Victor Gonzalez | UNAM Universidad Nacional Autónoma de México (original) (raw)

Papers by Victor Gonzalez

Research paper thumbnail of Managing Currents of Work: Multi-tasking Among Multiple Collaborations

ECSCW 2005, 2005

This research reports on a study of the interplay between multi-tasking and collaborative work. W... more This research reports on a study of the interplay between multi-tasking and collaborative work. We conducted an ethnographic study in two different companies where we observed the experiences and practices of thirty-six information workers. We observed that people continually switch between different collaborative contexts throughout their day. We refer to activities that are thematically connected as working spheres. We discovered that to multi-task and cope with the resulting fragmentation of their work, individuals constantly renew overviews of their working spheres, they strategize how to manage transitions between contexts and they maintain flexible foci among their different working spheres. We argue that system design to support collaborative work should include the notion that people are involved in multiple collaborations with contexts that change continually. System design must take into account these continual changes: people switch between local and global perspectives of their working spheres, have varying states of awareness of their different working spheres, and are continually managing transitions between contexts due to interruptions.

Research paper thumbnail of Context-Aware Mobile Communication in Hospitals

IEEE Computer, 2003

A collaborative handheld system extends the instant messaging paradigm by adding context-awarenes... more A collaborative handheld system extends the instant messaging paradigm by adding context-awareness to support the intensive and distributed nature of information management within a hospital setting.

Research paper thumbnail of Benefits of Information Visualization Systems for Administrative Data Analysts

International Conference on Information Visualisation, 2003

We report results from a study on the adoption of an information visualization system by administ... more We report results from a study on the adoption of an information visualization system by administrative data analysts. Despite the fact that the system was neither fully integrated with their current software tools nor with their existing data analysis practices, analysts identified a number of key benefits that visualization systems provide to their work. These benefits for the most part occurred when analysts went beyond their habitual and well-mastered data analysis routines and engaged in creative discovery processes. We analyze the conditions under which these benefits arose, to inform the design of visualization systems that can better assist the work of administrative data analysts.

Research paper thumbnail of Integrating context-aware public displays into a mobile hospital information system

IEEE Transactions on Information Technology in Biomedicine, 2004

Hospitals are convenient settings for deployment of ubiquitous computing technology. Not only are... more Hospitals are convenient settings for deployment of ubiquitous computing technology. Not only are they technologyrich environments, but their workers experience a high level of mobility resulting in information infrastructures with artifacts distributed throughout the premises. Hospital information systems (HISs) that provide access to electronic patient records are a step in the direction of providing accurate and timely information to hospital staff in support of adequate decision-making. This has motivated the introduction of mobile computing technology in hospitals based on designs which respond to their particular conditions and demands. Among those conditions is the fact that worker mobility does not exclude the need for having shared information artifacts at particular locations. In this paper, we extend a handheld-based mobile HIS with ubiquitous computing technology and describe how public displays are integrated with handheld and the services offered by these devices. Public displays become aware of the presence of physicians and nurses in their vicinity and adapt to provide users with personalized, relevant information. An agent-based architecture allows the integration of proactive components that offer information relevant to the case at hand, either from medical guidelines or previous similar cases.

Research paper thumbnail of Context-aware mobile communication in hospitals

IEEE Computer, 2003

A, collaborative handheld system extends the instant messaging paradigm by adding context-awarene... more A, collaborative handheld system extends the instant messaging paradigm by adding context-awareness to support the intensive and distributed nature of information management within a hospital setting.

Research paper thumbnail of Managing Currents of Work: Multi-tasking among Multiple Collaborations

European Conference on Computer Supported Cooperative Work, 2005

This research reports on a study of the interplay between multi-tasking and collaborative work. W... more This research reports on a study of the interplay between multi-tasking and collaborative work. We conducted an ethnographic study in two different companies where we observed the experiences and practices of thirty-six information workers. We observed that people continually switch between different collaborative contexts throughout their day. We refer to activities that are thematically connected as working spheres. We discovered that to multi-task and cope with the resulting fragmentation of their work, individuals constantly renew overviews of their working spheres, they strategize how to manage transitions between contexts and they maintain flexible foci among their different working spheres. We argue that system design to support collaborative work should include the notion that people are involved in multiple collaborations with contexts that change continually. System design must take into account these continual changes: people switch between local and global perspectives of their working spheres, have varying states of awareness of their different working spheres, and are continually managing transitions between contexts due to interruptions.

Research paper thumbnail of Spatial-temporal characterization of an urban environment using Twitter

2014 International Conference on Collaboration Technologies and Systems (CTS), 2014

This paper presents a study of the usage of Twitter within the context of urban activity. We retr... more This paper presents a study of the usage of Twitter within the context of urban activity. We retrieved a set of tweets submitted by users located in Mexico City. Tweets were labeled as either positive or negative mood using a sentiment analyzer implementation. By calculating the average mood, we were able to run a Mann-Withney's U test to evaluate differences in the calculated mood per day of week. We found that all days of the week had significantly different medians with Sunday being the most positive day and Thursday the most negative. Additionally, we study the location for the tweets as an indicator important events and landmarks around the city.

