discussion of how multimedia might be used to address some of those problems.

Exotic grass competition in suppressing native shrubland re-establishment

Abstract: Disturbance of coastal sage scrub in southern California has led to extensive displacement of native shrubs by exotic annual grasses. The initial conversion from shrubland to exotic grassland is typically associated with disturbance caused by intense grazing, high fire frequency, or mechanical vegetation removal. While native shrubs have been shown to recolonize annual grasslands under some conditions, other annual grasslands are persistent and show no evidence of shrub recolonization. This study examined the mechanisms by which annual grasses may exclude native shrubs and persist after release from disturbance. Grass density was manipulated in experimental plots to achieve a series of prescribed densities. Artemisia californica, a dominant native shrub, was seeded or planted into the plots and responses to the grass density treatments were measured over two growing seasons. A. californica germination, first season growth, and survival were all negatively related to the density of neighboring annual grasses. The most probable mechanism underlying the reduction of first season growth and survival was depletion of soil water by the grasses. The effects of the grasses on A. californica were no longer significant in the second season. The results of this study indicate that Mediterranean annual grasses reduce recruitment and can persist by inhibiting post-disturbance establishment of A. californica from seed. Although succession alone may not return disturbed annual grasslands to their former shrubland composition, the results suggest that restoration can be achieved by using container plantings or grass removal followed by seeding.

Effects of a low-velocity zone on a dynamic rupture

Abstract: Dynamic-crack earthquake simulations generally assume that the crustal material surrounding faults is laterally homogeneous. Tomographic and near-fault seismic studies indicate that the crust near faults is instead comprised of rocks of varying material velocities. We have tested the effects of adding material-velocity variation to simulations of spontaneously propagating earthquakes. We used two-dimensional plane strain conditions coupled with a slip-weakening fracture criterion and examined earthquakes on faults that bisect finite-width low-velocity zones embedded in country rock and earthquakes on faults that bound two different-velocity materials. When a fault bisects a low-velocity zone, the normal stress remains unchanged, but both the rupture velocity and slip-velocity pulse shape are perturbed. The presence of the low-velocity zone induces high-frequency oscillations in the slip function near the rupture front. When the fault is on the edge of the low-velocity zone, the oscillations are more pronounced, and repeated sticking and slipping can occur near the rupture front. For the slip-weakening (velocity-independent) friction model, however, the temporary sticking does not lead to permanent arrest of slip, and slip duration is still controlled by the overall rupture dimension. When an earthquake ruptures a fault juxtaposing a lower-velocity material against a higher-velocity material, the normal stress across the fault near the crack tip is perturbed. The sign of the normal stress perturbation depends on the direction of rupture, leading in some cases to a directional dependence of rupture velocity. When slip is accompanied by stress reduction, a positive feedback develops between the normal and shear stress changes, as previously noted by Andrews and Ben-Zion (1997), resulting in an apparently unavoidable grid-size dependence in computation of stress change near the rupture front. Numerical experiments indicate, however, that the rupture velocity is insensitive to this zone size dependence, which is highly localized immediately behind the crack tip. The factors controlling the rupture velocity in the simulations, including directional dependence, are further elucidated by a new analytical solution for rupture of an asperity on a frictionless interface.

The effect of outdoor fungal spore concentrations on daily asthma severity.

Abstract: The relationship between day-to-day changes in asthma severity and combined exposures to community air pollutants and aeroallergens remains to be clearly defined. We examined the effects of outdoor...

What is civil disobedience

Abstract: Soulevant la question de la nature, de la justification morale et du role de la desobeissance civile dans le cadre de la conception de la societe bien ordonnee developpee par J Rawls, l'A se propose de modifier l'analyse rawlsienne en 'brouillant' la distinction entre les actes nonviolents de desobeissance et les actes de violence A travers l'exemple du terrorisme et le cas des fermiers americains defendant le Liberty Bell, l'A montre que le recours a la menace coercitive et l'appel direct ou indirect au sens de la justice au sein de la communaute permettent d'etendre le domaine traditionnel de la desobeissance civile

Longitudinal analysis of multiple indicators of health decline among spousal caregivers.

