Foraging as an evidence accumulation process

A canonical foraging task is the patch-leaving problem, in which a forager must decide to leave a current resource in search for another. Theoretical work has derived optimal strategies for when to leave a patch, and experiments have tested for conditions where animals do or do not follow an optimal strategy. Nevertheless, models of patch-leaving decisions do not consider the imperfect and noisy sampling process through which an animal gathers information, and how this process is constrained by neurobiological mechanisms. In this theoretical study, we formulate an evidence accumulation model of patch-leaving decisions where the animal averages over noisy measurements to estimate the state of the current patch and the overall environment. Evidence accumulation models belong to the class of drift diffusion processes and have been used to model decision making in different contexts. We solve the model for conditions where foraging decisions are optimal and equivalent to the marginal value theorem, and perform simulations to analyze deviations from optimal when these conditions are not met. By adjusting the drift rate and decision threshold, the model can represent different strategies, for example an increment-decrement or counting strategy. These strategies yield identical decisions in the limiting case but differ in how patch residence times adapt when the foraging environment is uncertain. To account for sub-optimal decisions, we introduce an energy-dependent utility function that predicts longer than optimal patch residence times when food is plentiful. Our model provides a quantitative connection between ecological models of foraging behavior and evidence accumulation models of decision making. Moreover, it provides a theoretical framework for potential experiments which seek to identify neural circuits underlying patch leaving decisions

Management of Noncatastrophic Internal Carotid Artery Injury in Endoscopic Skull Base Surgery.

Arterial injuries are the most feared complication of endoscopic skull base surgery. During resection of the middle fossa component of a large ventral skull base chondrosarcoma, arterial bleeding was encountered near the right internal carotid artery (ICA). Durable hemostasis could not be achieved with packing and the patient was taken for an emergent angiogram that revealed a pseudoaneurysm of the proximal intradural ICA. Given the presence of good collateral flow through the anterior and posterior communicating arteries, the right ICA was sacrificed by coil embolization. The patient was taken back to the operating room for closure then transferred to the intensive care unit and maintained on vasopressors for five days to ensure adequate perfusion. The right ICA was coil embolized and the patient was taken back to the operating room for closure. The patient recovered without complication. Arterial injuries, although serious, are not always catastrophic. Critical steps are immediate recognition of bleeding, vascular imaging, and vessel sacrifice if necessary

An Examination of the Determinants and Contents of Corporate Voluntary Disclosure of Management\u27s Responsibilities For Financial Reporting

The Sarbanes-Oxley Act (S-O Act) of 2002 requires principal officers to certify under oath to the veracity of information contained in SEC filings and opine on the effectiveness of the internal control system. This study examines the determinants and contents of corporate voluntary disclosure of management\u27s responsibilities during the five-year period preceding the S-O Act. We predict that the voluntary disclosure of management\u27s responsibilities for financial information signals certain incentives and characteristics of the reporting firm that are relevant to financial statement users and regulators. Consistent with our predictions, our findings reveal significant differences between issuing and non-issuing firms as to the effectiveness of an individual firm\u27s internal control system, access to capital markets, audit committee characteristics, and ownership structure. An empirical analysis of the contents of these assertions also reveals different areas of emphasis and selectivity by management, which represents an informative link to existing disclosure mandates. The results of this study contribute to our knowledge of management\u27s motivations for voluntary disclosure and lend credence to the mandatory certification requirements and related disclosure reforms established in the post-Enron era

Market Revaluations of Foreign Listings’ Reconciliations to U.S. Financial Reporting GAAP

The Securities and Exchange Commission (SEC) requires foreign firms wishing to list their securities on the U.S. exchanges to convert their financial statements to U.S.-based generally accepted accounting principles (GAAP) in a reconciliation filing known as Form 20-F. This paper extends prior research analyzing the importance of the SEC requirement by examining the value relevance to U.S. capital markets of Form 20-F reconciliation information under two additional hypotheses related to: i) investors\u27 anticipation of the reconciliation, and ii) investors\u27 perception of foreign countries\u27 enforcement and reliability in applying local accounting rules. We argue that the information content of the Form 20-F reconciliation data is preempted (at least partially) on the date of foreign earnings announcements because of investor anticipation of these reconciliations. Therefore, only significant unanticipated reconciliations exhibit value relevance on the date of filing. In addition, investor perception of the reliability of the reconciliations and the degree of confidence in foreign authorities enforcing local GAAP also affect the value relevance of the reconciliation data. We hypothesize that reconciliations made by firms from countries with mature and developed capital markets should be more value relevant to U.S. investors. Our results show that both unexpected foreign earnings and anticipated reconciliations to U.S. GAAP are significantly associated with unexpected market returns during the week of earnings announcements. The region of the foreign country is also significantly associated with market returns. However, unexpected reconciliations are not significantly associated with unexpected market returns during the week of Form 20-F filing

