Tuesday, March 24, 2015
Sunday, March 22, 2015
|JMU Physics & Astronomy seniors Keely Criddle (left)|
and Nicole Creange (right).
Of course, once constructed, we now need to launch these bottle rockets! The videos are in SLOW-MOTION so you get the full effect of the tension at mission control as they wondered how their design would fare!
Thursday, March 19, 2015
Mechanical Properties of Hydrogel Beads
Fragile solids made of dense disordered packing of bubbles, droplets, and grains are able to withstand small stresses by virtue of system-wide force chains that lock the system into a jammed state. The nature of the jamming transition in such soft materials has been the subject of intense research, but despite much effort, a deep understanding remains elusive. In this experiment we study the mechanical properties of hydrogel beads to exploit them as force transducers in densely packed systems. The experiment consists of applying uniaxial planar compressions on the beads and correlating the force to the bead’s strain and contact area. The results show that while the strain scales linearly with the radius of the contact area, the force and strain are found to obey a power law relation with a range of exponents from 1.9 to 2.7. This result leads to a power law dependence of the force on the contact area radius of the compressed beads of similar size.
Understanding the optical and electronic properties of Ga-doped graphene
Determination of superexchange correlations in magnetically substituted graphene
We investigate the electronic and magnetic properties between two homogeneous magnetic impurities (vanadium, chromium, or manganese) in a 128-atom graphene superlattice. With varying the impurity distance, we calculate these properties using a first principles approach. For each configuration, we determine the electronic bandstructure and density of states, along with the Mullikan populations for each atom. Furthermore, we calculate the exchange parameter between the two magnetic ions through the analysis of the change in total energy for different magnetic configurations. We found that the magnetic impurities induce a mangetic moment in the graphene superlattice, helping to meditate the superexchange between the impurities. Depending on the choice of ion used, the interactions between the two ions can exhibit either a ferromagnetic or an antiferromagnetic behavior. These correlations indicate an RKKY-like behavior in the system.
Generalization of Magnetic Dimer Excitations
Magnetic dimers commonly appear in the study of molecular magnets and quantum dots. Here, we discuss analytical representations for the inelastic neutron scattering excitation cross sections and static structure factor for the general SS dimeric system. Employing generalized Pauli matrices and the Kronecker tensor product to construct the matrix representation of the spin Heisenberg spin-spin Hamiltonian. After using exact diagonalization to determine the eigenstates of the spin Hamiltonian, we formulated an analytical solution to find the structure factor coefficients used in determining the inelastic neutron scattering excitation cross section from both the ground state and first excited state. We also detail a method for finding the S polarization constant within an applied field that may represent the presence of an external magnetic field. Furthermore, we provide a sample set of data and intensity plot generated from our results to illustrate experimental representations for split energy levels.
Variational calculations for spin canting at ferromagnetic/antiferromagnetic
Granular gas mediated attraction of intruders in a granular Casimir effect
|From Left to Right: Hosts Feitosa and Constatin, Dr. Brycelyn Boardman, |
Mikhail, Shelby, Alan, and Abigail
Brycelyn Boardman has been at JMU as a faculty member since 2011. She was a student at JMU (and even still has the same JMU email address!), where she pursued her undergraduate degree before attending the University of California at Santa Barbara where she earned her Ph.D. in Chemistry. Before returning to JMU she did a postdoc at Columbia University.
|Our Wonderful Audience Members!|
|All of these events were recorded for those of you unfortunate enough to not attend!|
Thursday, March 12, 2015
Saturday, February 28, 2015
Kudos to Geary Albright, Art Fovargue, the physics faculty lecturers, the physics majors, and last but not least our dear participants (students, teachers and parents) who contributed to yet another great edition of the program! Well done everybody! So long!
See photos here from the wrap up event today, Feb. 28, 2015!
Thursday, February 05, 2015
|From left to right: Feitosa, Constantin, Rosenhouse, and panelists|
photo from breezejmu.org
On Thursday, January 29, 2015 the third installment of JMuse Café's series, Demystifying the Expert, took place. Through teaming up with physics professors Anca Constantin and Klebert Feitosa to present this series, JMuse Café has been able to close the gap between scientists and the JMU public. This is done through back-and-forth guessing, joking, and discussion of the expert's expertise between our hosts (Constantin & Feitosa), the expert, and 4 members of JMU's only improv comedy group New & Improv.'d. As I mentioned in the post about the most recent event, the format for this series was borrowed from a Boston NPR show entitled You're the Expert.
Our expert this event was Jason Rosenhouse, a professor of Mathematics at JMU. As one of the hosts aptly pointed out at the beginning of the show, JMuse Café could easily run at least 4 events focused on Rosenhouse (further speculation has led me to believe that 4 events may still not be enough, considering his potential for both engaging and entertaining the public); unfortunately, we only had one. Before coming to JMU in 2003, he spent three years at Kansas State University after earning his Ph.D. in Mathematics from Dartmouth and his B.S. from Brown. In addition to a number of publications pertaining to his research, Rosenhouse has authored 3 award-winning books (all of which found their way into my Amazon shopping cart while I wrote this...).
