2,738 research outputs found
Bis(4-methyl-N-{(2Z,4E)-4-[(4-methylphenyl)imino]pent-2-en-2-yl}anilinido)zinc
The title compound, [Zn(C19H21N2)2], appears to be the first example of a zinc complex supported by two β-diketiminate (nacnac) ligands. This complex crystallizes with a distorted tetrahedrally coordinated ZnII atom that diposes the two nacnac ligands approximately orthogonally to one another [angle between the two N—Zn—N mean planes is 89.91 (10)°], with average Zn—N bond lengths of 1.992 (4) Å
Genetic Correlations in Mutation Processes
We study the role of phylogenetic trees on correlations in mutation
processes. Generally, correlations decay exponentially with the generation
number. We find that two distinct regimes of behavior exist. For mutation rates
smaller than a critical rate, the underlying tree morphology is almost
irrelevant, while mutation rates higher than this critical rate lead to strong
tree-dependent correlations. We show analytically that identical critical
behavior underlies all multiple point correlations. This behavior generally
characterizes branching processes undergoing mutation.Comment: revtex, 8 pages, 2 fig
Evolution Equation of Phenotype Distribution: General Formulation and Application to Error Catastrophe
An equation describing the evolution of phenotypic distribution is derived
using methods developed in statistical physics. The equation is solved by using
the singular perturbation method, and assuming that the number of bases in the
genetic sequence is large. Applying the equation to the mutation-selection
model by Eigen provides the critical mutation rate for the error catastrophe.
Phenotypic fluctuation of clones (individuals sharing the same gene) is
introduced into this evolution equation. With this formalism, it is found that
the critical mutation rate is sometimes increased by the phenotypic
fluctuations, i.e., noise can enhance robustness of a fitted state to mutation.
Our formalism is systematic and general, while approximations to derive more
tractable evolution equations are also discussed.Comment: 22 pages, 2 figure
College students’ perceptions of alcohol’s role in disclosures of sexual assault and intimate partner violence
Objective: Much is known about how alcohol increases the risk of sexual assault or intimate partner violence victimization during college. This research qualitatively explores perceptions about how alcohol influences disclosures about these events to informal supports.
Participants: Participants included college students who received a disclosure wherein they or the survivor were drinking during the disclosure (n = 81).
Methods: Responses were coded with regard to who was drinking and whether the effect of drinking during the disclosure was perceived as positive, negative, mixed, or neutral/none.
Results: Participants perceived alcohol to have both positive (e.g., increasing the likelihood of discussing difficult topics) and negative (e.g., cognitive impairment increased negative emotions) effects on disclosures.
Conclusion: Prevention and intervention efforts should identify targeted strategies (e.g., remembering one or two easy and helpful phrases; revisiting the topic again while sober) to help survivors and disclosure recipients have constructive conversations in the presence of alcohol
Autoantigens in Vitiligo Identified by the Serological Selection of a Phage-Displayed Melanocyte cDNA Expression Library
Vitiligo is an acquired idiopathic hypomelanotic disorder characterized by circumscribed depigmented macules resulting from the loss of cutaneous melanocytes. Although the exact cause of vitiligo remains obscure, autoimmunity may play a role in the development of the disease. The present study was undertaken to investigate the applicability of phage display technology to identify B-cell autoantigens in vitiligo. A melanocyte cDNA phage display library was subjected to rounds of enrichment with vitiligo patient IgG. Subsequently, enriched IgG-binding peptides representing putative autoantigens were identified by sequencing their encoding cDNAs. Radioimmunoassays were used to confirm the immunoreactivity of vitiligo patient (n=61) and control (n=28) sera to several of the putative autoantigens. Non-segmental vitiligo patient sera (n=53) were positive for antibody (Ab) reactivity to gamma-enolase (8%); alpha-enolase (9%); heat-shock protein 90 (13%); osteopontin (4%); ubiquitin-conjugating enzyme (15%); translation-initiation factor 2 (6%); and GTP-binding protein, Rab38 (15%). Ab reactivity to at least one of the previously unknown autoantigens was detected in 51% of patients with non-segmental vitiligo. In contrast, Ab reactivity in a group of patients with segmental vitiligo (n=8) was not demonstrated. Overall, the study indicated that the targets of autoantibodies in vitiligo patients can be revealed by employing the methodology of phage display
Addition-Deletion Networks
We study structural properties of growing networks where both addition and
deletion of nodes are possible. Our model network evolves via two independent
processes. With rate r, a node is added to the system and this node links to a
randomly selected existing node. With rate 1, a randomly selected node is
deleted, and its parent node inherits the links of its immediate descendants.
