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Papers by Jose Roberto Espinoza Gonzalez

Research paper thumbnail of Marginal-Fermi-liquid behavior from two-dimensional Coulomb interaction

Research paper thumbnail of Auditory Display as an Aid for Prosthetic Hand Manipulation: Preliminary Results

Upper limb amputees have to rely extensively on visual feedback in order to monitor and manipulat... more Upper limb amputees have to rely extensively on visual feedback in order to monitor and manipulate successfully their prosthetic device. This situation leads to high consciousness burden, which generates fatigue and frustration. Therefore, in order to enhance motor-sensory performance and awareness, sonification of the prosthetic hand's spatio-temporal and force information was implemented in a real setting. The main purpose is to explore the difficulties people face when using a prosthetic hand and how the usage of auditory information affects their performance. Preliminary results showed that the temporal performance and the grasping performance was improved, also that the mental effort was reduced, when using auditive feedback.

Research paper thumbnail of Multichannel audio aided dynamical perception for prosthetic hand biofeedback

Visual input is one of the prerequisites for most biofeedback studies for prosthetic hand control... more Visual input is one of the prerequisites for most biofeedback studies for prosthetic hand control, since amputees lost part of their proprioception. This study explores whether it is possible to use audio feedback alone to convey more than one independent variable, without relying on visual input, to improve the learning of new perceptions; in this case artificial proprioception of a prosthetic hand. This way different features of the audio feedback can be observed to design applications capable of coupling different sensory inputs that will improve the acceptance and control of prosthetic devices. Experiments were conducted to determine whether the audio signals can be used as a multi-variable dynamical sensory substitution in reaching movements. The results showed that it is possible to use auditive feedback to create a body image without using the visual contact as a guide, thus to assist prosthetic hand users by internalizing new perceptions.

Research paper thumbnail of The electronic spectrum of fullerenes from the Dirac equation

Research paper thumbnail of Prostate Volume Reduction With Androgen Deprivation Therapy Before Interstitial Brachytherapy

The Journal of Urology, 2002

Purpose: We assessed the degree of prostate downsizing using androgen deprivation, and determined... more Purpose: We assessed the degree of prostate downsizing using androgen deprivation, and determined its relation to clinical and pathological variables. Materials and Methods: From June 1994 to January 2000, 107 patients with prostate cancer received androgen deprivation before interstitial brachytherapy at our hospital. All charts were reviewed for clinical, pathological and treatment related variables. Prostate volume was measured using transrectal ultrasound. All variables were analyzed with regard to the degree of prostate downsizing. Results: Mean percent volume reduction of the prostate was 33% after a 3.7-month average duration of androgen deprivation. Larger prostate volume before androgen deprivation and longer deprivation duration statistically correlated with mean percent volume reduction. Simple linear and multiple regression analyses revealed that these 2 variables remained significant predictors of percent volume reduction. Subgroup analysis indicated that a significant difference was seen in patients who received androgen deprivation with luteinizing hormone releasing hormone agonists alone versus those who received treatment with total androgen blockade (luteinizing hormone releasing hormone agonists plus antiandrogens 30% versus 35%, p ϭ 0.04), and when prostate volume before androgen deprivation was less than 50 cc versus larger volumes (30% versus 35%, p ϭ 0.01). Of patients with an initial prostate volume of greater than 50 cc 82% achieved a volume of less than 50 cc after androgen deprivation therapy. Conclusions: Androgen deprivation therapy before brachytherapy is a method of downsizing the prostate to overcome anatomical limitations, including larger gland volume and pubic arch interference.

Research paper thumbnail of Steady and Unsteady Radial Forces for a Centrifugal Pump With Impeller to Tongue Gap Variation

Journal of Fluids Engineering, 2005

Experimental and numerical studies are presented on the steady and unsteady radial forces produce... more Experimental and numerical studies are presented on the steady and unsteady radial forces produced in a single volute vaneless centrifugal pump. Experimentally, the unsteady pressure distributions were obtained using fast response pressure transducers. These measurements were compared with equivalent numerical results from a URANS calculation, using the commercial code FLUENT. Two impellers with different outlet diameters were tested for the same volute, with radial gaps between the blade and tongue of 10.0% and 15.8% of the impeller radius, for the bigger and smaller impeller diameters, respectively. Very often, pump manufacturers apply the similarity laws to this situation, but the measured specific speeds in this case were found to be slightly different. The steady radial forces for the two impellers were calculated from both the measured average pressure field and the model over a wide range of flow rates in order to fully characterize the pump behavior. Again, a deviation from ...

