This paper reports results of a qualitative study of sixteen students enrolled in a second year organic chemistry course for chemistry and chemical engineering majors. The focus of the study was student use of the arrow-pushing formalism that plays a central role in both the teaching and practice of organic chemistry. The goal of the study was to probe how students made sense of the arrow-pushi...

In this article we propose a calculus of qualitative geographic coordinates which allows reasoning about cardinal directions on grid-based reference systems in maps. Grids in maps can be considered as absolute reference systems. The analysis reveals that the basic information coded in these reference systems is ordering information. Therefore, no metric information is required. We show that it ...

It is well known that an equilibrium in the Arrow-Debreu model may fail to exist if a very restrictive condition called the survival assumption is not satisfied. We study two approaches that allow for the relaxation of this condition. Danilov and Sotskov (1990), and Florig (2001) developed a concept of a generalized equilibrium based on a notion of hierarchic prices. Marakulin (1990) proposed a...

In this paper we study the introduction of new assets which are oftenly observed to be de…ned in expected values rather than state by state, called the Arrow-Lind-Malinvaud (ALM) assets. We demonstrate that individual default emerges naturally in an economy where such ALM assets are introduced without completing all contingency markets. We further provide conditions under which individual defau...

The objective of this paper is to adopt a general equilibrium model and determine the socially e¢ cient discount factor, risk free rate and discount rate when there are heterogeneous anticipations about the growth of the economy as well as heterogeneous time preference rates. Among others we tackle the following questions. Is the socially e¢ cient discount factor an arithmetic average of the in...

Visual attention can be automatically re-oriented by another person's non-predictive gaze as well as by symbolic arrow cues. We investigated whether the shifts of attention triggered by biologically relevant gaze cues and biologically non-relevant arrow cues rely on the same neural systems by comparing the effects of gaze-cued and arrow-cued orienting on blood oxygenation level-dependent (BOLD)...

An 84-year-old Japanese man presented with abdominal fullness and anorexia in September 2006. Computed tomography demonstrated extension of the stomach and the duodenum with a thickened wall. It showed marked dilatation of the main pancreatic duct (MPD) (A; arrowhead) and fistulization into the stomach (A; arrow) and the duodenum (B; arrow). Endoscopic examination demonstrated the skip ulcerati...

images of VPM-PET (left), Ktrans from ETM (middle), and EFPM (right). Choroid Plexus (thick arrow) and pituitary gland (arrow heads) are clearly depicted. The GCV shows high Ktrans on the maps of ETM, rendered with red color, but not EFPM. Note that GCV and other large vessels were not found on the PET image render blue representing lowest intensity. Figure 2. Axial (1st row) and sagittal (2nd ...

The main purpose of the paper is to show that the process of household formation in a competitive market does not necessarily lead to outcomes that are efficient at the economy level, even assuming that members of each household take efficient collective consumption decisions. To this end, we consider a generalization of the Arrow-Debreu exchange economy model in which endogenous household form...