Research paper thumbnail of Constant, constant, multi-tasking craziness

Computer Human Interaction, 2004

Most current designs of information technology are based on the notion of supporting distinct tas... more Most current designs of information technology are based on the notion of supporting distinct tasks such as document production, email usage, and voice communication. In this paper we present empirical results that suggest that people organize their work in terms of much larger and thematically connected units of work. We present results of fieldwork observation of information workers in three different roles: analysts, software developers, and managers. We discovered that all of these types of workers experience a high level of discontinuity in the execution of their activities. People average about three minutes on a task and somewhat more than two minutes using any electronic tool or paper document before switching tasks. We introduce the concept of working spheres to explain the inherent way in which individuals conceptualize and organize their basic units of work. People worked in an average of ten different working spheres. Working spheres are also fragmented; people spend about 12 minutes in a working sphere before they switch to another. We argue that design of information technology needs to support people's continual switching between working spheres.

Research paper thumbnail of No task left behind?: examining the nature of fragmented work

Computer Human Interaction, 2005

We present data from detailed observation of 24 information workers that shows that they experien... more We present data from detailed observation of 24 information workers that shows that they experience work fragmentation as common practice. We consider that work fragmentation has two components: length of time spent in an activity, and frequency of interruptions. We examined work fragmentation along three dimensions: effect of collocation, type of interruption, and resumption of work. We found work to be highly fragmented: people average little time in working spheres before switching and 57% of their working spheres are interrupted. Collocated people work longer before switching but have more interruptions. Most internal interruptions are due to personal work whereas most external interruptions are due to central work. Though most interrupted work is resumed on the same day, more than two intervening activities occur before it is. We discuss implications for technology design: how our results can be used to support people to maintain continuity within a larger framework of their working spheres.

Research paper thumbnail of Geodetic and seismic constraints on some seismogenic zone processes in Costa Rica

Journal of Geophysical Research, 2004

Abstract[1] New seismic and geodetic data from Costa Rica provide insight into seismogenic zone p... more Abstract[1] New seismic and geodetic data from Costa Rica provide insight into seismogenic zone processes in Central America, where the Cocos and Caribbean plates converge. Seismic data are from combined land and ocean bottom deployments in the Nicoya peninsula in northern Costa Rica and near the Osa peninsula in southern Costa Rica. In Nicoya, inversion of GPS data suggests two locked patches centered at 14 ± 2 and 39 ± 6 km depth. Interplate microseismicity is concentrated in the more freely slipping intermediate zone, suggesting that small interseismic earthquakes may not accurately outline the updip limit of the seismogenic zone, the rupture zone for future large earthquakes, at least over the short (∼1 year) observation period. We also estimate northwest motion of a coastal “sliver block” at 8 ± 3 mm/yr, probably related to oblique convergence. In the Osa region to the south, convergence is orthogonal to the trench. Cocos-Caribbean relative motion is partitioned here, with ∼8 cm/yr on the Cocos-Panama block boundary (including a component of permanent shortening across the Fila Costeña fold and thrust belt) and ∼1 cm/yr on the Panama block–Caribbean boundary. The GPS data suggest that the Cocos plate–Panama block boundary is completely locked from ∼10–50 km depth. This large locked zone, as well as associated forearc and back-arc deformation, may be related to subduction of the shallow Cocos Ridge and/or younger lithosphere compared to Nicoya, with consequent higher coupling and compressive stress in the direction of plate convergence.

Research paper thumbnail of Fluid generation and pathways beneath an active compressional orogen, the New Zealand Southern Alps, inferred from magnetotelluric data

Journal of Geophysical Research, 2002

Abstract[1] Forty-one wideband magnetotelluric (MT) soundings were collected in a 150-km-long tra... more Abstract[1] Forty-one wideband magnetotelluric (MT) soundings were collected in a 150-km-long transect across the Southern Alps of the central South Island of New Zealand, an active compressional orogen. Decomposed MT impedance tensors, vertical magnetic field relations, and reconnaissance soundings at two locations off line imply an approximately two-dimensional geometry here with average regional geoelectric strike of ∼N40°E, similar to surface geologic trends. Two independent, two-dimensional inversion algorithms were applied to the MT data, and both imply a concave-upward (U-shaped), middle to lower crustal conductive zone beneath the west central portion of the island. The average conductivity of this zone in the strike direction appears to be much higher than that required across strike and may represent anisotropy or along-strike conductive strands narrower than the transverse magnetic (cross-strike) mode MT data can resolve. The deep crustal conductor under the Southern Alps is interpreted to represent mainly a volume of fluids arising from prograde metamorphism within a thickening crust. Fluid interconnection and electrical conduction are promoted by shear deformation. The conductor rises northwestward toward the trace of the Alpine Fault but attains a near-vertical configuration at a depth of ∼10 km and reaches close to the surface 5–10 km inland of the fault trace itself. The transition to vertical orientation at this depth is interpreted to occur as fluids ascend across the brittle-ductile transition in uplifting schist and approach the surface through induced hydrofractures. The high-grade schist becomes resistive after depletion of fluids and continues to extrude toward the Alpine Fault. Shallow extensions of the deep high conductivity are coincident with modern, hydrothermal veining and gold mineralization interpreted to be of deep crustal provenance. To the southeast, high conductivity also reaches the surface coincident with a major back thrust fault zone of the doubly vergent Southern Alps orogen, which also exhibits evidence for expulsion of high-temperature fluids. The higher conductivity inferred along strike (possible anisotropy) could reflect more efficient fluid interconnection in this higher-strain direction, as well as possible contributions by sheared, fluid-deposited graphite. Conductivity of the uppermost mantle of the South Island is low, consistent with advection of cold mantle lithosphere into the underlying asthenosphere as suggested by P wave delay studies.

