1,385 research outputs found
Conventional versus single-ladder-splitting contributions to double parton scattering production of two quarkonia, two Higgs bosons and
The double parton distributions (dPDF), both conventional and those
corresponding to parton splitting, are calculated and compared for different
two-parton combinations. The conventional and splitting dPDFs have very similar
shape in and . We make a first quantitative evaluation of the
single-ladder-splitting contribution to double parton scattering (DPS)
production of two S- or P-wave quarkonia, two Higgs bosons and . The ratio of the single-ladder-splitting to conventional contributions is
discussed as a function of centre-of-mass energy, mass of the produced system
and other kinematical variables. Using a simple model for the dependence of the
conventional two-parton distribution on transverse parton separation (Gaussian
and independent of and scales), we find that the 2v1 contribution is as
big as the 2v2 contribution discussed in recent years in the literature. This
means that the phenomenological analyses of including only the
conventional DPS mechanism have to be revised including explicitly the
single-ladder-splitting contributions discussed here. The differential
distributions in rapidity and transverse momenta calculated for conventional
and single-ladder-splitting DPS processes are however very similar which causes
their experimental separation to be rather difficult, if not impossible. The
direct consequence of the existence of the two components (conventional and
splitting) is the energy and process dependence of the empirical parameter
. This is illustrated in our paper for the considered processes.Comment: 20 pages, 11 figures, 3 table
Is Transhumanism Heading Towards Redefinition of Human Being or Towards Utopia?
Transhumanism has enormous affect on temporary philosophical thought by forcing philosophers to take on many intellectual challenges generated by scientists who try to create technological solutions that enable implementation of transhuman-istic ideas. The question is whether all these ideas will be realized. The purpose of the article is to show that the ulitmate goal of transhumanism, to create posthumanistic society, is impossible to realize. The first reason is that transhumanism limits human’s understanding to the material dimension (from a theological viewpint). While this is understandable in the naturalistic paradigm, this approach is insufficient when it comes to all complexity of human being and for this reason transhumanism represents too narrow a human’s understanding to be able to implement its all assumptions. The second reason is that to enable people to become posthumans the latest technologies would have to be available to everyone and this seems impossible. If so, such a sit-uation will divide people into ordinary ones and posthumans and this could lead to conflicts that transhumanists want to avoid after all. Finally, the body-mind problem is essentially limited to emergentism, which corresponds to the naturalistic paradigm. It seems, however, that without the concept of the soul it is impossible to understand who a man is, their identity and consciousness and this is crucial for mind uploading
Observation of thermally-induced magnetic relaxation in a magnetite grain using off-axis electron holography
A synthetic basalt comprising magnetic Fe3O4 grains (~ 50 nm to ~ 500 nm in diameter) is
investigated using a range of complementary nano-characterisation techniques. Off-axis electron
holography combined with in situ heating allowed for the visualisation of the thermally-induced
magnetic relaxation of an Fe3O4 grain (~ 300 nm) from an irregular domain state into a vortex state at
550˚C, just below its Curie temperature, with the magnetic intensity of the vortex increasing on cooling
Open charm meson production at LHC
We discuss charm production at the LHC. The production of single
pairs is calculated in the -factorization approach. We use
Kimber-Martin-Ryskin unintegrated gluon distributions in the proton. The
hadronization is included with the help of Peterson fragmentation functions.
Transverse momentum and pseudorapidity distributions of charmed mesons are
presented and compared to recent results of the ALICE, LHCb and ATLAS
collaborations. Furthermore we discuss production of two pairs of
within a simple formalism of double-parton scattering (DPS). Surprisingly large
cross sections, comparable to single-parton scattering (SPS), are predicted for
LHC energies. We discuss perspectives how to identify the double scattering
contribution. We predict much larger cross section for large rapidity distance
between charm quarks from different hard parton scatterings compared to single
scattering.Comment: 5 pages, 4 figures, talk given by R. Maciula at the MESON2012 - 12th
International Workshop on Meson Production, Properties and Interaction, 31
May - 5 June 2012, Krakow, Polan
Homotopy Brunnian links and the -invariant
We provide an alternative proof that Koschorke's -invariant is
injective on the set of link homotopy classes of -component homotopy
Brunnian links . The existing proof (by Koschorke \cite{Koschorke97})
is based on the Pontryagin--Thom theory of framed cobordisms, whereas ours is
closer in spirit to techniques based on Habegger and Lin's string links. We
frame the result in the language of Fox's torus homotopy groups and the
rational homotopy Lie algebra of the configuration space of
points in . It allows us to express the relevant Milnor's
--invariants as homotopy periods of .Comment: 15 pages, 2 figures, to appear in PAM
Admissibility of retarded diagonal systems with one-dimensional input space
We investigate infinite-time admissibility of a control operator in a
Hilbert space state-delayed dynamical system setting of the form
, where generates a diagonal
-semigroup, is also diagonal and . Our approach is based on the Laplace embedding
between and the Hardy space . The results are
expressed in terms of the eigenvalues of and and the sequence
representing the control operator.Comment: 25 pages, 2 figure
Interactions of the Gasotransmitters Contribute to Microvascular Tone (Dys)regulation in the Preterm Neonate
Background & Aims
Hydrogen sulphide (H2S), nitric oxide (NO), and carbon monoxide (CO) are involved in transitional microvascular tone dysregulation in the preterm infant; however there is conflicting evidence on the interaction of these gasotransmitters, and their overall contribution to the microcirculation in newborns is not known. The aim of this study was to measure the levels of all 3 gasotransmitters, characterise their interrelationships and elucidate their combined effects on microvascular blood flow.
