162 results match your criteria: "Harvard School of Engineering and Applied Sciences[Affiliation]"
Mol Microbiol
October 2012
Departments of Physics and Harvard School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
Many bacteria organize themselves into structurally complex communities known as biofilms in which the cells are held together by an extracellular matrix. In general, the amount of extracellular matrix is related to the robustness of the biofilm. Yet, the specific signals that regulate the synthesis of matrix remain poorly understood.
View Article and Find Full Text PDFPhys Chem Chem Phys
September 2012
Harvard School of Engineering and Applied Sciences, Cambridge, MA 02138, USA.
The perovskite SrTiO(3) is arguably one of the most important oxide systems in condensed matter research. In this study, we report measurement of the orientation dependence of oxygen exchange on SrTiO(3) single crystal surfaces by dynamic conductivity measurements under electrochemical perturbations. Activation energy for electrical conduction in the 923-1223 K range at an oxygen partial pressure of ∼10(-11) Pa of (100), (111), and (110) single crystals was found to be 2.
View Article and Find Full Text PDFAdv Mater
August 2012
Harvard School of Engineering and Applied Sciences, 33 Oxford Street, Cambridge, MA 02138, USA.
A two-dimensional array of gold optical antennas integrated with a one-dimensional array of gold strips and mirrors is introduced and fabricated. The experimental results show that this design achieves average surface-enhanced Raman scattering (SERS) enhancement factors as high as 1.2 × 10(10) , which is more than two orders of magnitude larger than optical antennas without the gold strips and gold mirror.
View Article and Find Full Text PDFIEEE Trans Pattern Anal Mach Intell
August 2012
Harvard School of Engineering and Applied Sciences, Cambridge, MA 02138, USA.
We introduce an efficient maximum likelihood approach for one part of the color constancy problem: removing from an image the color cast caused by the spectral distribution of the dominating scene illuminant. We do this by developing a statistical model for the spatial distribution of colors in white balanced images (i.e.
View Article and Find Full Text PDFNano Lett
July 2012
Harvard School of Engineering and Applied Sciences, Cambridge, Massachusetts 02138, United States.
The power output of hydrogen fuel cells quickly decreases to zero if the fuel supply is interrupted. We demonstrate thin film solid oxide fuel cells with nanostructured vanadium oxide anodes that generate power for significantly longer time than reference porous platinum anode thin film solid oxide fuel cells when the fuel supply is interrupted. The charge storage mechanism was investigated quantitatively with likely identified contributions from the oxidation of the vanadium oxide anode, its hydrogen storage properties, and different oxygen concentration at the electrodes.
View Article and Find Full Text PDFInf Process Comput Assist Interv (2012)
June 2012
Harvard School of Engineering and Applied Sciences, Cambridge, MA USA 02138.
Real-time 3D ultrasound (3DUS) imaging offers improved spatial orientation information relative to 2D ultrasound. However, in order to improve its efficacy in guiding minimally invasive intra-cardiac procedures where real-time visual feedback of an instrument tip location is crucial, 3DUS volume visualization alone is inadequate. This paper presents a set of enhanced visualization functionalities that are able to track the tip of an instrument in slice views at real-time.
View Article and Find Full Text PDFCurr Protoc Chem Biol
March 2012
Department of Genetics, Harvard Medical School, Boston, Massachusetts ; Wyss Institute for Biologically Inspired Engineering, Boston, Massachusetts.
synthesis of long double-stranded DNA constructs has a myriad of applications in biology and biological engineering. However, its widespread adoption has been hindered by high costs. Cost can be significantly reduced by using oligonucleotides synthesized on high-density DNA chips.
View Article and Find Full Text PDFAnnu Int Conf IEEE Eng Med Biol Soc
May 2012
Harvard School of Engineering and Applied Sciences, Cambridge, MA 02138, USA.
Strokes affect over 750,000 people annually in the United States. This significant and disabling condition can result in paralysis that must be treated by regular sessions with a dedicated physical therapist in order to regain motor function. However, the use of therapists is expensive, in high demand, and requires patient travel to a rehabilitation clinic.
View Article and Find Full Text PDFAnnu Int Conf IEEE Eng Med Biol Soc
July 2012
Harvard School of Engineering and Applied Sciences, Cambridge, MA, USA.
Successful manipulation of an object requires exerting grip forces (GF) sufficient to prevent slippage. To prevent slip in more uncertain environments, GF would need to increase. Here we investigate the brain's ability to efficiently control grasp by producing GFs that correspond to confidence estimates of uncertain environments that are characterized by probability density functions of different variances and higher order moments.
