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Search Results: 1 - 10 of 248130 matches for " John C. Hoffman "
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A High-Speed Dynamic Partial Reconfiguration Controller Using Direct Memory Access Through a Multiport Memory Controller and Overclocking with Active Feedback
John C. Hoffman,Marios S. Pattichis
International Journal of Reconfigurable Computing , 2011, DOI: 10.1155/2011/439072
Abstract: Dynamically reconfigurable computing platforms provide promising methods for dynamic management of hardware resources, power, and performance. Yet, progress in dynamically reconfigurable computing is fundamentally limited by the reconfiguration time overhead. Prior research in the development of dynamic partial reconfiguration (DPR) controllers has been limited by its use of the Processor Local Bus (PLB). As a result, the bus was unavailable during DPR. This resulted in significant time overhead. To minimize the overhead, we introduce the use of a multiport memory controller (MPMC) that frees the PLB during the reconfiguration process. The processor is thus allowed to switch to other tasks during the reconfiguration operation. This effectively limits the reconfiguration overhead. An interrupt is used to inform the processor when the operation is complete. Therefore, the system can multitask during the reconfiguration operation. Furthermore, to maximize performance, we introduce the use of overclocking with active feedback. During overclocking, the use of active feedback is used to ensure that the device voltage and temperature are within nominal operating conditions. All of these contributions lead to significant performance improvements over current partial reconfiguration subsystems. The portability of the system, demonstrated on the Virtex-4 and the Virtex-5, consists of four different hardware platforms. 1. Introduction As the speed and size of FPGA reconfigurable fabric has grown, the ability to perform multiple complex parallel applications, using a single device, has become a reality. For example, as early as 2003, the BMW Williams F1 team was running its fifth generation vehicle control and monitoring (VCM) unit with a Texas Instruments DSP and a Xilinx Virtex family of FPGA devices to control mission critical operations [1]. Today, FPGAs have increased product features and decreased product time to market and given system designers abilities that were only possible with the use of custom ASICs. Dynamic partial reconfiguration allows the FPGA programmable fabric to change its mode of operation during run time. Effectively, dynamic partial reconfiguration (DPR) allows for time-division multiplexing portions of the FPGA fabric, while the system is operating. Future systems are likely to benefit from the development of effective systems that use DPR to provide for dynamic performance and power control. Currently, when considering partial reconfiguration, the largest bottleneck is the time it takes to switch hardware resources. When a device is
Power-law rheology and mechano-sensing in a cytoskeleton model with forced protein unfolding
Brenton D. Hoffman,Gladys Massiera,John C. Crocker
Physics , 2005,
Abstract: We describe a model of cytoskeletal mechanics based on the force-induced conformational change of protein cross-links in a stressed polymer network. Slow deformation of simulated networks containing cross-links that undergo repeated, serial domain unfolding leads to an unusual state--with many cross-links accumulating near the critical force for further unfolding. Thermal activation of these links gives rise to power-law rheology resembling the previously unexplained mechanical response of living cells. Moreover, we hypothesize that such protein cross-links function as biochemical mechano-sensors of cytoskeletal deformation.
Disproportionate Contribution of Right Middle Lobe to Emphysema and Gas Trapping on Computed Tomography
Surya P. Bhatt, Jessica C. Sieren, John D. Newell, Alejandro P. Comellas, Eric A. Hoffman
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0102807
Abstract: Rationale Given that the diagnosis of chronic obstructive pulmonary disease (COPD) relies on demonstrating airflow limitation by spirometry, which is known to be poorly sensitive to early disease, and to regional differences in emphysema, we sought to evaluate individual lobar contributions to global spirometric measures. Methods Subjects with COPD were compared with smokers without airflow obstruction, and non-smokers. Emphysema (% low attenuation area, LAAinsp<?950 HU, at end-inspiration) and gas trapping (%LAAexp<?856 HU at end-expiration) on CT were quantified using density mask analyses for the whole lung and for individual lobes, and distribution across lobes and strength of correlation with spirometry were compared. Results The right middle lobe had the highest %LAAinsp<?950 HU in smokers and controls, and the highest %LAAexp<?856 HU in all three groups. While RML contributed to emphysema and gas trapping disproportionately to its relatively small size, it also showed the least correlation with spirometry. There was no change in correlation of whole lung CT metrics with spirometry when the middle lobe was excluded from analyses. Similarly, RML had the highest %LAAexp<?856 HU while having the least correlation with spirometry. Conclusions Because of the right middle lobe’s disproportionate contribution to CT-based emphysema measurements, and low contribution to spirometry, longitudinal studies of emphysema progression may benefit from independent analysis of the middle lobe in whole lung quantitative CT assessments. Our findings may also have implications for heterogeneity assessments and target lobe selection for lung volume reduction. Clinical Trial Registration ClinicalTrials.gov NCT00608764
Stellar Polarimetry: Where Are We and Where Are We Going?