Research paper thumbnail of Lack of benefit from a short course of androgen deprivation for unfavorable prostate cancer patients treated with an accelerated hypofractionated regime

International Journal of Radiation Oncology*Biology*Physics, 2005

High-dose radiotherapy, delivered in an accelerated hypofractionated course, was utilized to trea... more High-dose radiotherapy, delivered in an accelerated hypofractionated course, was utilized to treat prostate cancer. Therapy consisted of external beam radiotherapy (EBRT) and transrectal ultrasound (TRUS)-guided conformally modulated high-dose rate (HDR) brachytherapy. The purpose of this report is (1) to assess long-term comparative outcomes from three trials using similar accelerated hypofractionated regimes; and (2) to examine the long-term survival impact of a short course of < or =6 months adjuvant/concurrent androgen deprivation when a very high radiation dose was delivered. Between 1986 and 2000, 1,260 patients were treated at three institutions with pelvic EBRT (36-50 Gy) integrated with HDR…

Research paper thumbnail of Binary black holes on a budget: simulations using workstations

Classical and Quantum Gravity, 2007

Binary black hole simulations have traditionally been computationally very expensive: current sim... more Binary black hole simulations have traditionally been computationally very expensive: current simulations are performed in supercomputers involving dozens if not hundreds of processors, thus systematic studies of the parameter space of binary black hole encounters still seem prohibitive with current technology. Here we show how the multi-layered refinement level code BAM can be used on dual processor workstations to simulate certain binary black hole systems. BAM, based on the moving punctures method, provides grid structures composed of boxes of increasing resolution near the center of the grid. In the case of binaries, the highest resolution boxes are placed around each black hole and they track them in their orbits until the final merger when a single set of levels surrounds the black hole remnant. This is particularly useful when simulating spinning black holes since the gravitational fields gradients are larger. We present simulations of binaries with equal mass black holes with spins parallel to the binary axis and intrinsic magnitude of S/m 2 = 0.75. Our results compare favorably to those of previous simulations of this particular system. We show that the moving punctures method produces stable simulations at maximum spatial resolutions up to M/160 and for durations of up to the equivalent of 20 orbital periods.

Research paper thumbnail of A simple acoustic model to characterize the internal low frequency sound field in centrifugal pumps

Applied Acoustics, 2011

Conventional centrifugal pumps with volute casing generate fluid-dynamic noise particularly at th... more Conventional centrifugal pumps with volute casing generate fluid-dynamic noise particularly at the so-called blade-passing frequency, which is attributed to the interaction of the flow exiting the pump impeller with the volute tongue. Following previous work by the authors to characterize the effect of that blade–tongue interaction on the tonal sound produced, this paper presents a simple acoustic model for centrifugal

Research paper thumbnail of Efficient binary black hole simulations

Bulletin of the American Physical Society, Apr 15, 2007

We present results of simulations of spinning black hole binaries in circular orbits, which cover... more We present results of simulations of spinning black hole binaries in circular orbits, which cover several orbits as well as the merger and ringdown phases. These simulations are performed using a moving punctures implementation within the BAM code. This code uses moving mesh refinement boxes. It is so efficient that our simulations can be performed on dual processor workstations. In particular, we compute the initial and final ADM mass and angular momentum and show their dependence on grid size and resolution. In addition, ...

Research paper thumbnail of The Market Orientation of Internet Support Companies

Journal of Internet Commerce, 2008

Several studies have expanded the work by Jaworski and Kohli (1993) by using their market orienta... more Several studies have expanded the work by Jaworski and Kohli (1993) by using their market orientation framework model and applying it to a variety of industries. The results of recent studies have uncovered moderate to strong relationships between the concepts of market orientation and organizational performance. Although there is a large body of research on the topic of market orientation, there is a gap pertaining to market orientation across organizations that comprise fast-paced environments such as those that exist within the Internet commerce environment. This study explores market orientation in the context of Web Hosting and Internet service providers to understand the impact market orientation can have on new and emerging industries. The study results indicate that market orientation is positively related to performance. Implications for theory construction and managerial practice are discussed.

