Bounded Rationality and Irreversible Network Change

A network change is said to be irreversible if the initial network equilibrium cannot be restored by revoking the change. The phenomenon of irreversible network change has been observed in reality. To model this phenomenon, we develop a day-to-day dynamic model whose fixed point is a boundedly rational user equilibrium (BRUE) flow. Our BRUE based approach to modeling irreversible network change has two advantages over other methods based on Wardrop user equilibrium (UE) or stochastic user equilibrium (SUE). First, the existence of multiple network equilibria is necessary for modeling irreversible network change. Unlike UE or SUE, the BRUE multiple equilibria do not rely on non-separable link cost functions, which makes our model applicable to real-world large-scale networks, where well-calibrated non-separable link cost functions are generally not available. Second, travelers\u27 boundedly rational behavior in route choice is explicitly considered in our model. The proposed model is applied to the Twin Cities network to model the flow evolution during the collapse and reopening of the I-35W Bridge. The results show that our model can to a reasonable level reproduce the observed phenomenon of irreversible network change

A Link-Based Day-to-Day Traffic Assignment Model

Existing day-to-day traffic assignment models are all built upon path flow variables. This paper demonstrates two essential shortcomings of these path-based models. One is that their application requires a given initial path flow pattern, which is typically unidentifiable, i.e., mathematically nonunique and practically unobservable. In particular, we show that, for the path-based models, different initial path flow patterns constituting the same link flow pattern generally gives different day-to-day link flow evolutions. The other shortcoming of the path-based models is the path-overlapping problem. That is, the path-based models ignore the interdependence among paths and thus can give very unreasonable results for networks with paths overlapping with each other. These two path-based problems exist for most (if not all) deterministic day-to-day dynamics whose fixed points are the classic Wardrop user equilibrium. To avoid the two path-based problems, we propose a day-to-day traffic assignment model that directly deals with link flow variables. Our link-based model captures travelers\u27 cost-minimization behavior in their path finding as well as their inertia. The fixed point of our link-based dynamical system is the classic Wardrop user equilibrium

Spin Squeezing under Non-Markovian Channels by Hierarchy Equation Method

We study spin squeezing under non-Markovian channels, and consider an ensemble of $N$ independent spin-1/2 particles with exchange symmetry. Each spin interacts with its own bath, and the baths are independent and identical. For this kind of open system, the spin squeezing under decoherence can be investigated from the dynamics of the local expectations, and the multi-qubit dynamics can be reduced into the two-qubit one. The reduced dynamics is obtained by the hierarchy equation method, which is a exact without rotating-wave and Born-Markov approximation. The numerical results show that the spin squeezing displays multiple sudden vanishing and revival with lower bath temperature, and it can also vanish asymptotically.Comment: 7 pages, 4 figure

Disentangling the Dynamical Mechanisms for Cluster Galaxy Evolution

The determination of the dynamical causes of the morphological Butcher-Oemler (BO) effect, or the rapid transformation of a large population of late-type galaxies to earlier Hubble types in the rich cluster environment between intermediate redshifts and the local universe, has been an important unsolved problem which is central to our understanding of the general problems of galaxy formation and evolution. In this article, we survey the existing proposed mechanisms for cluster galaxy transformation, and discuss their relevance and limitations to the explanation of the morphological BO effect. A new infrared diagnostic approach is devised to disentangle the relative importance of several major physical mechanisms to account for the BO effect, and an example of the first application of this procedure to a single rich, intermediate redshift galaxy cluster is given to demonstrate the viability of this approach. The preliminary result of this analysis favors the interaction-enhanced secular evolution process as the major cause of the cluster-galaxy morphological transformation. This conclusion is also supported by a wide range of other published results which are assembled here to highlight their implications on a coherent physical origin for the morphological BO effect.Comment: Accepted for publication in the PAS

Using the Utah Population Database to assess familial risk of primary open angle glaucoma