Jennifer L. Hoffman,John C. Brown,Kenneth Nordsieck,Nicole St-Louis,Gregg Wade
Physics , 2012, DOI: 10.1063/1.3701943
Abstract: On the final day of the Stellar Polarimetry conference, participants split up into three "breakout sessions" to discuss the future of the field in the areas of instrumentation, upcoming opportunities, and community priorities. This contribution compiles the major recommendations arising from each breakout session. We hope that the polarimetric community will find these ideas useful as we consider how to maintain the vitality of polarimetry in the coming years.
Charge transfer and interfacial magnetism in (LaNiO3)n/(LaMnO3)2 superlattices
Jason Hoffman,I. C. Tung,Brittany Nelson-Cheeseman,Ming Liu,John Freeland,Anand Bhattacharya
Physics , 2013, DOI: 10.1103/PhysRevB.88.144411
Abstract: (LaNiO3)n/(LaMnO3)2 superlattices were grown using ozone-assisted molecular beam epitaxy, where LaNiO3 is a paramagnetic metal and LaMnO3 is an antiferromagnetic insulator. The superlattices exhibit excellent crystallinity and interfacial roughness of less than 1 unit cell. X-ray spectroscopy and dichroism measurements indicate that electrons are transferred from the LaMnO3 to the LaNiO3, inducing magnetism in LaNiO3. Magnetotransport measurements reveal a transition from metallic to insulating behavior as the LaNiO3 layer thickness is reduced from 5 unit cells to 2 unit cells and suggest a modulated magnetic structure within LaNiO3.
Embedded minimal ends asymptotic to the helicoid
John McCuan,David Hoffman
Mathematics , 1997,
Abstract: The ends of a complete embedded minimal surface of {\em finite total curvature} are well understood (every such end is asymptotic to a catenoid or to a plane). We give a similar characterization for a large class of ends of {\em infinite total curvature}, showing that each such end is asymptotic to a helicoid. The result applies, in particular, to the genus one helicoid and implies that it is embedded outside of a compact set in ${\mathbb R}^3$.
Sexual dimorphism in immune response genes as a function of puberty
Rebecca Lamason, Po Zhao, Rashmi Rawat, Adrian Davis, John C Hall, Jae Chae, Rajeev Agarwal, Phillip Cohen, Antony Rosen, Eric P Hoffman, Kanneboyina Nagaraju
BMC Immunology , 2006, DOI: 10.1186/1471-2172-7-2
Abstract: After the onset of puberty, female mice showed a higher expression of adaptive immune response genes, while males had a higher expression of innate immune genes. This result suggested a requirement for sex hormones. Using in vivo and in vitro assays in normal and mutant mouse strains, we found that reverse signaling through FasL was directly influenced by estrogen, with downstream consequences of increased CD8+ T cell-derived B cell help (via cytokines) and enhanced immunoglobulin production.These results demonstrate that sexual dimorphism in innate and adaptive immune genes is dependent on puberty. This study also revealed that estrogen influences immunoglobulin levels in post-pubertal female mice via the Fas-FasL pathway.The incidence and severity of human diseases vary between the sexes: For example, autoimmune diseases are generally more common in females than in males and are most marked in women of childbearing age [1-3]. Thus, it appears that susceptibility to autoimmunity is expressed at the time of puberty. Puberty is a period of intense molecular, physiological and anatomical reorganization in the body, and the hormonal changes occurring at the time of puberty lay the framework for biological differences that persist throughout life and may contribute to the variable onset and progression of disease in males and females [4]. Sex-related differences in disease susceptibility have also been observed in several mouse models of infectious and autoimmune diseases and may be related to differences in the expression patterns of immune response genes [5,6].Immune responses are sexually dimorphic, both in type and magnitude. Two general systems of immunity to infectious agents have been selected during evolution: innate (natural) immunity, and acquired (adaptive or specific) immunity. The innate immune system uses proteins encoded in the germline (on macrophages, mast cells, natural killer cells) to recognize conserved products of infectious non-self (i.e., microbi
Estimating myocardial perfusion from dynamic contrast-enhanced CMR with a model-independent deconvolution method
Nathan A Pack, Edward VR DiBella, Thomas C Rust, Dan J Kadrmas, Christopher J McGann, Regan Butterfield, Paul E Christian, John M Hoffman
Journal of Cardiovascular Magnetic Resonance , 2008, DOI: 10.1186/1532-429x-10-52