Research paper thumbnail of Marginal-Fermi-liquid behavior from two-dimensional Coulomb interaction

Research paper thumbnail of Auditory Display as an Aid for Prosthetic Hand Manipulation: Preliminary Results

Upper limb amputees have to rely extensively on visual feedback in order to monitor and manipulat... more Upper limb amputees have to rely extensively on visual feedback in order to monitor and manipulate successfully their prosthetic device. This situation leads to high consciousness burden, which generates fatigue and frustration. Therefore, in order to enhance motor-sensory performance and awareness, sonification of the prosthetic hand's spatio-temporal and force information was implemented in a real setting. The main purpose is to explore the difficulties people face when using a prosthetic hand and how the usage of auditory information affects their performance. Preliminary results showed that the temporal performance and the grasping performance was improved, also that the mental effort was reduced, when using auditive feedback.

Research paper thumbnail of Multichannel audio aided dynamical perception for prosthetic hand biofeedback

Visual input is one of the prerequisites for most biofeedback studies for prosthetic hand control... more Visual input is one of the prerequisites for most biofeedback studies for prosthetic hand control, since amputees lost part of their proprioception. This study explores whether it is possible to use audio feedback alone to convey more than one independent variable, without relying on visual input, to improve the learning of new perceptions; in this case artificial proprioception of a prosthetic hand. This way different features of the audio feedback can be observed to design applications capable of coupling different sensory inputs that will improve the acceptance and control of prosthetic devices. Experiments were conducted to determine whether the audio signals can be used as a multi-variable dynamical sensory substitution in reaching movements. The results showed that it is possible to use auditive feedback to create a body image without using the visual contact as a guide, thus to assist prosthetic hand users by internalizing new perceptions.

Research paper thumbnail of The electronic spectrum of fullerenes from the Dirac equation

Research paper thumbnail of Prostate Volume Reduction With Androgen Deprivation Therapy Before Interstitial Brachytherapy

The Journal of Urology, 2002

Purpose: We assessed the degree of prostate downsizing using androgen deprivation, and determined... more Purpose: We assessed the degree of prostate downsizing using androgen deprivation, and determined its relation to clinical and pathological variables. Materials and Methods: From June 1994 to January 2000, 107 patients with prostate cancer received androgen deprivation before interstitial brachytherapy at our hospital. All charts were reviewed for clinical, pathological and treatment related variables. Prostate volume was measured using transrectal ultrasound. All variables were analyzed with regard to the degree of prostate downsizing. Results: Mean percent volume reduction of the prostate was 33% after a 3.7-month average duration of androgen deprivation. Larger prostate volume before androgen deprivation and longer deprivation duration statistically correlated with mean percent volume reduction. Simple linear and multiple regression analyses revealed that these 2 variables remained significant predictors of percent volume reduction. Subgroup analysis indicated that a significant difference was seen in patients who received androgen deprivation with luteinizing hormone releasing hormone agonists alone versus those who received treatment with total androgen blockade (luteinizing hormone releasing hormone agonists plus antiandrogens 30% versus 35%, p ϭ 0.04), and when prostate volume before androgen deprivation was less than 50 cc versus larger volumes (30% versus 35%, p ϭ 0.01). Of patients with an initial prostate volume of greater than 50 cc 82% achieved a volume of less than 50 cc after androgen deprivation therapy. Conclusions: Androgen deprivation therapy before brachytherapy is a method of downsizing the prostate to overcome anatomical limitations, including larger gland volume and pubic arch interference.

Research paper thumbnail of Steady and Unsteady Radial Forces for a Centrifugal Pump With Impeller to Tongue Gap Variation

Journal of Fluids Engineering, 2005

Experimental and numerical studies are presented on the steady and unsteady radial forces produce... more Experimental and numerical studies are presented on the steady and unsteady radial forces produced in a single volute vaneless centrifugal pump. Experimentally, the unsteady pressure distributions were obtained using fast response pressure transducers. These measurements were compared with equivalent numerical results from a URANS calculation, using the commercial code FLUENT. Two impellers with different outlet diameters were tested for the same volute, with radial gaps between the blade and tongue of 10.0% and 15.8% of the impeller radius, for the bigger and smaller impeller diameters, respectively. Very often, pump manufacturers apply the similarity laws to this situation, but the measured specific speeds in this case were found to be slightly different. The steady radial forces for the two impellers were calculated from both the measured average pressure field and the model over a wide range of flow rates in order to fully characterize the pump behavior. Again, a deviation from ...

