"Antiscepticism and Easy Justification" - Ch 5 of Seemings and Epistemic Justification

In this chapter I investigate epistemological consequences of the fact that seeming-based justification is elusive, in the sense that the subject can lose this justification simply by reflecting on her seemings. I argue that since seeming-based justification is elusive, the antisceptical bite of phenomenal conservatism is importantly limited. I also contend that since seeming-based justification has this feature, phenomenal conservatism isn’t actually afflicted by easy justification problems

Bolometric luminosities and infrared properties of carbon stars in the Magellanic Clouds and the Galaxy

Broad band J, H, K photometry and narrow band CO and H_2O indices have been obtained for 89 luminous red stars in the Large Magellanic Cloud (LMC) and 21 in the Small Magellanic Cloud (SMC), chosen largely from the sample of Blanco, McCarthy, and Blanco. Most are known to be carbon stars, and their infrared properties are compared with new observations of 33 galactic carbon stars. The bolometric luminosity distributions of an unbiased sample of Magellanic Cloud carbon stars are compared with those predicted from evolutionary calculations by Renzini and Voli for double shell burning stars undergoing He shell flashes. The observed and theoretical distributions disagree markedly: nearly all the observed stars have lower luminosities than even the faintest theoretical carbon star. In addition, we find many fewer than expected high luminosity stars with initial mass greater than 3 M_⊙. Possible explanations for this include a steep initial mass function for intermediate mass stars, a star formation rate significantly higher in the past than at present, or a neglected physical effect, such as underestimation of the importance of mass loss. Nevertheless, it appears that the hypothesis that He shell flashes lead to a dredge-up of carbon into the envelope, which results in a carbon star, can be maintained, if dredging occurs after fewer shell flashes than are predicted by presently available stellar evolutionary calculations. The colors and indices of the late M giants in the LMC field are similar to those of late M giants in the Galaxy. The narrow band infrared data are interpreted qualitatively in terms of the effects of molecular band absorption, which also strongly influences the infrared broad band colors of carbon stars. The small differences in the color-color relationships of the SMC and LMC samples are consistent with the differences in heavy metal abundance between the LMC, SMC, and Galaxy

Loss of buoyancy control in the copepod Calanus finmarchicus

A mechanism is demonstrated that could explain large-scale aggregations of lipid-rich copepods in the surface waters of marine environments. Laboratory experiments establish that changes in salinity and temperature induce lipid-mediated buoyancy instability that entrains copepods in surface waters. Reduced hydrostatic pressure associated with forced ascent of copepods at fjordic sills, shelf breaks and seamounts would also reduce the density of the lipid reserves, forcing copepods and particularly those in diapause to the surface. We propose that salinity, temperature and hydrodynamics of the physical environment, in conjunction with the biophysical properties of lipids, explain periodic high abundances of lipid-rich copepods in surface waters

Categorification of persistent homology

We redevelop persistent homology (topological persistence) from a categorical point of view. The main objects of study are diagrams, indexed by the poset of real numbers, in some target category. The set of such diagrams has an interleaving distance, which we show generalizes the previously-studied bottleneck distance. To illustrate the utility of this approach, we greatly generalize previous stability results for persistence, extended persistence, and kernel, image and cokernel persistence. We give a natural construction of a category of interleavings of these diagrams, and show that if the target category is abelian, so is this category of interleavings.Comment: 27 pages, v3: minor changes, to appear in Discrete & Computational Geometr

HIV-1 Vpr up-regulates expression of ligands for the activating NKG2D receptor and promotes NK cell-mediated killing

HIV upregulates cell-surface expression of specific ligands for the activating NKG2D receptor, including ULBP-1, -2, -3, but not MICA or MICB, in infected cells both in vitro and in vivo. However, the viral factor(s) involved in NKG2D ligand expression still remains undefined. HIV-1 Vpr activates the DNA damage/stress-sensing ATR kinase and promotes G2 cell-cycle arrest, conditions known to upregulate NKG2D ligands. We report here that HIV-1 selectively induces cell-surface expression of ULBP-2 in primary CD4+ T-lymphocytes by a process that is Vpr-dependent. Importantly, Vpr enhanced the susceptibility of HIV-1-infected cells to NK cell-mediated killing. Strikingly, Vpr alone was sufficient to upregulate expression of all NKG2D ligands and thus promoted efficient NKG2D-dependent NK cell-mediated killing. Delivery of virion-associated Vpr via defective HIV-1 particles induced analogous biological effects in non-infected target cells, suggesting that Vpr may act similarly beyond infected cells. All these activities relied on Vpr ability to activate the ATR-mediated DNA damage/stress checkpoint. Overall, these results indicate that Vpr is a key determinant responsible for HIV-1-induced upregulation of NKG2D ligands and further suggest an immunomodulatory role for Vpr that may not only contribute to HIV-1-induced CD4+ T-lymphocyte depletion but may also take part in HIV-1-induced NK cell dysfunction.JR is recipient of a Frederick Banting and Charles Best scholarship from the Canadian Institutes of Health Research (CIHR) while JPB is recipient of a CIHR studentship. EAC holds the Canada Research Chair in Human Retrovirology. This work was supported by grants from CIHR and the Fonds de recherche en santé du Québec AIDS network to EAC

Assessing neural tuning for object perception in schizophrenia and bipolar disorder with multivariate pattern analysis of fMRI data.