Research paper thumbnail of The March 25, 1990 (M w =7.0, M L =6.8), earthquake at the entrance of the Nicoya Gulf, Costa Rica: Its prior activity, foreshocks, aftershocks, and triggered seismicity

Journal of Geophysical Research, 1995

On March 25, 1990 a large earthquake (Mw=7.0, ML=6.8) occurred at the entrance of the Nicoya Gulf... more On March 25, 1990 a large earthquake (Mw=7.0, ML=6.8) occurred at the entrance of the Nicoya Gulf, Costa Rica, at 1322:55.6 UTC, producing considerable damage in central Costa Rica and generating much interest about whether or not the Nicoya seismic gap (Nishenko, 1989) had broken. The local country-wide seismographic network recorded 6 years of activity prior to this large earthquake, 16 hours of foreshocks, the mainshock, and its aftershocks. This network is operated jointly by the Costa Rica Volcanological and Seismological Observatory at the National University (OVSICORI-UNA), and the Charles F. Richter Seismological Laboratory at the University of California, Santa Cruz (CFRSL-UCSC). We obtained high resolution locations from this network and located the mainshock at 9ø38.5'N, 84ø55.6'W (depth is 20.0 km) and the largest foreshock (Mw=6.0, March 25, 1990, at 1316:05.8 UTC) at 9ø36.4'N, 84ø57.1'W (depth is 22.4 km). We find that the aftershock zone abuts the southeast boundary of the Nicoya seismic gap, suggesting that the seismic gap did not rupture. Since the installation of the local network in April 1984 to March 24, 1990, nearly 1900 earthquakes with magnitudes from 1.7 to 4.8 (318 with magnitude 3.0 or larger) have been located at the entrance of the Nicoya Gulf, one of the most active regions in Costa Rica. The March 25 earthquake occurred at the northwest edge of this region, where a sequence of foreshocks began 16 hours prior to the mainshock. The spatialtemporal distribution of aftershocks and directivity analysis of the mainshock rupture process using teleseismic records both indicate a southeast propagating rupture. The mainshock ruptured an asperity of approximately 600 km 2 of area, with this area expanding to 4000 km 2 after 7 days. We present evidence that suggests that the ruptured asperity is produced by the subduction of a seamount. Inversion of teleseismic broadband and long-period P and SH waves yields a thrust faulting mechanism with the shallow plane striking 292 ø, dipping 26 ø, and with a rake of 88 ø, in agreement with the subduction of the Cocos plate under the Caribbean plate. Local first motions for the largest foreshock and the mainshock agree with this solution. We also present evidence suggesting that the March 25, 1990, earthquake triggered and reactivated several seismic swarms in central Costa Rica and temporally decreased the activity in the epicentral area of the July 3, 1983 (Ms=6.2), P6rez Zeled6n earthquake. 1Observatorio Vulcano16gico Paper number 94JB03099. 0148-0227/95/94JB-03099505.00 seismic gaps" in the Circum-Pacific). On March 25, 1990, a large earthquake (Mb=6.3, MsZ=7.0 (Preliminary Determination of Epicenters (PDE)), Mw=7.0, ML=6.8) occurred at the entrance of the Nicoya Gulf, Costa Rica, at 1322:55.6 UTC, near this seismic gap. This earthquake produced considerable damage in central Costa Rica, was felt from southern Nicaragua to western Panama, and generated much interest about whether or not the Nicoya seismic gap had broken (see boundaries in map by Nishenko [1989]). Costa Rica, as part of Central America, is located on the western margin of the Caribbean plate (Figure 1). There, the Cocos plate subducts under the Caribbean plate along the Middle American Trench at a rate between 70 and 94 mrn/yr from Guatemala to southern Costa Rica respectively (computed from De Mets et al., [ 1990]). It is along this plate boundary, at the western coast of Costa Rica, where most of the recent large destructive earthquakes have occurred. Coupling between the Cocos and Caribbean plates changes along strike of the subduction zone in Costa Rica and correlates with the bathymetric characteristics of the subducted oceanic floor: smooth, rough, and rough-smooth ocean floors in northern, 20,345 20,346 PROTTI ET AL.: MARCH 25, 1990, COSTA RICA EARTHQUAKE Nicaragua 11 o 1916 North American Nic_oya 195 Rica 'Panama Nicoya Gulf 1991 Panama 1983 Cocos Plate Panama Block 87 o 86 ø 85 o 84 o 83 o 82 ø Aftershocks A' ee•e ß ß ß ß ß ß ß . % ß .0 11 * * ß ß ß tt ß ß t t ß ß ß ß . '**'** ß $ * ß ß ß ß '-' ß ß -.-.. ß %. '% ß ß ß ß ß ß ß ß ß ß ee e ß i © • ß e ee ß 20 40 60 80

Research paper thumbnail of Determinants of Debt Maturity Structure Across Firm Size

SSRN Electronic Journal, 2000

... JEL classification: G32 * Víctor M. González Méndez, Departamento de Administración de Empres... more ... JEL classification: G32 * Víctor M. González Méndez, Departamento de Administración de Empresas, Universidad de Oviedo. Avda. del Cristo s/n, 33071 Oviedo, ESPAÑA. Tel.: ++34 985102826; Fax: ++34 985103708; e-mail: vmendez@uniovi.es ...