AbstractPurposePrimary open angle glaucoma (POAG) is a leading cause of irreversible blindness in the elderly. Previous epidemiological studies have identified family history, ethnic origin, age, high intraocular pressure and diabetes mellitus as risk factors. However, it is difficult to assess the extent family history plays in this disease process. The Utah Population Database (UPDB), created by the University of Utah, has recently become a resource for which greater than 9 million records are available for use. The UPDB is divided into two major data sets from which family members can be identified, namely 1.6 million genealogy records and 2 million Utah birth certificates. This study utilizes these resources to assess the familial risk of POAG within the Utah Population.MethodsThe University of Utah’s hospital and clinic records were searched for patients with primary and chronic open angle glaucoma (ICD9 codes 365.04 and 365.11) between the years 1995 and 2005. A case-control analysis was then performed with specialized UPDB software that was modified to constrain the control and pedigree populations to over 1 million University of Utah-UPDB linked records. Controls were matched to cases by gender and birth year (±2.5years) with only one control being used per case. Population-attributable risk (PAR) to familial factors and relative risk (RR) were computed using conditional logistic regression (CLR).ResultsFrom the original 1.5 million medical records, 6198 patients with glaucoma were identified. Of these, 3391 met the inclusion criteria, which required patients to have at least one parent or one child in the UPDB. The PAR in this population was found to be 0.20, indicating 20% of the risk for glaucoma is attributable to genetic factors. CLR computations also showed a significantly increased relative risk (p<0.05) in first cousins (RR=1.45 (95% confidence interval (CI) 1.16–1.8)), second cousins (RR=1.19 (95% CI 1.08–1.32)), siblings (RR=3.76 (95% CI 2.66–5.31)), parents (RR=6.25 (95% CI 3.94–9.9)) and children (RR=6.77 (95% CI 3.39–13.5)).ConclusionsBased on these familial data, there is a significantly higher prevalence of glaucoma in both first and second generation relatives of those affected as compared to relatives in the control group. When compared with other epidemiologic studies, such as an analysis of first-degree relatives of patients from the Rotterdam study, which showed a PAR of 16%, our study actually demonstrates a greater familial contribution to glaucoma. The UPDB is a valuable and unique resource providing a large population from which to analyze the familial risk of glaucoma

The Potential-Density Phase Shift Method for Determining the Corotation Radii in Spiral and Barred Galaxies

We have developed a new method for determining the corotation radii of density waves in disk galaxies, which makes use of the radial distribution of an azimuthal phase shift between the potential and density wave patterns. The approach originated from improved theoretical understandings of the relation between the morphology and kinematics of galaxies, and on the dynamical interaction between density waves and the basic-state disk stars which results in the secular evolution of disk galaxies. In this paper, we present the rationales behind the method, and the first application of it to several representative barred and grand-design spiral galaxies, using near-infrared images to trace the mass distributions, as well as to calculate the potential distributions used in the phase shift calculations. We compare our results with those from other existing methods for locating the corotations, and show that the new method both confirms the previously-established trends of bar-length dependence on galaxy morphological types, as well as provides new insights into the possible extent of bars in disk galaxies. Application of the method to a larger sample and the preliminary analysis of which show that the phase shift method is likely to be a generally-applicable, accurate, and essentially model-independent method for determining the pattern speeds and corotation radii of single or nested density wave patterns in galaxies. Other implications of this work are: most of the nearby bright disk galaxies appear to possess quasi-stationary spiral modes; that these density wave modes and the associated basic state of the galactic disk slowly transform over time; and that self-consistent N-particle systems contain physics not revealed by the passive orbit analysis approaches.Comment: 48 pages, 16 figures. Accepted for publication in the Astronomical Journa

Superconductivity in HfTe5 across weak to strong topological insulator transition induced via pressures

Recently, theoretical studies show that layered HfTe5 is at the boundary of weak & strong topological insulator (TI) and might crossover to a Dirac semimetal state by changing lattice parameters. The topological properties of 3D stacked HfTe5 are expected hence to be sensitive to pressures tuning. Here, we report pressure induced phase evolution in both electronic & crystal structures for HfTe5 with a culmination of pressure induced superconductivity. Our experiments indicated that the temperature for anomaly resistance peak (Tp) due to Lifshitz transition decreases first before climbs up to a maximum with pressure while the Tp minimum corresponds to the transition from a weak TI to strong TI. The HfTe5 crystal becomes superconductive above ~5.5 GPa where the Tp reaches maximum. The highest superconducting transition temperature (Tc) around 5 K was achieved at 20 GPa. Crystal structure studies indicate that HfTe5 transforms from a Cmcm phase across a monoclinic C2/m phase then to a P-1 phase with increasing pressure. Based on transport, structure studies a comprehensive phase diagram of HfTe5 is constructed as function of pressure. The work provides valuable experimental insights into the evolution on how to proceed from a weak TI precursor across a strong TI to superconductors

