Publications by authors named "Arun Ramakrishnan"

8 Publications

  • Page 1 of 1

A Cross University-Led COVID-19 Rapid-Response Effort: Design, Build, and Distribute Drexel AJFlex Face Shields.

Ann Biomed Eng 2021 Mar 26;49(3):950-958. Epub 2021 Feb 26.

Drexel University, Philadelphia, PA, USA.

The purpose of this article is to demonstrate how a new cross-community leadership team came together, collaborated, coordinated across academic units with external community partners, and executed a joint mission to address the unmet clinical need for medical face shields during these unprecedented times. Key aspects of this success include the ability to forge and leverage new opportunities, overcome challenges, adapt to changing constraints, and serve the significant need across the Philadelphia region and healthcare systems. We teamed to design-build durable face shields (AJFlex Shields). This was accomplished by high-volume manufacturing via injection molding and by 3-D printing the key headband component that supports the protective shield. Partnering with industry collaborators and civic-minded community allies proved to be essential to bolster production and deliver approximately 33,000 face shields to more than 100 organizations in the region. Our interdisciplinary team of engineers, clinicians, product designers, manufacturers, distributors, and dedicated volunteers is committed to continuing the design-build effort and providing Drexel AJFlex Shields to our communities.
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http://dx.doi.org/10.1007/s10439-021-02743-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7908945PMC
March 2021

Outcomes of Visual Self-Expression in Virtual Reality on Psychosocial Well-Being With the Inclusion of a Fragrance Stimulus: A Pilot Mixed-Methods Study.

Front Psychol 2020 8;11:589461. Epub 2020 Dec 8.

Department of Psychology, The College of New Jersey, Ewing Township, NJ, United States.

Aims: In this pilot mixed-methods study, we examined the participants experiences of engaging in virtual drawing tasks and the impact of an olfactory stimulus (calming fragrance blend) on outcomes of affect, stress, self-efficacy, anxiety, creative agency, and well-being (satisfaction with life).

Methods: This study used a parallel mixed-methods, simple block randomization design. The study participants included 24 healthy adults aged 18 to 54 years, including 18 women and six men. The participants completed two 1-h immersive virtual art making sessions and were randomly assigned to receive either a fragrance or a non-fragrance condition for the first session. Quantitative (standardized self-report measures) and qualitative (open-ended survey responses and virtual artwork) datasets were collected concurrently and integrated during data analysis.

Results: The quantitative results indicated that the fragrance condition demonstrated a significant reduction in negative affect (e.g., feeling hostile, jittery, upset, distressed, etc.), namely, reduced feelings of negativity when compared to the non-fragrance condition. A trend toward improvement in self-efficacy was also seen in the fragrance condition. No significant changes were found for fragrance or non-fragrance conditions for positive affect, anxiety, and creative agency. The qualitative findings included five themes related to art making experiences in virtual reality in both conditions: fun and joy; novelty of virtual media, experimentation, and play; relaxation and calm; learning curve; and physical discomfort and disorientation. Four themes were identified for virtual art content and visual qualities: nature imagery, references to memories and personal symbols, fantasy and play within imagery, and depiction of everyday objects.

Conclusions: Overall, the participants reported positive responses to the novel virtual art making experiences which were further heightened by the inclusion of the fragrance stimulus for negative affect. These preliminary findings need to be replicated with larger sample sizes to confirm the outcomes and the trends that were seen in this pilot study. Further research is recommended to examine the differences between experiences of virtual and traditional art media and to examine different olfactory stimuli promoting focus and concentration.
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http://dx.doi.org/10.3389/fpsyg.2020.589461DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7793948PMC
December 2020

Using Virtual Reality in Biomedical Engineering Education.

J Biomech Eng 2020 11;142(11)

School of Biomedical Engineering, Sciences and Health Systems, Drexel University, Philadelphia, PA 19104.