We show that the in-component size distribution decays algebraically, c_k ~
k^{-beta}, as k-->infty. The exponent beta=2+1/(r-1) varies continuously with
the addition rate r. Structural properties of the network including the height
distribution, the diameter of the network, the average distance between two
nodes, and the fraction of dangling nodes are also obtained analytically.
Interestingly, the deletion process leads to a giant hub, a single node with a
macroscopic degree whereas all other nodes have a microscopic degree.Comment: 8 pages, 5 figure
Rank Statistics in Biological Evolution
We present a statistical analysis of biological evolution processes.
Specifically, we study the stochastic replication-mutation-death model where
the population of a species may grow or shrink by birth or death, respectively,
and additionally, mutations lead to the creation of new species. We rank the
various species by the chronological order by which they originate. The average
population N_k of the kth species decays algebraically with rank, N_k ~ M^{mu}
k^{-mu}, where M is the average total population. The characteristic exponent
mu=(alpha-gamma)/(alpha+beta-gamma)$ depends on alpha, beta, and gamma, the
replication, mutation, and death rates. Furthermore, the average population P_k
of all descendants of the kth species has a universal algebraic behavior, P_k ~
M/k.Comment: 4 pages, 3 figure
Recommended from our members
A RISC-V Vector Processor With Simultaneous-Switching Switched-Capacitor DC-DC Converters in 28 nm FDSOI
This work demonstrates a RISC-V vector microprocessor implemented in 28 nm FDSOI with fully integrated simultaneous-switching switched-capacitor DC-DC (SC DC-DC) converters and adaptive clocking that generates four on-chip voltages between 0.45 and 1 V using only 1.0 V core and 1.8 V IO voltage inputs. The converters achieve high efficiency at the system level by switching simultaneously to avoid charge-sharing losses and by using an adaptive clock to maximize performance for the resulting voltage ripple. Details about the implementation of the DC-DC switches, DC-DC controller, and adaptive clock are provided, and the sources of conversion loss are analyzed based on measured results. This system pushes the capabilities of dynamic voltage scaling by enabling fast transitions (20 ns), simple packaging (no off-chip passives), low area overhead (16%), high conversion efficiency (80%-86%), and high energy efficiency (26.2 DP GFLOPS/W) for mobile devices
Plant Genome Size Influences Stress Tolerance of Invasive and Native Plants via Plasticity
Plant genome size influences the functional relationships between cellular and whole‐plant physiology, but we know little about its importance to plant tolerance of environmental stressors and how it contributes to range limits and invasion success. We used native and invasive lineages of a wetland plant to provide the first experimental test of the Large Genome Constraint Hypothesis (LGCH)—that plants with large genomes are less tolerant of environmental stress and less plastic under stress gradients than plants with small genomes. We predicted that populations with larger genomes would have a lower tolerance and less plasticity to a stress gradient than populations with smaller genomes. In replicated experiments in northern and southern climates in the United States, we subjected plants from 35 populations varying in genome size and lineage to two salinity treatments. We measured traits associated with growth, physiology, nutrition, defense, and plasticity. Using AICc model selection, we found all plant traits, except stomatal conductance, were influenced by environmental stressors and genome size. Increasing salinity was stressful to plants and affected most plant traits. Notably, biomass in the high‐salinity treatment was 3.0 and 4.9 times lower for the invasive and native lineages, respectively. Plants in the warmer southern greenhouse had higher biomass, stomate density, stomatal conductance, leaf toughness, and lower aboveground percentage of N and total phenolics than in the northern greenhouse. Moreover, responses to the salinity gradient were generally much stronger in the southern than northern greenhouse. Aboveground biomass increased significantly with genome size for the invasive lineage (43% across genome sizes) but not for the native. For 8 of 20 lineage trait comparisons, greenhouse location × genome size interaction was also significant. Interestingly, the slope of the relationship between genome size and trait means was in the opposite direction for some traits between the gardens providing mixed support for LGCH. Finally, for 30% of the comparisons, plasticity was significantly related to genome size—for some plant traits, the relationship was positive, and in others, it was negative. Overall, we found mixed support for LGCH and for the first time found that genome size is associated with plasticity, a trait widely regarded as important to invasion success
Higher maximum doses of oxytocin are associated with an unacceptably high risk for uterine rupture in patients attempting vaginal birth after cesarean delivery
- …