8,038 research outputs found
Atom interferometry in the presence of an external test mass
The influence of an external test mass on the phase of the signal of an atom
interferometer is studied theoretically. Using traditional techniques in atom
optics based on the density matrix equations in the Wigner representation, we
are able to extract the various contributions to the phase of the signal
associated with the classical motion of the atoms, the quantum correction to
this motion resulting from atomic recoil that is produced when the atoms
interact with Raman field pulses, and quantum corrections to the atomic motion
that occur in the time between the Raman field pulses. By increasing the
effective wave vector associated with the Raman field pulses using modified
field parameters, we can increase the sensitivity of the signal to the point
where the quantum corrections can be measured. The expressions that are derived
can be evaluated numerically to isolate the contribution to the signal from an
external test mass. The regions of validity of the exact and approximate
expressions are determined.Comment: 23 pages, 3 figures, 2 table
Evaluation of a pulsed quasi-steady MPD thruster and associated subsystems
The performance of quasi-steady magnetoplasmadynamic (MPD) thrusters at high power levels is discussed. An axisymmetric configuration is used for the MPD thruster, with various cathode and anode sizes, over a wide range of experimental conditions. Thrust is determined from impulse measurements with current waveforms, while instantaneous measurements are made for all other variables. It is demonstrated that the thrust produced has a predominately self-magnetic origin and is directly proportional to the square of the current. The complete set of impulse measurement data is presented
Quasi-steady MPD propulsion at high power Final technical report
Quasi-steady MPD propulsion at power levels in range 1 to 10 megawatt
Investigation of Mechanical Regulation on STAT3 Activity and MMP Production
Transcription factor, STAT3, is inappropriately expressed in cancer cells, and has contrasting activation in 2D versus 3D microenvironments. 2D plates are often used for drug screening and do not always recapitulate in vivo responses. To combat inaccurate 2D drug studies, a 3D hydrogel was created to support the growth of cancer cells into a tumor-like environment. The hydrogel consists of a biocompatible dextran homopolysaccharide, cell adhesion RGD sequences, and crosslinker MMP labile peptides. A pH dependent reaction couples the RGD sequences to dextran then the polymers are crosslinked into a gel. Crosslinking is accomplished using terminal cysteine peptide sequences, allowing for gel stiffness tunability. Some of the breast cancer cell lines used do not readily form spheroids. Therefore, the cells were embedded in the hydrogel, then incubated to allow for spheroid formation from single cells. OVCAR-8 cancer cells acted as a control cell line that forms spheroids without 3D extracellular matrix (ECM) support. The dextran hydrogels provided mechanical regulation and promoted tumor spheroids formation. Antibody staining of KI67, a proliferation protein, showed cellular growth and not only aggregation of cells. Compounds that inhibit STAT3 were then tested to compare 3D to 2D viability responses. A difference was seen in each of the compounds tested suggesting the 3D environment has an effect on the cell signaling not seen in 2D. An array of treatments was done to test mechanical stimulus effect on the cells at various time points. The effect of 3D growth on STAT3 activation is also being studied. The results show that 3D microenvironments can change the survival and proliferative signals in cells to promote spheroid formation which modifies their response to treatment. Thus, it is important to screen drugs in a 3D environment whenever possible
Alien Registration- Miller, Alice R. (Auburn, Androscoggin County)
https://digitalmaine.com/alien_docs/31140/thumbnail.jp
Report of conference evaluation committee
A general classification is made of a number of approaches used for the prediction of turbulent shear flows. The sensitivity of these prediction methods to parameter values and initial data are discussed in terms of variable density, pressure fluctuation, gradient diffusion, low Reynolds number, and influence of geometry
When do analysts adjust for biases in management guidance? Effects of guidance track record and analysts' incentives
Prior research indicates that analysts do not fully adjust for the general downward bias in earnings guidance issued by management. We report the results of two experiments designed to investigate how guidance track record and analysts incentives jointly explain the extent to which analysts adjust for guidance bias. Our results suggest that analysts with accuracy incentives adjust for managements track record of downwardly biased guidance when the bias is relatively small (one cent), but those with relationship incentives do not. Furthermore, the difference in adjustment is larger when the bias track record is inconsistent than when it is consistent. Also, when guidance bias is larger (two cents) relative to smaller (one cent), analysts with relationship incentives partially adjust, as they appear to strike a balance between accuracy and their desire to please management. These findings hold implications for investors, regulators, and the interpretation of prior research
Dissipation enhanced vibrational sensing in an olfactory molecular switch
Motivated by a proposed olfactory mechanism based on a
vibrationally-activated molecular switch, we study electron transport within a
donor-acceptor pair that is coupled to a vibrational mode and embedded in a
surrounding environment. We derive a polaron master equation with which we
study the dynamics of both the electronic and vibrational degrees of freedom
beyond previously employed semiclassical (Marcus-Jortner) rate analyses. We
show: (i) that in the absence of explicit dissipation of the vibrational mode,
the semiclassical approach is generally unable to capture the dynamics
predicted by our master equation due to both its assumption of one-way
(exponential) electron transfer from donor to acceptor and its neglect of the
spectral details of the environment; (ii) that by additionally allowing strong
dissipation to act on the odorant vibrational mode we can recover exponential
electron transfer, though typically at a rate that differs from that given by
the Marcus-Jortner expression; (iii) that the ability of the molecular switch
to discriminate between the presence and absence of the odorant, and its
sensitivity to the odorant vibrational frequency, are enhanced significantly in
this strong dissipation regime, when compared to the case without mode
dissipation; and (iv) that details of the environment absent from previous
Marcus-Jortner analyses can also dramatically alter the sensitivity of the
molecular switch, in particular allowing its frequency resolution to be
improved. Our results thus demonstrate the constructive role dissipation can
play in facilitating sensitive and selective operation in molecular switch
devices, as well as the inadequacy of semiclassical rate equations in analysing
such behaviour over a wide range of parameters.Comment: 12 pages, 6 figures, close to published version, comments welcom
Correspondence from a Maine Citizen
Typewritten letter from a Maine citizen expressing homophobic views to former University of Maine President Winthrop Libby through the Ellsworth American. Libby forwarded the missive to President Howard Neville
- …