Research paper thumbnail of Diversification, Size and Risk at Spanish Banks

SSRN Electronic Journal, 2000

Page 1. Diversification, Size and Risk at Spanish Banks Fernando Gascón and Víctor González (*) U... more Page 1. Diversification, Size and Risk at Spanish Banks Fernando Gascón and Víctor González (*) Universidad de Oviedo (*) Corresponding Author: Fernando Gascón Área de Economía Financiera Facultad de Económicas Universidad de Oviedo Avda. ...

Research paper thumbnail of Erratum: Sentiment Characterization of an Urban Environment via Twitter

Lecture Notes in Computer Science, 2013

Research paper thumbnail of No task left behind

Computer Human Interaction, 2005

We present data from detailed observation of 24 information workers that shows that they experien... more We present data from detailed observation of 24 information workers that shows that they experience work fragmentation as common practice. We consider that work fragmentation has two components: length of time spent in an activity, and frequency of interruptions. We examined work fragmentation along three dimensions: effect of collocation, type of interruption, and resumption of work. We found work to be highly fragmented: people average little time in working spheres before switching and 57% of their working spheres are interrupted. Collocated people work longer before switching but have more interruptions. Most internal interruptions are due to personal work whereas most external interruptions are due to central work. Though most interrupted work is resumed on the same day, more than two intervening activities occur before it is. We discuss implications for technology design: how our results can be used to support people to maintain continuity within a larger framework of their working spheres.

Research paper thumbnail of A Workplace Study of the Adoption of Information Visualization Systems

This paper reports an ongoing longitudinal study of the adoption of information visualization sys... more This paper reports an ongoing longitudinal study of the adoption of information visualization systems by administrative data analysts. Participants were initially excited about the anticipated potential of visual data analysis for their work, but gradually discovered difficulties that eventually precluded a true integration of the visualization system into their daily work practices. These difficulties are unrelated to the specific visualization system used. We conclude that data analysts can take much better advantage of the benefits of information visualization systems when these systems are redesigned to be complementary products of current data analysis and workflow systems, rather than being stand-alone products as is currently the case. Our study offers some insights about how this complementarity can be achieved.

Research paper thumbnail of Do Four Eyes See Better than Two? Collaborative Versus Individual Discovery in Data Visualization Systems

International Conference on Information Visualisation, 2002

We present an empirical study investigating collaborative and individual decision-making about da... more We present an empirical study investigating collaborative and individual decision-making about data using two different information visualization systems. Based on previous research, one system is considered more transparent than the other in terms of visual representation and functionality. We found that people who worked in groups were more correct in their answers for objective questions, based on searching a large dataset. These results held for the more transparent system, but not the less transparent system. In a second task, groups were more accurate in their results for a free data discovery task. Again, these results held for the more transparent system only. Subjects using this system also produced results that were higher in complexity but judged lower in importance. Groups and individuals did not differ. We suggest that given the right visualization system, groups do better than individuals in finding more accurate results, but not necessarily increased or more meaningful results.

Research paper thumbnail of Stock repurchases with legal restrictions. Evidence from Spain

The European Journal of Finance, 2004

This paper analyses the consequences of legal restrictions on the volume of shares firms can repu... more This paper analyses the consequences of legal restrictions on the volume of shares firms can repurchase. Our results suggest that the imposition of a limit on the volume of common stock favours the use of open market repurchases (OMRs) compared to other methods of repurchase such as tender offer repurchases (TORs) and Dutch auctions (DAs). The positive share abnormal returns around both announcements of open market buybacks and sellbacks in the full sample suggest that they are basically used to change the ownership structure of the firm in a consistent way with the convergence of interest hypothesis. The positive abnormal stock returns around open market repurchases which are significantly different to the negative ones around sellbacks when there are no changes in ownership structure also indicates the existence of a signalling and free cash flow effects.

Research paper thumbnail of Influence of bank concentration and institutions on capital structure: New international evidence

Journal of Corporate Finance, 2008

This paper analyzes how bank market concentration and institutions affect capital structure in 39... more This paper analyzes how bank market concentration and institutions affect capital structure in 39 countries. Results for 12,049 firms over the period 1995-2004 indicate that firm leverage increases with bank concentration and the protection of creditor rights, but decreases with the protection of property rights. Our results also indicate that higher bank concentration substitutes for creditor protection and asset tangibility to reduce the agency cost of debt between shareholders and debtholders. Weak protection of property rights increases the agency cost of external funds, leading to the preferential use of internal funds proposed by the Pecking Order Theory. The validity of the Trade-Off Theory, however, increases in countries with better protection of property rights.

