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Full-Text Articles in Physics

Prepare For Landing, Gregory A. Dilisi, Richard A. Rarick Apr 2007

Prepare For Landing, Gregory A. Dilisi, Richard A. Rarick

Gregory A. DiLisi

An ad-hoc experiment that the author constructed during a flight to measure the airplane's motion during its descent is described. The apparatus comprised a pendulum formed from a USB memory stick with a string attached, which was fixed to the airplane's window using medical tape, with a Post-it note used as a backdrop for measuring the position of the pendulum. Pictures of the pendulum were taken with a digital camera, so that the angular displacement could later be measured using a computer. From a spec sheet that lists a range of performance and flight parameters of the airplane ...


Monday Night Football: Physics Decides Controversial Call, Gregory A. Dilisi, Richard A. Rarick Oct 2003

Monday Night Football: Physics Decides Controversial Call, Gregory A. Dilisi, Richard A. Rarick

Gregory A. DiLisi

A problem regarding a controversial refereeing decision of a videotaped football play is discussed. Vector analysis is used to show that the refereeing decision was correct; the camera's projection of the play onto the football field created an observational error.


Viscoelastic Properties Of A Bent And Straight Dimeric Liquid Crystal, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Eugene M. Terentjev Apr 1993

Viscoelastic Properties Of A Bent And Straight Dimeric Liquid Crystal, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Eugene M. Terentjev

Gregory A. DiLisi

Absolute values for the elastic constants and viscosities are reported in the nematic phase for two dimers based upon the monomer 4.4'-dipentyloxyphenylbenzoate. One dimer has an even number of methylene units in the spacer and, in consequence, is approximately straight in the all-trans conformation. The other dimer has one less methylene unit, and is therefore bent. We find that the ratio K33/K11 for the odd dimer is reduced relative to that for the even member of the series. Moreover, we find that the absolute elastic constants for the odd dimer are of order one-half that of the ...


Bend Elastic-Modulus Of A Bent And Straight Dimeric Liquid-Crystal, Gregory A. Dilisi Apr 1992

Bend Elastic-Modulus Of A Bent And Straight Dimeric Liquid-Crystal, Gregory A. Dilisi

Gregory A. DiLisi

Light scattering measurements in the nematic phase are reported for two dimers based upon the monomer 4,4'-dipentyloxyphenylbenzoate. One dimer has an even number of methylene units in the spacer and, in consequence, is approximately straight in the all-trans conformation. The other dimer has one less methylene unit in the spacer and is, therefore, bent at the spacer group. We find that the ratio of the twist to splay elastic modulus is nearly the same for both species, but that the ratio of the bend to splay modulus is considerably smaller in the bent dimer.


Viscoelastic Properties Of A Liquid-Crystalline Monomer And Its Dimer, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Uma Hari Mar 1992

Viscoelastic Properties Of A Liquid-Crystalline Monomer And Its Dimer, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Uma Hari

Gregory A. DiLisi

Quasielastic-light-scattering measurements are reported for a dialkoxyphenylbenzoate monomer and its dimer in their respective nematic phases. The splay and twist elastic moduli of the dimer are found to be nearly independent of molecular length. The dimer's bend modulus, however, shows an anomalous increase with decreasing temperature well below the nematic-isotropic phase transition. Monomer viscosities are consistent with typical literature values, although y, /g, pf y and gb,„d seem to be larger than expected for the dimer, where y& is the twist viscosity. The results are discussed in terms of viscoelastic properties of semiflexible rods. The elastic properties in ...