View Article and Find Full Text PDFAnnu Int Conf IEEE Eng Med Biol Soc
July 2012
Harvard-MIT Division of Health Sciences andTechnology, Harvard School of Engineering and Applied Sciences, Cambridge, MA, USA.
The shape of the directional generalization function for adaptation to a viscous force-field environment has been controversial. Some studies have suggested wide, essentially global generalization and others have suggested narrow, local generalization. Here, we show definitively that motor adaptation displays narrow generalization with a minimal global component and a peak at the trained movement direction for both single-trial and asymptotic adaptation.
View Article and Find Full Text PDFSurgical repair of the mitral valve is a difficult procedure that is often avoided in favor of less effective valve replacement because of the associated technical challenges facing non-expert surgeons. In the interest of increasing the rate of valve repair, an accurate, interactive surgical simulator for mitral valve repair was developed. With a haptic interface, users can interact with a mechanical model during simulation to aid in the development of a surgical plan and then virtually implement the procedure to assess its efficacy.
View Article and Find Full Text PDFMed Image Anal
February 2012
Harvard School of Engineering and Applied Sciences, Cambridge, MA, USA.
Measurement of the shape and motion of the mitral valve annulus has proven useful in a number of applications, including pathology diagnosis and mitral valve modeling. Current methods to delineate the annulus from four-dimensional (4D) ultrasound, however, either require extensive overhead or user-interaction, become inaccurate as they accumulate tracking error, or they do not account for annular shape or motion. This paper presents a new 4D annulus segmentation method to account for these deficiencies.
View Article and Find Full Text PDFMed Image Anal
February 2012
Harvard School of Engineering and Applied Sciences, Cambridge, MA, USA.
Registration of three-dimensional ultrasound (3DUS) volumes is necessary in several applications, such as when stitching volumes to expand the field of view or when stabilizing a temporal sequence of volumes to cancel out motion of the probe or anatomy. Current systems that register 3DUS volumes either use external tracking systems (electromagnetic or optical), which add expense and impose limitations on acquisitions, or are image-based methods that operate offline and are incapable of providing immediate feedback to clinicians. This paper presents a real-time image-based algorithm for rigid registration of 3DUS volumes designed for acquisitions in which small probe displacements occur between frames.
View Article and Find Full Text PDFMed Image Comput Comput Assist Interv
November 2011
Harvard School of Engineering and Applied Sciences, Cambridge, MA, USA.
Segmenting the mitral valve during closure and throughout a cardiac cycle from four dimensional ultrasound (4DUS) is important for creation and validation of mechanical models and for improved visualization and understanding of mitral valve behavior. Current methods of segmenting the valve from 4DUS either require extensive user interaction and initialization, do not maintain the valve geometry across a cardiac cycle, or are incapable of producing a detailed coaptation line and surface. We present a method of segmenting the mitral valve annulus and leaflets from 4DUS such that a detailed, patient-specific annulus and leaflets are tracked throughout mitral valve closure, resulting in a detailed coaptation region.
View Article and Find Full Text PDFMed Image Comput Comput Assist Interv
November 2011
Harvard School of Engineering and Applied Sciences, Cambrige, MA 02138, USA.
Intra-cardiac 3D ultrasound imaging has enabled new minimally invasive procedures. Its narrow field of view, however, limits its efficacy in guiding beating heart procedures where geometrically complex and spatially extended moving anatomic structures are often involved. In this paper, we present a system that performs electrocardiograph gated 4D mosaicing and visualization of 3DUS volumes.
View Article and Find Full Text PDFIEEE Int Conf Robot Autom
January 2011
Harvard School of Engineering and Applied Sciences, Cambridge, MA, 02138 USA.
Recent developments in cardiac catheter technology promise to allow physicians to perform most cardiac interventions without stopping the heart or opening the chest. However, current cardiac devices, including newly developed catheter robots, are unable to accurately track and interact with the fast moving cardiac tissue without applying potentially damaging forces. This paper examines the challenges of implementing force control on a flexible robotic catheter.
View Article and Find Full Text PDFIEEE Trans Robot
July 2011
Harvard School of Engineering and Applied Sciences, Cambridge, MA, 02138 USA.
Robotic catheters have the potential to revolutionize cardiac surgery by enabling minimally invasive structural repairs within the beating heart. This paper presents an actuated catheter system that compensates for the fast motion of cardiac tissue using 3D ultrasound image guidance. We describe the design and operation of the mechanical drive system and catheter module and analyze the catheter performance limitations of friction and backlash in detail.
