Recombination and intrinsicality

In this paper I argue that warrant for Lewis' principle of recombination presupposes warrant for a combinatorial analysis of intrinsicality, which in turn presupposes warrant for the principle of recombination. This, I claim, leads to a vicious circularity: warrant for neither doctrine can get off the ground

Turtles all the way down: regress, priority and fundamentality in metaphysics

This paper is a discussion of an intuition commonly held by metaphysicians: that there must be a fundamental layer of reality; that chains of ontological dependence must terminate; that there cannot be turtles all the way down. I discuss application of this intuition with reference to Bradley’s regress, composition, realism about the mental and the cosmological argument. I discuss some arguments for the intuition, but argue that they are unconvincing. I conclude by making some suggestions for how the intuition should be argued for, and discussing the ramifications of giving the justification I think best

Truthmakers and necessary connections

In this paper I examine the objection to truthmaker theory, forcibly made by David Lewis and endorsed by many, that it violates the Humean denial of necessary connections between distinct existences. In Sect. 1 I present the argument that acceptance of truthmakers commits us to necessary connections. In Sect. 2 I examine Lewis' 'Things-qua-truthmakers' theory which attempts to give truthmakers without such a commitment, and find it wanting. In Sects. 3-5 I discuss various formulations of the denial of necessary connections and argue that each of them is either false or compatible with truthmaker theory. In Sect. 6 I show how the truthmaker theorist can resist the charge that they are committed to necessary exclusions between possible existents. I conclude that there is no good objection to truthmaker theory on the grounds that it violates the Humean dictum

How to be a truthmaker maximalist

When there is truth, there must be some thing to account for that truth: some thing that couldn’t exist and the true proposition fail to be true. That is the truthmaker principle. True propositions are made true by entities in the mind-independently existing external world. The truthmaker principle seems attractive to many metaphysicians, but many have wanted to weaken it and accept not that every true proposition has a truthmaker but only that some important class of propositions require truthmakers. Let us, following Armstrong, call the claim that all true propositions, without exception, have a truthmaker, Truthmaker Maximalism. Why might one be tempted to the spirit of truthmaker theory but reject Truthmaker Maximalism? Well, you might deny that necessary truths need truthmakers, for one, and insist that only contingent truths have truthmakers. But I think it’s fair to say that the most common motivation for rejecting maximalism concerns negative truths. (Continues...

Superpositions of up to six plane waves without electric-field interference

Superpositions of coherent light waves typically interfere. We present superpositions of up to six plane waves that defy this expectation by having a perfectly homogeneous mean square of the electric field. For many applications in optics, these superpositions can be seen as having a homogeneous intensity. Our superpositions show interesting one-, two-, and three-dimensional patterns in their helicity densities, including several that support bright regions of superchirality. Our superpositions might be used to write chiral patterns in certain materials, and, conversely, such materials might be used as the basis of an “optical helicity camera” capable of recording spatial variations in helicity

Truthmaker necessitarianism and maximalism

In this paper I examine two principles of orthodox truthmaker theory: truthmaker maximalism - the doctrine that every (contingent) truth has a truthmaker, and truthmaker necessitarianism - the doctrine that the existence of a truthmaker necessitates the truth of any proposition which it in fact makes true. I argue that maximalism should be rejected and that once it is we only have reason to hold a restricted form of necessitarianism

Theoretical proposal for the experimental realisation of a monochromatic electromagnetic knot

Quantum Matter and Optic

Evaluation of a general practice based Hepatitis C virus screening intervention

In 2003 an estimated 37,500 of Scotland's population was chronically infected with HCV; 44% were undiagnosed former injecting drug users (IDU) - a priority group for arrival therapy. Aims to evaluate a hepatitis C virus (HCV) screening intervention. Outcomes measures among two similar general practice populations in an area of high HCV and drug use prevalence, one of which was exposed to an HCV screening intervention, were compared. Thirty to fifty four year old attendees of the intervention practice were opportunistically offered testing and counselling, where clinically appropriate, (November 2003 - April 2004). Outcomes: HCV test uptake, case detection, referral and treatment administration rates. Of 584 eligible attendees, 421 (72%) were offered and 117 (28%) accepted testing in the intervention practice; no testing was undertaken in the comparison practice. Prevalences of HCV antibody were 13% (15/117), 75% (3/4) and 91% (10/11) among all tested persons, current IDUs and former IDUs respectively. For 4/15 (27%) evidence of binge drinking following the receipt of their positive result, was available. Of the 11 referred to specialist care because they were HCV RNA positive, nine attended at least one appointment. Two received treatment: one had achieved a sustained viral response as of February 2008. While non targeted HCV screening in the general practice setting can detect infected former IDU, the low diagnostic yield among non IDUs limited the effectiveness of the intervention. A more targeted approach for identifying former IDUs is recommended. Additionally, the low uptake of treatment among chronically infected persons four years after diagnosis demonstrates the difficulties in clinically managing such individuals. Strategies, including support for those with a history of problem alcohol use, to improve treatment uptake are required

