Gaussian Process Conditional Copulas with Applications to Financial Time Series

The estimation of dependencies between multiple variables is a central problem in the analysis of financial time series. A common approach is to express these dependencies in terms of a copula function. Typically the copula function is assumed to be constant but this may be inaccurate when there are covariates that could have a large influence on the dependence structure of the data. To account for this, a Bayesian framework for the estimation of conditional copulas is proposed. In this framework the parameters of a copula are non-linearly related to some arbitrary conditioning variables. We evaluate the ability of our method to predict time-varying dependencies on several equities and currencies and observe consistent performance gains compared to static copula models and other time-varying copula methods

Effect of Planting Dates of No-Till and Conventional Corn on Soils with Restricted Drainage

No-till corn is best adapted to well drained soils. It is on these soils that no-till has been most successful and the practice most widely accepted. On soils that are moderately well to somewhat poorly drained, no-till corn can also be successful but more management is required. Three areas which require more attention are weed control, nitrogen management and planting. It has long been recognized that no-tilling results in cooler soil temperatures which can delay and reduce seed germination and seedling emergence. Additional research also indicates that diseases which attack the corn seedling in the emergence stage are more prevalent in no-till stands. These diseases are most active when the soil is both wet and cold, thus causing an already slowly growing seedling greater potential stress. It is presently recommended that no-till corn producers delay the start of planting four to five days on well drained soils to allow these cooler soils to warm sufficiently

Presence Of A Congenitally Bicuspid Aortic Valve Among Patients Having Combined Mitral And Aortic Valve Replacement

Although bicuspid aortic valve occurs in an estimated 1% of adults and mitral valve prolapse in an estimated 5% of adults, occurrence of the 2 in the same patient is infrequent. During examination of operatively excised aortic and mitral valves because of dysfunction (stenosis and/or regurgitation), we encountered 16 patients who had congenitally bicuspid aortic valves associated with various types of dysfunctioning mitral valves. Eleven of the 16 patients had aortic stenosis (AS): 5 of them also had mitral stenosis, of rheumatic origin in 4 and secondary to mitral annular calcium in 1; the other 6 with aortic stenosis had pure mitral regurgitation (MR) secondary to mitral valve prolapse in 3, to ischemia in 2, and to unclear origin in 1. Of the 5 patients with pure aortic regurgitation, each also had pure mitral regurgitation: in 1 secondary to mitral valve prolapse and in 4 secondary to infective endocarditis. In conclusion, various types of mitral dysfunction severe enough to warrant mitral valve replacement occur in patients with bicuspid aortic valves. A proper search for mitral valve dysfunction in patients with bicuspid aortic valves appears warranted. (C) 2012 Elsevier Inc. All rights reserved. (Am J Cardiol 2012;109:263-271)Integrative Biolog

Effect Of Coronary Bypass And Valve Structure On Outcome In Isolated Valve Replacement For Aortic Stenosis

Reports differ regarding the effect of concomitant coronary artery bypass grafting (CABG) in patients who undergo aortic valve replacement (AVR) for aortic stenosis (AS), and no reports have described the effect of aortic valve structure in patients who undergo AVR for AS. A total of 871 patients aged 24 to 94 years (mean 70) whose AVR for AS was their first cardiac operation, with or without first concomitant CABG, were included. Patients who underwent mitral valve procedures were excluded. In comparison with the 443 patients (51%) who did not undergo CABG, the 428 (49%) who underwent concomitant CABG were significantly older, were more often male, had lower transvalvular peak systolic pressure gradients and larger valve areas, had lower frequencies of congenitally malformed aortic valves, had lighter valves by weight, had higher frequencies of systemic hypertension, and had longer stays in the hospital after AVR. Early and late (to 10 years) mortality were similar by propensity-adjusted analysis in patients who did and did not undergo concomitant CABG. Congenitally unicuspid or bicuspid valves occurred in approximately 90% of those aged 21 to 50, in nearly 70% in those aged 51 to 70 years, and in just over 30% in those aged 71 to 95 years. Unadjusted and adjusted survival was significantly higher in patients with unicuspid or bicuspid valves compared to those with tricuspid valves. In conclusion, although concomitant CABG had no effect on the adjusted probability of survival, the type of aortic valve (unicuspid or bicuspid vs tricuspid) significantly affected the unadjusted and adjusted probability of survival. (C) 2012 Elsevier Inc. All rights reserved. (Am J Cardiol 2012;109:1334-1340)Statistic

