The forest resources of rural householders in Dent County, Missouri

This bulletin reports on School of Forestry research project 124, Timber Economics--P. [3].Digitized 2007 AES.Includes bibliographical references (page 21)

Centrosome-independent mitotic spindle formation in vertebrates

AbstractBackground: In cells lacking centrosomes, the microtubule-organizing activity of the centrosome is substituted for by the combined action of chromatin and molecular motors. The question of whether a centrosome-independent pathway for spindle formation exists in vertebrate somatic cells, which always contain centrosomes, remains unanswered, however. By a combination of labeling with green fluorescent protein (GFP) and laser microsurgery we have been able to selectively destroy centrosomes in living mammalian cells as they enter mitosis.Results: We have established a mammalian cell line in which the boundaries of the centrosome are defined by the constitutive expression of γ-tubulin–GFP. This feature allows us to use laser microsurgery to selectively destroy the centrosomes in living cells. Here we show that this method can be used to reproducibly ablate the centrosome as a functional entity, and that after destruction the microtubules associated with the ablated centrosome disassemble. Depolymerization–repolymerization experiments reveal that microtubules form in acentrosomal cells randomly within the cytoplasm. When both centrosomes are destroyed during prophase these cells form a functional bipolar spindle. Surprisingly, when just one centrosome is destroyed, bipolar spindles are also formed that contain one centrosomal and one acentrosomal pole. Both the polar regions in these spindles are well focused and contain the nuclear structural protein NuMA. The acentrosomal pole lacks pericentrin, γ-tubulin, and centrioles, however.Conclusions: These results reveal, for the first time, that somatic cells can use a centrosome-independent pathway for spindle formation that is normally masked by the presence of the centrosome. Furthermore, this mechanism is strong enough to drive bipolar spindle assembly even in the presence of a single functional centrosome

Observed and Expected Mortality in Cohort Studies

Epidemiologists often compare the observed number of deaths in a cohort with the expected number of deaths, obtained by multiplying person-time accrued in the cohort by mortality rates for a reference population (ideally, a reference that represents the mortality rate in the cohort in the absence of exposure). However, if exposure is hazardous (or salutary), this calculation will not consistently estimate the number of deaths expected in the absence of exposure because exposure will have affected the distribution of person-time observed in the study cohort. While problems with interpretation of this standard calculation of expected counts were discussed more than 2 decades ago, these discussions had little impact on epidemiologic practice. The logic of counterfactuals may help clarify this topic as we revisit these issues. In this paper, we describe a simple way to consistently estimate the expected number of deaths in such settings, and we illustrate the approach using data from a cohort study of mortality among underground miners

A novel PCFT gene mutation (p.Cys66LeufsX99) causing hereditary folate malabsorption

Hereditary folate malabsorption (HFM) is a rare autosomal recessive disorder which is characterized by impaired intestinal folate malabsorption and impaired folate transport into the central nervous system. Mutations in the intestinal folate transporter PCFT have been reported previously in only 10 individuals with this disorder. The purpose of the current study was to describe the clinical phenotype and determine the molecular basis for this disorder in a family with four affected individuals. A consanguineous family of Pakistani origin with autosomal recessive HFM was ascertained and clinically phenotyped. After genetic linkage studies all coding exons of the PCFT gene were screened for mutations by direct sequencing. The clinical phenotype of four affected patients is described. Direct sequencing of PCFT revealed a novel homozygous frameshift mutation (c.194dupG) at a mononucleotide repeat in exon 1 predicted to result in a truncated protein (p.Cys66LeufsX99). This report extends current knowledge on the phenotypic manifestations of HFM and the PCFT mutation spectrum

Behavior change interventions: the potential of ontologies for advancing science and practice