Abstract: The hazards for experiencing major health events were studied longitudinally among 150 spousal caregivers of Alzheimer's disease (AD) patients and 46 married control participants. Based on longitudinal assessments from one to six years, the hazards of reaching any of three health events (extended physical illness or disability > 1 month, unhealthy medical rating from a nurse interview, or hospitalization) were not significantly different in a group comparison of caregivers to controls (Cox proportional hazards assumption, p > .05). However, there was a trend [X2(1, N = 107) = 3.13, p = .08] for caregivers to have a greater hazard for serious illness. Among caregivers only, a greater hazard for reaching at least one of these health events was associated with providing more activities of daily living (ADL) assistance [X2(1, N = 125) = 3.83, p = .05] but not with problem behaviors of the AD patient (p > .05). These results suggest that providing extensive ADL assistance may have health implications for spousal AD caregivers, while caregiving, per se, does not. Furthermore, these physical health impacts of caregiving may be best characterized using multidimensional assessments. Contrary to our guiding hypothesis, caregivers encountering more problem behaviors of their AD spouse were less likely to be hospitalized, X2(1, N = 145) = 5.88, p = .02. This finding may reflect a reluctance by caregivers to schedule necessary medical care when their spouses are most problematic, and this may have further long-term health implications for caregivers.

Prospective Evaluation of Three Smoking Interventions in 205 Recovering Alcoholics: One-Year Results of Project SCRAP-Tobacco

Abstract: A total of 205 (113 male, 92 female) nonhospitalized recovering alcoholics with >3 months of continuous abstinence from alcohol and drugs and relatively heavy tobacco dependence (Fagerstrom Tolerance Questionnaire score = 7.7; mean number of cigarettes per day, 26.8; mean number of years smoked, 24.4) were randomized to standard treatment (ST) American Lung Association quit program plus nicotine anonymous meetings (n = 70), behavioral counseling plus physical exercise (BEX; n = 72), or behavioral counseling plus nicotine gum (BNIC; n = 63). A 3 X 4 repeated measures design was used to evaluate the effectiveness of the interventions on smoking outcome at baseline, posttreatment, and 6- and 12-month follow-ups. Self-reported smoking status was verified with biochemical and informant report. Verified self-report indicated that significantly more smokers in BEX quit by posttreatment (60%) than in either BNIC (52%) or ST (31%), *2(2, N = 205) = 17.85, p < .01, but not at the 6-month (29%, 27%, and 21%, respectively) or 12-month (27%, 27%, and 26%, respectively) follow-up. Only 4% (7 of 188) relapsed to alcohol or drugs. Alcohol relapse did not differ by treatment group or smoking status. Length of alcohol abstinence was not associated with smoking cessation outcome. The prevalence of smoking in alcoholics, whether abstinent or not, is substantial, with estimates ranging from 80% to 95% (Bobo, 1989). Given that between 5% and 10% or more of the population may be alcoholics (Helzer, 1987), this constitutes a considerable number of individuals. These smokers are at high risk for cardiovascular and other diseases associated with both excessive drinking and cigarette smoking (Criqui, Wallace, Mishkel, Barrett-Connor, & Hess, 1981). Furthermore, recovering alcoholics tend to be the most heavily addicted to nicotine (Kozlowski, Jelinek, & Pope, 1986) and the most resistant to smoking intervention (Hughes, 1993). Despite these observa

Claiming Insufficient Knowledge

Abstract: When speakers produce “I don't knows” in ordinary conversation, they claim insufficient knowledge about the matters at hand. Analysis of diverse conversational environments reveal, however, that speakers’claims nevertheless accomplish a variety of subtle actions. “I don't knows” may be strategically and ambiguously deployed across the following achievements: (a) marking uncertainty and concerns about next-positioned opinions, assessments, or troubles; (b) constructing neutral positions, designed to mitigate agreement and disagreement, by disattending and seeking closure on other-initiated topics (e.g., moving toward completing stories or working to avoid troubling issues); and (c) postponing or withholding acceptance of others’invited and requested actions. By examining moments where insufficient knowledge claims are contingently used as a resource, understandings of proactive yet delicately managed interactional conduct are forwarded. Such conduct is shown to be anchored in ordinary conversations but adapted in similar yet distinct ways within institutional interactions such as courtroom cross-examination.

