Slow and Long-ranged Dynamical Heterogeneities in Dissipative Fluids

A two-dimensional bidisperse granular fluid is shown to exhibit pronounced long-ranged dynamical heterogeneities as dynamical arrest is approached. Here we focus on the most direct approach to study these heterogeneities: we identify clusters of slow particles and determine their size, $N_c$, and their radius of gyration, $R_G$. We show that $N_c\propto R_G^{d_f}$, providing direct evidence that the most immobile particles arrange in fractal objects with a fractal dimension, $d_f$, that is observed to increase with packing fraction $\phi$. The cluster size distribution obeys scaling, approaching an algebraic decay in the limit of structural arrest, i.e., $\phi\to\phi_c$. Alternatively, dynamical heterogeneities are analyzed via the four-point structure factor $S_4(q,t)$ and the dynamical susceptibility $\chi_4(t)$. $S_4(q,t)$ is shown to obey scaling in the full range of packing fractions, $0.6\leq\phi\leq 0.805$, and to become increasingly long-ranged as $\phi\to\phi_c$. Finite size scaling of $\chi_4(t)$ provides a consistency check for the previously analyzed divergences of $\chi_4(t)\propto (\phi-\phi_c)^{-\gamma_{\chi}}$ and the correlation length $\xi\propto (\phi-\phi_c)^{-\gamma_{\xi}}$. We check the robustness of our results with respect to our definition of mobility. The divergences and the scaling for $\phi\to\phi_c$ suggest a non-equilibrium glass transition which seems qualitatively independent of the coefficient of restitution.Comment: 14 pages, 25 figure

Age-related changes of apoptotic cell death in human lymphocytes

Apoptosis seems to be involved in immunosenescence associated with aging. Moreover, in lymphocytes (PBL) of patients with Alzheimer's disease, an increased susceptibility to the apoptotic pathway has been described possibly due to impaired protection of oxidative stress. Accordingly, it seemed to be of particular interest to investigate the contribution of normal aging to the susceptibility from human lymphocytes to programmed cell death. We could show that PBL from elderly individuals (>60 years) accumulate apoptosing cells to a significant higher extent in spontaneous and activation-induced cell death compared to younger controls (<35 years). Treatment with the oxidative stressor 2-deoxy-D-ribose or with agonistic-CD95-antibody pronounced this effect even more implicating a higher sensitivity to reactive oxygen species and a higher functional CD95 expression, respectively. In addition, expression of the activation markers HLA-DR and CD95 was significantly increased in CD3+-cells of aged subjects, while expression of CD25 did not seem to be affected by age. Expression of Bcl-2 was increased in aging and correlated with the number of apoptotic cells

Universal Scaling in the Aging of the Strong Glass Former SiO2_2

We show that the aging dynamics of a strong glass former displays a strikingly simple scaling behavior, connecting the average dynamics with its fluctuations, namely the dynamical heterogeneities. We perform molecular dynamics simulations of SiO$_2$ with BKS interactions, quenching the system from high to low temperature, and study the evolution of the system as a function of the waiting time $t_{\rm w}$ measured from the instant of the quench. We find that both the aging behavior of the dynamic susceptibility $\chi_4$ and the aging behavior of the probability distribution $P(f_{{\rm s},{\mathbf r}})$ of the local incoherent intermediate scattering function $f_{{\rm s},{\mathbf r}}$ can be described by simple scaling forms in terms of the global incoherent intermediate scattering function $C$. The scaling forms are the same that have been found to describe the aging of several fragile glass formers and that, in the case of $P(f_{{\rm s},{\mathbf r}})$, have been also predicted theoretically. A thorough study of the length scales involved highlights the importance of intermediate length scales. We also analyze directly the scaling dependence on particle type and on wavevector $q$, and find that both the average and the fluctuations of the slow aging dynamics are controlled by a unique aging clock, which is not only independent of the wavevector $q$, but is the same for O and Si atoms.Comment: 13 pages, 21 figures (postscript