Research paper thumbnail of Managing Currents of Work: Multi-tasking Among Multiple Collaborations

ECSCW 2005, 2005

This research reports on a study of the interplay between multi-tasking and collaborative work. W... more This research reports on a study of the interplay between multi-tasking and collaborative work. We conducted an ethnographic study in two different companies where we observed the experiences and practices of thirty-six information workers. We observed that people continually switch between different collaborative contexts throughout their day. We refer to activities that are thematically connected as working spheres. We discovered that to multi-task and cope with the resulting fragmentation of their work, individuals constantly renew overviews of their working spheres, they strategize how to manage transitions between contexts and they maintain flexible foci among their different working spheres. We argue that system design to support collaborative work should include the notion that people are involved in multiple collaborations with contexts that change continually. System design must take into account these continual changes: people switch between local and global perspectives of their working spheres, have varying states of awareness of their different working spheres, and are continually managing transitions between contexts due to interruptions.

Research paper thumbnail of Context-Aware Mobile Communication in Hospitals

IEEE Computer, 2003

A collaborative handheld system extends the instant messaging paradigm by adding context-awarenes... more A collaborative handheld system extends the instant messaging paradigm by adding context-awareness to support the intensive and distributed nature of information management within a hospital setting.

Research paper thumbnail of Benefits of Information Visualization Systems for Administrative Data Analysts

International Conference on Information Visualisation, 2003

We report results from a study on the adoption of an information visualization system by administ... more We report results from a study on the adoption of an information visualization system by administrative data analysts. Despite the fact that the system was neither fully integrated with their current software tools nor with their existing data analysis practices, analysts identified a number of key benefits that visualization systems provide to their work. These benefits for the most part occurred when analysts went beyond their habitual and well-mastered data analysis routines and engaged in creative discovery processes. We analyze the conditions under which these benefits arose, to inform the design of visualization systems that can better assist the work of administrative data analysts.

Research paper thumbnail of Integrating context-aware public displays into a mobile hospital information system

IEEE Transactions on Information Technology in Biomedicine, 2004

Hospitals are convenient settings for deployment of ubiquitous computing technology. Not only are... more Hospitals are convenient settings for deployment of ubiquitous computing technology. Not only are they technologyrich environments, but their workers experience a high level of mobility resulting in information infrastructures with artifacts distributed throughout the premises. Hospital information systems (HISs) that provide access to electronic patient records are a step in the direction of providing accurate and timely information to hospital staff in support of adequate decision-making. This has motivated the introduction of mobile computing technology in hospitals based on designs which respond to their particular conditions and demands. Among those conditions is the fact that worker mobility does not exclude the need for having shared information artifacts at particular locations. In this paper, we extend a handheld-based mobile HIS with ubiquitous computing technology and describe how public displays are integrated with handheld and the services offered by these devices. Public displays become aware of the presence of physicians and nurses in their vicinity and adapt to provide users with personalized, relevant information. An agent-based architecture allows the integration of proactive components that offer information relevant to the case at hand, either from medical guidelines or previous similar cases.

Research paper thumbnail of Context-aware mobile communication in hospitals

IEEE Computer, 2003

A, collaborative handheld system extends the instant messaging paradigm by adding context-awarene... more A, collaborative handheld system extends the instant messaging paradigm by adding context-awareness to support the intensive and distributed nature of information management within a hospital setting.

Research paper thumbnail of Managing Currents of Work: Multi-tasking among Multiple Collaborations

European Conference on Computer Supported Cooperative Work, 2005

This research reports on a study of the interplay between multi-tasking and collaborative work. W... more This research reports on a study of the interplay between multi-tasking and collaborative work. We conducted an ethnographic study in two different companies where we observed the experiences and practices of thirty-six information workers. We observed that people continually switch between different collaborative contexts throughout their day. We refer to activities that are thematically connected as working spheres. We discovered that to multi-task and cope with the resulting fragmentation of their work, individuals constantly renew overviews of their working spheres, they strategize how to manage transitions between contexts and they maintain flexible foci among their different working spheres. We argue that system design to support collaborative work should include the notion that people are involved in multiple collaborations with contexts that change continually. System design must take into account these continual changes: people switch between local and global perspectives of their working spheres, have varying states of awareness of their different working spheres, and are continually managing transitions between contexts due to interruptions.

Research paper thumbnail of Spatial-temporal characterization of an urban environment using Twitter

2014 International Conference on Collaboration Technologies and Systems (CTS), 2014

This paper presents a study of the usage of Twitter within the context of urban activity. We retr... more This paper presents a study of the usage of Twitter within the context of urban activity. We retrieved a set of tweets submitted by users located in Mexico City. Tweets were labeled as either positive or negative mood using a sentiment analyzer implementation. By calculating the average mood, we were able to run a Mann-Withney's U test to evaluate differences in the calculated mood per day of week. We found that all days of the week had significantly different medians with Sunday being the most positive day and Thursday the most negative. Additionally, we study the location for the tweets as an indicator important events and landmarks around the city.

