Relationships between bacterial groups nodulating Sesbania rostrata were evaluated through examination of electrophoretic polymorphism of esterases and metabolic enzymes. The following conclusions ...were drawn: (i) the differentiation of two genomic species within Azorhizobium strains and a group of non-identified strains (probably Rhizobium) was strongly supported by enzyme electrophoresis; (ii) esterases were more electrophoretically polymorphic than metabolic enzymes, since 35 and 11 electrophoretic types, respectively, were detected within the 57 strains studied; (iii) strains isolated from stem or root nodules were genetically very similar and could not be differentiated; (iv) six Azorhizobium strains isolated from plants growing in saline soils could not be grouped separately from the other strains, which might be attributed to the adaptation of azorhizobia to epiphytic conditions; and (v) a comparative study of esterase patterns of azorhizobia showed that strains isolated in the Philippines probably originated in northern Senegal, but did not reveal a clear separation between strains originating from northern and central Senegal.
The cross sections for the production of single charged and neutral intermediate vector bosons were measured using integrated luminosities of 52 pb–1 and 154 pb–1 collected by the experiment at ...centre-of-mass energies of 182.6 GeV and 188.6 GeV, respectively. The cross sections for the reactions were determined in limited kinematic regions. The results found are in agreement with the Standard Model predictions for these channels.
A measurement of the W mass and width has been performed by the DELPHI Collaboration using the data collected during 1998. The data sample has an integrated luminosity of 155 pb
−1 and an average ...centre-of-mass energy of 188.6 GeV. Results are obtained by applying the method of direct reconstruction of the mass of the W from its decay products in both the
W
+W
−
→
ℓ
ν
̄
ℓ
q
q
̄
′
and
W
+W
−
→
q
q
̄
′
q
̄
q′
channels. The W mass result for the 1998 data set is
M
W=80.387±0.087(stat)±0.034(syst)±0.017(LEP)±0.035(FSI) GeV/
c
2, where FSI represents the uncertainty due to final state interaction effects in the
q
q
̄
′
q
̄
q′
channel, and LEP represents that arising from the knowledge of the beam energy of the accelerator. Combining this result with those previously published by the DELPHI Collaboration gives the result
M
W=80.359±0.074(stat)±0.032(syst)±0.017(LEP)±0.033(FSI) GeV/
c
2. The combined value for the W width is
Γ
W=2.266±0.176(stat)±0.056(syst)±0.052(FSI) GeV/
c
2.
Searches for pair production of gauginos and squarks in
e
+
e
− collisions at a centre-of-mass energy of 189 GeV have been performed on data corresponding to an integrated luminosity of 158 pb
−1 ...collected by the DELPHI detector at LEP. The data were analyzed under the assumption of non-conservation of
R-parity through a single dominant
U
̄
D
̄
D
̄
coupling between squarks and quarks. Typical final states contain between 4 and 10 jets with or without additional leptons. No excess of data above Standard Model expectations was observed. The results were used to constrain domains of the MSSM parameter space and derive limits on the masses of supersymmetric particles. The following mass limits at 95% CL were obtained from these searches: neutralino mass:
m
χ
̃
0
1
⩾32
GeV; chargino mass:
m
χ
̃
+
1
⩾94
GeV; stop and sbottom mass (indirect decay) with
ΔM>5 GeV:
m
t
̃
1
⩾74
GeV for
Φ
mix=0 rad,
m
t
̃
1
⩾59
GeV for
Φ
mix=0.98 rad,
m
b
̃
1
⩾72
GeV for
Φ
mix=0 rad. The angle
φ
mix is the mixing angle between left and right handed quarks.
Recent advances in technology leads to increasing high speed performance of submicrometer electron devices by the scaling of both process and geometry. In order to aid the design of these devices it ...is necessary to utilize powerful numerical simulation tools. In an industrial environment the simulation codes based on the Drift‐Diffusion models have been widely used. However the shrinking dimension of the devices causes the Drift‐Diffusion based simulators to become less accurate. Then it is necessary to utilize more refined models (including higher order moments of the distribution function) in order to correctly predict the behaviour of these devices. Several hydrodynamical models have been considered as viable simulation tools. It is possible to discriminate among the several hydrodynamical models on the basis of their results on the output characteristics of the electron device which are measurable (I‐V curves). We have analyzed two classes of hydrodynamical models: i) HFIELDS hydrodynamical models and HFIELDS drift‐diffusion model; ii) self‐consistent extended hydrodynamical models with relaxation times determined from Monte Carlo simulations.
Searches for spontaneous
R-parity-violating signals at
s
=183
GeV and
s
=189
GeV have been performed using the 1997 and 1998 DELPHI data, under the assumption of
R-parity breaking in the third ...lepton family. The expected topology for the decay of a pair of charginos into two acoplanar taus plus missing energy was investigated and no evidence for a signal was found. The results were used to derive a limit on the chargino mass and to constrain the allowed domains of the MSSM parameter space.
A new precise measurement of |
V
cb
| and of the branching ratio BR
(
B
̄
0
→D
∗+ℓ
−
ν
̄
ℓ
) has been performed using a sample of about 5000 semileptonic decays
B
̄
0
→D
∗+ℓ
−
ν
̄
ℓ
, selected by the ...DELPHI detector at LEP I by tagging the soft pion from
D
∗+→D
0π
+
. The results are:
V
cb=(39.0±1.5
(stat.)
+2.5
−2.6
(syst. exp.)±1.3
(syst. th.))×10
−3
,
BR(
B
̄
0
→D
∗+ℓ
−
ν
̄
ℓ)=(4.70±0.13
(stat.)
+0.36
−0.31
(syst. exp.))%
. The analytic dependencies of the differential cross-section and of the Isgur–Wise form factor as functions of the variable
w=v
B
0
·v
D
∗
have also been obtained by unfolding the experimental resolution.
Characterization of superconducting localized structures Greco, M.; Lacquaniti, V.; Maggi, S. ...
Philosophical magazine. B, Physics of condensed matter. Structural, electronic, optical, and magnetic properties.,
05/2000, Letnik:
80, Številka:
5
Journal Article
We studied electron localization effects in superconducting Nb/Al bilayers. These effects are characterized by a decrease in resistivity with increasing temperature typical of a semiconductor and by ...an enhancement of the critical temperature T
c
. The samples, made by superposition of Nb and Al films, each 50-200 nm thick, show a sharp superconducting transition between 8 and 9K. The electron localization effects are detectable only when the resistivity at 10 K is larger than about 100μΩcm. We discuss the fabrication conditions leading to the observed electron localization. We also present some measurements of the current-voItage characteristics in localized and metallic Nb/Al bilayers and we analyse them in terms of a simple thermal picture.
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