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Gutierrez D.B.,Medical University of South Carolina | Gutierrez D.B.,Vanderbilt University | Garland D.L.,U.S. National Institutes of Health | Garland D.L.,Massachusetts Eye and Ear Infirmary | And 4 more authors.
Experimental Eye Research | Year: 2016

In the human ocular lens it is now realized that post-translational modifications can alter protein function and/or localization in fiber cells that no longer synthesize proteins. The specific sites of post-translational modification to the abundant ocular lens membrane proteins AQP0 and MP20 have been previously identified and their functional effects are emerging. To further understand how changes in protein function and/or localization induced by these modifications alter lens homeostasis, it is necessary to determine the spatial distributions of these modifications across the lens. In this study, a quantitative LC-MS approach was used to determine the spatial distributions of phosphorylated AQP0 and MP20 peptides from manually dissected, concentric layers of fiber cells from young and aged human lenses. The absolute amounts of phosphorylation were determined for AQP0 Ser235 and Ser229 and for MP20 Ser170 in fiber cells from the lens periphery to the lens center. Phosphorylation of AQP0 Ser229 represented a minor portion of the total phosphorylated AQP0. Changes in spatial distributions of phosphorylated APQ0 Ser235 and MP20 Ser170 correlated with regions of physiological interest in aged lenses, specifically, where barriers to water transport and extracellular diffusion form. © 2016


Boyd S.W.,Scientific Research Corporation | Boyd S.W.,Clemson University | Frye J.M.,Johns Hopkins University | Frye J.M.,Clemson University | And 3 more authors.
IEEE Transactions on Communications | Year: 2012

If a frequency band has primary and secondary users, then the cognitive radios of the secondary users must monitor the band and be prepared to cease their transmissions if a primary user's radio begins to transmit. Traditional spectrum sensing requires the secondary radios to refrain from communicating while they check for the emergence of primary signals. We propose and evaluate methods by which the secondary radios can continue their communications while simultaneously monitoring the band to detect any transmissions that are initiated by the primary radios. Our methods for spectrum monitoring supplement traditional spectrum sensing and improve the communications efficiency of the secondary radios. © 2012 IEEE.


Biswas P.K.,Scientific Research Corporation
IEEE Systems Journal | Year: 2010

Multicasting is an important and challenging goal for heterogeneous wireless ad hoc networks, as it allows transmission and routing of packets to multiple destinations using fewer network resources. In mission-critical environments, the same information needs to reach multiple destinations with minimum delay and loss. This calls for formal and systematic techniques that can capture requirements adequately and implement them accurately, thereby providing the desired level of quality of service (QoS) for multicast communications. This paper provides a formal model for the heterogeneous wireless network and proposes a formal language that can specify and implement requirements, policies, instructions and abstractions for multicast communication over such networks. The language, named Multicast Specification and Implementation Language (MSIL), is also presented as a communication and control language for multicast configuration management, transmission, routing and QoS. The syntax and semantics of MSIL are described and discussed in detail. The applicability of MSIL constructs in modeling requirements for multicast network management is analyzed and demonstrated. Example MSIL programs, illustrating the expressiveness of the language, are developed for multicast QoS. © 2010 IEEE.


Barsanti R.J.,The Citadel | Larue J.,Scientific Research Corporation
Conference Proceedings - IEEE SOUTHEASTCON | Year: 2011

The recently published DVB-T2 standard provides for the use of two separate methods directed at reducing the signal peak to average power ratio. This paper investigates the effectiveness of the Active Constellation Extension method, and the Reserve Carrier Algorithm method through the use of simulations using Matlab software. Enhanced performance is demonstrated by using both techniques simultaneously. © 2011 IEEE.


Walters D.,Scientific Research Corporation | Shauger J.,Space and Naval Warfare Systems Center Pacific
International Journal of System of Systems Engineering | Year: 2011

The system of systems (SoS) engineering (SoSE) methodology is a rigorous engineering analysis that invests heavily in the understanding and framing of an SoS problem under study. It is a guide to be adapted to the particular circumstances that define its application. By requiring a rigorous engineering analysis of the SoS problem and its associated context, the SoSE methodology minimises the chance that a Type III error of solving the wrong problem will be committed at the outset of an SoSE analysis. This approach was applied to a specific SoS issue affecting the US Navy in order to expose engineers and technicians to SoSE thinking, techniques, and methods with which Navy technical personnel can effectively deal with 21st century SoS challenges. The application's primary goal of applying the knowledge, skills, and abilities acquired by the participants was realised with execution of a capstone exercise. The secondary goal of influencing fleet capability has yet to be realised. © 2011 Inderscience Enterprises Ltd.


Walters D.,Scientific Research Corporation
International Journal of System of Systems Engineering | Year: 2011

The application of a formal systems-based methodology for the analysis of a system of systems engineering problem has provided a rigorous framework that invests heavily in the understanding and framing of the problem under study. This paper discusses how a unique perspective was designed and applied during the analysis of complex US Navy system of systems. © 2011 Inderscience Enterprises Ltd.