One-Shot Learning in Discriminative Neural Networks

We consider the task of one-shot learning of visual categories. In this paper we explore a Bayesian procedure for updating a pretrained convnet to classify a novel image category for which data is limited. We decompose this convnet into a fixed feature extractor and softmax classifier. We assume that the target weights for the new task come from the same distribution as the pretrained softmax weights, which we model as a multivariate Gaussian. By using this as a prior for the new weights, we demonstrate competitive performance with state-of-the-art methods whilst also being consistent with 'normal' methods for training deep networks on large data

Too many firms ignore their abusive boss problem

Some think that abuse and employee fear and silence are recipes for success, argue Christian Kiewitz, Simon Lloyd D. Restubog, Mindy Shoss, Patrick Raymund James M. Garcia and Robert L. Tan

Suffering in Silence: Investigating the Role of Fear in the Relationship Between Abusive Supervision and Defensive Silence

Drawing from an approach-avoidance perspective, we examine the relationships between subordinates’ perceptions of abusive supervision, fear, defensive silence, and ultimately abusive supervision at a later time point. We also account for the effects of subordinates’ assertiveness and individual perceptions of a climate of fear on these predicted mediated relationships. We test this moderated mediation model with data from three studies involving different sources collected across various measurement periods. Results corroborated our predictions by showing (a) a significant association between abusive supervision and subordinates’ fear, (b) second-stage moderation effects of subordinates’ assertiveness and their individual perceptions of a climate of fear in the abusive supervision–fear– defensive silence relationship (with lower assertiveness and higher levels of climate-of-fear perceptions exacerbating the detrimental effects of fear resulting from abusive supervision), and (c) first-stage moderation effects of subordinates’ assertiveness and climate-of-fear perceptions in a model linking fear to defensive silence and abusive supervision at a later time. Theoretical and practical implications are discussed

Hypothenar hammer syndrome: Proposed etiology

AbstractPurpose: Finger ischemia caused by embolic occlusion of digital arteries originating from the palmar ulnar artery in a person repetitively striking objects with the heel of the hand has been termed hypothenar hammer syndrome (HHS). Previous reports have attributed the arterial pathology to traumatic injury to normal vessels. A large experience leads us to hypothesize that HHS results from trauma to intrinsically abnormal arteries. Methods: We reviewed the arteriography, histology, and clinical outcome of all patients treated for HHS in a university clinical research center study of hand ischemia, which prospectively enrolled more than 1300 subjects from 1971 to 1998. Results: Twenty-one men had HHS. All had occupational (mechanic, carpenter, etc) or avocational (woodworker) exposure to repetitive palmar trauma. All patients underwent upper-extremity and hand arteriography, unilateral in eight patients (38%) and bilateral in 13 patients (62%). By means of arteriogram, multiple digital artery occlusions were shown in the symptomatic hand, with either segmental ulnar artery occlusion in the palm or characteristic “corkscrew” elongation, with alternating stenoses and ectasia. Similar changes in the contralateral asymptomatic (and less traumatized) hand were shown by means of 12 of 13 bilateral arteriograms (92%). Twenty-one operations, consisting of segmental ulnar artery excision in the palm and vein grafting, were performed on 19 patients. Histology was compatible with fibromuscular dysplasia with superimposed trauma. Patency of arterial repairs at 2 years was 84%. One patient (5%) required amputative debridement of necrotic finger tips. No other tissue loss occurred. There have been no recurrences of ischemia in patients with patent bypass grafts. Conclusion: To our knowledge, this is the largest reported group of HHS patients. The characteristic angiographic appearance, histologic findings, and striking incidence of bilateral abnormalities in patients with unilateral symptoms lead us to conclude that HHS occurs when persons with preexisting palmar ulnar artery fibrodysplasia experience repetitive palmar trauma. This revised theory for the etiology of HHS explains why HHS does not develop in most patients with repetitive palmar trauma. (J Vasc Surg 2000;31:104-13.

