10,407 research outputs found
Understanding the ideal glass transition: Lessons from an equilibrium study of hard disks in a channel
We use an exact transfer-matrix approach to compute the equilibrium
properties of a system of hard disks of diameter confined to a
two-dimensional channel of width at constant longitudinal
applied force. At this channel width, which is sufficient for
next-nearest-neighbor disks to interact, the system is known to have a great
many jammed states. Our calculations show that the longitudinal force
(pressure) extrapolates to infinity at a well-defined packing fraction
that is less than the maximum possible , the latter
corresponding to a buckled crystal. In this quasi-one-dimensional problem there
is no question of there being any \emph{real} divergence of the pressure at
. We give arguments that this avoided phase transition is a structural
feature -- the remnant in our narrow channel system of the hexatic to crystal
transition -- but that it has the phenomenology of the (avoided) ideal glass
transition. We identify a length scale as our equivalent of the
penetration length for amorphous order: In the channel system, it reaches a
maximum value of around at , which is larger than the
penetration lengths that have been reported for three dimensional systems. It
is argued that the -relaxation time would appear on extrapolation to
diverge in a Vogel-Fulcher manner as the packing fraction approaches .Comment: 17 pages, 16 figure
Absence of hyperuniformity in amorphous hard-sphere packings of nonvanishing complexity
We relate the structure factor in a system of
jammed hard spheres of number density to its complexity per particle
by the formula . We have verified this formula for
the case of jammed disks in a narrow channel, for which it is possible to find
and analytically. Hyperuniformity, which is the
vanishing of , will therefore not occur if the
complexity is nonzero. An example is given of a jammed state of hard disks in a
narrow channel which is hyperuniform when generated by dynamical rules that
produce a non-extensive complexity.Comment: 5 pages, 3 figure
Long-Range Electron Transfer and Electronic Transport Through Macromolecules
A theory of electrical transport through molecular wires is used to estimate
the electronic factor in the intramolecular electron transfer (ET) in
porphyrin-nitrobenzene supermolecules, and to analyze its structure. The chosen
molecules have complex donor and acceptor configurations, and relatively simple
structure of the bridge, which enables us to concentrate our studies on the
donor/acceptor coupling to the bridge. We present analytical and numerical
results concerning the effect of donor/acceptor coupling to the bridge on the
ET process in molecules with complex donor/acceptor subsystems.
PACS 05.60.Gg, 36.20.-rComment: 4 pages, 2 figures, text edde
Ileostomy Adenocarcinoma : a case report
Proctocolectomy is the standard treatment for patients suffering from ulcerative colitis which is long-standing, refractory to pharmacotherapy or otherwise associated with complications. An ileal pouch with pouch-anal anastomosis is fashioned in the majority of cases; however, in some instances terminal ileostomy is preferable. Ileostomy cancer is rare but a number of cases have been reported over the past twenty years suggesting a rising incidence. We report a case that developed thirty years post-operatively.peer-reviewe
Compact 85 fs frequency doubled 810 nm fiber system with 60 mW of average power
We demonstrate a sub-100 fs frequency doubled fiber laser operating at 810 nm. The laser produces 60 mW of average power at a repetition rate of 50 MHz. Extremely low amplitude noise (below 0.1%) and compact size makes this source ideal replacement for low power ultrafast Ti:Spphire lasers
Electromagnetic Wave Transmission Through a Subwavelength Nano-hole in a Two-dimensional Plasmonic Layer
An integral equation is formulated to describe electromagnetic wave
transmission through a sub-wavelength nano-hole in a thin plasmonic sheet in
terms of the dyadic Green's function for the associated Helmholtz problem.
Taking the subwavelength radius of the nano-hole to be the smallest length of
the system, we have obtained an exact solution of the integral equation for the
dyadic Green's function analytically and in closed form. This dyadic Green's
function is then employed in the numerical analysis of electromagnetic wave
transmission through the nano-hole for normal incidence of the incoming wave
train. The electromagnetic transmission involves two distinct contributions,
one emanating from the nano-hole and the other is directly transmitted through
the thin plasmonic layer itself (which would not occur in the case of a perfect
metal screen). The transmitted radiation exhibits interference fringes in the
vicinity of the nano-hole, and they tend to flatten as a function of increasing
lateral separation from the hole, reaching the uniform value of transmission
through the sheet alone at large separations.Comment: 14 pages, 24 individual figures organized in 9 captioned group
An unusual case of intertrigo in an adult caused by purely cutaneous Langerhans cell histiocytosis
We report a case of persistent intertrigo in an adult, eventually diagnosed as cutaneous Langerhans cell histiocytosis (LCH). It is known that LCH has a predilection for intertriginous areas, however purely cutaneous disease as in our case, is uncommon and usually other systems are affected. Following the report, literature of similar cases is reviewed to determine possible outcomes and to decide on the best possible treatment options.peer-reviewe
- ā¦