322 research outputs found
Controle da vitrificação do cravo (Dianthus caryophyllus L.) in vitro
Low levels of benzyl adenine (BAP), low water potential of the growth medium and low humidity due to cotton covers, inhibited vitrification of carnation (Dianthus caryophyllus L.) in vitro. However, under these conditions, a low development of plants and a decrease in the multiplication ratio, were observed. High levels of amonium nitrate enhanced vitrification with an increase in the total soluble protein content. An inverse correlation was observed in the presence of high levels of calcium chloride. The latter was correlated to an increase in peroxidase activity. The results allowed the establishment of a protocol to control vitrification during carnation meristein growth, as follows: "Gelrite", 4 g/1; naphtalene acetic acid, 0.5 mg/l; BAP, 0.05 mg/l; normal dosis of MS salts; cotton covers. For in vitro multiplication the protocol should be altered to BAP, 0.5 mg/1; amoniuin nitrate 10.3 mM; calcium chloride 12.0 mM.Baixos níveis de benziladenina (BAP), baixo potencial de água no meio e baixa umidade condicionada por tampas de algodão foram capazes de inibir a vitrificação de cravo (Dianthus caryophyllus L.) cultivado In vitro, mas essas condições implicaram no baixo desenvolvimento das plantas e da taxa de propagação. Elevados níveis de NH4NO3 demonstraram serem altamente promotores da vitrifícação assinalada pelo alto conteúdo de proteína, enquanto relação inversa foi constatada para altos níveis de CaCl2, aos quais seguiu-se aumento na atividade da peroxidase. Os resultados permitiram estabelecer um protocolo para controle da vitrificação do cravo, constituído de 4,0 g/1 de "Gelrite", 0,5 mg/1 de ácido naftalenoacético (ANA), 0,05 mg/1 de BAP, doses normais das soluções salinas do meio MS e vedação do tipo tampas de algodão para cultivo de ápices meristemáticos. Para a fase de multiplicação, este protocolo deve ser alterado para 0,5 mg/1 de BAP, 10,3 mM de NH4NO3 e 12,0 mM de CaCl2
Evaluación genética en etapa de vivero de áreas productoras de semillas (APS) de Pino Ponderosa en Nordpatagonia
El Pino Ponderosa (Pinus ponderosa Dougl. ex Laws) es la principal especie forestal implantada en secanoen la Patagonia. Su potencialidad productiva y la disponibilidad de tierras para su cultivo permiten proyectarla continuidad de su uso en plantaciones comerciales, para lo que es indispensable asegurar la provisión desemillas de adecuada calidad genética. Las semillas utilizadas en la última década se produjeron en una seriede rodales mediante ensayos para evaluar su descendencia. El objetivo del presente trabajo es evaluar estosrodales ensayando su descendencia. En este primer reporte presentamos los resultados de una evaluaciónen etapa de vivero. Se ensayaron 31 procedencias locales seleccionadas (Áreas Productoras de Semillas,APS) en dos sitios, midiendo altura y diámetro a la altura del cuello en plantines de 2 años de edad. A través de análisis de la varianza se probó un claro efecto de interacción entre las APS y los sitios, y también diferencias entre las APS dentro de cada sitio. Seguidamente, se establecieron rankings de las APS por sitio y variable evaluada. A través de comparaciones de a pares se formaron grupos homogéneos. También se estimó la estabilidad genotípica de las APS por medio del cálculo de sus ecovalencias. Los resultados son aún preliminares, pero el haber probado diferencias en tan temprana edad nos alerta sobre la importancia de la procedencia de las semillas a utilizar para la producción comercial. Se espera que estas diferencias se acentúen en edades más avanzadas. Para probarlo, ya se han establecido ensayos de plantación
Multi-GeV Electron Spectrometer
The advance in laser plasma acceleration techniques pushes the regime of the
resulting accelerated particles to higher energies and intensities. In
particular the upcoming experiments with the FLAME laser at LNF will enter the
GeV regime with almost 1pC of electrons. From the current status of
understanding of the acceleration mechanism, relatively large angular and
energy spreads are expected. There is therefore the need to develop a device
capable to measure the energy of electrons over three orders of magnitude (few
MeV to few GeV) under still unknown angular divergences. Within the PlasmonX
experiment at LNF a spectrometer is being constructed to perform these
measurements. It is made of an electro-magnet and a screen made of
scintillating fibers for the measurement of the trajectories of the particles.
The large range of operation, the huge number of particles and the need to
focus the divergence present unprecedented challenges in the design and
construction of such a device. We will present the design considerations for
this spectrometer and the first results from a prototype.Comment: 7 pages, 6 figures, submitted to NIM
Search for lepton-flavor violation at HERA
A search for lepton-flavor-violating interactions and has been performed with the ZEUS detector using the entire HERA I
data sample, corresponding to an integrated luminosity of 130 pb^{-1}. The data
were taken at center-of-mass energies, , of 300 and 318 GeV. No
evidence of lepton-flavor violation was found, and constraints were derived on
leptoquarks (LQs) that could mediate such interactions. For LQ masses below
, limits were set on , where
is the coupling of the LQ to an electron and a
first-generation quark , and is the branching ratio of
the LQ to the final-state lepton ( or ) and a quark . For
LQ masses much larger than , limits were set on the four-fermion
interaction term for LQs that couple to an electron and a quark
and to a lepton and a quark , where and are
quark generation indices. Some of the limits are also applicable to
lepton-flavor-violating processes mediated by squarks in -Parity-violating
supersymmetric models. In some cases, especially when a higher-generation quark
is involved and for the process , the ZEUS limits are the most
stringent to date.Comment: 37 pages, 10 figures, Accepted by EPJC. References and 1 figure (Fig.
