523 research outputs found
Conicoid Mirrors
The first order equation relating object and image location for a mirror of
arbitrary conic-sectional shape is derived. It is also shown that the parabolic
reflecting surface is the only one free of aberration and only in the limiting
case of distant sources.Comment: 9 page
Two-ply channels for faster wicking in paper-based microfluidic devices
This article describes the development of porous two-ply channels for paper-based microfluidic devices that wick fluids significantly faster than conventional, porous, single-ply channels. The two-ply channels were made by stacking two single-ply channels on top of each other and were fabricated entirely out of paper, wax and toner using two commercially available printers, a convection oven and a thermal laminator. The wicking in paper-based channels was studied and modeled using a modified Lucas–Washburn equation to account for the effect of evaporation, and a paper-based titration device incorporating two-ply channels was demonstrated
Transversality of Electromagnetic Waves in the Calculus-Based Introductory Physics Course
Introductory calculus-based physics textbooks state that electromagnetic
waves are transverse and list many of their properties, but most such textbooks
do not bring forth arguments why this is so. Both physical and theoretical
arguments are at a level appropriate for students of courses based on such
books, and could be readily used by instructors of such courses. Here, we
discuss two physical arguments (based on polarization experiments and on lack
of monopole electromagnetic radiation), and the full argument for the
transversality of (plane) electromagnetic waves based on the integral Maxwell
equations. We also show, at a level appropriate for the introductory course,
why the electric and magnetic fields in a wave are in phase and the relation of
their magnitudes.Comment: 10 pages, 6 figure
Analysis of 19 Minerals and Cortisol in Red Deer Hair in Two Different Areas of the Stelvio National Park: A Preliminary Study
The aim of the study was to perform an investigation on the concentration of 19 minerals and cortisol in red deer (Cervuselaphus) hair, a matrix that is easy to collect with non-invasive and painless sampling, able to represent an integrative values of long-term substance concentrations, and able to give useful information, also when performed on dead animals, given its extreme stability over time. In the study thirty-five animals were included, coming from two different sides of a valley in the Stelvio National Park, where official water analysis had pointed out elevated concentrations of As in one of the two orographic sides. Hair cortisol concentrations were measured using a RIA(Radio Immuno Assay), while minerals were detected using ICP-MS (Inductively Coupled Plasma- Mass Spectrometry). Results showed a negative relationship between cortisol and some mineral concentrations (Li, Co, As, Cd, Cr and Tl) and significant differences in some mineral concentrations between park areas (Al, Co, Cu, Cd and Ni). As, Cr and cortisol differences approached statistical significance. This preliminary study represents a step forward in the study of wildlife allostatic load and a valid method for applications in wildlife management programs, in environmental studies and in public health programs
Ultrafast time-resolved spectroscopy of 1D metal-dielectric photonic crystals
We study the all-optical switching behavior of one-dimensional
metal-dielectric photonic crystals due to the nonlinearity of the free metal
electrons. A polychromatic pump-probe setup is used to determine the wavelength
and pump intensity dependence of the ultrafast transmission suppression as well
as the dynamics of the process on a subpicosecond timescale. We find ultrafast
(sub-picosecond) as well as a slow (millisecond) behavior. We present a model
of the ultrafast dynamics and nonlinear response which can fit the measured
data well and allows us to separate the thermal and the electronic response of
the system.Comment: 7 pages, 5 figure
The case report of a 31-year-old man with giant cell myocarditis successfully treated with combined immunosuppression and veno-arterial extracorporeal membrane oxygenation for 21 days
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Il rischio di saturnismo negli uccelli necrofagi in relazione alle attuali modalità di caccia degli ungulati
Summary Wildlife may be exposed to lead contamination as a consequence of hunting activities. Waterfowls
and grouses may directly assume lead from the ground (primary assumption), while in raptors lead
intoxication may be due to the ingestion of preys with elevated lead concentrations in their tissues (secondary
assumption). Recent studies demonstrated that viscera of shot ungulates are quite often directly contaminated
with lead due to bullet fragmentation after the shot. If released on the ground, viscera represent a
threat for scavenger species. In Europe, saturnism in birds of prey has been quite rarely described and some
reports are available for large raptors as griffon vulture Gyps fulvus, golden eagle Aquila chrysaetos and
bearded vulture Gypaetus barbatus. In the Alps this problem affects the abundant population of golden
eagle and the recently re-introduced population of bearded vulture that is still considered as vulnerable. For
the bearded vulture two cases of lead intoxication have already been described in dispersing juveniles. The
most viable nucleus of bearded vultures is distributed in the central Alps, between Italy and Switzerland
and is characterized by the highest reproductive rates. Hunting management of ungulates is here commonly
performed with lead ammunition. The practice of leaving on the ground the ungulate viscera after the shot is
still frequent. Hunting season partially overlaps with the most limiting season, in terms of food availability,
for birds. The extraordinary conservation value of this bearded vulture population led the Stelvio National
Park and the Sondrio Province to implement a study for monitoring the potential risk of lead intoxication
for raptors tied to the practice of ungulate viscera deposition after the shot. The viscera of 153 ungulates shot
in the Sondrio Province during hunting season 2009-2010 have been collected and examined to detect and
quantify lead presence. Information regarding the hunted animal, the type of ammunition, the condition
and the outcome of the shot have been collected as ancillary data. Lead fragments in the samples have been
investigated through CAT (computed axial tomography) and digital radiography and subsequently manually
collected. Overall, in 62.1% of samples lead fragments have been detected. Preliminary results refer
to a partial sample of 147 viscera of roe deer, red deer, chamois, wild boar and mouflon. Higher frequencies
have been recorded in roe deer (77.7%), chamois (69.6%) while lower in red deer (50%). The highest
frequencies of lead in viscera have been detected in ungulates shot in the thorax or in the thigh and hind
parts. These first preliminary outcomes confirm the high risk of lead intoxication for large raptors in areas
where ungulates are commonly hunted and demonstrate the need of more sustainable hunting practices as
the substitution of lead ammunition with non-toxic bullets or concealing under the ground the viscera of the
shot ungulates
Constructing Fresnel reflection coefficients by ruler and compass
A simple and intuitive geometical method to analyze Fresnel formulas is
presented. It applies to transparent media and is valid for perpendicular and
parallel polarizations. The approach gives a graphical characterization
particularly simple of the critical and Brewster angles. It also provides an
interpretation of the relation between the reflection coefficients for both
basic polarizations as a symmetry in the plane
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