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Papers by Daniel Hernandez

The Journal of Strength and Conditioning Research, 2003

Net O 2 uptake was measured from maximal-effort 3-set, 8repetition seated leg press protocols on ... more Net O 2 uptake was measured from maximal-effort 3-set, 8repetition seated leg press protocols on an isoinertial ergometer. Subjects (25 women, 9 men) did 2 workouts each exerting concentric-eccentric (CE) and concentric-only (CO) knee extensor forces to measure work and net caloric cost. Significant (p Ͻ 0.05) relationships between work and net caloric cost resulted from CE and CO workouts for the male, female, and total subject sample. Two-way repeated-measures analyses of variance showed CE workouts resulted in significantly higher work but not net caloric cost and values. CE workouts likely relied on the knee extensors series elastic element to perform an additional ϳ3,600 J of eccentric work at no additional net caloric cost. Unlike other exercise modes, maximal-effort eccentric actions on the isoinertial ergometer, as done in the current study, provide no additional net caloric cost and is thus safe to administer to populations in whom metabolic cost is a concern.

Molecular biology of the cell, Dec 12, 2016

In the hearts of patients bearing nebulette mutations, a severe general disorganization in cardio... more In the hearts of patients bearing nebulette mutations, a severe general disorganization in cardiomyocytes of the extrasarcomeric desmin intermediate filament system is frequently observed. However, the molecular and functional relationship between the desmin cytoskeleton and nebulette-containing sarcomeres is still unclear. Here we report a high-affinity in vitro interaction between nebulette and desmin filaments. A major interaction site has been mapped to the desmin α-helical rod domain indicating that the filament core is directly involved in the binding of nebulette. The disease-mutant desmin variants E245D and T453I exhibited increased binding affinity for nebulette, delayed filament assembly kinetics and caused significant weakening of networks. In isolated chick cardiomyocytes and sections from canine heart, we revealed by ground-state-depletion and confocal microscopies that module 5 of nebulette extends outward from Z-disk associated desmin filaments toward the center of th...

Biomedical engineering online, Jan 21, 2015

In high field MRI capable of multi-channel radio frequency (RF) transmission, B 1 shimming is a t... more In high field MRI capable of multi-channel radio frequency (RF) transmission, B 1 shimming is a time-consuming job because conventional B 1 shimming techniques require B 1 mapping for each channel. After acquiring the complex-numbered B 1 field maps, the optimal amplitude and phase of the driving RF pulse are determined for each channel to maximize the B 1 field uniformity in conventional B 1 shimming. However, time-consuming B 1 shimming procedures at the pre-scan may not be tolerated in the clinical imaging in which patient throughput is one of the important factors. To avoid the time-consuming B 1 mapping, the first spin echo and the stimulated echo were repeatedly acquired in the slice-selective stimulated echo sequence without imaging gradients. A cost function of the amplitudes and phases of the driving RF pulse for every channel was defined in a way that the ratio between the spin echo and stimulated echo amplitudes rapidly converged to √ 2. The amplitude and phase of the dri...

SPIE Proceedings, 2012

ABSTRACT Scan time of spectral-CTs is much longer than conventional CTs due to limited number of ... more ABSTRACT Scan time of spectral-CTs is much longer than conventional CTs due to limited number of x-ray photons detectable by photon-counting detectors. However, the spectral pixel information in spectral-CT has much richer information on physiological and pathological status of the tissues than the CT-number in conventional CT, which makes the spectral- CT one of the promising future imaging modalities. One simple way to reduce the scan time in spectral-CT imaging is to reduce the number of views in the acquisition of projection data. But, this may result in poorer SNR and strong streak artifacts which can severely compromise the image quality. In this work, spectral-CT projection data were obtained from a lab-built spectral-CT consisting of a single CdTe photon counting detector, a micro-focus x-ray tube and scan mechanics. For the image reconstruction, we used two iterative image reconstruction methods, the simultaneous iterative reconstruction technique (SIRT) and the total variation minimization based on conjugate gradient method (CG-TV), along with the filtered back-projection (FBP) to compare the image quality. From the imaging of the iodine containing phantoms, we have observed that SIRT and CG-TV are superior to the FBP method in terms of SNR and streak artifacts.