Methods
90 preterm neonates were studied at 24h postnatal age. Microvascular studies were performed by laser Doppler. Arterial COHb levels (a measure of CO) were determined through co-oximetry. NO was measured as nitrate and nitrite in urine. H2S was measured as thiosulphate by liquid chromatography. Relationships between levels of the gasotransmitters and microvascular blood flow were assessed through partial correlation controlling for the influence of gestational age. Structural equation modelling was used to examine the combination of these effects on microvascular blood flow and derive a theoretical model of their interactions.
Results
No relationship was observed between NO and CO (p = 0.18, r = 0.18). A positive relationship between NO and H2S (p = 0.008, r = 0.28) and an inverse relationship between CO and H2S (p = 0.01, r = -0.33) exists. Structural equation modelling was used to examine the combination of these effects on microvascular blood flow. The model with the best fit is presented.
Conclusions
The relationships between NO and H2S, and CO and H2S may be of importance in the preterm newborn, particularly as NO levels in males are associated with higher H2S levels and higher microvascular blood flow and CO in females appears to convey protection against vascular dysregulation. Here we present a theoretical model of these interactions and their overall effects on microvascular flow in the preterm newborn, upon which future mechanistic studies may be based.The authors would like to acknowledge the parents of the neonates enrolled in the 2CANS
study for their participation, the staff of the Kaleidoscope Neonatal Intensive Care Unit at the
John Hunter Children’s Hospital, and Kimberly-Clark Australia for providing the diapers used
in this stud
Soul, mind – brain, body – what makes us the same?
The question whether I am the same person at different moments has brought many difficulties for a long time. The problem with identity of things through time was already known in the ancient times especially when Plutarch asked whether a ship of Theseus with exchanged elements is still the same ship as before renovation. Today, we continue these considerations asking, for instance, if things, apart from their physical parts, also have temporal parts. The number of the proposed solutions to the problem of identity and identity of persons at different times resembles wandering in a dark room with a scarf on your eyes. As a result, rather than coming closer to the light switch, we find concepts which suggest that personal identity is not important, or what is important is psychological continuity or identity which is only a matter of degree. So I can be the same person as I was in some part, in some degree. It sounds like a constitution person who likes darkness and does not need light anymore. Unfortunately, first of all, we still use successfully the concept of identity in an ordinary language, and what is more, the abandonment of the notion of personal identity results in a greater number of absurdities, so in consequence, we still do not have an idea how to treat personal identity
Mechanisms of the release of anterogradely transported neurotrophin-3 from axon terminals
Neurotrophins have profound effects on synaptic function and structure. They can be derived from presynaptic, as well as postsynaptic, sites. To date, it has not been possible to measure the release of neurotrophins from axon terminals in intact tissue. We implemented a novel, extremely sensitive assay for the release and transfer of anterogradely transported neurotrophin-3 (NT-3) from a presynaptic to a postsynaptic location that uses synaptosomal fractionation after introduction of radiolabeled NT-3 into the retinotectal projection of chick embryos. Release of the anterogradely transported NT-3 in intact tissue was assessed by measuring the amount remaining in synaptosomal preparations after treatment of whole tecta with pharmacological agents. Use of this assay reveals that release of NT-3 from axon terminals is increased by depolarization, calcium influx via N-type calcium channels, and cAMP analogs, and release is most profoundly increased by excitation with kainic acid or mobilization of calcium from intracellular stores. NT-3 release depends on extracellular sodium, CaM kinase II activity, and requires intact microtubules and microfilaments. Dantrolene inhibits the high potassium-induced release of NT-3, indicating that release of calcium from intracellular stores is required. Tetanus toxin also inhibits NT-3 release, suggesting that intact synaptobrevin or synaptobrevin-like molecules are required for exocytosis. Ultrastructural autoradiography and immunolabel indicate that NT-3 is packaged in presumptive large dense-core vesicles. These data show that release of NT-3 from axon terminals depends on multiple regulatory proteins and ions, including the mobilization of local calcium. The data provide insight in the mechanisms of anterograde neurotrophins as synaptic modulators
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