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Search Results: 1 - 10 of 313749 matches for " D. H. Barkhuff "
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An Energy Feedback System for the MIT/Bates Linear Accelerator
D. H. Barkhuff,S. P. Wells,T. Averett,D. H. Beck,E. J. Beise,D. Cheever,G. Dodson,S. Kowalski,R. D. McKeown,B. A. Mueller,M. Pitt,D. Spayde,C. Tschalaer,A. Zolfaghari
Physics , 1999, DOI: 10.1016/S0168-9002(00)00260-6
Abstract: We report the development and implementation of an energy feedback system for the MIT/Bates Linear Accelerator Center. General requirements of the system are described, as are the specific requirements, features, and components of the system unique to its implementation at the Bates Laboratory. We demonstrate that with the system in operation, energy fluctuations correlated with the 60 Hz line voltage and with drifts of thermal origin are reduced by an order of magnitude.
Measurement of the vector analyzing power in elastic electron-proton scattering as a probe of double photon exchange amplitudes
S. P. Wells,T. Averett,D. Barkhuff,D. H. Beck,E. J. Beise,C. Benson,H. Breuer,R. Carr,S. Covrig,J. DelCorso,G. Dodson,C. Eppstein,M. Farkhondeh,B. W. Filippone,T. Forest,P. Frasier,R. Hasty,T. M. Ito,C. Jones,W. Korsch,S. Kowalski,P. Lee,E. Maneva,K. McCarty,R. D. McKeown,J. Mikell,B. Mueller,P. Naik,M. L. Pitt,J. Ritter,V. Savu,D. T. Spayde,M. Sullivan,R. Tieulent,E. Tsentalovich,B. Yang,T. Zwart
Physics , 2000, DOI: 10.1103/PhysRevC.63.064001
Abstract: We report the first measurement of the vector analyzing power in inclusive transversely polarized elastic electron-proton scattering at Q^2 = 0.1 (GeV/c)^2 and large scattering angles. This quantity should vanish in the single virtual photon exchange, plane wave impulse approximation for this reaction, and can therefore provide information on double photon exchange amplitudes for electromagnetic interactions with hadronic systems. We find a non-zero value of A=-15.4+/-5.4 ppm. No calculations of this observable for nuclei other than spin 0 have been carried out in these kinematics, and the calculation using the spin orbit interaction from a charged point nucleus of spin 0 cannot describe these data.
Targeted Disruption of TgPhIL1 in Toxoplasma gondii Results in Altered Parasite Morphology and Fitness
Whittney Dotzler Barkhuff, Stacey D. Gilk, Ryan Whitmarsh, Lucas D. Tilley, Chris Hunter, Gary E. Ward
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0023977
Abstract: The inner membrane complex (IMC), a series of flattened vesicles at the periphery of apicomplexan parasites, is thought to be important for parasite shape, motility and replication, but few of the IMC proteins that function in these processes have been identified. TgPhIL1, a Toxoplasma gondii protein that was previously identified through photosensitized labeling with 5-[125I] iodonapthaline-1-azide, associates with the IMC and/or underlying cytoskeleton and is concentrated at the apical end of the parasite. Orthologs of TgPhIL1 are found in other apicomplexans, but the function of this conserved protein family is unknown. As a first step towards determining the function of TgPhIL1 and its orthologs, we generated a T. gondii parasite line in which the single copy of TgPhIL1 was disrupted by homologous recombination. The TgPhIL1 knockout parasites have a distinctly different morphology than wild-type parasites, and normal shape is restored in the knockout background after complementation with the wild-type allele. The knockout parasites are outcompeted in culture by parasites expressing functional TgPhIL1, and they generate a reduced parasite load in the spleen and liver of infected mice. These findings demonstrate a role for TgPhIL1 in the morphology, growth and fitness of T. gondii tachyzoites.
Measurement of the Induced Proton Polarization P_n in the 12C(e,e'\vec{p}) Reaction
R. J. Woo,D. H. Barkhuff,W. Bertozzi,D. Dale,G. Dodson,K. A. Dow,M. B. Epstein,M. Farkhondeh,J. M. Finn,S. Gilad,M. K. Jones,K. Joo,J. J. Kelly,S. Kowalski,R. W. Lourie,R. Madey,D. J. Margaziotis,P. Markowitz,J. I. McIntyre,C. Mertz,B. D. Milbrath,J. Mitchell,C. F. Perdrisat,V. Punjabi,P. M. Rutt,A. J. Sarty,D. Tieger,C. Tschalaer,W. Turchinetz,P. E. Ulmer,C. Vellidis,S. P. Van Verst,G. A. Warren,L. Weinstein
Physics , 1997, DOI: 10.1103/PhysRevLett.80.456
Abstract: The first measurements of the induced proton polarization, P_n, for the 12C (e,e'\vec{p}) reaction are reported. The experiment was performed at quasifree kinematics for energy and momentum transfer (\omega,q) \approx (294 MeV, 756 MeV/c) and sampled a recoil momentum range of 0-250 MeV/c. The induced polarization arises from final-state interactions and for these kinematics is dominated by the real part of the spin-orbit optical potential. The distorted-wave impulse approximation provides good agreement with data for the 1p_{3/2} shell. The data for the continuum suggest that both the 1s_{1/2} shell and underlying l > 1 configurations contribute.
