When Repurchases Resemble Dividends: Frequent versus Infrequent Repurchasers

I demonstrate that frequent repurchasers resemble dividend payers and their repurchases are sticky and inflexible, like dividends. In contrast, infrequent repurchasers follow a flexible buyback policy and quickly respond to earnings changes. Investors react more positively to infrequent repurchasers’ repurchase announcements and actual repurchases, consistent with stronger signals of undervaluation and improvement in future prospects. Frequent repurchasers, however, repurchase to offset dilution caused by equity compensation. The shift in repurchase behavior from infrequent to frequent explains why traditional motives such as flexibility and signaling fail to describe the recent surge in repurchases

Stable Non-BPS States and Their Holographic Duals

Stable non-BPS states can be constructed and studied in a variety of contexts in string theory. Here we review some interesting constructions that arise from suspended and wrapped branes. We also exhibit some stable non-BPS states that have holographic duals.Comment: 10 pages, LaTeX, 10 .eps figures (included); based on a talk given at Strings 2000, Michiga

Counting Wobbling Dual-Giants

We derive the BPS equations for D3-branes embedded in AdS_5 X S^5 that preserve at least two supercharges. These are given in terms of conditions on the pullbacks of some space-time differential four-forms. Solutions to our equations are shown to describe all the known giant and dual-giant gravitons in AdS_5 X S^5. We then argue that the configuration spaces of dual-giants can be mapped to non-compact hyperbolic versions of complex projective spaces, in contrast with the giants, whose configuration spaces have been mapped to complex projective spaces. We quantize the configuration space of the 1/8-BPS dual-giants with two angular momenta in AdS_5 and one angular momentum in S^5 and find agreement with the partition function in the literature obtained both from counting appropriate 1/8-BPS configurations of giants and the boundary gauge theory considerations.Comment: 36 page

Gerstmann-Sträussler-Scheinker disease revisited: accumulation of covalently-linked multimers of internal prion protein fragments

Despite their phenotypic heterogeneity, most human prion diseases belong to two broadly defined groups: Creutzfeldt-Jakob disease (CJD) and Gerstmann-Sträussler-Scheinker disease (GSS). While the structural characteristics of the disease-related proteinase K-resistant prion protein (resPrPD) associated with the CJD group are fairly well established, many features of GSS-associated resPrPD are unclear. Electrophoretic profiles of resPrPD associated with GSS variants typically show 6-8 kDa bands corresponding to the internal PrP fragments as well as a variable number of higher molecular weight bands, the molecular nature of which has not been investigated. Here we have performed systematic studies of purified resPrPD species extracted from GSS cases with the A117V (GSSA117V) and F198S (GSSF198S) PrP gene mutations. The combined analysis based on epitope mapping, deglycosylation treatment and direct amino acid sequencing by mass spectrometry provided a conclusive evidence that high molecular weight resPrPD species seen in electrophoretic profiles represent covalently-linked multimers of the internal ~ 7 and ~ 8 kDa fragments. This finding reveals a mechanism of resPrPD aggregate formation that has not been previously established in prion diseases

Infertility in WNIN Obese Mutant Rats—Causes?

We are maintaining two obese mutant rat strains (WNIN/Ob and WNIN/GR-Ob) in our animal facility since 1997. These rat colonies are perpetuated by crossing heterozygous littermates, since the obese phenotypes of both genders turned out be infertile. The present study revealed the reasons for this infertility. The male obese rats, though appeared normal in terms of sperm count, sperm motility and testis histology, however found wanting in terms of libido. This appeared to be due to low circulating testosterone levels seen in these animals, which should also account for low testis and accessory gland weights seen in them. The females exhibited delayed puberty, in terms of days taken for opening of vagina, irregular oestrus cycles and had small ovaries and short and stumpy uterine horns. The FSH peak observed in control lean animals during oestrus stage of the sexual cycle and also the E2 peak of normal oestrus cycle was conspicuously absent in these animals. They also showed elevated levels of progesterone throughout the sexual cycle. Thus the infertility seen in these mutants could be attributed to their abnormal gonadosteroid levels and the resulting anatomical and physiological defects