Research paper thumbnail of Lack of benefit from a short course of androgen deprivation for unfavorable prostate cancer patients treated with an accelerated hypofractionated regime

International Journal of Radiation Oncology*Biology*Physics, 2005

High-dose radiotherapy, delivered in an accelerated hypofractionated course, was utilized to trea... more High-dose radiotherapy, delivered in an accelerated hypofractionated course, was utilized to treat prostate cancer. Therapy consisted of external beam radiotherapy (EBRT) and transrectal ultrasound (TRUS)-guided conformally modulated high-dose rate (HDR) brachytherapy. The purpose of this report is (1) to assess long-term comparative outcomes from three trials using similar accelerated hypofractionated regimes; and (2) to examine the long-term survival impact of a short course of < or =6 months adjuvant/concurrent androgen deprivation when a very high radiation dose was delivered. Between 1986 and 2000, 1,260 patients were treated at three institutions with pelvic EBRT (36-50 Gy) integrated with HDR…

Research paper thumbnail of Binary black holes on a budget: simulations using workstations

Classical and Quantum Gravity, 2007

Binary black hole simulations have traditionally been computationally very expensive: current sim... more Binary black hole simulations have traditionally been computationally very expensive: current simulations are performed in supercomputers involving dozens if not hundreds of processors, thus systematic studies of the parameter space of binary black hole encounters still seem prohibitive with current technology. Here we show how the multi-layered refinement level code BAM can be used on dual processor workstations to simulate certain binary black hole systems. BAM, based on the moving punctures method, provides grid structures composed of boxes of increasing resolution near the center of the grid. In the case of binaries, the highest resolution boxes are placed around each black hole and they track them in their orbits until the final merger when a single set of levels surrounds the black hole remnant. This is particularly useful when simulating spinning black holes since the gravitational fields gradients are larger. We present simulations of binaries with equal mass black holes with spins parallel to the binary axis and intrinsic magnitude of S/m 2 = 0.75. Our results compare favorably to those of previous simulations of this particular system. We show that the moving punctures method produces stable simulations at maximum spatial resolutions up to M/160 and for durations of up to the equivalent of 20 orbital periods.

Research paper thumbnail of A simple acoustic model to characterize the internal low frequency sound field in centrifugal pumps

Applied Acoustics, 2011

Conventional centrifugal pumps with volute casing generate fluid-dynamic noise particularly at th... more Conventional centrifugal pumps with volute casing generate fluid-dynamic noise particularly at the so-called blade-passing frequency, which is attributed to the interaction of the flow exiting the pump impeller with the volute tongue. Following previous work by the authors to characterize the effect of that blade–tongue interaction on the tonal sound produced, this paper presents a simple acoustic model for centrifugal

Research paper thumbnail of Efficient binary black hole simulations

Bulletin of the American Physical Society, Apr 15, 2007

We present results of simulations of spinning black hole binaries in circular orbits, which cover... more We present results of simulations of spinning black hole binaries in circular orbits, which cover several orbits as well as the merger and ringdown phases. These simulations are performed using a moving punctures implementation within the BAM code. This code uses moving mesh refinement boxes. It is so efficient that our simulations can be performed on dual processor workstations. In particular, we compute the initial and final ADM mass and angular momentum and show their dependence on grid size and resolution. In addition, ...

Research paper thumbnail of The Market Orientation of Internet Support Companies

Journal of Internet Commerce, 2008

Several studies have expanded the work by Jaworski and Kohli (1993) by using their market orienta... more Several studies have expanded the work by Jaworski and Kohli (1993) by using their market orientation framework model and applying it to a variety of industries. The results of recent studies have uncovered moderate to strong relationships between the concepts of market orientation and organizational performance. Although there is a large body of research on the topic of market orientation, there is a gap pertaining to market orientation across organizations that comprise fast-paced environments such as those that exist within the Internet commerce environment. This study explores market orientation in the context of Web Hosting and Internet service providers to understand the impact market orientation can have on new and emerging industries. The study results indicate that market orientation is positively related to performance. Implications for theory construction and managerial practice are discussed.