81 research outputs found
Conductance through atomic point contacts between fcc(100) electrodes of gold
Electrical conductance through various nanocontacts between gold electrodes
is studied by using the density functional theory, scalar-relativistic
pseudopotentials, generalized gradient approximation for the
exchange-correlation energy and the recursion-transfer-matrix method along with
channel decomposition. The nanocontact is modeled with pyramidal fcc(100) tips
and 1 to 5 gold atoms between the tips. Upon elongation of the contact by
adding gold atoms between the tips, the conductance at Fermi energy E_F evolves
from G ~ 3 G_0 to G ~ 1 G_0 (G_0 = 2e/h^2). Formation of a true one-atom point
contact, with G ~ 1 G_0 and only one open channel, requires at least one atom
with coordination number 2 in the wire. Tips that share a common vertex atom or
tips with touching vertex atoms have three partially open conductance channels
at E_F, and the symmetries of the channels are governed by the wave functions
of the tips. The long 5-atom contact develops conductance oscillations and
conductance gaps in the studied energy range -3 < E-E_F < 5 eV, which reflects
oscillations in the local density of electron states in the 5-atom linear "gold
molecule" between the electrodes, and a weak coupling of this "molecule" to the
tips
Conductance through analytic constrictions
We study the dependence of the intrinsic conductance of a nanocontact on its
shape by using the recursion-transfer-matrix method. Hour-glass, torus, and
spherical shapes are defined through analytic potentials, the latter two
serving as rough models for ring-like and spherical molecules, respectively.
The sensitivity of the conductance to geometric details is analyzed and
discussed. Strong resonance effects are found for a spherical contact weakly
coupled to electron reservoirs.Comment: 7 pages, 12 figure
Within- and Between-Persons Effects of Self-Esteem and Affective State as Antecedents and Consequences of Dysfunctional Behaviors in the Everyday Lives of Patients With Borderline Personality Disorder
Dysfunctional behaviors are conceptualized as maladaptive affective coping attempts in borderline personality disorder (BPD). The recent benefits-and-barriers model extended the affective function assumption by adding self-esteem as a barrier to engaging in dysfunctional behaviors. Patients with BPD (N = 119) carried e-diaries to report their current selfesteem, emotional valence, tense arousal, and whether they engaged in dysfunctional behaviors 12 times a day for 4 days. Dynamic structural equation modeling revealed that on the within-person level, high momentary negative affect predicted dysfunctional behaviors, and on the between-person level, low trait self-esteem predicted dysfunctional behaviors. We also found an association between engaging in dysfunctional behaviors and momentary self-esteem and trait levels of valence and tense arousal. Moreover, our results indicate a deterioration of, rather than relief from, negative affective state after dysfunctional behaviors. These findings highlight the importance of emotion-regulation skills and reestablishing a positive self-view as important treatment targets to reduce dysfunctional behaviors in BPD
Caryospora bigenetica (Apicomplexa: Eimeriidae) in South America: new hosts and distribution records
Quarkonia and QGP studies
We summarize results of recent studies of heavy quarkonia correlators and
spectral functions at finite temperatures from lattice QCD and systematic
T-matrix studies using QCD motivated finite-temperature potentials. We argue
that heavy quarkonia dissociation shall occur in the temperature range by the interplay of both screening and absorption in the
strongly correlated plasma medium. We discuss these effects on the quantum
mechanical evolution of quarkonia states within a time-dependent harmonic
oscillator model with complex oscillator strength and compare the results with
data for from RHIC and SPS experiments. We
speculate whether the suppression pattern of the rather precise NA60 data from
In-In collisions may be related to the recently discovered X(3872) state.
Theoretical support for this hypothesis comes from the cluster expansion of the
plasma Hamiltonian for heavy quarkonia in a strongly correlated medium.Comment: 6 pages, 5 figures, contribution to the proceedings of QUARKONIUM
2010: Three Days Of Quarkonium Production in pp and pA Collisions, 29-31 July
2010, Palaiseau, Franc
Effects of kefir on coccidial oocysts excretion and performance of dairy goat kids following weaning
The aim of this study was to investigate effects of kefir, a traditional source of probiotic, on coccidial oocysts excretion and on the performance of dairy goat kids following weaning. Twin kids were randomly allocated to one of two groups at weaning. Kids of the first group received 20 ml of kefir daily for 6 weeks (KEF), while kids in the control group were given a placebo (CON). Individual faecal samples were regularly (n = 18 per kid) taken to quantify the number of coccidial oocysts per gram of faeces (OpG). There were no differences between the groups in terms of body weight development (P > 0.05) and feed consumption. Kids of both groups were not able to consume enough feed to meet their nutrient requirements during the first 3 weeks following weaning. KEF had a lower frequency of OpG positive samples than CON (P = 0.043). Kefir did not affect the maximum oocyst excretion and age of the kids at the highest oocyst excretion (P > 0.05). KEF shed numerically 35% lower coccidial oocysts than the controls, which corresponded to a statistical tendency (P = 0.074) in lowering Log-OpG in comparison to CON. While KEF had a lower frequency of OpG positive samples and tended to shed lower OPG by around one-third, the frequency of diarrhea, level of highest oocyst excretion, and performance of the kids remained unaffected. Therefore, it is concluded that overall effects of kefir do not have a significant impact on sub-clinical infection and performance in weaned kids under relatively high-hygienic farming conditions
Genome analysis and comparative genomics of a Giardia intestinalis assemblage E isolate
<p>Abstract</p> <p>Background</p> <p><it>Giardia intestinalis </it>is a protozoan parasite that causes diarrhea in a wide range of mammalian species. To further understand the genetic diversity between the <it>Giardia intestinalis </it>species, we have performed genome sequencing and analysis of a wild-type <it>Giardia intestinalis </it>sample from the assemblage E group, isolated from a pig.</p> <p>Results</p> <p>We identified 5012 protein coding genes, the majority of which are conserved compared to the previously sequenced genomes of the WB and GS strains in terms of microsynteny and sequence identity. Despite this, there is an unexpectedly large number of chromosomal rearrangements and several smaller structural changes that are present in all chromosomes. Novel members of the VSP, NEK Kinase and HCMP gene families were identified, which may reveal possible mechanisms for host specificity and new avenues for antigenic variation. We used comparative genomics of the three diverse <it>Giardia intestinalis </it>isolates P15, GS and WB to define a core proteome for this species complex and to identify lineage-specific genes. Extensive analyses of polymorphisms in the core proteome of <it>Giardia </it>revealed differential rates of divergence among cellular processes.</p> <p>Conclusions</p> <p>Our results indicate that despite a well conserved core of genes there is significant genome variation between <it>Giardia </it>isolates, both in terms of gene content, gene polymorphisms, structural chromosomal variations and surface molecule repertoires. This study improves the annotation of the <it>Giardia </it>genomes and enables the identification of functionally important variation.</p
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