Anchoring Strength Coefficient Of A Monomer And Its Dimer At A Polymer-Coated Interface, Gregory A. Dilisi, Charles Rosenblatt, Robert B. Akins, Anselm Griffin, Uma Hari Dec 1991

Anchoring Strength Coefficient Of A Monomer And Its Dimer At A Polymer-Coated Interface, Gregory A. Dilisi, Charles Rosenblatt, Robert B. Akins, Anselm Griffin, Uma Hari

Gregory A. DiLisi

The dialkoxyphenylbenzoate monomer ‘5005’ (C5H11OC6H4COOC6H4OC5H11) and its dimer were aligned parallel to a buffed polyimide-coated glass substrate. A magnetically induced Freedericksz transition in both thick and thin cells was used in conjunction with a capacitance technique to determine the anchoring strength coefficient Was a function of temperature in the nematic phase. It was found that for both monomer and dimer, Wincreases with decreasing temperature. The anchoring coefficient for the dimer, however, was found to be an order of magnitude larger than for the monomer at comparable reduced temperatures. The splay elastic moduli were also determined for both species, and found ...


Anomaly In The Dynamic Behavior Of The Electroclinic Effect Below The Nematic—Smectic-A Phase Transition, Gregory A. Dilisi, Zili Li, Robert B. Akins, Charles Rosenblatt, Rolfe G. Petscheck Dec 1990

Anomaly In The Dynamic Behavior Of The Electroclinic Effect Below The Nematic—Smectic-A Phase Transition, Gregory A. Dilisi, Zili Li, Robert B. Akins, Charles Rosenblatt, Rolfe G. Petscheck

Gregory A. DiLisi

The electroclinic effect and dielectric response have been investigated in the British Drug House material SCE12 over its entire 15-K smectic-A range. Near the smectic-A —srnectic-C -phase transition both the electroclinic coefficient and dynamic response behave normally, the former diverging and the latter exhibiting a critical slowing down on approaching T + from above. Similar behav- A-C ior is seen in the dielectric response. Approximately 10 to 12 K above T ~, however, it was found A-C that the electroclinic relaxation time levels off and even begins to increase again on approaching the nematic —smectic-A transition from below. The magnitude of the ...


Splay Elasticity In An Oligomeric Liquid-Crystal, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Uma Hari Aug 1990

Splay Elasticity In An Oligomeric Liquid-Crystal, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Uma Hari

Gregory A. DiLisi

A magnetically-induced Freedericksz transition was used in conjunction with capacitance techniques to determine the splay elastic constant of the 4,4′-dialkoxyphenylbenzoate monomer ‘5OO5rsquo; [C5H11OC6H4COOC6H4OC5H11] and its dimer. As a function of reduced temperature in the nematic phase, it was found that K 11 of the dimer is only about 20 per cent larger than that of the monomer. Moreover, the values of K 11/S 2 versus reduced temperature, where S is the scalar order parameter, are equal to within experimental noise. These results suggest that for short oligomers Meyer's entropic model for splay elasticity in polymer liquid ...


Behavior Of The Anchoring Strength Coefficient Near A Structural Transition At A Nematic Substrate Interface, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Uma Hari Feb 1990

Behavior Of The Anchoring Strength Coefficient Near A Structural Transition At A Nematic Substrate Interface, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Uma Hari

Gregory A. DiLisi

A nearly symmetric alkoxyphenylbenzoate monomer is found to exhibit a transition from perpendicular to tilted alignment at a lecithin-treated glass substrate several degrees below the nematic-isotropic phase transition. By means of the Freedericksz transition the coefficient B of the anchoring energy has been obtained. It is found that B rapidly decreases, and the tilt susceptibility increases on approaching this transition.


Nematic Electroclinic Effect, Gregory A. Dilisi, Zili Li, Rolfe G. Pescheck, Charles Rosenblatt Dec 1989

Nematic Electroclinic Effect, Gregory A. Dilisi, Zili Li, Rolfe G. Pescheck, Charles Rosenblatt

Gregory A. DiLisi

A tilt 0 of the principal axis of the optical dielectric tensor linear in a transverse electric field was observed for a surface-stabilized nematic liquid crystal. The electroclinic coefficient dOldE was observed to increase rapidly on approaching the nematic —smectic-A phase transition from above. This was not expected, and indicates that the incipient translational order is important to the electroclinic effect. The data are consistent with a critical exponent only over a narrow range of temperature, and in this range the apparent exponent is not that expected from theory. In addition, dielectric data are presented for this transition, and birefringence ...