Images of asteroid 21 Lutetia: a remnant planetesimal from the early Solar System

Images obtained by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras onboard the Rosetta spacecraft reveal that asteroid 21 Lutetia has a complex geology and one of the highest asteroid densities measured so far, 3.4 ± 0.3 grams per cubic centimeter. The north pole region is covered by a thick layer of regolith, which is seen to flow in major landslides associated with albedo variation. Its geologically complex surface, ancient surface age, and high density suggest that Lutetia is most likely a primordial planetesimal. This contrasts with smaller asteroids visited by previous spacecraft, which are probably shattered bodies, fragments of larger parents, or reaccumulated rubble piles.     

Gastric Helicobacter species as a cause of feline gastric lymphoma: A viable hypothesis

Gastric Helicobacter spp. are associated with chronic inflammation and neoplastic transformation in humans as well as domestic and laboratory species. The present study examined the association of Helicobacter heilmannii (Hhe) infection in pet cats with feline gastric mucosa associated lymphoid tissue (MALT) lymphoma. Tissues were collected via gastric biopsy or at necropsy from 47 pet cats with clinical signs of gastrointestinal disease, including vomiting and inappetance, and classified as gastritis (14/47), lymphoma (31/37), or normal (2/47). Tissues positive for argyrophilic organisms with Warthin–Starry stain (29/47) were assessed by fluorescent in situ hybridization (FISH) for the presence of Hhe strains 1–4 as well as with a fifth probe that detected Helicobacter salomonis, Helicobacter bizzozeronii, or Helicobacter felis. A significant association of positive Warthin–Starry status with Hhe infection was found in cases of sick cats (22/29; p < 0.05 by Chi-square; χ² = 7.034). Interestingly, a significant association between Hhe status and a diagnosis of lymphoblastic or lymphocytic lymphoma was observed as well in a subset of 24 Warthin–Starry positive lymphoma cases: of lymphoblastic lymphoma cases, 13/17 were positive for Hhe (p < 0.05; χ² = 4.854). Hhe strains 2 and 4 were most commonly found (18/29 and 17/29, respectively) among sick cats, although a higher than expected number of cats was also positive for Hhe1, which initial reports have described as rare in cats and common in humans. The association found between a positive Hhe status with the presence of feline gastric lymphoma, especially lymphoblastic lymphoma, argues for the need to conduct prospective studies to better identify the frequency and strain distribution of Hhe infection in both healthy and clinically ill cats, particularly those cats with gastric lymphoma.     

Estimating the economic effects of US state and local fiscal policy: A synthetic control method matching-regression approach

In this paper, we advance the empirical literature on US state and local fiscal policymaking by using the synthetic control method (SCM) to create pairwise matches for states in subsequent regression analysis of the relationships between state and local fiscal policies and several state economic outcomes. Additional contributions include the use of principal component analysis to construct broader narratives of state economic performance and to reduce the dimensionality of the characteristics used in SCM matching, while the regressions also include variables to control for post-matching economic shocks. Compared to conventional regression analysis, the SCM matching-regression approach better addresses potential endogeneity, reduces interpolation bias, and creates fiscal policy measures that better reflect policy differences. The SCM-matched regressions produce more statistically significant relationships between state and local fiscal variables and economic outcomes than do the conventional unmatched regressions, suggesting improved identification of state and local fiscal policy effects on economic outcomes. Robust relationships found include negative economic effects of the own-source revenue burden and property taxes. Consistent with the existing literature, the estimated fiscal policy effects are quantitatively small and unlikely to drive differences in state economic performance.     

The strange periodic comet machholz

The recently discovered periodic comet Machholz 1986 VIII (1986e) travels closer to the sun than any known planet and any known comet with an orbital period of less than 150 years, thus providing astronomers with a unique object for studying cometary evolution. The comet is spiraling steadily closer to the sun, from perihelion distance q [unknown] 0.9 astronomical unit at about A.D. 700 to q [unknown] 0.13 at present (orbital period, 5.25 years), to an expected q [unknown] 0.03 by about 2450; should the comet survive such increasingly close perihelion passages, q will begin steadily to increase shortly thereafter. A review of observations made since discovery is presented, together with a discussion of numerical investigations of the comet's orbit over 4000 years and prospects for observing the upcoming return to perihelion in 1991.     

Piloleiomyosarcoma in seven ferrets.

In each of seven ferrets (Mustela putorius furo) with leiomyosarcoma, a single dermal mass was identified and biopsied. Each mass consisted of a well-demarcated but nonencapsulated proliferation of large spindle- to strap-shaped cells arranged in interwoven bundles. The cells resembled the smooth muscle cells of the adjacent arrector pili muscles, but with marked nuclear pleomorphism. Immunohistochemical staining for smooth muscle actin, desmin, and vimentin was positive and staining for myoglobin and cytokeratin was negative. Follow-up on three of the ferrets indicates that the prognosis is good following complete surgical excision.     

Allozyme and microsatellite data reveal small clone size and high genetic diversity in aspen in the southern Cascade Mountains

The most widely distributed tree in North America, quaking aspen (Populus tremuloides, Michx.), reproduces sexually via seed and clonally via suckers. The size of aspen clones varies geographically, generally smaller in the east and large in the arid Intermountain West. In order to describe clone size and genetic structure of aspen in the southern Cascade Mountains, 864 stems from six sites were assayed at 15 isozyme and 6 microsatellite loci. Although isozymes reveal significantly lower levels of allelic richness (P < 0.001) and expected heterozygosity (P < 0.01), differences in genet diversity (isozyme G/N = 0.45, microsatellite G/N = 0.47) and allele frequency variation (isozyme F_ST = 0.02, microsatellite F_ST = 0.03) were nonsignificant. While a majority of stands were monoclonal, such stands were small, and the number of clones per stand was positively correlated with stand size (P < 0.0001). High genetic diversity, low genetic differentiation, and a rapid decay of spatial genetic structure consistent with long distance gene flow during seedling recruitment indicate that sexual reproduction is a significant factor contributing to the genetic structure of these populations. These findings further resolve the geographic variation in clonal structure observed in aspen across North America, providing novel information for land management and conservation efforts.