Research paper thumbnail of Constant, constant, multi-tasking craziness

Computer Human Interaction, 2004

Most current designs of information technology are based on the notion of supporting distinct tas... more Most current designs of information technology are based on the notion of supporting distinct tasks such as document production, email usage, and voice communication. In this paper we present empirical results that suggest that people organize their work in terms of much larger and thematically connected units of work. We present results of fieldwork observation of information workers in three different roles: analysts, software developers, and managers. We discovered that all of these types of workers experience a high level of discontinuity in the execution of their activities. People average about three minutes on a task and somewhat more than two minutes using any electronic tool or paper document before switching tasks. We introduce the concept of working spheres to explain the inherent way in which individuals conceptualize and organize their basic units of work. People worked in an average of ten different working spheres. Working spheres are also fragmented; people spend about 12 minutes in a working sphere before they switch to another. We argue that design of information technology needs to support people's continual switching between working spheres.

Research paper thumbnail of No task left behind?: examining the nature of fragmented work

Computer Human Interaction, 2005

We present data from detailed observation of 24 information workers that shows that they experien... more We present data from detailed observation of 24 information workers that shows that they experience work fragmentation as common practice. We consider that work fragmentation has two components: length of time spent in an activity, and frequency of interruptions. We examined work fragmentation along three dimensions: effect of collocation, type of interruption, and resumption of work. We found work to be highly fragmented: people average little time in working spheres before switching and 57% of their working spheres are interrupted. Collocated people work longer before switching but have more interruptions. Most internal interruptions are due to personal work whereas most external interruptions are due to central work. Though most interrupted work is resumed on the same day, more than two intervening activities occur before it is. We discuss implications for technology design: how our results can be used to support people to maintain continuity within a larger framework of their working spheres.

Research paper thumbnail of Geodetic and seismic constraints on some seismogenic zone processes in Costa Rica

Journal of Geophysical Research, 2004

Abstract[1] New seismic and geodetic data from Costa Rica provide insight into seismogenic zone p... more Abstract[1] New seismic and geodetic data from Costa Rica provide insight into seismogenic zone processes in Central America, where the Cocos and Caribbean plates converge. Seismic data are from combined land and ocean bottom deployments in the Nicoya peninsula in northern Costa Rica and near the Osa peninsula in southern Costa Rica. In Nicoya, inversion of GPS data suggests two locked patches centered at 14 ± 2 and 39 ± 6 km depth. Interplate microseismicity is concentrated in the more freely slipping intermediate zone, suggesting that small interseismic earthquakes may not accurately outline the updip limit of the seismogenic zone, the rupture zone for future large earthquakes, at least over the short (∼1 year) observation period. We also estimate northwest motion of a coastal “sliver block” at 8 ± 3 mm/yr, probably related to oblique convergence. In the Osa region to the south, convergence is orthogonal to the trench. Cocos-Caribbean relative motion is partitioned here, with ∼8 cm/yr on the Cocos-Panama block boundary (including a component of permanent shortening across the Fila Costeña fold and thrust belt) and ∼1 cm/yr on the Panama block–Caribbean boundary. The GPS data suggest that the Cocos plate–Panama block boundary is completely locked from ∼10–50 km depth. This large locked zone, as well as associated forearc and back-arc deformation, may be related to subduction of the shallow Cocos Ridge and/or younger lithosphere compared to Nicoya, with consequent higher coupling and compressive stress in the direction of plate convergence.

Research paper thumbnail of Fluid generation and pathways beneath an active compressional orogen, the New Zealand Southern Alps, inferred from magnetotelluric data

Journal of Geophysical Research, 2002

Abstract[1] Forty-one wideband magnetotelluric (MT) soundings were collected in a 150-km-long tra... more Abstract[1] Forty-one wideband magnetotelluric (MT) soundings were collected in a 150-km-long transect across the Southern Alps of the central South Island of New Zealand, an active compressional orogen. Decomposed MT impedance tensors, vertical magnetic field relations, and reconnaissance soundings at two locations off line imply an approximately two-dimensional geometry here with average regional geoelectric strike of ∼N40°E, similar to surface geologic trends. Two independent, two-dimensional inversion algorithms were applied to the MT data, and both imply a concave-upward (U-shaped), middle to lower crustal conductive zone beneath the west central portion of the island. The average conductivity of this zone in the strike direction appears to be much higher than that required across strike and may represent anisotropy or along-strike conductive strands narrower than the transverse magnetic (cross-strike) mode MT data can resolve. The deep crustal conductor under the Southern Alps is interpreted to represent mainly a volume of fluids arising from prograde metamorphism within a thickening crust. Fluid interconnection and electrical conduction are promoted by shear deformation. The conductor rises northwestward toward the trace of the Alpine Fault but attains a near-vertical configuration at a depth of ∼10 km and reaches close to the surface 5–10 km inland of the fault trace itself. The transition to vertical orientation at this depth is interpreted to occur as fluids ascend across the brittle-ductile transition in uplifting schist and approach the surface through induced hydrofractures. The high-grade schist becomes resistive after depletion of fluids and continues to extrude toward the Alpine Fault. Shallow extensions of the deep high conductivity are coincident with modern, hydrothermal veining and gold mineralization interpreted to be of deep crustal provenance. To the southeast, high conductivity also reaches the surface coincident with a major back thrust fault zone of the doubly vergent Southern Alps orogen, which also exhibits evidence for expulsion of high-temperature fluids. The higher conductivity inferred along strike (possible anisotropy) could reflect more efficient fluid interconnection in this higher-strain direction, as well as possible contributions by sheared, fluid-deposited graphite. Conductivity of the uppermost mantle of the South Island is low, consistent with advection of cold mantle lithosphere into the underlying asthenosphere as suggested by P wave delay studies.

