Books by David Pritchard
Holding the Media Accountable: Citizens, Ethics, and the Law
Collection of empirical studies of media accountability in action.
Les journalistes canadiens: Un portrait de fin de siècle
First-ever survey of a representative sample of Canadian journalists from all kinds of media, inc... more First-ever survey of a representative sample of Canadian journalists from all kinds of media, including television, radio, daily and weekly newspapers, wire services, and magazines.
Papers by David Pritchard
International Journal For Parasitology, 1995
Brophy P. M., Ben-Smith A., Brown A., Behnke J. M. & Pritchard D. I. 1995. Differential expressio... more Brophy P. M., Ben-Smith A., Brown A., Behnke J. M. & Pritchard D. I. 1995. Differential expression of glutathione S-transferase (GST) by adult Heligmosomoides polygyrus during primary infection in fast and slow responding hosts. Znternutionaf
Journal of the Optical Society of America a Optics and Image Science, Sep 1, 1992
A numerical model of a multiple-grating interferometer is presented. The foundation of the model ... more A numerical model of a multiple-grating interferometer is presented. The foundation of the model is an efficient algorithm that computes the propagation of a wave governed by the Helmholtz equation between two parallel planes in O(N log N) time, where N is the number of transverse sample points. The algorithm provides a large improvement in computational time over O(N 2 ) brute-force approaches and has the advantage that the computational time increases linearly with the number of planes in the interferometer. The model is applied to a three-grating atom interferometer to calculate the loss of contrast in the interference signal as a function of longitudinal grating misposition and to investigate the effects of wide beam-collimating slits.
Triple-acting Lytic Enzyme Treatment of Drug-Resistant and Intracellular Staphylococcus aureus
Scientific reports, Apr 28, 2016
Multi-drug resistant bacteria are a persistent problem in modern health care, food safety and ani... more Multi-drug resistant bacteria are a persistent problem in modern health care, food safety and animal health. There is a need for new antimicrobials to replace over used conventional antibiotics. Here we describe engineered triple-acting staphylolytic peptidoglycan hydrolases wherein three unique antimicrobial activities from two parental proteins are combined into a single fusion protein. This effectively reduces the incidence of resistant strain development. The fusion protein reduced colonization by Staphylococcus aureus in a rat nasal colonization model, surpassing the efficacy of either parental protein. Modification of a triple-acting lytic construct with a protein transduction domain significantly enhanced both biofilm eradication and the ability to kill intracellular S. aureus as demonstrated in cultured mammary epithelial cells and in a mouse model of staphylococcal mastitis. Interestingly, the protein transduction domain was not necessary for reducing the intracellular path...
Immunosuppressive proteins secreted by the gastrointestinal nematode parasite Heligmosomoides polygyrus
International Journal For Parasitology, Jul 31, 1994
New Experimental Evidence on the Van der Waals Interaction between Alkalis
Physics of Electronic and Atomic Collisions Icpeac Vi, 1969
Diffraction of Atoms by a Transmission Grating
Physical Review Letters, Oct 1, 1988
Diffraction of Atoms by a Transmission Grating. DW Keith, ML Schattenburg, Henry I. Smith, and DE... more Diffraction of Atoms by a Transmission Grating. DW Keith, ML Schattenburg, Henry I. Smith, and DE Pritchard Massachusetts Institute of Technology, Cambridge, Massachusetts 02139. Received 11 July 1988 We have demonstrated a novel diffraction grating for atoms. ...
Diffraction of atomic waves by non-orthogonal standing waves
AIP Conference Proceedings, 1987
Immunosuppressive but Non-LasR-Inducing Analogues of the Pseudomonas aeruginosa Quorum-Sensing Molecule N-(3-Oxododecanoyl)-L-homoserine Lactone
Journal of Medicinal Chemistry, May 12, 2011
The Pseudomonas aeruginosa quorum-sensing molecule N-(3-oxododecanoyl)-l-homoserine lactone (1) i... more The Pseudomonas aeruginosa quorum-sensing molecule N-(3-oxododecanoyl)-l-homoserine lactone (1) is involved not only in bacterial activation but also in subversion of the host immune system, and this compound might thus be used as a template to design immunosuppressive agents, provided derivatives devoid of quorum-sensing activity could be discovered. By use of a leukocyte proliferation assay and a newly developed bioluminescent P. aeruginosa reporter assay, systematic modification of 1 allowed us to delineate the bacterial LasR-induction and host immunosuppressive activities. The main determinant is replacement of the methylene group proximal to the β-ketoamide in the acyl chain of 1 with functions containing heteroatoms, especially an NH group. This modification can be combined with replacement of the homoserine lactone system in 1 with stable cyclic groups. For example, we found the simple compound N(1)-(5-chloro-2-hydroxyphenyl)-N(3)-octylmalonamide (25d) to be over twice as potent as 1 as an immune suppressor while displaying LasR-induction antagonist activity.