UA3/3/1 Analysis of the Demand for Married Student Housing at WKU, 1966-1967

The purpose of this study is to bring forth relevant information needed to determine the feasibility of an investment project for a married student housing complex on the campus of Western Kentucky University. Only the demand side of the market is analyzed; a potential investor will have the construction and land costs for such an enterprise at his disposal. With the information presented in this study it is hoped that a decision to construct a housing complex will be forthcoming. The study group attempted to present information that will allow a potential investor to make an intelligent decision as to the profitability of the investment. It is hoped that the critical questions concerning the investment have been answered by this study. The time period in which the study was carried out was January, 1967 to June, 1967, i.e., the second semester of the 1966-67 school year. The information presented was obtained from a single sample of the married population. Seventy married family units (8.4 percent of the population) were stratified according to class standing (Freshman, Sophomore, Junior, Senior, and Graduate) and then picked randomly within the class stratifications. A more desirable method would have been a sequential sampling method, but the time and expense of the method did not allow its use. Future studies can be carried out in order to substantiate the data presented at this time. The estimated size of the investment would seem to warrant at least one more comprehensive examination of the market in order that a more exact market character can be determined. The study group contacted state institutions that have married housing units in order to see if any useful information could be obtained from their experience in the determination of market character and size of their married students. None of the schools contacted had conducted a market study prior to the construction of such a housing unit. Discovering this factor did not disturb the study group. It was assumed that the market character at the various educational institutions would be significantly different with reference to income, rent, family size, etc., that no useful comparison could be made. The reason for this assumption rests on the fact that the educational institutions differ in such things as type and size of the graduate program and community size and industrial development. These factors have a direct influence on the family unit\u27s income, numbers, and the rate of growth of the married student body. The purpose of contacting the various institutions was to examine the methodology used in the study of the market for married student housing

Potential Drivers of Mid-Infrared Variability in Young Stars: Testing Physical Models with Multiepoch Near-Infrared Spectra of YSOs in ρ Oph

Recent studies have identified several young stellar objects (YSOs) which exhibit significant mid-infrared (mid-IR) variability. A wide range of physical mechanisms may be responsible for these variations, including changes in a YSO’s accretion rate or in the extinction or emission from the inner disk. We have obtained and analyzed multiepoch near-infrared (NIR) spectra for five actively accreting YSOs in the ρ Oph star-forming region along with contemporaneous mid-IR light curves obtained as part of the YSOVAR Spitzer/IRAC survey. Four of the five YSOs exhibit mid-IR light curves with modest (∼0.2–0.4 mag) but statistically significant variations over our 40-day observation window. Measuring the strengths of prominent photospheric absorption lines and accretion sensitive H I and He I lines in each NIR spectrum, we derive estimates of each YSO’s spectral type, effective temperature (T_eff), and H-band extinction (A_H), and analyze the time evolution of their NIR veiling (r_H and r_K) and mass accretion rates (Ṁ_acc). Defining a YSO’s evolutionary stage such that heavily veiled, high accretion rate objects are less evolved than those with lower levels of veiling and ongoing accretion, we infer that GY 314 is the most evolved YSO in our sample, with GY 308 and GY 292 at progressively earlier evolutionary stages. Leveraging our multiepoch, multiwavelength dataset, we detect significant variations in mass accretion rates over timescales of days to weeks, but find that extinction levels in these YSOs remain relatively constant. We find no correlation between these YSO mid-IR light curves and time-resolved veiling or mass accretion rates, such that we are unable to link their mid-IR variability with physical processes localized near the inner edge of the circumstellar disk or within regions which are directly responsive to mass accretion. We do find, however, that redshifted He I λ10830 emission, where present in our spectra, shows both quantitative and qualitative temporal correlations with accretion-sensitive H I emission lines. Blueshifted He I absorption, on the other hand, does not demonstrate a similar correlation, although the time-averaged strength of this blueshifted absorption is correlated with the time-averaged accretion rate in our sample of YSOs