Research paper thumbnail of The March 25, 1990 (M w =7.0, M L =6.8), earthquake at the entrance of the Nicoya Gulf, Costa Rica: Its prior activity, foreshocks, aftershocks, and triggered seismicity

Journal of Geophysical Research, 1995

On March 25, 1990 a large earthquake (Mw=7.0, ML=6.8) occurred at the entrance of the Nicoya Gulf... more On March 25, 1990 a large earthquake (Mw=7.0, ML=6.8) occurred at the entrance of the Nicoya Gulf, Costa Rica, at 1322:55.6 UTC, producing considerable damage in central Costa Rica and generating much interest about whether or not the Nicoya seismic gap (Nishenko, 1989) had broken. The local country-wide seismographic network recorded 6 years of activity prior to this large earthquake, 16 hours of foreshocks, the mainshock, and its aftershocks. This network is operated jointly by the Costa Rica Volcanological and Seismological Observatory at the National University (OVSICORI-UNA), and the Charles F. Richter Seismological Laboratory at the University of California, Santa Cruz (CFRSL-UCSC). We obtained high resolution locations from this network and located the mainshock at 9ø38.5'N, 84ø55.6'W (depth is 20.0 km) and the largest foreshock (Mw=6.0, March 25, 1990, at 1316:05.8 UTC) at 9ø36.4'N, 84ø57.1'W (depth is 22.4 km). We find that the aftershock zone abuts the southeast boundary of the Nicoya seismic gap, suggesting that the seismic gap did not rupture. Since the installation of the local network in April 1984 to March 24, 1990, nearly 1900 earthquakes with magnitudes from 1.7 to 4.8 (318 with magnitude 3.0 or larger) have been located at the entrance of the Nicoya Gulf, one of the most active regions in Costa Rica. The March 25 earthquake occurred at the northwest edge of this region, where a sequence of foreshocks began 16 hours prior to the mainshock. The spatialtemporal distribution of aftershocks and directivity analysis of the mainshock rupture process using teleseismic records both indicate a southeast propagating rupture. The mainshock ruptured an asperity of approximately 600 km 2 of area, with this area expanding to 4000 km 2 after 7 days. We present evidence that suggests that the ruptured asperity is produced by the subduction of a seamount. Inversion of teleseismic broadband and long-period P and SH waves yields a thrust faulting mechanism with the shallow plane striking 292 ø, dipping 26 ø, and with a rake of 88 ø, in agreement with the subduction of the Cocos plate under the Caribbean plate. Local first motions for the largest foreshock and the mainshock agree with this solution. We also present evidence suggesting that the March 25, 1990, earthquake triggered and reactivated several seismic swarms in central Costa Rica and temporally decreased the activity in the epicentral area of the July 3, 1983 (Ms=6.2), P6rez Zeled6n earthquake. 1Observatorio Vulcano16gico Paper number 94JB03099. 0148-0227/95/94JB-03099505.00 seismic gaps" in the Circum-Pacific). On March 25, 1990, a large earthquake (Mb=6.3, MsZ=7.0 (Preliminary Determination of Epicenters (PDE)), Mw=7.0, ML=6.8) occurred at the entrance of the Nicoya Gulf, Costa Rica, at 1322:55.6 UTC, near this seismic gap. This earthquake produced considerable damage in central Costa Rica, was felt from southern Nicaragua to western Panama, and generated much interest about whether or not the Nicoya seismic gap had broken (see boundaries in map by Nishenko [1989]). Costa Rica, as part of Central America, is located on the western margin of the Caribbean plate (Figure 1). There, the Cocos plate subducts under the Caribbean plate along the Middle American Trench at a rate between 70 and 94 mrn/yr from Guatemala to southern Costa Rica respectively (computed from De Mets et al., [ 1990]). It is along this plate boundary, at the western coast of Costa Rica, where most of the recent large destructive earthquakes have occurred. Coupling between the Cocos and Caribbean plates changes along strike of the subduction zone in Costa Rica and correlates with the bathymetric characteristics of the subducted oceanic floor: smooth, rough, and rough-smooth ocean floors in northern, 20,345 20,346 PROTTI ET AL.: MARCH 25, 1990, COSTA RICA EARTHQUAKE Nicaragua 11 o 1916 North American Nic_oya 195 Rica 'Panama Nicoya Gulf 1991 Panama 1983 Cocos Plate Panama Block 87 o 86 ø 85 o 84 o 83 o 82 ø Aftershocks A' ee•e ß ß ß ß ß ß ß . % ß .0 11 * * ß ß ß tt ß ß t t ß ß ß ß . '**'** ß $ * ß ß ß ß '-' ß ß -.-.. ß %. '% ß ß ß ß ß ß ß ß ß ß ee e ß i © • ß e ee ß 20 40 60 80

Research paper thumbnail of Determinants of Debt Maturity Structure Across Firm Size

SSRN Electronic Journal, 2000

... JEL classification: G32 * Víctor M. González Méndez, Departamento de Administración de Empres... more ... JEL classification: G32 * Víctor M. González Méndez, Departamento de Administración de Empresas, Universidad de Oviedo. Avda. del Cristo s/n, 33071 Oviedo, ESPAÑA. Tel.: ++34 985102826; Fax: ++34 985103708; e-mail: vmendez@uniovi.es ...

