Bruce Hoff - Academia.edu (original) (raw)

Papers by Bruce Hoff

Journal of Motor Behavior, 1993

Our goal was to create a principled account of a body of behavioral kinematic data on reaching an... more Our goal was to create a principled account of a body of behavioral kinematic data on reaching and grasping. We show how to transform an optimality principle for overall hand transport into a feedback control law and then incorporate look-ahead modules in the controller to compensate for delays in sensory feedback. This model describes the kinematics of hand transport under a variety of circumstances, including target perturbations. We then develop a model for the temporal coordination of reach and grasp. We provide an optimization principle for hand preshaping that trades off the costs of maintaining the hand in an open position and the cost of accelerating the change in grip size. This yields a control system for preshaping. We then show that a model that uses only expected duration for coordination, rather than kinematic or dynamic variables, can describe the kinematics of interaction of hand transport and preshape under a variety of circumstances, including perturbations of object position and object size.

Lipids in health and disease, 2006

Herein, we expand our previous work on the effects of long chain polyunsaturated fatty acids (LC-... more Herein, we expand our previous work on the effects of long chain polyunsaturated fatty acids (LC-PUFA) on the murine hepatic transcriptome using novel statistical and bioinformatic approaches for evaluating microarray data. The analyses focuses on key differences in the transcriptomic response that will influence metabolism following consumption of FUNG (rich in 20:4n6), FISH (rich in 20:5n3, 22:5n3, and 22:6n3) and COMB, the combination of the two. Using a variance-stabilized F-statistic, 371 probe sets (out of 13 K probe sets in the Affymetrix Mu11K chip set) were changed by dietary treatment (P < 0.001). Relative to other groups, COMB had unique affects on murine hepatic transcripts involved in cytoskeletal and carbohydrate metabolism; whereas FUNG affected amino acid metabolism via CTNB1 signaling. All three diets affected transcripts linked to apoptosis and cell proliferation, with evidence FISH may have increased apoptosis and decreased cell proliferation via various transc...

Neural Networks in Robotics, 1993

Developing Augmented Reality systems that work outdoors, rather than indoors in constrained envir... more Developing Augmented Reality systems that work outdoors, rather than indoors in constrained environments, will open new application areas and motivate the construction of new, more general tracking approaches. Accurate tracking outdoors is difficult because we have little control over the environment and fewer resources available compared to an indoor application. This position paper examines the individual tracking technologies available and concludes that for the near term, a hybrid solution is the only viable approach. The distortion measured from an electronic compass and tilt sensor is discussed.

Current opinion in drug discovery & development, 2001

A microarray experiment is a sequence of complicated molecular biology procedures relying on vari... more A microarray experiment is a sequence of complicated molecular biology procedures relying on various laboratory tools, instrumentation and experimenter's skills. This paper discusses statistical models for distinguishing small changes in gene expression from the noise in the system. It describes methods for assigning statistical confidence to gene expression values derived from a single array slide. Some of the theory is discussed in the context of practical applications via software usage.

Proceedings IEEE Virtual Reality (Cat. No. 99CB36316), 1999

Almost all previous Augmented Reality (AR) systems work indoors. Outdoor AR systems offer the pot... more Almost all previous Augmented Reality (AR) systems work indoors. Outdoor AR systems offer the potential for new application areas. However, building an outdoor AR system is difficult due to portability constraints, the inability to modify the environment, and the greater range of operating conditions. We demonstrate a hybrid tracker that stabilizes an outdoor AR display with respect to user motion, achieving more accurate registration than previously shown in an outdoor AR system. The hybrid tracker combines rate gyros with a compass and tilt orientation sensor in a near real-time system. Sensor distortions and delays required compensation to achieve good results. The measurements from the two sensors are fused together to compensate for each other's limitations. From static locations with moderate head rotation rates, peak registration errors are ~2 degrees, with typical errors under 1 degree, although errors can become larger over long time periods due to compass drift. Without our stabilization, even small motions make the display nearly unreadable.

Frontiers in Neuroscience, 2001

Laboratory Robotics and Automation, 2000

... Technology Alexander Kuklin, Shishir Shah, Bruce Hoff, ... This approach could potentially of... more ... Technology Alexander Kuklin, Shishir Shah, Bruce Hoff, ... This approach could potentially offer great time savings over the manual spot finding method since the user needs only to identify a few points in the image and make minor adjustments to a few spot lo-cations, if required. ...

Mobile Robots XV and Telemanipulator and Telepresence Technologies VII, 2001

International Symposium on Mixed and Augmented Reality, 2000

Accurate registration in an augmented reality system requires accurate trackers. An electronic co... more Accurate registration in an augmented reality system requires accurate trackers. An electronic compass can be a valuable sensor in an outdoor augmented reality system because it provides absolute heading estimates. However, compasses are vulnerable to distortion caused by environmental disturbances to Earth's magnetic field. These disturbances vary with geographic location and are not trivial to model. Static calibration methods exist

Biological Cybernetics, 1994

Bioinformatics, 2003

Motivation: A crucial step in microarray data analysis is the selection of subsets of interesting... more Motivation: A crucial step in microarray data analysis is the selection of subsets of interesting genes from the initial set of genes. In many cases, especially when comparing a specific condition to a reference, the genes of interest are those which are differentially expressed. Two common methods for gene selection are: (a) selection by fold difference (at least n fold variation) and (b) selection by altered ratio (at least n standard deviations away from the mean ratio). Results: The novel method proposed here is based on ANOVA and uses replicate spots to estimate an empirical distribution of the noise. The measured intensity range is divided in a number of intervals. A noise distribution is constructed for each such interval. Bootstrapping is used to map the desired confidence levels from the noise distribution corresponding to a given interval to the measured log ratios in that interval. If the method is applied on individual arrays having replicate spots, the method can calculate an overall width of the noise distribution which can be used as an indicator of the array quality. We compared this method with the fold change and unusual ratio method. We also discuss the relationship with an ANOVA model proposed by Churchill et al.

Nature Methods, 2016

It remains unclear whether causal, rather than merely correlational, relationships in molecular n... more It remains unclear whether causal, rather than merely correlational, relationships in molecular networks can be inferred in complex biological settings. Here we describe the HPN-DREAM network inference challenge, which focused on learning causal influences in signaling networks. We used phosphoprotein data from cancer cell lines as well as in silico data from a nonlinear dynamical model. Using the phosphoprotein data, we scored more than 2,000 networks submitted by challenge participants. The networks spanned 32 biological contexts and were scored in terms of causal validity with respect to unseen interventional data. A number of approaches were effective, and incorporating known biology was generally advantageous. Additional sub-challenges considered time-course prediction and visualization. Our results suggest that learning causal relationships may be feasible in complex settings such as disease states. Furthermore, our scoring approach provides a practical way to empirically assess inferred molecular networks in a causal sense.