4,817 research outputs found
Lepton Flavor Violating Radiative Decays in EW-Scale Model: An Update
We perform an updated analysis for the one-loop induced lepton flavor
violating radiative decays in an extended mirror model.
Mixing effects of the neutrinos and charged leptons constructed with a
horizontal symmetry are also taken into account. Current experimental
limit and projected sensitivity on the branching ratio of
are used to constrain the parameter space of the model. Calculations of two
related observables, the electric and magnetic dipole moments of the leptons,
are included. Implications concerning the possible detection of mirror leptons
at the LHC and the ILC are also discussed.Comment: 9 figures, 36 single-side pages. Updated email addresses and
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The economics of land fragmentation in the north of Vietnam
Land fragmentation, where a single farm has a number of parcels of land, is a common feature of agriculture in many countries, especially in developing countries. In Vietnam, land fragmentation is common, especially in the north. For the whole country, there are about 75 million parcels of land, an average of seven to eight plots per farm household. Such fragmentation can be seen to have negative and positive benefits for farm households and the community generally. Comparative statics analysis and analysis of survey data have led to the conclusion that small-sized farms are likely to be more fragmented, and that fragmentation had a negative impact on crop productivity and increased family labour use and other money expenses. Policies which allow the appropriate opportunity cost of labour to be reflected at the farm level may provide appropriate incentives to trigger farm size change and land consolidation. Policies which tip the benefits in favour of fewer and larger plots, such as strong and effective research and development, an active extension system and strong administrative management, may also lead to land consolidation.development economics, land fragmentation, land use and tenure, production economics, Resource /Energy Economics and Policy,
The economics of land fragmentation in the north of Vietnam
Land fragmentation, in which a single farm household operates more than one separate piece of land, is significant issue in Vietnamese agriculture, especially in the North. For the whole country, there are about 75 million plots of land, an average of 7-8 plots per farm household. Such fragmentation can be seen to have negative and positive benefits for farm households and the community generally. The negative impacts can be reduced mechanisation, higher cost, loss of land due to boundaries, increased negative externalities, and more limited application of new technologies. On the other hand, land fragmentation may have some benefits to farmers such as spreading output risk, seasonal labour use, and crop diversification. Comparative static analysis and analysis of survey data have led to the conclusion that small sized farms are likely to be more fragmented and the number of plots held by a household is not a significant determinant of yield and output risk spreading but is a significant factor in crop diversification. Policies which allow the appropriate opportunity cost of labour to be reflected at the farm level may provide appropriate incentives to trigger farm size change and land consolidation. Policies which tip the benefits in favour of fewer and larger plots such as strong and effective research and development, an active extension system and strong administrative management may also lead to land consolidation and thus allow some of the benefits which will accrue to the economy more generally to be obtained by farmers.Land Economics/Use,
On the completeness and decidability of duration calculus with iteration
AbstractThe extension of the duration calculus (DC) by iteration, which is also known as Kleene star, enables the straightforward specification of repetitive behaviour in DC and facilitates the translation of design descriptions between DC, timed regular expressions and timed automata. In this paper we present axioms and a proof rule about iteration in DC. We consider abstract-time DC and its extension by a state-variable binding existential quantifier known as higher-order DC (HDC). We show that the Ï-complete proof systems for DC and HDC known from our earlier work can be extended by our axioms and rule in various ways in order to axiomatise iteration completely. The additions we propose include either the proof rule or an induction axiom. We also present results on the decidability of a subset of the extension DC* of DC by iteration
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Developing a scalable training model in global mental health: pilot study of a video-assisted training Program for Generalist Clinicians in Rural Nepal.