Cervical radiculopathy: Incidence and treatment of 1,420 consecutive cases

Study DesignRetrospective case series.PurposeTo determine the incidence of cervical radiculopathy requiring operative intervention by level and to report on the methods of treatment.Overview of LiteratureCervical radiculopathy is a common cause of pain and can result in progressive neurological deficits. Although the pathology is well understood, the actual incidence of cervical radiculopathy at particular spinal levels ultimately requiring operative intervention is unknown.MethodsA large consecutive series of patients operated on by a single surgeon were retrospectively analyzed. The incidence of cervical radiculopathy at each level was defined for every patient. Procedures used for operative treatment were noted. Health related quality of life (HRQL) scores were collected both pre-operatively and postoperatively.ResultsThere were 1305 primary and 115 revision operations performed. The most common primary procedures performed were anterior cervical discectomy and fusion (ACDF, 50%) and anterior cervical corpectomy and fusion (ACCF, 28%). The most commonly affected levels were C6 (66%) and C7 (62%). Reasons for revision were pseudarthrosis (27%), clinical adjacent segment pathology (CASP, 63%), persistent radiculopathy (11%), and hardware-related (2.6%). The most common procedures performed in the revision group were posterior cervical decompression and fusion (PCDF, 42%) and ACDF (40%). The most commonly affected levels were C7 (43%) and C5 (30%). Among patients that had their index surgery at our institution, the revision rate was 6.4%. In both primary and revision cases there was a significant improvement in Neck Disability Index and visual analogue scale scores postoperatively. Postoperative HRQL scores in the revision cases were significantly worse than those in the primary cases (p <0.01).ConclusionsThis study provides the largest description of the incidence of cervical radiculopathy by level and operative outcomes in patients undergoing cervical decompression. The incidence of CASP was 4.2% in 3.3 years in this single institution series

A Regression Strategy for Analyzing Environmental Data Generated by Spatio- Temporal Processes

Abstract Highly complex spatio-temporal environmental data sets are becoming common in ecology because of the increasing use of large-scale simulation models and automated data collection devices. The spatial and temporal dimensions present real and difficult challenges for the interpretation of these data. A particularly difficult problem is that the relationship among variables can vary in dramatically in response to environmental variation; consequently, a single model may not provide adequate fit. The temporal dimension presents both opportunities for improved prediction because explanatory variables sometimes exert delayed effects on response variables, and problems because variables are often serially correlated. This article presents a regression strategy for accommodating these problems. The strategy is illustrated by a case study of simulated net primary production (SNPP) that compares ocean-atmosphere indices to terrestrial climate variables as predictors of SNPP across the conterminousUnited States, and describes spatial variation in the relative importance of terrestrial climate variables towards predicting SNPP. We found that the relationship between ocean-atmosphere indices and SNPP varies substantially over the United States, and that there is evidence of a substantive link States . E only in the western portions of the United vidence of multi-year delays in the effect of terrestrial climate effects on SNPP were also found

Amazon rainforests green-up with sunlight in dry season

Metabolism and phenology of Amazon rainforests significantly influence global dynamics of climate, carbon and water, but remain poorly understood. We analyzed Amazon vegetation phenology at multiple scales with Moderate Resolution Imaging Spectroradiometer (MODIS) satellite measurements from 2000 to 2005. MODIS Enhanced Vegetation Index (EVI, an index of canopy photosynthetic capacity) increased by 25% with sunlight during the dry season across Amazon forests, opposite to ecosystem model predictions that water limitation should cause dry season declines in forest canopy photosynthesis. In contrast to intact forests, areas converted to pasture showed dry-season declines in EVI-derived photosynthetic capacity, presumably because removal of deep-rooted forest trees reduced access to deep soil water. Local canopy photosynthesis measured from eddy flux towers in both a rainforest and forest conversion site confirm our interpretation of satellite data, and suggest that basin-wide carbon fluxes can be constrained by integrating remote sensing and local flux measurements

Changes in growing season duration and productivity of northern vegetation inferred from long-term remote sensing data

Monitoring and understanding climate-induced changes in the boreal and arctic vegetation is critical to aid in prognosticating their future. Weused a 33 year (1982-2014) long record of satellite observations to robustly assess changes in metrics of growing season (onset: SOS, end: EOS and length: LOS) and seasonal total gross primary productivity. Particular attention was paid to evaluating the accuracy of these metrics by comparing them to multiple independent direct and indirect growing season and productivity measures. These comparisons reveal that the derived metrics capture the spatio-temporal variations and trends with acceptable significance level (generally p < 0.05). We find that LOS has lengthened by 2.60 d dec(-1) (p < 0.05) due to an earlier onset of SOS (-1.61 d dec(-1), p < 0.05) and a delayed EOS (0.67 d dec(-1), p < 0.1) at the circumpolar scale over the past three decades. Relatively greater rates of changes in growing season were observed in Eurasia (EA) and in boreal regions than in North America (NA) and the arctic regions. However, this tendency of earlier SOS and delayed EOS was prominent only during the earlier part of the data record (1982-1999). During the later part (2000-2014), this tendency was reversed, i.e. delayed SOS and earlier EOS. As for seasonal total productivity, we find that 42.0% of northern vegetation shows a statistically significant (p < 0.1) greening trend over the last three decades. This greening translates to a 20.9% gain in productivity since 1982. In contrast, only 2.5% of northern vegetation shows browning, or a 1.2% loss of productivity. These trends in productivity were continuous through the period of record, unlike changes in growing season metrics. Similarly, we find relatively greater increasing rates of productivity in EA and in arctic regions than in NA and the boreal regions. These results highlight spatially and temporally varying vegetation dynamics and are reflective of biome-specific responses of northern vegetation during last three decades