The relationship between immunological responsiveness controlled by T-helper 2 lymphocytes and infections with parasitic helminths
Parasitology, Dec 1, 1997
It should have been difficult until relatively recently for immunologists to ascribe a sound biol... more It should have been difficult until relatively recently for immunologists to ascribe a sound biological reason for the continued possession of the allergic phenotype in human populations. Nevertheless, for the past 20 years or so textbooks of immunology have routinely exhibited fanciful and perhaps exaggerated diagrams as to how IgE and eosinophils killed all helminth parasites. These diagrams were largely based on perhaps selective in vitro observations, and it is only now that immunoparasitologists, working on human populations under arduous conditions in the field, are able to provide data to corroborate these findings, and perhaps ascribe a useful purpose for a generally pathological immune response termed Type I hypersensitivity. The present paper reviews much of this recent literature, and asks a number of pertinent questions relating to the relationship between what we now know to be T-helper 2 lymphocyte-driven immunological responsiveness and infections with parasitic helminths.
Development of a mechanics reasoning inventory
ABSTRACT Strategic knowledge is required to appropriately organize procedures and concepts to sol... more ABSTRACT Strategic knowledge is required to appropriately organize procedures and concepts to solve problems. We are developing a standardized instrument assessing strategic knowledge in the domain of introductory mechanics. This instrument is inspired in part by Lawson's Classroom Test of Scientific Reasoning and Van Domelen's Problem Decomposition Diagnostic. The predictive validity of the instrument has been suggested by preliminary studies showing significant correlation with performance on final exams administered in introductory mechanics courses at the Massachusetts Institute of Technology and the Georgia Institute of Technology. In order to study the validity of the content from the student's perspective, we have administered the instrument in free-response format to 40 students enrolled in calculus-based introductory mechanics at the University of Wisconsin-Platteville. This procedure has the additional advantage of improving the construct validity of the inventory, since student responses suggest effective distractors for the multiple-choice form of the inventory.
Ion Balance Mass Spectrometry
AIP Conference Proceedings, 2005
ABSTRACT We have developed a technique to simultaneously compare the cyclotron frequencies of two... more ABSTRACT We have developed a technique to simultaneously compare the cyclotron frequencies of two single ions to obtain atomic mass ratios with fractional accuracies at or below 10−11. Much like a balance scale, this two‐ion technique cancels many sources of noise and error — chief among them magnetic field noise. The new mass comparisons are used in combination with γ‐ray wavelength measurements, performed by the Institut Laue‐Langevin/National Institute of Standards and Technology, to perform the most direct test of Einstein’s mass‐energy relationship E = mc2. The increased precision and long measurement times also lead to the discovery of a new cyclotron frequency shift arising from polarization forces. This shift allowed the most accurate measurement of the dipole moment of a charged molecule (CO+), as well as a new method for non‐destructively measuring the quantum state of a single molecule. © 2005 American Institute of Physics
Immunology, biochemistry and molecular biology of hookworm antigens
Atom loss in a two-component Fermi gas near a Feshbach resonance
We present our recent progress on the study of the inelastic atom loss in a two-component ^6Liato... more We present our recent progress on the study of the inelastic atom loss in a two-component ^6Liatoms near a Feshbach resonance at 834G. A degenerate ^6Liatoms in the lowest two hyperfine states are prepared in an optical dipole trap after sympathetic cooling with bosonic ^23Na atoms. The magnetic field is rapidly ramped up to a Feshbach resonance, and the inelastic atom loss is monitored. The rapid ramp-up of the magnetic fields offers the opportunity to study the non-equilibrium situation and the time-dependence of atom-atom correlations. We have tried to map out the atom loss in a cold Lithium gas as a function of magnetic field and the temperature. We present current experiments revealing the non-monotonic behavior which has been observed in preliminary experiments.