Solar-Cycle Characteristics Examined in Separate Hemispheres: Phase, Gnevyshev Gap, and Length of Minimum

Research results from solar-dynamo models show the northern and southern hemispheres may evolve separately throughout the solar cycle. The observed phase lag between the hemispheres provides information regarding the strength of hemispheric coupling. Using hemispheric sunspot-area and sunspot-number data from Cycles 12 - 23, we determine how out of phase the separate hemispheres are during the rising, maximum, and declining period of each solar cycle. Hemispheric phase differences range from 0 - 11, 0 - 14, and 2 - 19 months for the rising, maximum, and declining periods, respectively. The phases appear randomly distributed between zero months (in phase) and half of the rise (or decline) time of the solar cycle. An analysis of the Gnevyshev gap is conducted to determine if the double-peak is caused by the averaging of two hemispheres that are out of phase. We confirm previous findings that the Gnevyshev gap is a phenomenon that occurs in the separate hemispheres and is not due to a superposition of sunspot indices from hemispheres slightly out of phase. Cross hemispheric coupling could be strongest at solar minimum, when there are large quantities of magnetic flux at the Equator. We search for a correlation between the hemispheric phase difference near the end of the solar cycle and the length of solar-cycle minimum, but found none. Because magnetic flux diffusion across the Equator is a mechanism by which the hemispheres couple, we measured the magnetic flux crossing the Equator by examining magnetograms for Solar Cycles 21 - 23. We find, on average, a surplus of northern hemisphere magnetic flux crossing during the mid-declining phase of each solar cycle. However, we find no correlation between magnitude of magnetic flux crossing the Equator, length of solar minima, and phase lag between the hemispheres.Comment: 15 pages, 7 figure

Cartilage-specific ablation of XBP1 signaling in mouse results in a chondrodysplasia characterized by reduced chondrocyte proliferation and delayed cartilage maturation and mineralization

SummaryObjectiveTo investigate the in vivo role of the IRE1/XBP1 unfolded protein response (UPR) signaling pathway in cartilage.DesignXbp1flox/flox.Col2a1-Cre mice (Xbp1CartΔEx2), in which XBP1 activity is ablated specifically from cartilage, were analyzed histomorphometrically by Alizarin red/Alcian blue skeletal preparations and X-rays to examine overall bone growth, histological stains to measure growth plate zone length, chondrocyte organization, and mineralization, and immunofluorescence for collagen II, collagen X, and IHH. Bromodeoxyuridine (BrdU) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analyses were used to measure chondrocyte proliferation and cell death, respectively. Chondrocyte cultures and microdissected growth plate zones were analyzed for expression profiling of chondrocyte proliferation or endoplasmic reticulum (ER) stress markers by Quantitative PCR (qPCR), and of Xbp1 mRNA splicing by RT-PCR to monitor IRE1 activation.ResultsXbp1CartΔEx2 displayed a chondrodysplasia involving dysregulated chondrocyte proliferation, growth plate hypertrophic zone shortening, and IRE1 hyperactivation in chondrocytes. Deposition of collagens II and X in the Xbp1CartΔEx2 growth plate cartilage indicated that XBP1 is not required for matrix protein deposition or chondrocyte hypertrophy. Analyses of mid-gestation long bones revealed delayed ossification in Xbp1CartΔEx2 embryos. The rate of chondrocyte cell death was not significantly altered, and only minimal alterations in the expression of key markers of chondrocyte proliferation were observed in the Xbp1CartΔEx2 growth plate. IRE1 hyperactivation occurred in Xbp1CartΔEx2 chondrocytes but was not sufficient to induce regulated IRE1-dependent decay (RIDD) or a classical UPR.ConclusionOur work suggests roles for XBP1 in regulating chondrocyte proliferation and the timing of mineralization during endochondral ossification, findings which have implications for both skeletal development and disease