1,487 research outputs found
Parity nonconserving two-pion exchange in elastic proton-proton scattering
Parity nonconserving two-pion exchange in elastic pp scattering is
investigated in the presence of phenomenological strong distortions in various
models. Parity violation is included in the nucleon-pion vertex considering NN
and N Delta(1232) intermediate states in box and crossed box diagrams. Using
the derived parity nonconserving two-pion exchange potential we calculate the
longitudinal analyzing power A_L in elastic scattering. The predicted
effect is of the same order as vector meson exchanges.Comment: 13 pages, 8 eps figure
Positive pion absorption on 3He using modern trinucleon wave functions
We study pion absorption on 3He employing trinucleon wave functions
calculated from modern realistic NN interactions (Paris, CD Bonn). Even though
the use of the new wave functions leads to a significant improvement over older
calculations with regard to both cross section and polarization data, there are
hints that polarization data with quasifree kinematics cannot be described by
just two-nucleon absorption mechanisms.Comment: 14 pages, 6 figure
Exact solutions of the isoholonomic problem and the optimal control problem in holonomic quantum computation
The isoholonomic problem in a homogeneous bundle is formulated and solved
exactly. The problem takes a form of a boundary value problem of a variational
equation. The solution is applied to the optimal control problem in holonomic
quantum computer. We provide a prescription to construct an optimal controller
for an arbitrary unitary gate and apply it to a -dimensional unitary gate
which operates on an -dimensional Hilbert space with . Our
construction is applied to several important unitary gates such as the Hadamard
gate, the CNOT gate, and the two-qubit discrete Fourier transformation gate.
Controllers for these gates are explicitly constructed.Comment: 19 pages, no figures, LaTeX2
Electronic cooling of a submicron-sized metallic beam
We demonstrate electronic cooling of a suspended AuPd island using
superconductor-insulator-normal metal tunnel junctions. This was achieved by
developing a simple fabrication method for reliably releasing narrow submicron
sized metal beams. The process is based on reactive ion etching and uses a
conducting substrate to avoid charge-up damage and is compatible with e.g.
conventional e-beam lithography, shadow-angle metal deposition and oxide tunnel
junctions. The devices function well and exhibit clear cooling; up to factor of
two at sub-kelvin temperatures.Comment: 4 pages, 3 figure
Complete next-to-leading order calculation for pion production in nucleon-nucleon collisions at threshold
Based on a counting scheme that explicitly takes into account the large
momentum sqrt(M m_pi) characteristic for pion production in nucleon-nucleon
collisions we calculate all diagrams for the reaction NN --> NN pi at threshold
up to next-to-leading order. At this order there are no free parameters and the
size of the next-to-leading order contributions is in line with the expectation
from power counting. The sum of loop corrections at that order vanishes for the
process pp --> pp pi^0 at threshold. The total contribution at next-to-leading
order from loop diagrams that include the delta degree of freedom vanishes at
threshold in both reaction channels pp --> pp pi^0, pn pi^+.Comment: 9 pages, 4 figure
Mortonin jalan ja Freibergin taudin yleisyyden ja variaation arviointi Pohjois-Suomen 1966 syntymÀkohortista
TiivistelmÀ. Mortonin jalka tarkoittaa jalkaterÀn anatomista poikkeavuutta, jossa ensimmÀisen varpaan metatarsaali (jalkapöydÀnluu) on lyhyt suhteessa toisen varpaan metatarsaaliin. Mortonin jalka on vÀestössÀ yleinen anatominen variaatio. Sen esiintyvyys vaihtelee eri maissa muutamasta prosentista kymmeniin prosentteihin. Freibergin taudilla tarkoitetaan vÀestössÀ suhteellisen harvinaista jalan toisen (harvemmin myös kolmannen tai neljÀnnen) metatarsaalin distaalipÀÀn nivelpinnan nekrotisoitumista ja sitÀ seuraavaa kiputilaa. Tauti on yleisempi naisilla kuin miehillÀ (suhteessa 5:1).
TÀssÀ tutkimuksessa luokiteltiin Pohjois-Suomen syntymÀkohortti 1966 osaotoksen jalkaterÀröntgenaineistoa ja selvitettiin metatarsaalien pituuksia ja Freibergin taudin yleisyyttÀ ja variaatiota, sekÀ sitÀ, lisÀÀkö pitkÀ toinen metatarsaali Freibergin taudin kehittymisen riskiÀ. Yleisesti vakiintunutta menetelmÀÀ metatarsaalien pituuksien mittaamiseen ei ole, joten tutkimuksen alussa vertailtiin kolmea toisistaan poikkeavaa menetelmÀÀ; Hardy-Clapham, Maestron ja Coughlinin menetelmiÀ. Lukijan sisÀisen ja lukijoiden vÀlisen toistettavuuden mittauksissa yhtÀpitÀvimmÀksi ja siten lopulliseksi luokitusmenetelmÀksi valikoitui Coughlinin menetelmÀ, jolla mittaukset aineistoon suoritettiin.
Tutkimus osoitti, ettÀ Freibergin tauti on suomalaisessa vÀestössÀ hyvin harvinainen, ja ettei toisen metatarsaalin pituus korreloi Freibergin taudin esiintyvyyden kanssa
Re-analysis of the Levanluhta skeletal material : Sex and stature estimation of individuals in an Iron Age water burial in Finland
Levanluhta, an Iron Age water burial site in Finland, and its material consisting of commingled skeletal remains and artifacts, has been studied by several researchers over the past 100 years, resulting in multiple interpretations of the people and the site. Previous skeletal analyses have concluded that the majority of the individuals represented in the remains were females and children and were of relatively short stature, so possibly nutritionally deprived. This study re-analyzed the commingled adult human remains with updated methods. The methods applied in this study to estimate sex and stature were based on more representative European reference samples than the previously applied methods. The methods included morphology, osteometrics, and computed tomography (CT) scans. Our results indicated that depending on the reference data, the majority of the individual adult bones including os coxae (73%, n = 45) and long bones (humerus 83%-89%, n = 52; radius 72%-89%, n = 47; ulna 50%-65%, n = 58; femur 92%-100%, n = 25; tibia 77%-85%, n = 26) were classified as females based on their size and morphology. The cross-sectional bone properties of humerii, femora, and tibiae visualized using CT scanning also supported these findings. However, the cranial morphology did not show as clear female-biased sex ratio as other methods (42% females, 33% males, 24% undetermined, n = 33). In females, the mean stature based on the tibia (155.3 cm, n = 10) was within the range of the coeval European females and did not necessarily indicate nutritional deprivation, which is in line with previously published stable isotope findings from the site. The mean stature based on the tibia suggested that the Levanluhta males were short (164.0 cm, n = 3), but final interpretations were limited due to the small number of male individuals. The current study affirmed that the Levanluhta skeletal assemblage was female biased and gave new insights into interpretation of the stature.Peer reviewe
Unitarity constraint for threshold coherent pion photoproduction on the deuteron and chiral perturbation theory
The contribution of the two-step process gamma + d -> p + n -> pi0 + d to the
imaginary part of the amplitude for coherent pion production on the deuteron is
calculated exploiting unitarity constraints. The result shows that this
absorptive process is not negligible and has to be considered in an extraction
of the elementary neutron production amplitude from the gamma + d -> pi0 + d
cross section at threshold. In addition, it is argued that a consistent
calculation of gamma + d -> pi0 + d in baryon chiral perturbation theory beyond
next-to-leading order requires the inclusion of this absorptive process.Comment: 11 pages revtex including 2 postscript figure
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