A Comparison of Polarization Observables in Electron Scattering from the Proton and Deuteron
B. D. Milbrath,J. I. McIntyre,C. S. Armstrong,D. H. Barkhuff,W. Bertozzi,D. Dale,G. Dodson,K. A. Dow,M. B. Epstein,M. Farkhondeh,J. M. Finn,S. Gilad,M. K. Jones,K. Joo,J. J. Kelly,S. Kowalski,R. W. Lourie,R. Madey,D. J. Margaziotis,P. Markowitz,C. Mertz,J. Mitchell,C. F. Perdrisat,V. Punjabi,L. Qin,P. M. Rutt,A. J. Sarty,D. Tieger,C. Tschalaer,W. Turchinetz,P. E. Ulmer,S. P. Van Verst,G. A. Warren,L. B. Weinstein,R. J. Woo
Physics , 1997, DOI: 10.1103/PhysRevLett.82.2221
Abstract: Recoil proton polarization observables were measured for both the p($\vec {\rm e}$,e$^\prime\vec{\rm p}\,$) and d($\vec {\rm e}$,e$^\prime\vec{\rm p}\,)$n reactions at two values of Q$^2$ using a newly commissioned proton Focal Plane Polarimeter at the M.I.T.-Bates Linear Accelerator Center. The hydrogen and deuterium spin-dependent observables $D_{\ell\ell}$ and $D_{{\ell}t}$, the induced polarization $P_n$ and the form factor ratio $G^p_E/G^p_M$ were measured under identical kinematics. The deuterium and hydrogen results are in good agreement with each other and with the plane-wave impulse approximation (PWIA).
Search for Quadrupole Strength in the Electro-excitation of the Delta(1232)
C. Mertz,C. Vellidis,R. Alarcon,D. H. Barkhuff,A. M. Bernstein,W. Bertozzi,V. Burkert,J. Chen,J. R. Comfort,G. Dodson,S. Dolfini,K. Dow,M. Farkhondeh,J. M. Finn,S. Gilad,R. W. Gothe,X. Jiang,K. Joo,N. I. Kaloskamis,A. Karabarbounis,J. J. Kelly,S. Kowalski,C. Kunz,R. W. Lourie,J. I. McIntyre,B. D. Milbrath,R. Miskimen,J. H. Mitchell,C. N. Papanicolas,C. F. Perdrisat,A. J. Sarty,J. Shaw,S. -B. Soong,D. Tieger,C. Tschalaer,W. Turchinetz,P. E. Ulmer,S. Van Verst,G. A. Warren,L. B. Weinstein,S. Williamson,R. J. Woo,A. Young
Physics , 1999, DOI: 10.1103/PhysRevLett.86.2963
Abstract: High-precision H(e,e'p)pi0 measurements at Q2=0.126 (GeV/c)2 are reported, which allow the determination of quadrupole amplitudes in the gamma* N->Delta transition; they simultaneously test the reliability of electroproduction models. The derived quadrupole-to-dipole amplitude ratios, Rsm=(-6.5 +- 0.2{stat+sys} +- 2.5{mod}) % and Rem=(-2.1 +- 0.2{stat+sys} +- 2.0{mod}) %, are dominated by model error. Previous Rsm and Rem results should be reconsidered after the model uncertainties associated with the method of their extraction are taken into account.
Deriving the Kutta-Joukowsky Equation and Some of Its Generalizations Using Momentum Balances  [PDF]
D. H. Wood
Open Journal of Fluid Dynamics (OJFD) , 2011, DOI: 10.4236/ojfd.2011.11002
Abstract: Momentum balances are used to derive the Kutta-Joukowsky equation for an infinite cascade of aerofoils and an isolated aerofoil. These derivations are simpler than those based on the Blasius theorem or more complex unsteady control volumes, and show the close relationship between a single aerofoil and an infinite cascade. The modification of lift due to the presence of another lifting body is similarly derived for a wing in ground effect, a biplane, and tandem aerofoils. The results are identical to those derived from the vector form of the Kutta-Joukowsky equation.