The 27–year decline of coral cover on the Great Barrier Reef and its causes

This study investigates the spatial and temporal dynamics of coral cover, identifies the main drivers of coral mortality, and quantifies the rates of potential recovery of the Great Barrier Reef.The world’s coral reefs are being degraded, and the need to reduce local pressures to offset the effects of increasing global pressures is now widely recognized. This study investigates the spatial and temporal dynamics of coral cover, identifies the main drivers of coral mortality, and quantifies the rates of potential recovery of the Great Barrier Reef. Based on the world’s most extensive time series data on reef condition (2,258 surveys of 214 reefs over 1985–2012), we show amajor decline in coral cover from 28.0%to 13.8% (0.53%y−1), a loss of 50.7% of initial coral cover. Tropical cyclones, coral predation by crown-of-thorns starfish (COTS), and coral bleaching accounted for 48%, 42%,and 10%of the respective estimated losses,amounting to 3.38% y−1 mortality rate. Importantly, the relatively pristine northern region showed no overall decline. The estimated rate of increase in coral cover in the absence of cyclones, COTS, and bleaching was 2.85%y−1, demonstrating substantial capacity for recovery of reefs. In the absence of COTS, coral cover would increase at 0.89% y−1, despite ongoing losses due to cyclones and bleaching. Thus, reducing COTS populations, by improvingwater quality and developing alternative control measures, could prevent further coral decline and improve the outlook for the Great Barrier Reef. Such strategies can, however, only be successful if climatic conditions are stabilized, as losses due to bleaching and cyclones will otherwise increase. Image: Wibble_Roisin / flick

Age-related increase of oxidative stress-induced apoptosis in mice prevention by Ginkgo biloba extract (EGb761)

Enhanced apoptosis and elevated levels of reactive oxygen species (ROS) play a major role in aging. In addition, several neurodegenerative diseases are associated with increased oxidative stress and apoptosis in neuronal tissue. Antioxidative treatment has neuro-protective effects. The aim of the present study was to evaluate changes of susceptibility to apoptotic cell death by oxidative stress in aging and its inhibition by the antioxidant Ginkgo biloba extract EGb761. We investigated basal and ROS-induced levels of apoptotic lymphocytes derived from the spleen in young (3 months) and old (24 months) mice. ROS were induced by 2-deoxy-D-ribose (dRib) that depletes the intracellular pool of reduced glutathione. Lymphocytes from aged mice accumulate apoptotic cells to a significantly higher extent under basal conditions compared to cells from young mice. Treatment with dRib enhanced this difference, implicating a higher sensitivity to ROS in aging. Apoptosis can be reduced in vitro by treatment with EGb761. In addition, mice were treated daily with 100mg/kg EGb761 per os over a period of two weeks. ROS-induced apoptosis was significantly reduced in the EGb761 group. Interestingly, this effect seemed to be more pronounced in old mice

Age-related impairment of human T lymphocytes' activation: specific differences between CD4+ and CD8+ subsets

The relevance of physiological immune aging is of great interest with respect to determining disorders with pathologic immune function in aging individuals. In recent years, the relevance of changes in peripheral lymphocytes in age-associated neurologic diseases has become more evident. Due to the lack of immunological studies, covering more than one event after mitogenic activation, we envisaged a new concept in the present study, aiming to investigate several events, starting from T cell receptor (TCR) ligation up to T cell proliferation. In addition, we addressed the question whether changes are present in the subsets (CD4, CD8) with aging. Phosphorylation of tyrosine residues declines with increasing age in CD4+ cells. Fewer levels of CD69 positive cells after 4 h mitogenic activation, altered expression of cytokines (IL2, IFN-gamma and TNF-alpha; 22 h) and lower proliferation (72 h) were determined in aging. Moreover, it could be shown that CD8+ lymphocytes react more effectively to mitogenic stimulation with reference to CD69 expression and proliferation in both age groups (60 years old). These data indicate that T cell activation, mediated by TCR engagement, is significantly impaired in aging and both subsets are affected. However, bypassing the TCR does not fully restore T cell function, indicating that there are more mechanisms involved than impaired signal transduction through TCR only. The results will be discussed in relation to their relevance in neurodegenerative and psychiatric disorders

