A comment on Mermin's “Understanding Einstein's 1905 derivation of E=mc2”

N. D. Mermin has proposed an “elaboration” of Einstein's 1905 derivation that supposedly fixes the flaws that I identified in this derivation. By specific examples taken from Einstein's own later work, I show that Mermin's elaboration is fraught with misconceptions.     

Did de Vries discover the law of segregation independently?

It is argued that de Vries did not see Mendel's paper until 1900, and that, while his own theory of inheritance may have incorporated the notion of independent units, this pre-Mendelian formulation was not the same as Mendel's since it did not apply to paired hereditary units. Moreover, the way in which the term ‘segregation’ has been applied in the secondary literature has blurred the distinction between what is explained and the law which facilitates explanation.     

Can we trust Einstein’s accounts of the genesis of special relativity?

There are three kinds of sources available to reconstruct the reflections that led Einstein to special relativity: a few contemporary letters and documents, his impersonal accounts of the genesis of this theory, and recollections of his own path. At first glance, contradictions within and between these sources hamper the reliability of Einstein’s accounts. Yet, a closer analysis reveals much more consistency than foreseen and helps eliminate the dubious, contradictory elements. It then becomes possible to combine the three kinds of sources to produce a minimally speculative and yet fairly coherent account of the genesis of special relativity.     

Did Ptolemy make novel predictions? Launching Ptolemaic astronomy into the scientific realism debate

The goal of this paper, both historical and philosophical, is to launch a new case into the scientific realism debate: geocentric astronomy. Scientific realism about unobservables claims that the non-observational content of our successful/justified empirical theories is true, or approximately true. The argument that is currently considered the best in favor of scientific realism is the No Miracles Argument: the predictive success of a theory that makes (novel) observational predictions while making use of non-observational content would be inexplicable unless such non-observational content approximately corresponds to the world “out there”. Laudan's pessimistic meta-induction challenged this argument, and realists reacted by moving to a “selective” version of realism: the approximately true part of the theory is not its full non-observational content but only the part of it that is responsible for the novel, successful observational predictions. Selective scientific realism has been tested against some of the theories in Laudan's list, but the first member of this list, geocentric astronomy, has been traditionally ignored. Our goal here is to defend that Ptolemy's Geocentrism deserves attention and poses a prima facie strong case against selective realism, since it made several successful, novel predictions based on theoretical hypotheses that do not seem to be retained, not even approximately, by posterior theories. Here, though, we confine our work just to the detailed reconstruction of what we take to be the main novel, successful Ptolemaic predictions, leaving the full analysis and assessment of their significance for the realist thesis to future works.     

Einstein׳s Equations for Spin 2 Mass 0 from Noether׳s Converse Hilbertian Assertion

An overlap between the general relativist and particle physicist views of Einstein gravity is uncovered. Noether׳s 1918 paper developed Hilbert׳s and Klein׳s reflections on the conservation laws. Energy-momentum is just a term proportional to the field equations and a ‘curl’ term with identically zero divergence. Noether proved a converse “Hilbertian assertion”: such “improper” conservation laws imply a generally covariant action.Later and independently, particle physicists derived the nonlinear Einstein equations assuming the absence of negative-energy degrees of freedom (“ghosts”) for stability, along with universal coupling: all energy-momentum including gravity׳s serves as a source for gravity. Those assumptions (all but) imply (for 0 graviton mass) that the energy-momentum is only a term proportional to the field equations and a symmetric “curl,” which implies the coalescence of the flat background geometry and the gravitational potential into an effective curved geometry. The flat metric, though useful in Rosenfeld׳s stress-energy definition, disappears from the field equations. Thus the particle physics derivation uses a reinvented Noetherian converse Hilbertian assertion in Rosenfeld-tinged form.The Rosenfeld stress-energy is identically the canonical stress-energy plus a Belinfante curl and terms proportional to the field equations, so the flat metric is only a convenient mathematical trick without ontological commitment. Neither generalized relativity of motion, nor the identity of gravity and inertia, nor substantive general covariance is assumed. The more compelling criterion of lacking ghosts yields substantive general covariance as an output. Hence the particle physics derivation, though logically impressive, is neither as novel nor as ontologically laden as it has seemed.     

Morphological effects of prostaglandins E1, E2 and F2α on fibroblast-like cultures of human synovial cells

Summary In medium supplemented with serum, PGE₁ and PGE₂ were equally potent in inducing cells with a fenestrated appearance, whereas PGF₂ was comparatively ineffective. In BSA without serum the effects were more persistent and characterized by a high proportion of astrocyte-like cells. The effects were reversed upon removal of the prostaglandins.This work was supported by the National Health and Medical Research Council of Australia.     