Scanning Head for the Apertureless near Field Optical Microscope  [PDF]
D. V. Kazantsev, H. Ryssel
Modern Instrumentation (MI) , 2013, DOI: 10.4236/mi.2013.22006

The design and characterization of a tip control unit for an apertureless scanning near field optical microscope (ASNOM) is reported. To make the instrument operation easier, the cantilever control parts (piezo excitation of the cantilever vibration for the dynamic mode feedback and the parts necessary for the optical lever scheme of the vibration control) were placed in a separate detachable assembly. To suppress the influence of vibrations of the setup, the assembly was made lightweight. Good optical access to the ASNOM tip from various directions is provided in the system. High long-term mechanical stability of the system (~50 nm lateral drift in 18 hours) as well as low sensitivity to seismic vibrations (~400 pm RMS) is demonstrated. It is shown that external sound is not a main source of noise in the topography image (~200 pm RMS). The light field distribution (with its amplitude and phase) around the ASNOM tip was acquired by scanning the focal spot around the tip, and a high optical quality of the system is demonstrated.

Utilizing simulation curriculum to decentralize mental health concepts  [PDF]
D. M. H. Michelle Beckford
Open Journal of Nursing (OJN) , 2013, DOI: 10.4236/ojn.2013.32031

The International Society of Psychiatric Nurses as well as The American Psychiatric Nurses Association called for decentralization of psychiatric concepts in undergraduate nursing education. The author developed a series of simulation scenarios to address therapeutic communication and psychosocial needs in a variety of patient care settings. In terms of holistic care, psychological well-being is relevant to all realms of nursing practice. Mental health assessment and intervention need to be included in all areas of an undergraduate-nursing curriculum. The purpose of this project was to create a BSN curriculum that reflects the mental health needs of patients not only in acute care psychiatric facilities but also in medical-surgical disciplines, maternity units, and community settings. The curriculum is designed to also cover mental health throughout the lifespan-from infancy to end of life. A goal was to develop educational techniques, which translate into safe practice. A series of five simulations have been created with additional scenarios to be established in the following academic year. Topics include: alcohol withdrawal, end of life care, post-traumatic stress disorder, post-partum depression, serotonin syndrome, benzodiazepine over dose, elder abuse, depression in military veterans, and geriatric depression. All incorporate QSEN competencies [1]. The overall learning objectives are for undergraduate nursing students to initiate and implement an appropriate mental status assessment using therapeutic communication, and also to provide safe care by identifying risk factors and using clinical decision making to establish requisite nursing interventions. The methodology included relevant documentation through the use of appropriate assessment tools. Learning objectives were assessed through pre-simulation and post-simulation ten-question inventory and anecdotal feedback. QSEN competencies were utilized in creating scenarios as well as pre and post testing. Students voiced an ability to connect the didactic material to their clinical experiences following simulation.

Measurement of the R$_{LT}$ response function for $π^0$ electroproduction at $Q^2$ = 0.070 (GeV/c)$^2$ in the $N\toΔ$ transition}
N. Sparveris,R. Alarcon,D. Barkhuff,A. Bernstein,W. Bertozzi,J. Calarco,F. Casagrande,J. Chen,J. Comfort,M. Distler,G. Dodson,A. Dooley,K. Dow,M. Farkondeh,S. Gilad,R. Hicks,M. Holtrop,A. Hotta,X. Jiang,N. Kaloskamis,A. Karabarbounis,S. Kowalski,C. Kunz,D. Margaziotis,C. Mertz,R. Milner,R. Miskimen,I. Nakagawa,C. Papanicolas,M. Pavan,G. Peterson,A. Ramirez,D. Rowntree,A. Sarty,J. Shaw,E. Six,S. Soong,S. Stiliaris,D. Tieger,C. Tschalaer,W. Turchinetz,C. Vellidis,G. Warren,A. Young,J. Zhao,Z. Zhou,T. Zwart
Physics , 2002, DOI: 10.1103/PhysRevC.67.058201
Abstract: Quadrupole amplitudes in the $\gamma^{*}N\to\Delta$ transition are associated with the issue of nucleon deformation. A search for these small amplitudes has been the focus of a series of measurements undertaken at Bates/MIT by the OOPS collaboration. We report on results from H$(e,e^\prime p)\pi^0$ data obtained at $Q^2= 0.070$ (GeV/c)$^2$ and invariant mass of W=1155 MeV using the out-of-plane detection technique with the OOPS spectrometers. The $\sigma_{LT}$ and $\sigma_{T}+\epsilon\cdot$ $\sigma_{L}$ response functions were isolated. These results, along with those of previous measurements at $W$=1172 MeV and $Q^2= 0.127$ (GeV/c)$^2$, aim in elucidating the interplay between resonant and non resonant amplitudes.
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