A central goal of behavioral medicine is the creation of evidence-based interventions for promoting behavior change. Scientific knowledge about behavior change could be more effectively accumulated using "ontologies." In information science, an ontology is a systematic method for articulating a "controlled vocabulary" of agreed-upon terms and their inter-relationships. It involves three core elements: (1) a controlled vocabulary specifying and defining existing classes; (2) specification of the inter-relationships between classes; and (3) codification in a computer-readable format to enable knowledge generation, organization, reuse, integration, and analysis. This paper introduces ontologies, provides a review of current efforts to create ontologies related to behavior change interventions and suggests future work. This paper was written by behavioral medicine and information science experts and was developed in partnership between the Society of Behavioral Medicine's Technology Special Interest Group (SIG) and the Theories and Techniques of Behavior Change Interventions SIG. In recent years significant progress has been made in the foundational work needed to develop ontologies of behavior change. Ontologies of behavior change could facilitate a transformation of behavioral science from a field in which data from different experiments are siloed into one in which data across experiments could be compared and/or integrated. This could facilitate new approaches to hypothesis generation and knowledge discovery in behavioral science

Color Gradients and Surface Brightness Profiles of Galaxies in the Hubble Deep Field-North

We fit elliptical isophotes to the Hubble Deep Field-North WFPC-2 and NICMOS data to study the rest-frame UV_{218}-U_{300} color profiles and rest-frame B surface brightness profiles of 33 intermediate redshift galaxies (0.5 <= z <= 1.2) with I_{814} < 25 and 50 high redshift galaxies (2.0 <= z <= 3.5) with H_{160}< 27. From the weighted least-squares fit to the color profiles we find that, at intermediate redshifts, the galaxies possess negative color gradients indicating a reddening towards the center of the profile similar to local samples whereas, at high redshifts, the galaxies possess positive color gradients. This indicates that star formation is more centrally concentrated in the distant galaxy sample which differs from the prevalent mode of extended disk star formation that we observe in the local universe. Additionally, we find that it is critical to correct for PSF effects when evaluating the surface brightness profiles since at small scale lengths and faint magnitudes, an r^{1/4} profile can be smoothed out substantially to become consistent with an exponential profile. After correcting for PSF effects, we find that at higher look-back time, the fraction of galaxies possessing exponential profiles have slightly decreased while the fraction of galaxies possessing r^{1/4} profiles have slightly increased. Our results also suggest a statistically insignificant increase in the fraction of peculiar/irregular type galaxies. We compare our results with recent semi-analytical models which treat galaxy formation and evolution following the cold dark matter hierarchical framework.Comment: 31 pages, 10 JPEG figures. To be published in AJ Vol. 124, October 200

Efficient quantum algorithms for simulating sparse Hamiltonians

We present an efficient quantum algorithm for simulating the evolution of a sparse Hamiltonian H for a given time t in terms of a procedure for computing the matrix entries of H. In particular, when H acts on n qubits, has at most a constant number of nonzero entries in each row/column, and |H| is bounded by a constant, we may select any positive integer $k$ such that the simulation requires O((\log^*n)t^{1+1/2k}) accesses to matrix entries of H. We show that the temporal scaling cannot be significantly improved beyond this, because sublinear time scaling is not possible.Comment: 9 pages, 2 figures, substantial revision

An Illustration of Inverse Probability Weighting to Estimate Policy-Relevant Causal Effects

Traditional epidemiologic approaches allow us to compare counterfactual outcomes under 2 exposure distributions, usually 100% exposed and 100% unexposed. However, to estimate the population health effect of a proposed intervention, one may wish to compare factual outcomes under the observed exposure distribution to counterfactual outcomes under the exposure distribution produced by an intervention. Here, we used inverse probability weights to compare the 5-year mortality risk under observed antiretroviral therapy treatment plans to the 5-year mortality risk that would had been observed under an intervention in which all patients initiated therapy immediately upon entry into care among patients positive for human immunodeficiency virus in the US Centers for AIDS Research Network of Integrated Clinical Systems multisite cohort study between 1998 and 2013. Therapy-naïve patients (n = 14,700) were followed from entry into care until death, loss to follow-up, or censoring at 5 years or on December 31, 2013. The 5-year cumulative incidence of mortality was 11.65% under observed treatment plans and 10.10% under the intervention, yielding a risk difference of −1.57% (95% confidence interval: −3.08, −0.06). Comparing outcomes under the intervention with outcomes under observed treatment plans provides meaningful information about the potential consequences of new US guidelines to treat all patients with human immunodeficiency virus regardless of CD4 cell count under actual clinical conditions