IntroductionDeficits in visual perception are well-established in schizophrenia and are linked to abnormal activity in the lateral occipital complex (LOC). Related deficits may exist in bipolar disorder. LOC contains neurons tuned to object features. It is unknown whether neural tuning in LOC or other visual areas is abnormal in patients, contributing to abnormal perception during visual tasks. This study used multivariate pattern analysis (MVPA) to investigate perceptual tuning for objects in schizophrenia and bipolar disorder.MethodsFifty schizophrenia participants, 51 bipolar disorder participants, and 47 matched healthy controls completed five functional magnetic resonance imaging (fMRI) runs of a perceptual task in which they viewed pictures of four different objects and an outdoor scene. We performed classification analyses designed to assess the distinctiveness of activity corresponding to perception of each stimulus in LOC (a functionally localized region of interest). We also performed similar classification analyses throughout the brain using a searchlight technique. We compared classification accuracy and patterns of classification errors across groups.ResultsStimulus classification accuracy was significantly above chance in all groups in LOC and throughout visual cortex. Classification errors were mostly within-category confusions (e.g., misclassifying one chair as another chair). There were no group differences in classification accuracy or patterns of confusion.ConclusionsThe results show for the first time MVPA can be used successfully to classify individual perceptual stimuli in schizophrenia and bipolar disorder. However, the results do not provide evidence of abnormal neural tuning in schizophrenia and bipolar disorder

Activation of the endogenous coagulation system in patients with atrial flutter: Relationship to echocardiographic markers of thromboembolic risk

Background: Atrial thrombus formation in patients with atrial flutter raises concerns of stroke risk. We investigated patients with isthmus-dependent atrial flutter for coagulation abnormalities before and after cardioversion to sinus rhythm by catheter ablation, and evaluated the relationship of the abnormalities to the echocardiographic risk markers of stroke. Methods and results: Plasma samples were drawn prior to insertion of catheters, immediately after the procedure, and 24 hours afterwards. At baseline, coagulation abnormalities were found in 22 out of 25 patients (88%). von Willebrand factor antigen (vWF-Ag) and factor VIII:C were elevated in 17 patients (68%) and 15 patients (60%), respectively. At baseline, mean plasma levels of vWF-Ag (250.1 &#177; 144.4%) and factor VIII:C (215.0 &#177; 77.1%) were increased. Key markers of thrombin generation, thrombin-antithrombin III complex (TAT; 47.8 &#177; 30.9 &#956;g/L vs 14.5 &#177; 13.8 &#956;g/L; p < 0.05) and prothrombin fragments 1.2 (F1.2; 2.5 &#177; 0.5 nmoL/L vs 1.2 &#177; 1.0 nmoL/L) were significantly elevated in the presence of spontaneous echo contrast. Further, both markers of thrombin generation inversely correlated with left atrial appendage emptying velocity (r = -0.42 and -0.63, p < 0.05). Levels of TAT and F1.2 increased after conversion and ablation. Conclusions: Endothelial-dependent coagulation factors were enhanced in most patients with atrial flutter. Spontaneous echo contrast and decreased atrial contractility were associated with increased thrombin generation. After conversion and ablation, an increase in thrombin generation and fibrinolysis suggest a transient pro-thrombotic state. (Cardiol J 2010; 17, 4: 390-396

Photoperiodism and overwintering in boreal and sub-Arctic Calanus finmarchicus populations

The copepod Calanus finmarchicus, a key species in the North Atlantic, generally spends the non-productive season by descending into deep waters and entering diapause, a physiological state characterized by reduced metabolism and arrested development. In the open ocean, overwintering depths are below 600 m, where temperature and light conditions are favourable to initiate diapause. However, C. finmarchicus has also been reported diapausing in areas with shallow water depth such as fjords, coastal waters and shelf seas. In these environments, the temperature and light conditions are different, and it has been hypothesized that under such conditions C. finmarchicus may remain active throughout winter. Here, we investigated changes in the swimming activity of C. finmarchicus from shallow fjords in the eastern North Atlantic during overwintering in response to ambient photoperiod. We conducted monthly experiments with populations from 2 fjords from different latitudes (sub-Arctic Ramfjord, 69°N and boreal Loch Etive, 56°N), measuring the locomotor activity of individual C. finmarchicus stage CVs exposed to a natural light:dark cycle. At both locations, peaks in activity in response to the light cycle were observed to shift from nocturnal during the early overwintering phase to diurnal during mid and late overwintering phase, with a minimal intensity observed during the mid-overwintering phase. In Ramfjord, activity and rhythmicity were generally lower than in Loch Etive. We conclude that C. finmarchicus remains active throughout its overwintering period when in shallow (<200 m) locations but down-regulates its locomotor activity during the main overwintering phase, which we describe as a winter resting state as distinct from classical diapause