Before giving away too much about our expert, it's important to acknowledge the panel of comedians whose job it was that evening to try to extract that information from him. Trevor Knickerbocker is a senior intelligence analysis major, currently enrolled in one of Dr. Feitosa's classes. Despite this, he still maintained that Feitosa didn't feed him any information about the expert. Amanda Anzalone is a junior media arts & design major double-minoring in French and creative writing. She may have gotten answers wrong, but at least she could do so in two languages. Business major Mikail Faalasi came to this series with his knowledge of science limited to the science of making money. Lastly, Logan Brown is a junior theater major whose answers were both comedy (for the audience) and tragedy (for him).
|Our Panelists, from left to right: Mikhail, Amanda, Logan, and Trevor|
photo from breezejmu.org
In the first game, the panelists are given the opportunity to bombard the expert with 20-questions-style questions. During this time, the audience was able to gain long lists of things Rosenhouse does and does not do. On the former list are things like, theoretical math, getting cramps from writing theoretical math, graphs, solving equations, spending time inside, and escaping life. Of the latter, we learned that Rosenhouse does not apply his math to a "field" of study, because, as he mentioned earlier, he does not go outside.
What really sparked Rosenhouse's interest in math was a day in 6th grade when he was faced with the first theorem that was not obviously true to him: the Pythagorean theorem. He remarked that his teacher at the time just threw it up on the board without proving it, and this both impressed him and caused some skepticism. It was then that he saw that math is more than what most people think it is.
At this point, Rosenhouse surely made math-lovers out of anyone in the audience who was not one already; he pointed out that people who say they don't like math, simply don't like arithmetic, but the subject itself is,
A combination of art and science and beauty - it's the exact opposite of memorizing rules - it's discovering them and proving them.
He went on to comment that people who think that math is fundamentally about calculating things have missed the point entirely; it's about observing the beauty of math. For mathematicians, the fact that math is useful is simply a bonus on top of everything else math is. Rosenhouse commented, "We can make money and go back to our little enclaves to do math!"
Throughout the evening, there were brief discussions of the three books Rosenhouse has authored. The first book he discussed was The Monty Hall Problem: The Remarkable Story of Math's Most Contentious Brain Teaser. The Monty Hall problem was inspired by a game show where contestants are faced with 3 doors, one of which has a prize behind it. After choosing one door, the host (aware of what lies behind each door) opens one of the doors that does not contain the prize, giving the contestant the opportunity to change his or her guess now that the odds of guessing correctly have changed. The "problem" behind the Monty Hall problem, is whether or not being able to change guesses actually makes a difference. In addition to the mathematical implications of the problem, there are also psychological aspects of it as well. Secondly, Rosenhouse discussed a book he co-authored with Laura Taalman, another professor of Math at JMU: Taking Sudoku Seriously: The Math Behind the World's Most Popular Pencil Puzzle. This book addresses the questions mathematicians have about sudoku puzzles (which, contrary to popular belief, do require math to solve - just not arithmetic). On a topic not wholly unrelated to math, his third book, entitled Among the Creationists: Dispatches from the Anti-Evolutionist Front Line. On this topic, Rosenhouse said,
The evolution debate is where scientific ignorance has consequences – the earth isn’t 6,000 years old. These people don’t know what they’re talking about. They reference math and science and they whip out equations, but if you know anything, you know they’re wrong. Yet, they’ll say it with confidence. You have extreme insularity – that’s the problem. People will tell them what they want to hear as if it validates their opinions.
|Hosts Feitosa and Constantin with Rosenhouse and panelists in the background|
photo from breezejmu.org
Tuesday, January 27, 2015
“Starry Nights JMU” is designed to address the many serious—and, for the most part, unnecessary—consequences of light pollution. Defined as the overuse and misuse of artificial light at night, light pollution wastes energy and money, negatively impacts human and environmental health, and reduces our safety at night. For example, we waste more than $110 billion worldwide, and increasing numbers of studies show a link between light at night and cancers of the breast and prostrate. All of us benefit from light at night, and the question isn’t if we will use it but how. “Starry Nights JMU” exists to raise awareness that light pollution is well within our ability to solve. And now is the time. After a century of electric lighting, our society is moving toward electronic (LED) lighting. By acting now, we can recognize the energy-saving benefits of this new technology, rather than see the problems caused by light pollution grow worse. A Madison Trust Grant would allow us to act by taking following steps:
- campus-wide lighting assessment.
- retrofitting lights on campus and in the Edith J. Carrier Arboretum.
- establish demonstration plot of LED lights on campus.
- expansion of “Starry Nights” events in 2015.