Did Unexpectedly Strong Economic Growth Cause the Oil Price Shock of 2003–2008?

Recently developed structural models of the global crude oil market imply that the surge in the real price of oil between mid 2003 and mid 2008 was driven by repeated positive shocks to the demand for all industrial commodities, reflecting unexpectedly high growth mainly in emerging Asia. We evaluate this proposition using an alternative data source and a different econometric methodology. Rather than inferring demand shocks from an econometric model, we utilize a direct measure of global demand shocks based on revisions of professional real gross domestic product (GDP) growth forecasts. We show that forecast surprises during 2003–2008 were associated primarily with unexpected growth in emerging economies (in conjunction with much smaller positive GDP‐weighted forecast surprises in the major industrialized economies), that markets were repeatedly surprised by the strength of this growth, that these surprises were associated with a hump‐shaped response of the real price of oil that reaches its peak after 12–16 months, and that news about global growth predict much of the surge in the real price of oil from mid 2003 until mid 2008 and much of its subsequent decline. Copyright © 2012 John Wiley & Sons, Ltd.     

前列腺素E2受体生化性质及功能的研究进展

前列腺素E2受体(EP)是一类G蛋白偶联受体,主要与前列腺素E2(PGE2)结合,在多种疾病的发生中发挥作用.研究发现EP在机体几乎所有系统,如心血管系统、呼吸系统、生殖系统、神经系统等的病理反应中发挥重要作用,甚至与肿瘤的发生也有关联.研究并掌握EP相关性质对于临床疾病的治疗有着重要的意义,在国际上已成为研究和报道的热点.本文简要综述了关于EP前沿的研究成果,以期为广大研究者提供借鉴,为进一步阐释EP作用机制以及相关研究乃至临床治疗提供新的思路.     

A selective concentration-dependent dysrhythmogenic and antidysrhythmic action of prostaglandins E2, F2α and I2 (prostacyclin) on isolated rat hearts

Summary Prostaglandins (PGs) E₂, F₂, and I₂ were examined for their effects on the electrical and mechanical activities of isolated rat, rabbit and guinea-pig hearts. All PGs produced dysrhythmias in rat hearts at low concentrations only, while higher concentrations were antiarrhythmic. Guinea-pig hearts were less responsive while rabbit hearts were completely resistant.We thank the Manitoba Heart Foundation for financial support and Dr J. Pike (Upjohn, Kalamazoo, MI, USA) for gifts of prostaglandins. Dr M. Karmazyn is a Fellow of the Canadian Heart Foundation.     

What’s the hype about CDK5RAP2?

Cyclin dependent kinase 5 regulatory subunit-associated protein 2 (CDK5RAP2) has gained attention in the last years following the discovery, in 2005, that recessive mutations cause primary autosomal recessive microcephaly. This disease is seen as an isolated developmental defect of the brain, particularly of the cerebral cortex, and was thus historically also referred to as microcephalia vera. Unraveling the pathomechanisms leading to this human disease is fascinating scientists because it can convey insight into basic mechanisms of physiologic brain development (particularly of cortex formation). It also finds itself in the spotlight because of its implication in trends in mammalian evolution with a massive increase in the size of the cerebral cortex in primates. Here, we provide a timely overview of the current knowledge on the function of CDK5RAP2 and mechanisms that might lead to disease in humans when the function of this protein is disturbed.     

Did Samuel Clarke really disavow action at a distance in his correspondence with Leibniz?: Newton,Clarke, and Bentley on gravitation and action at a distance

In this paper I ague against John Henry's claim that Newton embraced unmediated action at a distance as an explanation of gravity (Henry, 1994, 1999, 2011, 2014). In particular, I take issue with his apparent suggestion that the fact, as he sees it, that two of Newton's prominent followers, namely, Richard Bentley and Samuel Clarke, embraced unmediated action at a distance as an explanation of gravity provides significant supporting evidence that Newton did as well (see Henry, 1994 and 1999). Instead, I argue that while Bentley did ultimately defend the notion of unmediated action at a distance as an explanation of gravity, Newton himself accepted that notion neither in his correspondence with Bentley, as Henry has maintained, nor in any of his later works. I also provide evidence that suggests that Newton did, in fact, accept both the principle of local causation and the passivity of matter. Finally, I argue that whatever the case may be with respect to Newton on the matter, it is clear from his correspondence with Leibniz, as well as from his Boyle lectures, that contrary to what Henry has maintained, Clarke was a stalwart opponent of unmediated action at a distance due to his strong commitment to both the principle of local causation and the passivity of matter.     

Insulin-like growth factor 2 mRNA-binding proteins (IGF2BPs): post-transcriptional drivers of cancer progression?

