The vertebrate retina is said to be inverted because the photoreceptors are oriented in the posterior direction and are thus unable to maximize photodetection under conditions of low illumination. The tapetum lucidum is a photoreflective structure located posterior to the photoreceptors in the eyes of some fish and terrestrial animals. The tapetum reflects light forward, giving incident photons a “second chance” to collide with a photoreceptor, substantially enhancing retinal photosensitivity in dim light. Across vertebrates (and arthropods), there are a (...) wide variety of tapeta that vary in structure, chemical composition, and even tissue architecture, indicating repeated convergent evolution. To date, the tapetum has not been observed in any cephalopod, however, which also possess a camera‐like eye, but with the retinal photoreceptors oriented in the anterior direction. We therefore hypothesize that the tapetum lucidum is a compensatory adaptation for the suboptimal design of the inverted retina of vertebrates. (shrink)

This Discussion Piece is a response to Mark Windsor's Discussion Piece (2023) 'Photographic Registers are Latent Images', which is a response to my article, (2021) 'Invisible Images and Indeterminacy: Why we need a Multi-stage Account of Photography' JAAC 79(2) 161-174.. -/- I argue that a photosensitive surface does not produce invisible pictorial features when it is exposed to light, and conclude, contra Windsor, that a photographic register is not a latent image. I argue that Windsor does not succeed in defending (...) a single-stage account of photography and I reconfirm that a multi-stage account is correct. (shrink)

Merely rhetorically, and answering in the negative, Kendall Walton has asked: "Isn't photography just another method people have of making pictures, one that merely uses different tools and materials – cameras, photosensitive paper, darkroom equipment, rather than canvas, paint, and brushes? And don't the results differ only contingently and in degree, not fundamentally, from pictures of other kinds?" Contra Walton and others, I wish to defend in this article a resounding "Yes" as being the correct answer to these questions. It (...) is a widely shared view that photographs are somehow special and that they fundamentally differ from hand-made pictures like paintings, both from a phenomenological point of view (in the way we experience them), and an epistemic point of view (since they are supposed to have a different – greater – epistemic value than paintings, giving us a privileged access to the world). In what follows, I shall reject almost the totality of these claims, and as a consequence there will remain little difference left between photographs and paintings. As we shall see, 'photographs are always partly paintings' – a claim that is true not only of retouched digital photographs but of all photographs, including traditional ones made using photosensitive film and development techniques. (shrink)

The goal of constructing artificial photosynthetic assemblies is to use sunlight for the generation of hydrogen from water; the hydrogen obtained should be an ideal energy source. The use of surfactant vesicle entrapped‐catalyst coated colloidal semiconductors and sacrificial electron donors for photosensitized water reduction illustrates how chemists mimic photosynthesis.

Organogenesis and metamorphosis require the intricate orchestration of multiple types of cellular interactions and signaling pathways. Glutamate (Glu) is an excitatory extracellular signaling molecule in the nervous system, while Ca2+ is a major intracellular signaling molecule. The first Glu receptors to be cloned are Ca2+‐permeable receptors in mammalian brains. Although recent studies have focused on Glu signaling in synaptic mechanisms of the mammalian central nervous system, it is unclear how this signaling functions in development. Our recent article demonstrated that Ca2+‐permeable (...) AMPA‐type Glu receptors (GluAs) are essential for formation of a photosensitive organ, development of some neurons, and metamorphosis, including tail absorption and body axis rotation, in ascidian embryos. Based on findings in these embryos and mammalian brains, we formed several hypotheses regarding the evolution of GluAs, the non‐synaptic function of Glu, the origin of GluA‐positive neurons, and the neuronal network that controls metamorphosis in ascidians. (shrink)

A major problem in the treatment of cancer is the specific targeting of anti‐tumor drugs to these abnormal cells. Ideally, such a drug should act over short distances to minimize damage to healthy cells, and target subcellular compartments that have the highest sensitivity to the drug. Photosensitizers, alpha‐emitting radionuclides and many other medicines could be considered as such drugs if they possessed cellular and subcellular specificity. The author describes a novel approach of using modular recombinant transporters to target photosensitizers and (...) alpha‐emitting radionuclides to the nucleus, where their action is most pronounced, of cancer cells. Photosensitizer‐transporter conjugates have up to 3000 times greater efficacy than free photosensitizers and display cell specificity in contrast to free photosensitizers. Alpha‐emitting radionuclides, conjugated with the modular transporters, acquired similar properties. The different modules of the transporters are interchangeable, meaning that they can be tailored for particular applications. BioEssays 30:278–287, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

This chapter traces the path of skepticism about photographic art through the history of thinking about photography. Flower 009 is a photogram, made by placing plumbago blossoms directly onto a photosensitive surface, then exposing it to light and developing the print. Flower 009 gives a glimpse of the four arts of photography that are to be found by taking a close look at the history of photography and the history of thinking about photography. The early theorists’ skepticism about photographic art (...) provoked a defensive reaction in pictorialist photography. Pictorialism was loudly, unremittingly denounced by the straight photography movement that succeeded it. The pictorialists expanded photography to include painterly touches that allow scope for artistic expression. One response to the early theorists’ dialectic remains, and that is to take up a stance of ambivalence. Ambivalence relegates the dialectic to the background without resolving it. (shrink)

Humans accumulate porphyrins in the body mostly during the course of porphyrias, diseases caused by defects in the enzymes of the heme biosynthesis pathway and that produce acute attacks, skin lesions and liver cancer. In contrast, some wild mammals and birds are adapted to accumulate porphyrins without injurious consequences. Here we propose viewing such physiological adaptations as potential solutions to human porphyrias, and suggest certain wild animals as models. Given the enzymatic activity and/or the patterns of porphyrin excretion and accumulation, (...) the fox squirrel, the great bustard and the Eurasian eagle owl may constitute overlooked models for different porphyrias. The Harderian gland of rodents, where large amounts of porphyrins are synthesized, presents an underexplored potential for understanding the carcinogenic/toxic effect of porphyrin accumulation. Investigating how these animals avoid porphyrin pathogenicity may complement the use of laboratory models for porphyrias and provide new insights into the treatment of these disorders. (shrink)