Abstract: An iterative model-independent analysis method was developed and tested to estimate regional and pixelwise myocardial perfusion in five normal subjects imaged with a saturation recovery turboFLASH sequence at 3 T CMR. Estimates of myocardial perfusion using model-independent analysis are dependent on the choice of the regularization weight parameter, which increases nonlinearly to handle large decreases in the contrast-to-noise ratio of the measured tissue enhancement data. Quantitative perfusion estimates in five subjects imaged with 3 T CMR were 1.1 ± 0.8 ml/min/g at rest and 3.1 ± 1.7 ml/min/g at adenosine stress. The perfusion estimates correlated with dynamic 13N-ammonia PET (y = 0.90x + 0.24, r = 0.85) and were similar to results from other validated CMR studies.This work shows that a model-independent analysis method that uses iterative minimization and temporal regularization can be used to quantify myocardial perfusion with dynamic contrast-enhanced perfusion CMR. Results from this method are robust to choices in the regularization weight parameter over relatively large ranges in the contrast-to-noise ratio of the tissue enhancement data.Dynamic contrast-enhanced cardiovascular magnetic resonance (DCE-CMR) is a commonly used tool for detecting and quantifying reductions in myocardial blood flow (perfusion) in patients with coronary artery disease (CAD). The early diagnosis of CAD can provide valuable information that may affect interventional strategies in patients with ischemia [1]. In DCE-CMR perfusion studies, a paramagnetic gadolinium (Gd) complex is injected into the patient while at rest and at stress–during which a pharmacological vasodilator (adenosine) is simultaneously administered to the patient. Once the Gd is injected, it flows through the heart and temporarily distributes in the myocardium before being 'washed out' of the body. The spatiotemporal distribution of Gd within the heart can be measured dynamically and the resultant blood and tissue
The Newly Developed CRF1-Receptor Antagonists, NGD 98-2 and NGD 9002, Suppress Acute Stress-Induced Stimulation of Colonic Motor Function and Visceral Hypersensitivity in Rats
Mulugeta Million, Jing-Fang Zhao, Andrew Luckey, József Czimmer, George D. Maynard, John Kehne, Diane C. Hoffman, Yvette Taché
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0073749
Abstract: Corticotropin releasing factor receptor 1 (CRF1) is the key receptor that mediates stress-related body responses. However to date there are no CRF1 antagonists that have shown clinical efficacy in stress-related diseases. We investigated the inhibitory effects of a new generation, topology 2 selective CRF1 antagonists, NGD 98-2 and NGD 9002 on exogenous and endogenous CRF-induced stimulation of colonic function and visceral hypersensitivity to colorectal distension (CRD) in conscious rats. CRF1 antagonists or vehicle were administered orogastrically (og) or subcutaneously (sc) before either intracerebroventricular (icv) or intraperitoneal (ip) injection of CRF (10 μg/kg), exposure to water avoidance stress (WAS, 60 min) or repeated CRD (60 mmHg twice, 10 min on/off at a 30 min interval). Fecal pellet output (FPO), diarrhea and visceromotor responses were monitored. In vehicle (og)-pretreated rats, icv CRF stimulated FPO and induced diarrhea in >50% of rats. NGD 98-2 or NGD 9002 (3, 10 and 30 mg/kg, og) reduced the CRF-induced FPO response with an inhibitory IC50 of 15.7 and 4.3 mg/kg respectively. At the highest dose, og NGD 98-2 or NGD 9002 blocked icv CRF-induced FPO by 67–87% and decreased WAS-induced-FPO by 23–53%. When administered sc, NGD 98-2 or NGD 9002 (30 mg/kg) inhibited icv and ip CRF-induced-FPO. The antagonists also prevented the development of nociceptive hyper-responsivity to repeated CRD. These data demonstrate that topology 2 CRF1 antagonists, NGD 98-2 and NGD 9002, administered orally, prevented icv CRF-induced colonic secretomotor stimulation, reduced acute WAS-induced defecation and blocked the induction of visceral sensitization to repeated CRD.
Spectroscopic and Spectropolarimetric Observations of V838 Mon
John P. Wisniewski,Nancy D. Morrison,Karen S. Bjorkman,Anatoly S. Miroshnichenko,Amanda C. Gault,Jennifer L. Hoffman,Marilyn R. Meade,Jason M. Nett
Physics , 2003, DOI: 10.1086/373897
Abstract: The spectroscopic and spectropolarimetric variability of the peculiar variable V838 Monocerotis during the brighter phases of its multiple outbursts in 2002 is presented. Significant line profile variability of H$\alpha$ and Si II 6347.10\AA & 6371.36\AA occurred in spectra obtained between 2002 February 5 and 2002 March 14, and a unique secondary absorption component was observed near the end of this time period. Our observations also suggest that multiple shifts in ionization states occurred during the outbursts. Spectropolarimetric observations reveal that V838 Mon exhibited both intrinsic and interstellar polarization components during the initial stages of the second outburst, indicating the presence of an asymmetric geometry; however, the intrinsic component had significantly declined by February 14. We determine the interstellar polarization to be $P_{max} = 2.746 \pm 0.011 %$, $\lambda_{max} = 5790 \pm 37\AA$, $PA = 153.43 \pm 0.12 ^{\circ} $, and we find the integrated intrinsic V band polarization on February 5 to be $P = 0.983 \pm 0.012 %$ at a position angle of $127.0 \pm 0.5^{\circ}$. The implications of these observations for the nature of V838 Monocerotis, its distance, and its ejecta are discussed.
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