Syvorotka I.I.,Scientific Research Company | Vetoshko P.M.,Institute of Radioengineering and Electronics | Skidanov V.A.,Institute for Design Problems in Microelectronics | Shavrov V.G.,Institute of Radioengineering and Electronics | Syvorotka I.M.,Scientific Research Company
IEEE Transactions on Magnetics | Year: 2015

Iron garnet films with various compositions Y3Fe5O12 (YIG), (LuPr)3Fe5O12 (LuPrIG), and Tm3(FeSc)5O12 (TmScIG) were grown by liquid phase epitaxy on gadolinium gallium garnet substrates. The angular dependences of in-plane transverse magnetic susceptibility χ′(φ) were investigated to estimate their applicability as a fluxgate core. The χ′(φ) dependence permitted the determination of the anisotropy field HC in the film plane. Experimentally obtained values of HC show good agreement with theoretical values and correspond to 2.5, 0.92, and 0.03 Oe for YIG, LuPrIG, and TmScIG epitaxial films, respectively. The influence of garnet composition on mechanisms of decreasing of induced in-plane anisotropy field was determined. TmScIG films exhibit about 100-fold reduction in the anisotropy in the plane of the film as compared with films of pure YIG. © 2015 IEEE.


Boyd S.W.,Scientific Research Corporation | Pursley M.B.,Clemson University
IEEE Transactions on Aerospace and Electronic Systems | Year: 2013

Our protocol adapts the error-control code and spreading factor on the links of a direct-sequence (DS) spread-spectrum packet radio network. The radios employ half-duplex transmission, and they operate with fixed power and bandwidth. There are no base stations, access points, or other infrastructure, and the protocol requires no power measurements or channel estimates. We compare the protocol with hypothetical ideal protocols that have perfect channel state information and maximize the throughput for each packet transmission. © 1965-2011 IEEE.


Spainhour J.C.G.,Medical University of South Carolina | Janech M.G.,Medical University of South Carolina | Schwacke J.H.,Scientific Research Corporation | Velez J.C.Q.,Medical University of South Carolina | And 2 more authors.
PLoS ONE | Year: 2014

Matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) coupled with stable isotope standards (SIS) has been used to quantify native peptides. This peptide quantification by MALDI-TOF approach has difficulties quantifying samples containing peptides with ion currents in overlapping spectra. In these overlapping spectra the currents sum together, which modify the peak heights and make normal SIS estimation problematic. An approach using Gaussian mixtures based on known physical constants to model the isotopic cluster of a known compound is proposed here. The characteristics of this approach are examined for single and overlapping compounds. The approach is compared to two commonly used SIS quantification methods for single compound, namely Peak Intensity method and Riemann sum area under the curve (AUC) method. For studying the characteristics of the Gaussian mixture method, Angiotensin II, Angiotensin-2-10, and Angiotenisn-1-9 and their associated SIS peptides were used. The findings suggest, Gaussian mixture method has similar characteristics as the two methods compared for estimating the quantity of isolated isotopic clusters for single compounds. All three methods were tested using MALDI-TOF mass spectra collected for peptides of the renin-angiotensin system. The Gaussian mixture method accurately estimated the native to labeled ratio of several isolated angiotensin peptides (5.2% error in ratio estimation) with similar estimation errors to those calculated using peak intensity and Riemann sum AUC methods (5.9% and 7.7%, respectively). For overlapping angiotensin peptides, (where the other two methods are not applicable) the estimation error of the Gaussian mixture was 6.8%, which is within the acceptable range. In summary, for single compounds the Gaussian mixture method is equivalent or marginally superior compared to the existing methods of peptide quantification and is capable of quantifying overlapping (convolved) peptides within the acceptable margin of error. © 2014 Spainhour et al.


PubMed | Medical University of South Carolina and Scientific Research Corporation
Type: Journal Article | Journal: PloS one | Year: 2014

Matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) coupled with stable isotope standards (SIS) has been used to quantify native peptides. This peptide quantification by MALDI-TOF approach has difficulties quantifying samples containing peptides with ion currents in overlapping spectra. In these overlapping spectra the currents sum together, which modify the peak heights and make normal SIS estimation problematic. An approach using Gaussian mixtures based on known physical constants to model the isotopic cluster of a known compound is proposed here. The characteristics of this approach are examined for single and overlapping compounds. The approach is compared to two commonly used SIS quantification methods for single compound, namely Peak Intensity method and Riemann sum area under the curve (AUC) method. For studying the characteristics of the Gaussian mixture method, Angiotensin II, Angiotensin-2-10, and Angiotenisn-1-9 and their associated SIS peptides were used. The findings suggest, Gaussian mixture method has similar characteristics as the two methods compared for estimating the quantity of isolated isotopic clusters for single compounds. All three methods were tested using MALDI-TOF mass spectra collected for peptides of the renin-angiotensin system. The Gaussian mixture method accurately estimated the native to labeled ratio of several isolated angiotensin peptides (5.2% error in ratio estimation) with similar estimation errors to those calculated using peak intensity and Riemann sum AUC methods (5.9% and 7.7%, respectively). For overlapping angiotensin peptides, (where the other two methods are not applicable) the estimation error of the Gaussian mixture was 6.8%, which is within the acceptable range. In summary, for single compounds the Gaussian mixture method is equivalent or marginally superior compared to the existing methods of peptide quantification and is capable of quantifying overlapping (convolved) peptides within the acceptable margin of error.

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