The insulin-like growth factor-2 mRNA-binding proteins 1, 2, and 3 (IGF2BP1, IGF2BP2, IGF2BP3) belong to a conserved family of RNA-binding, oncofetal proteins. Several studies have shown that these proteins act in various important aspects of cell function, such as cell polarization, migration, morphology, metabolism, proliferation and differentiation. In this review, we discuss the IGF2BP family’s role in cancer biology and how this correlates with their proposed functions during embryogenesis. IGF2BPs are mainly expressed in the embryo, in contrast with comparatively lower or negotiable levels in adult tissues. IGF2BP1 and IGF2BP3 have been found to be re-expressed in several aggressive cancer types. Control of IGF2BPs’ expression is not well understood; however, let-7 microRNAs, β-catenin (CTNNB1) and MYC have been proposed to be involved in their regulation. In contrast to many other RNA-binding proteins, IGF2BPs are almost exclusively observed in the cytoplasm where they associate with target mRNAs in cytoplasmic ribonucleoprotein complexes (mRNPs). During development, IGF2BPs are required for proper nerve cell migration and morphological development, presumably involving the control of cytoskeletal remodeling and dynamics, respectively. Likewise, IGF2BPs modulate cell polarization, adhesion and migration in tumor-derived cells. Moreover, they are highly associated with cancer metastasis and the expression of oncogenic factors (KRAS, MYC and MDR1). However, a pro-metastatic role of IGF2BPs remains controversial due to the lack of ‘classical’ in vivo studies. Nonetheless, IGF2BPs could provide valuable targets in cancer treatment with many of their in vivo roles to be fully elucidated.     

双钙钛矿Sr2Mn1-xGaxMoO6（x=0．0～1．0）化合物的制备及其结构的研究

采用固相反应法制备了双钙钛矿Sr2Mn1-xGaxMoO6（x=0．0～1．0）掺杂化合物。室温下的高分辨率X射线衍射分析表明,Sr2MnMoO6具有单斜晶体结构,空间群为P21／n。Ga的掺杂没有改变化合物的晶体结构,但衍射峰整体向高角度漂移。结构精修分析表明,Sr2Mn1-xGaxMoO6样品的晶胞体积随Ga含量的增加而逐渐减小;B／B’位离子占位有序度伴随Ga的掺入而逐渐降低;此外,Ga的引入导致〈B—O〉键长的缩短,〈B’-O〉键长的伸长。     

How do Shp2 mutations that oppositely influence its biochemical activity result in syndromes with overlapping symptoms?

Activating and inactivating mutations of SHP-2 are responsible, respectively, for the Noonan (NS) and the LEOPARD (LS) syndromes. Clinically, these developmental disorders overlap greatly, resulting in the apparent paradox of similar diseases caused by mutations that oppositely influence SHP-2 phosphatase activity. While the mechanisms remain unclear, recent functional analysis of SHP-2, along with the identification of other genes involved in NS and in other related syndromes (neurofibromatosis-1, Costello and cardio-facio-cutaneous syndromes), strongly suggest that Ras/MAPK represents the major signaling pathway deregulated by SHP-2 mutants. We discuss the idea that, with the exception of LS mutations that have been shown to exert a dominant negative effect, all disease-causing mutations involved in Ras/MAPK-mediated signaling, including SHP-2, might lead to enhanced MAPK activation. This suggests that a narrow range of MAPK signaling is required for appropriate development. We also discuss the possibility that LS mutations may not simply exhibit dominant negative activity. Received 30 November 2006; received after revision 8 February 2007; accepted 13 March 2007     

A simple synthesis of (E)-3-formylbut-2-enenitrile,and its use as a precursor of isotope-labelled zeatin and (±) dihydrozeatin

Summary (E)-3-Formylbut-2-enenitrile (4) is synthesized in 2 steps by reacting pyruvaldehyde dimethylacetal and acetonitrile in the presence of sodium methoxide, followed by acid hydrolysis to give 58% overall yield on distillation. The aldehyde4 can be stepwise and selectively reduced to (E)-3-hydroxymethylbut-2-enylamine (7a) in 37% total yield or exhaustivelyb reduced in 1 step to (±)-4-hydroxy-3-methylbutylamine (6) in 46% total yield. Compound7a and6 can be condensed with 6-chloropurine to give zeatin and (±)dihydrozeatin respectively. This provides a readily accessible method for isotope-labelled zeatin and its derivatives at side chain.Contribution No. 1064, Alberta Research CouncilProcess for the Preparation oftrans-3-formylbut-2-enenitrile S. Chen and J. MacTaggart, patent applicatioin registered in Canada and the United States of America.Acknowledgment. The author thanks Mr J. M. MacTaggart and Mrs C. M. Goulet for valuable experimental assistance and Dr R. M. Elofson for helpful discussions.