Cyclical changes in body composition in the annual cycle and migration of the Eared Grebe Podiceps nigricollis

Abstract: In changes that are among the most dramatic known for birds, Eared Grebes undergo 3-6 atrophy/hypertrophy cycles in major body constituents annually. The most pronounced takes place at staging areas in fall, when grebes become flightless for up to several months. At this season they accumulate huge fat stores (to 46% of lean body mass) and more than double the mass of body, liver, stomach, and intestine; leg and heart mass also increase. Concurrrently, pectoral muscles atrophy and can shrink below the size needed for flight (11% of total body mass). Before grebes depart for wintering areas these changes are reversed. In a 2-3 week predeparture period body mass drops by one-third as birds catabolize fat and reduce viscera mass by ?50%; leg mass also declines, while pectoral muscle increases. Similar cycles, which do not involve fattening to obesity, are repeated at wintering and breeding locations and, in some birds, on additional spring staging and fall molting areas. Heavy fat deposits in fall may insure that grebes can postpone their migration to wintering areas into the months of maximum darkness, thereby minimizing the risk of predation. The extreme predeparture reductions in leg and visceral mass, which occur in all seasons, reduce flight costs by minimizing wing loading and enhancing flight speed. Why grebes allow pectoral muscles to atrophy if they must rebuild them presently remains a puzzle. Several lines of evidence suggest that grebes attain a specific (optimal?) body composition prior to migrating. Further research into changes that may take place in other species prior to migration or at different times of the annual cycle is warranted.

On the Nova Rate in the Galaxy

Abstract: The Galactic nova rate is poorly known, with estimates in the literature ranging from as few as 11 to as many as 260 yr-1. At the lower end of the spectrum (50 yr-1), the predictions are based on scalings from extragalactic nova surveys, while estimates based on extrapolations of Galactic nova observations suggest rates that are significantly higher, in the range 50-100 yr-1 or more. In an attempt to reconcile this difference, the nova rate, based on Galactic nova observations, is recomputed. If the stellar mass distribution is axisymmetric about the Galactic center, a new estimate of the Galactic nova rate of ~35 ± 11 yr-1 is deduced. Although this value is marginally consistent with the highest estimates based on extragalactic surveys, the agreement is not entirely satisfactory. It is pointed out that a departure from axial symmetry, such as that caused by the presence of a Galactic bar, can potentially lower the estimated nova rate (perhaps approaching 50%) if the bar is sufficiently large, and has its long axis pointed toward the Sun. Alternatively, or perhaps in addition, it is possible that previous extragalactic surveys may have missed a significant fraction of novae (up to a factor of ~2) because of extinction internal to the galaxies. If this latter possibility can be ruled out, for example, through infrared surveys of nearby galaxies, the Galactic nova observations may provide additional support for the existence of a Galactic bar.

Planning in the USA: Policies, Issues and Processes

Abstract: Introduction Part I: Planning and Government 1. The Nature of Planning 2. Urbanization 3. Governing and Planning Urban Areas. Part II: Land Use Regulation 4. The Evolution of Zoning 5. The Institutional and Legal Framework 6. The Techniques of Zoning 7. Development Charges Part III: Quality of the Environment 8. Aesthetics 9. Historic Preservation Part IV: Growth Management 10. Growth Management and Local Government 11. Urban Growth Management and the States Part V: Development Issues 12. Transportation 13. Housing 14. Community and Economic Development Part VI: Environmental Planning 15. Environmental Policies 16. The Limits of Environmental Policy 17 Conclusion

An analysis of the housing market before and after the 1989 Loma Prieta earthquake

Abstract: Residential housing sales data from the San Francisco Bay area are merged with earthquake hazard measures, geologic measures, neighborhood quality measures, and community characteristics in order to estimate the hedonic price of earthquake risk before and after the October 17, 1989, Loma Prieta earthquake. The estimates suggest that the hedonic price fell after the earthquake, indicating that consumers had initially overestimated the earthquake hazard. This suggests that information about earthquake risks is imperfect and that some efficiency may be realized by devoting more resources to earthquake risk communication.