Referential Choice in the Written Narratives of Indonesian Adults

This study aims to describe the referential choice of two protagonist animate characters in a silent six-minute film entitled The Pear Story (Chafe, 1980). A total of 80 undergraduate and graduate Indonesian students were asked to watch the film and then retell the story by writing a narrative about the film in Indonesian. Findings indicate that when the protagonist animate referents are mentioned for the first time, a classifier seorang ‘a person’ is always used before the NP. When they are reactivated, they are mostly expressed by zero, pronouns dia or ia ‘he’, clitic –nya ‘his’ or ‘him’, NPs with determiners ini ‘this’, itu ‘that’, tersebut ‘aforementioned’, tadi ‘mentioned before’, NPs with relative clauses and NPs with definite articles si or sang ‘the’ which are often used in fables or tales. This study also demonstrates that the choice of anaphoric expressions of the protagonists is determined by factors such as referential distance and referential interference. This study confirms other cross-linguistic studies about referential choice – that there is a correlation between salience and referring expressions in discourse. AbstrakPenelitian ini bertujuan mendeskripsikan penggunaan acuan untuk dua tokoh utama dalam film bisu berdurasi enam menit yang berjudul The Pear Story (Chafe, 1980). Sebanyak 80 mahasiswa Indonesia tingkat Strata 1 dan Pascasarjana di sebuah universitas swasta diminta untuk menonton film tersebut dan kemudian menuliskan narasi mengenai film itu dalam bahasa Indonesia. Data menunjukkan bahwa jika referen kedua tokoh utama tersebut disebutkan untuk pertama kalinya, bentuk leksikal seorang selalu muncul sebelum frasa nomina (FN). Jika referennya diaktifkan kembali, maka yang digunakan adalah zero, pronomina dia atau ia, klitik –nya, FN + ini/itu/tersebut/tadi, FN + klausa relatif, dan si/sang + FN. Penelitian ini juga menunjukkan bahwa pilihan bentuk anaforik untuk kedua tokoh utama itu ditentukan oleh faktor jarak antara referen dan anteseden dan juga oleh adanya interferensi referen. Hasil penelitian ini sejalan dengan penelitian lintas bahasa mengenai pilihan acuan, yaitu bahwa ada korelasi antara referen utama dan bentuk acuannya

A Characterization of West Virginia Coyotes (Canis Latrans) Utilizing Skull Morphology

Coyotes (Canis latrans) are now found throughout North and Central America, but before European colonization were restricted to west of the Mississippi. Migration occurred in two major paths to the East; north over the Great Lakes (through Canada) and south below the Great Lakes. The location of these routes is significant because those migrating north interbred with the wolves that reside there. These hybrid animals are larger and behaviorally different from their western counterparts. It is possible to differentiate these hybrids morphologically and genetically. Hybrids are known to be located in Maine, New York, and Pennsylvania, but the interest of this study was to determine if their range has spread to include West Virginia. Fourteen measurements were taken by hand using digital calipers on 126 skulls from West Virginia and Ohio and 25 domestic dog skulls. Utilizing PCA, ANOVAs, and multivariate allometry, these data were compared to data collected on coyote populations from western and northeastern North America. Results conclude that while West Virginia coyotes show some similarities to both comparative populations, they are a distinct population with unique morphological variation, and additionally show no similarities to dogs. The distinct morphology of West Virginia coyotes may be due to ecological pressure to adapt that varies from the West and is influenced to lesser degree by admixture with other species than the Northeast