The Journal of Strength and Conditioning Research, 2003

Net O 2 uptake was measured from maximal-effort 3-set, 8repetition seated leg press protocols on ... more Net O 2 uptake was measured from maximal-effort 3-set, 8repetition seated leg press protocols on an isoinertial ergometer. Subjects (25 women, 9 men) did 2 workouts each exerting concentric-eccentric (CE) and concentric-only (CO) knee extensor forces to measure work and net caloric cost. Significant (p Ͻ 0.05) relationships between work and net caloric cost resulted from CE and CO workouts for the male, female, and total subject sample. Two-way repeated-measures analyses of variance showed CE workouts resulted in significantly higher work but not net caloric cost and values. CE workouts likely relied on the knee extensors series elastic element to perform an additional ϳ3,600 J of eccentric work at no additional net caloric cost. Unlike other exercise modes, maximal-effort eccentric actions on the isoinertial ergometer, as done in the current study, provide no additional net caloric cost and is thus safe to administer to populations in whom metabolic cost is a concern.

Molecular biology of the cell, Dec 12, 2016

In the hearts of patients bearing nebulette mutations, a severe general disorganization in cardio... more In the hearts of patients bearing nebulette mutations, a severe general disorganization in cardiomyocytes of the extrasarcomeric desmin intermediate filament system is frequently observed. However, the molecular and functional relationship between the desmin cytoskeleton and nebulette-containing sarcomeres is still unclear. Here we report a high-affinity in vitro interaction between nebulette and desmin filaments. A major interaction site has been mapped to the desmin α-helical rod domain indicating that the filament core is directly involved in the binding of nebulette. The disease-mutant desmin variants E245D and T453I exhibited increased binding affinity for nebulette, delayed filament assembly kinetics and caused significant weakening of networks. In isolated chick cardiomyocytes and sections from canine heart, we revealed by ground-state-depletion and confocal microscopies that module 5 of nebulette extends outward from Z-disk associated desmin filaments toward the center of th...

Biomedical engineering online, Jan 21, 2015

In high field MRI capable of multi-channel radio frequency (RF) transmission, B 1 shimming is a t... more In high field MRI capable of multi-channel radio frequency (RF) transmission, B 1 shimming is a time-consuming job because conventional B 1 shimming techniques require B 1 mapping for each channel. After acquiring the complex-numbered B 1 field maps, the optimal amplitude and phase of the driving RF pulse are determined for each channel to maximize the B 1 field uniformity in conventional B 1 shimming. However, time-consuming B 1 shimming procedures at the pre-scan may not be tolerated in the clinical imaging in which patient throughput is one of the important factors. To avoid the time-consuming B 1 mapping, the first spin echo and the stimulated echo were repeatedly acquired in the slice-selective stimulated echo sequence without imaging gradients. A cost function of the amplitudes and phases of the driving RF pulse for every channel was defined in a way that the ratio between the spin echo and stimulated echo amplitudes rapidly converged to √ 2. The amplitude and phase of the dri...

SPIE Proceedings, 2012

ABSTRACT Scan time of spectral-CTs is much longer than conventional CTs due to limited number of ... more ABSTRACT Scan time of spectral-CTs is much longer than conventional CTs due to limited number of x-ray photons detectable by photon-counting detectors. However, the spectral pixel information in spectral-CT has much richer information on physiological and pathological status of the tissues than the CT-number in conventional CT, which makes the spectral- CT one of the promising future imaging modalities. One simple way to reduce the scan time in spectral-CT imaging is to reduce the number of views in the acquisition of projection data. But, this may result in poorer SNR and strong streak artifacts which can severely compromise the image quality. In this work, spectral-CT projection data were obtained from a lab-built spectral-CT consisting of a single CdTe photon counting detector, a micro-focus x-ray tube and scan mechanics. For the image reconstruction, we used two iterative image reconstruction methods, the simultaneous iterative reconstruction technique (SIRT) and the total variation minimization based on conjugate gradient method (CG-TV), along with the filtered back-projection (FBP) to compare the image quality. From the imaging of the iodine containing phantoms, we have observed that SIRT and CG-TV are superior to the FBP method in terms of SNR and streak artifacts.