Research paper thumbnail of Diversification, Size and Risk at Spanish Banks

SSRN Electronic Journal, 2000

Page 1. Diversification, Size and Risk at Spanish Banks Fernando Gascón and Víctor González (*) U... more Page 1. Diversification, Size and Risk at Spanish Banks Fernando Gascón and Víctor González (*) Universidad de Oviedo (*) Corresponding Author: Fernando Gascón Área de Economía Financiera Facultad de Económicas Universidad de Oviedo Avda. ...

Research paper thumbnail of Erratum: Sentiment Characterization of an Urban Environment via Twitter

Lecture Notes in Computer Science, 2013

Research paper thumbnail of No task left behind

Computer Human Interaction, 2005

We present data from detailed observation of 24 information workers that shows that they experien... more We present data from detailed observation of 24 information workers that shows that they experience work fragmentation as common practice. We consider that work fragmentation has two components: length of time spent in an activity, and frequency of interruptions. We examined work fragmentation along three dimensions: effect of collocation, type of interruption, and resumption of work. We found work to be highly fragmented: people average little time in working spheres before switching and 57% of their working spheres are interrupted. Collocated people work longer before switching but have more interruptions. Most internal interruptions are due to personal work whereas most external interruptions are due to central work. Though most interrupted work is resumed on the same day, more than two intervening activities occur before it is. We discuss implications for technology design: how our results can be used to support people to maintain continuity within a larger framework of their working spheres.

Research paper thumbnail of A Workplace Study of the Adoption of Information Visualization Systems

This paper reports an ongoing longitudinal study of the adoption of information visualization sys... more This paper reports an ongoing longitudinal study of the adoption of information visualization systems by administrative data analysts. Participants were initially excited about the anticipated potential of visual data analysis for their work, but gradually discovered difficulties that eventually precluded a true integration of the visualization system into their daily work practices. These difficulties are unrelated to the specific visualization system used. We conclude that data analysts can take much better advantage of the benefits of information visualization systems when these systems are redesigned to be complementary products of current data analysis and workflow systems, rather than being stand-alone products as is currently the case. Our study offers some insights about how this complementarity can be achieved.

Research paper thumbnail of Do Four Eyes See Better than Two? Collaborative Versus Individual Discovery in Data Visualization Systems

International Conference on Information Visualisation, 2002

We present an empirical study investigating collaborative and individual decision-making about da... more We present an empirical study investigating collaborative and individual decision-making about data using two different information visualization systems. Based on previous research, one system is considered more transparent than the other in terms of visual representation and functionality. We found that people who worked in groups were more correct in their answers for objective questions, based on searching a large dataset. These results held for the more transparent system, but not the less transparent system. In a second task, groups were more accurate in their results for a free data discovery task. Again, these results held for the more transparent system only. Subjects using this system also produced results that were higher in complexity but judged lower in importance. Groups and individuals did not differ. We suggest that given the right visualization system, groups do better than individuals in finding more accurate results, but not necessarily increased or more meaningful results.

Research paper thumbnail of Stock repurchases with legal restrictions. Evidence from Spain

The European Journal of Finance, 2004

This paper analyses the consequences of legal restrictions on the volume of shares firms can repu... more This paper analyses the consequences of legal restrictions on the volume of shares firms can repurchase. Our results suggest that the imposition of a limit on the volume of common stock favours the use of open market repurchases (OMRs) compared to other methods of repurchase such as tender offer repurchases (TORs) and Dutch auctions (DAs). The positive share abnormal returns around both announcements of open market buybacks and sellbacks in the full sample suggest that they are basically used to change the ownership structure of the firm in a consistent way with the convergence of interest hypothesis. The positive abnormal stock returns around open market repurchases which are significantly different to the negative ones around sellbacks when there are no changes in ownership structure also indicates the existence of a signalling and free cash flow effects.

Research paper thumbnail of Influence of bank concentration and institutions on capital structure: New international evidence

Journal of Corporate Finance, 2008

This paper analyzes how bank market concentration and institutions affect capital structure in 39... more This paper analyzes how bank market concentration and institutions affect capital structure in 39 countries. Results for 12,049 firms over the period 1995-2004 indicate that firm leverage increases with bank concentration and the protection of creditor rights, but decreases with the protection of property rights. Our results also indicate that higher bank concentration substitutes for creditor protection and asset tangibility to reduce the agency cost of debt between shareholders and debtholders. Weak protection of property rights increases the agency cost of external funds, leading to the preferential use of internal funds proposed by the Pecking Order Theory. The validity of the Trade-Off Theory, however, increases in countries with better protection of property rights.