View Article and Find Full Text PDFIEEE ASME Trans Mechatron
July 2011
Harvard School of Engineering and Applied Sciences, Cambridge, MA, 02138 USA.
Force sensors provide critical information for robot manipulators, manufacturing processes, and haptic interfaces. Commercial force sensors, however, are generally not adapted to specific system requirements, resulting in sensors with excess size, cost, and fragility. To overcome these issues, 3D printers can be used to create components for the quick and inexpensive development of force sensors.
View Article and Find Full Text PDFJ Micromech Microeng
October 2010
Harvard School of Engineering and Applied Sciences, Cambridge, MA 02129, USA.
Precise flow control in microfluidic chips is important for many biochemical assays and experiments at microscale. While several technologies for controlling fluid flow have been implemented either on- or off-chip, these can provide either high-speed or high-precision control, but seldom could accomplish both at the same time. Here we describe a new on-chip, pneumatically activated flow controller that allows for fast and precise control of the flow rate through a microfluidic channel.
View Article and Find Full Text PDFPLoS Comput Biol
June 2011
Harvard School of Engineering and Applied Sciences, Cambridge, Massachusetts, USA.
In motor tasks, errors between planned and actual movements generally result in adaptive changes which reduce the occurrence of similar errors in the future. It has commonly been assumed that the motor adaptation arising from an error occurring on a particular movement is specifically associated with the motion that was planned. Here we show that this is not the case.
View Article and Find Full Text PDFJ Biomech Eng
April 2011
Harvard School of Engineering and Applied Sciences, Cambridge, MA 02138, USA.
We describe a modeling methodology intended as a preliminary step in the identification of appropriate constitutive frameworks for the time-dependent response of biological tissues. The modeling approach comprises a customizable rheological network of viscous and elastic elements governed by user-defined 1D constitutive relationships. The model parameters are identified by iterative nonlinear optimization, minimizing the error between experimental and model-predicted structural (load-displacement) tissue response under a specific mode of deformation.
View Article and Find Full Text PDFPhys Rev Lett
February 2011
Harvard School of Engineering and Applied Sciences, Cambridge Massachusetts 02138, USA.
We show that the "sputter patterning" topographical instability is determined by the effects of ion impact-induced prompt atomic redistribution and that erosion--the consensus predominant cause--is essentially irrelevant. We use grazing incidence small angle x-ray scattering to measure in situ the damping of noise or its amplification into patterns via the linear dispersion relation. A model based on the effects of impact-induced redistribution of those atoms that are not sputtered away explains both the observed ultrasmoothening at low angles from normal incidence and the instability at higher angles.
View Article and Find Full Text PDFJ Chem Phys
January 2011
Harvard School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
We report on oxygen surface exchange studies in ∼450-nm-thick nanocrystalline titania films with an average grain size of ∼13 nm by electrical conductivity relaxation along with the conductivity measurements at varying temperatures and oxygen partial pressures (pO(2)s). By electrochemical impedance spectroscopy technique, the high temperature conductivity was measured in the pO(2) range from ∼10(-16) to ∼10(-6) Pa at temperatures from 973 to 1223 K and activation energy, ΔE(a), for conduction was estimated as ∼3.23 eV at pO(2) ∼10(-11) Pa.
View Article and Find Full Text PDFWorld Haptics Conf
January 2011
Harvard-MIT Division of Health Sciences & Technology.
Catheter devices allow physicians to access the inside of the human body easily and painlessly through natural orifices and vessels. Although catheters allow for the delivery of fluids and drugs, the deployment of devices, and the acquisition of the measurements, they do not allow clinicians to assess the physical properties of tissue inside the body due to the tissue motion and transmission limitations of the catheter devices, including compliance, friction, and backlash. The goal of this research is to increase the tactile information available to physicians during catheter procedures by providing haptic feedback during palpation procedures.
View Article and Find Full Text PDFIEEE Trans Biomed Eng
March 2011
Harvard School of Engineering and Applied Sciences, Cambridge, MA 02138, USA.
This letter introduces MercuryLive, a platform to enable home monitoring of patients with Parkinson's disease (PD) using wearable sensors. MercuryLive contains three tiers: a resource-aware data collection engine that relies upon wearable sensors, web services for live streaming and storage of sensor data, and a web-based graphical user interface client with video conferencing capability. Besides, the platform has the capability of analyzing sensor (i.
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