Gesture based Human Computer Interaction for Athletic Training

The invention of depth sensors for mobile devices, has led to availability of relatively inexpensive high-resolution depth and visual (RGB) sensing for a wide range of applications. The complementary nature of the depth and visual information opens up new opportunities to solve fundamental problems in object and activity recognition, people tracking, 3D mapping and localization, etc. One of the most interesting challenges that can be tackled by using these sensors is tracking the body movements of athletes and providing natural interaction as a result. In this study depth sensors and gesture recognition tools will be used to analyze the position and angle of an athlete’s body parts thought out an exercise. The goal is to assess the training performance of an athlete and decrease injury risk by giving warnings when the trainer is performing a high risk activity

Organic−Inorganic Nanocomposites via Directly Grafting Conjugated Polymers onto Quantum Dots

Nanocomposites of poly(3-hexylthiophene)−cadmium selenide (P3HT−CdSe) were synthesized by directly grafting vinyl-terminated P3HT onto [(4-bromophenyl)methyl]dioctylphosphine oxide (DOPO-Br)-functionalized CdSe quantum dot (QD) surfaces via a mild palladium-catalyzed Heck coupling, thereby dispensing with the need for ligand exchange chemistry. The resulting P3HT−CdSe nanocomposites possess a well-defined interface, thus significantly promoting the dispersion of CdSe within the P3HT matrix and facilitating the electronic interaction between these two components. The photophysical properties of nanocomposites were found to differ from the conventional composites in which P3HT and CdSe QDs were physically mixed. Solid-state emission spectra of nanocomposites suggested the charge transfer from P3HT to CdSe QDs, while the energy transfer from 3.5 nm CdSe QD to P3HT was implicated in the P3HT/CdSe composites. A faster decay in lifetime further confirmed the occurrence of charge transfer in P3HT−CdSe nanocomposites

Targets for the MalI repressor at the divergent Escherichia coliK-12malX-malI promoters

Random mutagenesis has been used to identify the target DNA sites for the MalI repressor at the divergent Escherichia coli K-12 malX-malI promoters. The malX promoter is repressed by MalI binding to a DNA site located from position -24 to position -9, upstream of the malX promoter transcript start. The malI promoter is repressed by MalI binding from position +3 to position +18, downstream of the malI transcript start. MalI binding at the malI promoter target is not required for repression of the malX promoter. Similarly, MalI binding at the malX promoter target is not required for repression of the malI. Although the malX and malI promoters are regulated by a single DNA site for cyclic AMP receptor protein, they function independently and each is repressed by MalI binding to a different independent operator site

On the origin of tropospheric ozone and NOx over the tropical South Pacific

The budgets of ozone and nitrogen oxides (NOx = NO + NO2) in the tropical South Pacific troposphere are analyzed by photochemical point modeling of aircraft observations at 0-12 km altitude from the Pacific Exploratory Mission-Tropics A campaign flown in September-October 1996. The model reproduces the observed NO2/NO concentration ratio to within 30% and has similar success in simulating observed concentrations of peroxides (H2O2, CH3OOH), lending confidence in its use to investigate ozone chemistry. It is found that chemical production of ozone balances only half of chemical loss in the tropospheric column over the tropical South Pacific. The net loss is 1.8 x 1011 molecules cm-2 s-1. The missing source of ozone is matched by westerly transport of continental pollution into the region. Independent analysis of the regional ozone budget with a global three-dimensional model corroborates the results from the point model and reveals the importance of biomass burning emissions in South America and Africa for the ozone budget over the tropical South Pacific. In this model, biomass burning increases average ozone concentrations by 7-8 ppbv throughout the troposphere. The NOx responsible for ozone production within the South Pacific troposphere below 4 km can be largely explained by decomposition of peroxyacetylnitrate (PAN) transported into the region with biomass burning pollution at higher altitudes. Copyright 1999 by the American Geophysical Union

Carleson measures for Hilbert spaces of analytic functions on the complex half-plane

The notion of a Carleson measure was introduced by Lennart Carleson in his proof of the Corona Theorem for H∞(D). In this paper we will define it for certain type of reproducing kernel Hilbert spaces of analytic functions of the complex half-plane, C+, which will include Hardy, Bergman and Dirichlet spaces. We will obtain several necessary or sufficient conditions for a positive Borel measure to be Carleson by preforming tests on reproducing kernels, weighted Bergman kernels, and studying the tree model obtained from a decomposition of the complex half-plane. The Dirichlet space will be investigated in detail as a special case. Finally, we will present a control theory application of Carleson measures in determining admissibility of controls in well-posed linear evolution equations