This study explored virtual reality (VR) as an educational tool to offer immersive and experiential learning environments to biomedical engineering (BME) students. VR and traditional two-dimensional (2D) videos were created and used to teach required communication skills to BME students' while working with clinical partners in healthcare settings. The videos of interdisciplinary teams (engineering and nursing students) tackling medical device-related problems, similar to those commonly observed in healthcare settings, were shown to BME students. Student surveys indicated that, through VR videos, they felt more immersed in real-world clinical scenarios while learning about the clinical problems, each team-member's areas of expertise, their roles and responsibilities, and how an interdisciplinary team operated collectively to solve a problem in the presented settings. Students with a prior in-person immersion experience, in the presented settings, reported VR videos to serve as a possible alternative to in-person immersion and a useful tool for their preparedness for real-world clinical immersion. We concluded that VR holds promise as an educational tool to offer simulated clinical scenarios that are effective in training BME students for interprofessional collaborations.
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http://dx.doi.org/10.1115/1.4048005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7580657PMC
November 2020

How spinalized rats can walk: biomechanics, cortex, and hindlimb muscle scaling--implications for rehabilitation.

Ann N Y Acad Sci 2010 Jun;1198:279-93

Neurobiology and Anatomy, School of Bioengineering, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA.

Neonatal spinalized (NST) rats can achieve autonomous weight-supported locomotion never seen after adult injury. Mechanisms that support function in NST rats include increased importance of cortical trunk control and altered biomechanical control strategies for stance and locomotion. Hindlimbs are isolated from perturbations in quiet stance and act in opposition to forelimbs in locomotion in NST rats. Control of roll and yaw of the hindlimbs is crucial in their locomotion. The biomechanics of the hind limbs of NST rats are also likely crucial. We present new data showing the whole leg musculature scales proportional to normal rat musculature in NST rats, regardless of function. This scaling is a prerequisite for the NST rats to most effectively use pattern generation mechanisms and motor patterns that are similar to those present in intact rats. Pattern generation may be built into the lumbar spinal cord by evolution and matched to the limb biomechanics, so preserved muscle scaling may be essential to the NST function observed.
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http://dx.doi.org/10.1111/j.1749-6632.2010.05534.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3587114PMC
June 2010

A simple experimentally based model using proprioceptive regulation of motor primitives captures adjusted trajectory formation in spinal frogs.

J Neurophysiol 2010 Jan 5;103(1):573-90. Epub 2009 Aug 5.

Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA 19129, USA.

Spinal circuits may organize trajectories using pattern generators and synergies. In frogs, prior work supports fixed-duration pulses of fixed composition synergies, forming primitives. In wiping behaviors, spinal frogs adjust their motor activity according to the starting limb position and generate fairly straight and accurate isochronous trajectories across the workspace. To test whether a compact description using primitives modulated by proprioceptive feedback could reproduce such trajectory formation, we built a biomechanical model based on physiological data. We recorded from hindlimb muscle spindles to evaluate possible proprioceptive input. As movement was initiated, early skeletofusimotor activity enhanced many muscle spindles firing rates. Before movement began, a rapid estimate of the limb position from simple combinations of spindle rates was possible. Three primitives were used in the model with muscle compositions based on those observed in frogs. Our simulations showed that simple gain and phase shifts of primitives based on published feedback mechanisms could generate accurate isochronous trajectories and motor patterns that matched those observed. Although on-line feedback effects were omitted from the model after movement onset, our primitive-based model reproduced the wiping behavior across a range of starting positions. Without modifications from proprioceptive feedback, the model behaviors missed the target in a manner similar to that in deafferented frogs. These data show how early proprioception might be used to make a simple estimate initial limb state and to implicitly plan a movement using observed spinal motor primitives. Simulations showed that choice of synergy composition played a role in this simplicity. To generate froglike trajectories, a hip flexor synergy without sartorius required motor patterns with more proprioceptive knee flexor control than did patterns built with a more natural synergy including sartorius. Such synergy choices and control strategies may simplify the circuitry required for reflex trajectory construction and adaptation.
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http://dx.doi.org/10.1152/jn.01054.2007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2807239PMC
January 2010

Multiple types of movement-related information encoded in hindlimb/trunk cortex in rats and potentially available for brain-machine interface controls.

IEEE Trans Biomed Eng 2009 Nov 14;56(11 Pt 2):2712-6. Epub 2009 Jul 14.

Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, PA 19129, USA.