High-performance Apparatus for Bose-Einstein Condensation of Rubidium Atoms
We have developed a high-performance apparatus for producing Bose-Einstein condensates (BEC) of ^... more We have developed a high-performance apparatus for producing Bose-Einstein condensates (BEC) of ^87Rb atoms. It features a Zeeman slower that delivers up to 10^11 slowed atoms per second into the main UHV (< 10-11 torr) chamber, where the atoms are collected in a bright magneto-optical trap (MOT) and then transferred into a cloverleaf magnetic trap for rf-induced evaporative cooling. For the slowing and trapping light, we built a stable diode-laser-based optical system, including a high-power tapered amplifier. With this apparatus we can collect 10^10 atoms in the MOT within 2 s and create BECs containing 4 x 10^6 atoms in the F = 1, mF = -1 ground state every 25 s. This is, to our knowledge, the largest number ever achieved for the Rb condensates and about one order of magnitude larger than obtained with conventional double-MOT loading schemes.
2001 Physics Education Research Conference Proceedings, 2001
This paper addresses two questions: "Does conceptual understanding help students solve related qu... more This paper addresses two questions: "Does conceptual understanding help students solve related quantitative problems?" and "Does working through a quantitative problem help students understand the concepts involved?" A class of approximately 100 students was split into two equally skillful groups, A and B. Group A was administered a tutorial electronic program that led over 906 of students to the correct answer. Group B was administered the same problems in reverse order. Working through a conceptual problem first had little effect on students' ability to solve a related quantitative problem. Conversely, results suggest that working first through a quantitative problem improved students' ability to solve the subsequent conceptual problem. (Contains 15 references.) (MM) Reproductions supplied by EDRS are the best that can be made from the original document.
Measuring the Photon Recoil Frequency using Interferometry with Bose-Einstein Condensates
Aps Division of Atomic Molecular and Optical Physics Meeting Abstracts, May 1, 2002
One route to a high precision measurement of the fine-structure constant involves a precise deter... more One route to a high precision measurement of the fine-structure constant involves a precise determination of the ratio hbar / m_alkali [1]. This ratio can be determined from a measurement of the recoil energy due to photon absorption in an atom-light interferometer. We recently demonstrated a new type of interferometer to do this using Bragg scattering of BECs. The scheme utilizes three paths in a symmetric configuration and encodes the recoil induced phase in the fringe contrast rather than in the fringe phase. This makes the device immune to phase noise from vibrations, accelerations and rotations. Systematics from ac Stark shifts and magnetic field gradients are also suppressed in our scheme. A simple realization of our interferometer using sodium BECs yielded a value for the sodium recoil frequency to 15 ppm precision. We have also demonstrated the immunity to mirror vibrations and the fact that the precision of our interferometer scales quadratically with the maximum number of photon recoils transferred to the atoms. An extension of the new scheme with the use of multiple light pulses in a new and dedicated setup promises to enhance our present precision to the ppb level. [1] M.P.Bradley et al., PRL, 83, 4510, (1999).
Frequency-dependent polarization of light scattered near the Na D 2 resonance line
Phys Rev a, 1982
We report measurements of the degree of linear polarization of scattered light as a function of e... more We report measurements of the degree of linear polarization of scattered light as a function of excitation frequency near the Doppler-broadened Na D 2 resonance line. For resonant excitation of the D 2 line, the hyperfine interaction strongly depolarizes the emitted light due to precession of the electronic angular momentum J--> prior to spontaneous emission. However, as the laser frequency is tuned away from resonance, the polarization degree sharply rises to the level predicted using a simple JMJ basis, i.e., neglecting any coupling of the electronic angular momentum J--> with the nuclear spin I-->. Roughly speaking, there is a transition from F selection rules (F-->=I-->+J-->) for resonant excitation to J selection rules for off-resonant excitation. We present a rigorous calculation of the polarization degree with the use of multipole moments of the density matrix which agrees quantitatively with our data and also predicts complicated interference structure when Doppler broadening is negligible. We show that this structure may shift peaks observed in precision laser-spectroscopy experiments. For Doppler-broadened transitions we discuss a simplified approach (based on an approximation to the Voigt profile) which treats separately the contributions of resonant and off-resonant scattering.
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Books by David Pritchard
Papers by David Pritchard