6) adde
Multijet production in neutral current deep inelastic scattering at HERA and determination of alpha_s
Multijet production rates in neutral current deep inelastic scattering have
been measured in the range of exchanged boson virtualities 10 < Q2 < 5000 GeV2.
The data were taken at the ep collider HERA with centre-of-mass energy sqrt(s)
= 318 GeV using the ZEUS detector and correspond to an integrated luminosity of
82.2 pb-1. Jets were identified in the Breit frame using the k_T cluster
algorithm in the longitudinally invariant inclusive mode. Measurements of
differential dijet and trijet cross sections are presented as functions of jet
transverse energy E_{T,B}{jet}, pseudorapidity eta_{LAB}{jet} and Q2 with
E_{T,B}{jet} > 5 GeV and -1 < eta_{LAB}{jet} < 2.5. Next-to-leading-order QCD
calculations describe the data well. The value of the strong coupling constant
alpha_s(M_Z), determined from the ratio of the trijet to dijet cross sections,
is alpha_s(M_Z) = 0.1179 pm 0.0013(stat.) {+0.0028}_{-0.0046}(exp.)
{+0.0064}_{-0.0046}(th.)Comment: 22 pages, 5 figure
Measurement of (anti)deuteron and (anti)proton production in DIS at HERA
The first observation of (anti)deuterons in deep inelastic scattering at HERA
has been made with the ZEUS detector at a centre-of-mass energy of 300--318 GeV
using an integrated luminosity of 120 pb-1. The measurement was performed in
the central rapidity region for transverse momentum per unit of mass in the
range 0.3<p_T/M<0.7. The particle rates have been extracted and interpreted in
terms of the coalescence model. The (anti)deuteron production yield is smaller
than the (anti)proton yield by approximately three orders of magnitude,
consistent with the world measurements.Comment: 26 pages, 9 figures, 5 tables, submitted to Nucl. Phys.
Photoproduction of mesons associated with a leading neutron
The photoproduction of mesons associated with a leading
neutron has been observed with the ZEUS detector in collisions at HERA
using an integrated luminosity of 80 pb. The neutron carries a large
fraction, {}, of the incoming proton beam energy and is detected at
very small production angles, { mrad}, an indication of
peripheral scattering. The meson is centrally produced with
pseudorapidity {
GeV}, which is large compared to the average transverse momentum of the neutron
of 0.22 GeV. The ratio of neutron-tagged to inclusive production is
in the photon-proton
center-of-mass energy range { GeV}. The data suggest that the
presence of a hard scale enhances the fraction of events with a leading neutron
in the final state.Comment: 28 pages, 4 figures, 2 table
Measurement of beauty production in deep inelastic scattering at HERA
The beauty production cross section for deep inelastic scattering events with
at least one hard jet in the Breit frame together with a muon has been
measured, for photon virtualities Q^2 > 2 GeV^2, with the ZEUS detector at HERA
using integrated luminosity of 72 pb^-1. The total visible cross section is
sigma_b-bbar (ep -> e jet mu X) = 40.9 +- 5.7 (stat.) +6.0 -4.4 (syst.) pb. The
next-to-leading order QCD prediction lies about 2.5 standard deviations below
the data. The differential cross sections are in general consistent with the
NLO QCD predictions; however at low values of Q^2, Bjorken x, and muon
transverse momentum, and high values of jet transverse energy and muon
pseudorapidity, the prediction is about two standard deviations below the data.Comment: 18 pages, 4 figure
Measurement of charm fragmentation ratios and fractions in photoproduction at HERA
The production of D^*+, D^0, D^+, D_s^+ and Lambda_c^+ charm hadrons and
their antiparticles in ep scattering at HERA was measured with the ZEUS
detector using an integrated luminosity of 79 pb^-1. The measurement has been
performed in the photoproduction regime with the exchanged-photon virtuality
Q^2 < 1 GeV^2 and for photon-proton centre-of-mass energies in the range 130 <
W < 300 GeV. The charm hadrons were reconstructed in the range of transverse
momentum p_T(D, Lambda_c) > 3.8 GeV and pseudorapidity |eta(D, Lambda_c)| <
1.6. The production cross sections were used to determine the ratio of neutral
and charged D-meson production rates, R_u/d, the strangeness-suppression
factor, gamma_s, and the fraction of charged D mesons produced in a vector
state, P_v^d. The measured R_u/d and gamma_s values agree with those obtained
in deep inelastic scattering and in e^+e^- annihilations. The measured P_v^d
value is smaller than, but consistent with, the previous measurements. The
fractions of c quarks hadronising as a particular charm hadron, f(c -> D,
Lambda_c), were derived in the given kinematic range. The measured open-charm
fragmentation fractions are consistent with previous results, although the
measured f(c -> D^*+) is smaller and f(c -> Lambda_c^+) is larger than those
obtained in e^+e^- annihilations. These results generally support the
hypothesis that fragmentation proceeds independently of the hard sub-process.Comment: 29 pages, 5 figures, 6 tables; minor text revision
Observation of isolated high-E_T photons in deep inelastic scattering
First measurements of cross sections for isolated prompt photon production in
deep inelastic ep scattering have been made using the ZEUS detector at the HERA
electron-proton collider using an integrated luminosity of 121 pb^-1. A signal
for isolated photons in the transverse energy and rapidity ranges 5 < E_T^gamma
< 10 GeV and -0.7 < eta^gamma < 0.9 was observed for virtualities of the
exchanged photon of Q^2 > 35 GeV^2. Cross sections are presented for inclusive
prompt photons and for those accompanied by a single jet in the range E_T^jet
\geq 6 GeV and -1.5 \leq eta^jet < 1.8. Calculations at order alpha^3alpha_s
describe the data reasonably well.Comment: 16 pages, 5 figure
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