Chordal Graphs are Fully Orientable

Suppose that D is an acyclic orientation of a graph G. An arc of D is called dependent if its reversal creates a directed cycle. Let m and M denote the minimum and the maximum of the number of dependent arcs over all acyclic orientations of G. We call G fully orientable if G has an acyclic orientation with exactly d dependent arcs for every d satisfying m <= d <= M. A graph G is called chordal if every cycle in G of length at least four has a chord. We show that all chordal graphs are fully orientable.Comment: 11 pages, 1 figure, accepted by Ars Combinatoria (March 26, 2010

Estimating Property Values by Replication: An Alternative to the Traditional Grid and Regression Methods

This paper proposes and develops a replication method for estimating property values, in which optimal weights of comparable property attributes that best duplicate the subject property are determined. In a setting where the number of comparables is large compared to the number of attributes, replication weakly outperforms traditional general least squares regression by making use of potential correlations in the error structure. A similar result obtains in comparison to the grid method, which may suffer from subjective price adjustment factors. The replication method suggests using a large sample regression analysis to obtain the functional form of the error variance-covariance, and then replicating the subject with a smaller, attribute-close set of comparable properties.

Determining the physical conditions of extremely young Class 0 circumbinary disk around VLA1623A

We present detailed analysis of high-resolution C18O (2-1), SO (88-77), CO (3-2) and DCO+ (3-2) data obtained by the Atacama Large Millimeter/sub-millimeter Array (ALMA) towards a Class 0 Keplerian circumbinary disk around VLA1623A, which represents one of the most complete analysis towards a Class 0 source. From the dendrogram analysis, we identified several accretion flows feeding the circumbinary disk in a highly anisotropic manner. Stream-like SO emission around the circumbinary disk reveals the complicated shocks caused by the interactions between the disk, accretion flows and outflows. A wall-like structure is discovered south of VLA1623B. The discovery of two outflow cavity walls at the same position traveling at different velocities suggests the two outflows from both VLA1623A and VLA1623B overlays on top of each other in the plane of sky. Our detailed flat and flared disk modeling shows that Cycle 2 C18O J = 2-1 data is inconsistent with the combined binary mass of 0.2 Msun as suggested by early Cycle 0 studies. The combined binary mass for VLA1623A should be modified to 0.3 ~ 0.5 Msun.Comment: 26 pages, 20 figures, accepted by ApJ 2020.2.2

Survey of Telehealth Adoption by Neuro-ophthalmologists During the COVID-19 Pandemic: Benefits, Barriers and Utility

Background: During the COVID-19 pandemic tele-health modalities have come to prominence as a strategy for providing patient care when in-person care provision opportunities are limited. The degree of adoption by neuro-ophthalmologists has not been quantified. Methods: Telehealth utilization pre- and peri-COVID-19 was surveyed among practicing neuro-ophthalmologists in and outside the US using an on-line platform. Demographics, perceived benefits, barriers, and utility for different neuro-ophthalmic conditions were collected. Data collection occurred over a 2-week period in May, 2020. Results: 208 practicing neuro-ophthalmologists (81.3% US, 50.2% female, age range 65, mode 35-44 years) participated in the survey. Utilization of all telehealth modalities increased from pre-COVID to peri-COVID (video visit 3.9% to 68.3%, p<0.0005, remote interpretation of testing 26.7% to 32.2%, p=0.09, on-line second opinion 7.9% to 15.3%, p=0.001, interprofessional e-consult 4.4% to 18.7%, p<0.0005, McNemar). The majority selected access, continuity, and patient efficiency of care as benefits and data quality as a barrier. Telehealth was felt to be most helpful for conditions relying on history, external exam, and previously collected ancillary testing and not helpful for conditions requiring funduscopic exam. Conclusions: Telehealth modality usage by neuro-ophthalmologists increased during the COVID-19 pandemic. Identified benefits have relevance both during and beyond COVID-19. Further work is needed to address barriers in their current and future states to maintain these modalities as viable care delivery options

The Announcement Effect of Monetary Policy on the Corporate Bond Markets

This study investigates the impact of the central bank’s monetary policy announcements on the perceptions of yield spread in corporate bond markets under the event of extreme events. These results highlight that the coronavirus pandemic has caused a market panic in the global economy. This caused investors to withdraw their money from bond markets, which caused a liquidity crisis in bond markets. The Fed announcements caused statistically significant tightening on US and global investment grades and high-yield corporate bond spreads. The Euro investment grade and high-yield corporate bond spread narrowed when the Fed took additional actions to provide more funds and expanded the buying scope to support market liquidity. These results suggest that forward guidance that emphasizes the Fed’s monetary policy causes stronger information effects

Cyclin-dependent Kinase 5 (Cdk5)-dependent Phosphorylation of p70 Ribosomal S6 Kinase 1 (S6K) Is Required for Dendritic Spine Morphogenesis.

The maturation and maintenance of dendritic spines depends on neuronal activity and protein synthesis. One potential mechanism involves mammalian target of rapamycin, which promotes protein synthesis through phosphorylation of eIF4E-binding protein and p70 ribosomal S6 kinase 1 (S6K). Upon extracellular stimulation, mammalian target of rapamycin phosphorylates S6K at Thr-389. S6K also undergoes phosphorylation at other sites, including four serine residues in the autoinhibitory domain. Despite extensive biochemical studies, the importance of phosphorylation in the autoinhibitory domain in S6K function remains unresolved, and its role has not been explored in the cellular context. Here we demonstrated that S6K in neuron was phosphorylated at Ser-411 within the autoinhibitory domain by cyclin-dependent kinase 5. Ser-411 phosphorylation was regulated by neuronal activity and brain-derived neurotrophic factor (BDNF). Knockdown of S6K in hippocampal neurons by RNAi led to loss of dendritic spines, an effect that mimics neuronal activity blockade by tetrodotoxin. Notably, coexpression of wild type S6K, but not the phospho-deficient S411A mutant, could rescue the spine defects. These findings reveal the importance of cyclin-dependent kinase 5-mediated phosphorylation of S6K at Ser-411 in spine morphogenesis driven by BDNF and neuronal activity.published_or_final_versio