BackgroundIn low- and middle-income countries, mental health training often includes sending few generalist clinicians to specialist-led programs for several weeks. Our objective is to develop and test a video-assisted training model addressing the shortcomings of traditional programs that affect scalability: failing to train all clinicians, disrupting clinical services, and depending on specialists.MethodsWe implemented the program -video lectures and on-site skills training- for all clinicians at a rural Nepali hospital. We used Wilcoxon signed-rank tests to evaluate pre- and post-test change in knowledge (diagnostic criteria, differential diagnosis, and appropriate treatment). We used a series of 'Yes' or 'No' questions to assess attitudes about mental illness, and utilized exact McNemar's test to analyze the proportions of participants who held a specific belief before and after the training. We assessed acceptability and feasibility through key informant interviews and structured feedback.ResultsFor each topic except depression, there was a statistically significant increase (Î) in median scores on knowledge questionnaires: Acute Stress Reaction (Î = 20, p = 0.03), Depression (Î = 11, p = 0.12), Grief (Î = 40, p < 0.01), Psychosis (Î = 22, p = 0.01), and post-traumatic stress disorder (Î = 20, p = 0.01). The training received high ratings; key informants shared examples and views about the training's positive impact and complementary nature of the program's components.ConclusionVideo lectures and on-site skills training can address the limitations of a conventional training model while being acceptable, feasible, and impactful toward improving knowledge and attitudes of the participants
Evidence of early multi-strange hadron freeze-out in high energy nuclear collisions
Recently reported transverse momentum distributions of strange hadrons
produced in Pb(158AGeV) on Pb collisions and corresponding results from the
relativistic quantum molecular dynamics (RQMD) approach are examined. We argue
that the experimental observations favor a scenario in which multi-strange
hadrons are formed and decouple from the system rather early at large energy
densities (around 1 GeV/fm). The systematics of the strange and non-strange
particle spectra indicate that the observed transverse flow develops mainly in
the late hadronic stages of these reactions.Comment: 4 pages, 4 figure
Mass-Varying Neutrinos from a Variable Cosmological Constant
We consider, in a completely model-independent way, the transfer of energy
between the components of the dark energy sector consisting of the cosmological
constant (CC) and that of relic neutrinos. We show that such a cosmological
setup may promote neutrinos to mass-varying particles, thus resembling a
recently proposed scenario of Fardon, Nelson, and Weiner (FNW), but now without
introducing any acceleronlike scalar fields. Although a formal similarity of
the FNW scenario with the variable CC one can be easily established, one
nevertheless finds different laws for neutrino mass variation in each scenario.
We show that as long as the neutrino number density dilutes canonically, only a
very slow variation of the neutrino mass is possible. For neutrino masses to
vary significantly (as in the FNW scenario), a considerable deviation from the
canonical dilution of the neutrino number density is also needed. We note that
the present `coincidence' between the dark energy density and the neutrino
energy density can be obtained in our scenario even for static neutrino masses.Comment: 8 pages, minor corrections, two references added, to apear in JCA
Highly Sensitive Centrality Dependence of Elliptic Flow -- A Novel Signature of the Phase Transition in QCD
Elliptic flow of the hot, dense system which has been created in
nucleus-nucleus collisions develops as a response to the initial azimuthal
asymmetry of the reaction region. Here it is suggested that the magnitude of
this response shows a ``kinky'' dependence on the centrality of collisions for
which the system passes through a first-order or rapid transition between
quark-gluon plasma and hadronic matter. We have studied the system Pb(158AGeV)
on Pb employing a recent version of the transport theoretical approach RQMD and
find the conjecture confirmed. The novel phase transition signature may be
observable in present and forthcoming experiments at CERN-SPS and at RHIC, the
BNL collider.Comment: Version as published in PRL 82 (1999) 2048, title chang
One-loop divergences of the Einstein-Yang-Mills system
The one-loop ultraviolet divergences of the quantized coupled Einstein-Yang-Mills fields are evaluated. They are precisely of the same nonrenormalizable form as for a corresponding set of free Maxwell fields together with the usual flat-space Yang-Mills divergences. The two free Yang-Mills field parameters, namely the group dimension and the self-coupling constant, cannot be chosen to make the one-loop divergences renormalizable in the usual sense
Characterization of Single-Shot Attosecond Pulses with Angular Streaking Photoelectron Spectra
Most of the traditional attosecond pulse retrieval algorithms are based on a so-called attosecond streak camera technique, in which the momentum of the electron is shifted by an amount depending on the relative time delay between the attosecond pulse and the streaking infrared pulse. Thus, temporal information of the attosecond pulse is encoded in the amount of momentum shift in the streaked photoelectron momentum spectrogram S(p, Ï), where p is the momentum of the electron along the polarization direction and Ï is the time delay. An iterative algorithm is then employed to reconstruct the attosecond pulse from the streaking spectrogram. This method, however, cannot be applied to attosecond pulses generated from free-electron x-ray lasers where each single shot is different and stochastic in time. However, using a circularly polarized infrared laser as the streaking field, a two (or three)-dimensional angular streaking electron spectrum can be used to retrieve attosecond pulses for each shot, as well as the time delay with respect to the circularly polarized IR field. Here we show that a retrieval algorithm previously developed for the traditional streaking spectrogram can be modified to efficiently characterize single-shot attosecond pulses. The methods have been applied to retrieve 188 single shots from recent experiments. We analyze the statistical behavior of these 188 pulses in terms of pulse duration, bandwidth, pulse peak energy, and time delay with respect to the IR field. The retrieval algorithm is efficient and can be easily used to characterize a large number of shots in future experiments for attosecond pulses at free-electron x-ray laser facilities
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