Diammonium Glycyrrhizinate Upregulates PGC-1α and Protects against Aβ1–42-Induced Neurotoxicity

Mitochondrial dysfunction is a hallmark of beta-amyloid (Aβ)-induced neurotoxicity in Alzheimer's disease (AD), and is considered an early event in AD pathology. Diammonium glycyrrhizinate (DG), the salt form of Glycyrrhizin, is known for its anti-inflammatory effects, resistance to biologic oxidation and membranous protection. In the present study, the neuroprotective effects of DG on Aβ1–42-induced toxicity and its potential mechanisms in primary cortical neurons were investigated. Exposure of neurons to 2 µM Aβ1–42 resulted in significant viability loss and cell apoptosis. Accumulation of reactive oxygen species (ROS), decreased mitochondrial membrane potential, and activation of caspase-9 and caspase-3 were also observed after Aβ1–42 exposure. All these effects induced by Aβ1–42 were markedly reversed by DG treatment. In addition, DG could alleviate lipid peroxidation and partially restore the mitochondrial function in Aβ1–42-induced AD mice. DG also significantly increased the PGC-1α expression in vivo and in vitro, while knocking down PGC-1α partially blocked the protective effects, which indicated that PGC-1α contributed to the neuroprotective effects of DG. Furthermore, DG significantly decreased the escape latency and search distance and increased the target crossing times of Aβ1–42-induced AD mice in the Morris water maze test. Therefore, these results demonstrated that DG could attenuate Aβ1–42-induced neuronal injury by preventing mitochondrial dysfunction and oxidative stress and improved cognitive impairment in Aβ1–42-induced AD mice, indicating that DG exerted potential beneficial effects on AD

Double-Positive CD21+CD27+ B Cells Are Highly Proliferating Memory Cells and Their Distribution Differs in Mucosal and Peripheral Tissues

Several B-cell defects arise in HIV infected patients, particularly in patients with chronic infection and high viral load. Loss of memory B cells (CD27(+) B cells) in peripheral blood and lymphoid tissues is one of the major B cell dysfunctions in HIV and simian immunodeficiency virus (SIV) infection. Despite several studies, definitive identification of memory B cells based on CD27 surface expression has not been described. Similarly, the rates of cell turnover in different B cell subpopulation from lymphoid and mucosal tissues have not been well documented. In this study, we demonstrate the presence of memory B cell populations and define their distribution, frequency and immunophenotype with regards to activation, proliferation, maturation, and antibody production in normal rhesus macaques from different lymphoid tissues.Thirteen healthy, uninfected rhesus macaques were selected for this study. CD20(+) B cells were isolated from peripheral blood and sorted based on CD27 and CD21 surface markers to define memory B cell population. All the B cell subpopulation was further characterized phenotypically and their cell turnover rates were evaluated in vivo following bromodeoxyuridine (BrdU) inoculation. Double positive (DP) CD21(+)CD27(+) B cells in both peripheral and lymphoid tissues are memory B cells, able to produce antibody by polyclonal activation, and without T cell help. Peripheral and lymphoid DP CD21(+)CD27(+) B cells were also able to become activated and proliferate at higher rates than other B cell subpopulations. Increased turnover of tonsillar memory B cells were identified compared to other tissues examined.We suggest that this DP memory B cells play a major role in the immune system and their function and proliferation might have an important role in HIV/SIV mediated B cell dysregulation and pathogenesis

Microtubule sliding activity of a kinesin-8 promotes spindle assembly and spindle length control

Molecular motors play critical roles in the formation of mitotic spindles, either through controlling the stability of individual microtubules, or by cross-linking and sliding microtubule arrays. Kinesin-8 motors are best known for their regulatory roles in controlling microtubule dynamics. They contain microtubule-destabilizing activities, and restrict spindle length in a wide variety of cell types and organisms. Here, we report for the first time on an anti-parallel microtubule-sliding activity of the budding yeast kinesin-8, Kip3. The in vivo importance of this sliding activity was established through the identification of complementary Kip3 mutants that separate the sliding activity and microtubule destabilizing activity. In conjunction with kinesin-5/Cin8, the sliding activity of Kip3 promotes bipolar spindle assembly and the maintenance of genome stability. We propose a “slide-disassemble” model where Kip3’s sliding and destabilizing activity balance during pre-anaphase. This facilitates normal spindle assembly. However, Kip3’s destabilizing activity dominates in late anaphase, inhibiting spindle elongation and ultimately promoting spindle disassembly