Brain-machine interface (BMI) systems hold the potential to return lost functions to patients with motor disorders. To date, most efforts in BMI have concentrated on decoding neural activity from forearm areas of cortex to operate a robotic arm or perform other manipulation tasks. Efforts have neglected the locomotion functions of hindlimb/trunk cortex. However, the role of cortex in hindlimb locomotion of intact rats, which are often model systems for BMI testing, is usually considered to be small. Thus, the quality of representations of locomotion available in this area was uncertain. We designed a new rodent BMI system, and tested decoding of the kinematics of trunk and hindlimbs during locomotion using linear regression. Recordings were made from the motor cortex of the hindlimb/trunk area in rats using arrays of six tetrodes (24 channels total). We found that multiple movement-related variables could be decoded simultaneously during locomotion, ranging from the proximal robot/pelvis attachment point, and the distal toe position, through hindlimb joint angles and limb endpoint in a polar coordinate system. Remarkably, the best reconstructed motion parameters were the more proximal kinematics, which might relate to global task variables. The pelvis motion was significantly better reconstructed than any other motion features.
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http://dx.doi.org/10.1109/TBME.2009.2026284DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2883457PMC
November 2009

Trunk sensorimotor cortex is essential for autonomous weight-supported locomotion in adult rats spinalized as P1/P2 neonates.

J Neurophysiol 2008 Aug 28;100(2):839-51. Epub 2008 May 28.

Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA 19129, USA.

Unlike adult spinalized rats, approximately 20% of rats spinalized as postnatal day 1 or 2 (P1/P2) neonates achieve autonomous hindlimb weight support. Cortical representations of mid/low trunk occur only in such rats with high weight support. However, the importance of hindlimb/trunk motor cortex in function of spinalized rats remains unclear. We tested the importance of trunk sensorimotor cortex in their locomotion using lesions guided by cortical microstimulation in P1/P2 weight-supporting neonatal spinalized rats and controls. In four intact control rats, lesions of hindlimb/trunk cortex caused no treadmill deficits. All spinalized rats lesioned in trunk cortex (n = 16: 4 transplant, 6 transect, 6 transect + fibrin glue) lost an average of about 40% of their weight support. Intact trunk cortex was essential to their level of function. Lesion of trunk cortex substantially increased roll of the hindquarters, which correlated to diminished weight support, but other kinematic stepping parameters showed little change. Embryonic day 14 (E14) transplants support development of the trunk motor representations in their normal location. We tested the role of novel relay circuits arising from the grafts in such cortical representations in E14 transplants using the rats that received (noncellular) fibrin glue grafting at P1/P2 (8 allografts and 32 xenografts). Fibrin-repaired rats with autonomous weight support also had trunk cortical representations similar to those of E14 transplant rats. Thus acellular repair and intrinsic plasticity were sufficient to support the observed features. Our data show that effective cortical mechanisms for trunk control are essential for autonomous weight support in P1/P2 spinalized rats and these can be achieved by intrinsic plasticity.
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http://dx.doi.org/10.1152/jn.00866.2007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2525706PMC
August 2008

Robot application of elastic fields to the pelvis of the spinal transected rat: a tool for detailed assessment and rehabilitation.

Conf Proc IEEE Eng Med Biol Soc 2006;2006:3684-7

Sch. of Bioeng., Drexel Univ., Philadelphia, PA, USA.

We examine robotic rehabilitation and assessment of spinalized rats, using robot applied forces at the pelvis, as a prelude to a neurorobotic BMI. Using a surgically implanted pelvic orthosis, a cantilevered phantom robot is attached to the rat pelvis. An isotropic elastic field of constant stiffness is applied and the equilibrium is adjusted to provide a ;natural' trunk posture. Rats are trained daily for 20 minutes, 5 days per week in the field. Significant within trial, and long term adaptation occurs. The interaction force assessments from the robot reveal significant differences between spinalized control rats, and rats receiving implants of E14 dorsal raphe tissue to provide a serotonin source. Our system provides an animal model of rehabilitation through robot interaction at the pelvis.
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http://dx.doi.org/10.1109/IEMBS.2006.259633DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3770131PMC
March 2008
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