A jury of none: an essay on the last acceptable form of civic banishment

Though many socio-legal scholars have criticized those measures that deny convicted felons the right to vote, few have challenged the statutes that withhold a convicted felon’s opportunity to sit on a jury. A majority of US jurisdictions bar felons from jury service permanently, creating a class of citizens defined and punished by the criminal justice system but unable to impact its function. This essay considers the invisibility of felon jury exclusion, notes its unlikely supporters, and asserts that by preventing convicted felons from taking part in civic processes, authorities work against reentry initiatives.     

A pulse-labelling method to generate 13C- enriched plant materials

Plant materials labelled with ¹³C can be used to trace litter decomposition and root carbon flow, but only if the isotope is uniformly distributed in the plant. We postulated that if ¹³CO₂ were applied at regular intervals, in direct proportion to the rate of photosynthesis, then the abundance of ¹³C would be uniform among plant parts. To test this hypothesis, wheat plants were grown in the greenhouse, and exposed weekly to ¹³CO₂ for six hours in a closed chamber. A constant dose of ¹³CO₂ (about 33 atom%) was injected whenever CO₂ concentration fell below a prescribed limit, so that ¹³CO₂ was added in proportion to photosynthetic rate. Wheat exposed for 13 weeks (starting 11 days after seeding) had reasonably consistent ¹³C abundance among plant parts: grain = 3.41, chaff = 3.41, stem = 3.65, and root = 3.50 atom%. The `leaf' fraction had slightly higher abundance (3.99 atom%), perhaps because recently-fixed ¹³C was not translocated from senescing tissue. Exposing plants only during early stages of the growing season increased differences among plant parts. The approach offers a practical way to label plants with ¹³C.     

Knowing human moral knowledge to be true: an essay on intellectual conviction

The question addressed in this article is how people come to know the foundational axioms of their moral systems as true and correct. Drawing on my fieldwork among the Himba of northwestern Namibia, I argue that the most potent form of intellectual conviction is not generated through the external manipulations of ritual, but through a deeply internal experience in which moral knowledge coalesces with a subjectively perceived experience of timeless universality.     

A novel ROP/RAC GTPase effector integrates plant cell form and pattern formation

ROPs/RACs are the only known signaling Ras superfamily small GTPases in plants. As such they have been suggested to function as central regulators of diverse signaling cascades. The ROP/RAC signaling networks are largely unknown, however, because only few of their effector proteins have been identified. In a paper that was published in the June 5, 2007 issue of Current Biology we described the identification of a novel ROP/RAC effector designated ICR1 (Interactor of Constitutive active ROPs 1). We demonstrated that ICR1 functions as a scaffold that interacts with diverse but specific group of proteins including SEC3 subunit of the exocyst vesicle tethering complex. ICR1-SEC3 complexes can interact with ROPs in vivo and are thereby recruited to the plasma membrane. ICR1 knockdown or silencing leads to cell deformation and loss of the root stem cells population, and ectopic expression of ICR1 phenocopies activated ROPs/RACs. ICR1 presents a new paradigm in ROP/RAC signaling and integrates mechanisms regulating cell form and pattern formation at the whole plant level.Key words: Rho, auxin, root development, vesicle trafficking, RAC, ROP, polarity, Arabidopsis, exocyst     

From fungi to flies: pattern and form in the cell cycle

This review shows how, in some lower eukaryotes, recent studies have made important connections between cell cycle control processes and complex events such as organelle positioning and the differentiation of cells and tissues.     

High-throughput film-densitometry: an efficient approach to generate large data sets

A film-handling machine (robot) has been built which can, in conjunction with a commercially available film densitometer, exchange and digitize over 300 electron micrographs per day. Implementation of robotic film handling effectively eliminates the delay and tedium associated with digitizing images when data are initially recorded on photographic film. The modulation transfer function (MTF) of the commercially available densitometer is significantly worse than that of a high-end, scientific microdensitometer. Nevertheless, its signal-to-noise ratio (S/N) is quite excellent, allowing substantial restoration of the output to "near-to-perfect" performance. Due to the large area of the standard electron microscope film that can be digitized by the commercial densitometer (up to 10,000 x 13,680 pixels with an appropriately coded holder), automated film digitization offers a fast and inexpensive alternative to high-end CCD cameras as a means of acquiring large amounts of image data in electron microscopy.     

Unfinished business: an essay on finally leaving the bench

Spontaneous and induced chromosome aberrations have been studied over more than a century. The resolution of detection of aberrations has depended on the improvement of available techniques. An overview on the major high lights in this area of research, from the time of solid staining to fluorescence in situ hybridization technique is presented in this review.     

A synergic approach to plant pattern generation

The paper shows convergences between the results found in various models of phyllotaxis. It shows that a synergic approach is needed to deal with the problems of phyllotaxis. An algorithm, called the phi-model, based on the observation of the meaningful and symmetry-generating presence of the golden ratio phi in all types of spiral patterns, and consequently in all types of regular patterns in phyllotaxis, is proposed. The model is suggested by a property of the allometry-type model for pattern recognition in phyllotaxis. It extends recent morphological models developed around the idea of packing efficiency of plant primordia, models that yield the noble numbers, among which are the divergence angles of spiral patterns. The phi-model also gives the noble numbers and moreover orders them in a way that establishes connections with the morphogenetic principles used in models for pattern generation; the order has to do with the relative frequencies of the spiral patterns in nature. The phi-model is a link between the two entropy models in phyllotaxis and offers a nice correspondence with the minimal entropy model generated by a systemic and holistic approach. This latter type of approach is put forward as being able to give a general framework in which to organize the concepts, results, and models in phyllotaxis in a way that produces a synergy of efforts. The necessity of doing so is seen clearly when one considers that phyllotaxis-like patterns are encountered in other fields of research, so that the problem appears to transcend the strict botanical substratum.     

Effects of spatial pattern and relatedness in an experimental plant community

Many plant species show limited dispersal resulting in spatial and genetic substructures within populations. Consequently, neighbours are often related between each other, resulting in sibling competition. Using seed families of the annuals Capsella bursa-pastoris and Stachys annua we investigated effects of spatial pattern (i.e. random versus aggregated) on total and individual performance at the level of species and seed families under field conditions. At the level of species, we expected that inferior competitors increase, while superior competitors decrease their performance within neighbourhoods of conspecifics. Thus, we expected a species by spatial pattern interaction. Sibling competition, however, might reduce the performance of competitors, when genetically related, rather than non-related individuals are competing. Therefore, aggregations at the level of seed families could decrease the performance of competitors. Alternatively, if the opposite outcome would be observed, kin selection might be hypothesized to have occurred in the past. Because heavy seeds are expected to disperse less than light seeds, we further hypothesized that kin selection might be more likely to occur in superior competitors with heavy, locally dispersed seeds (e.g. Stachys) compared to inferior competitors with light, more distantly dispersed seeds (e.g. Capsella). We found a significant species by spatial pattern interaction. Indeed, the inferior competitor, Capsella, showed increased reproductive biomass production in aggregated compared to random patterns. Whereas, the performance of the superior competitor, Stachys, was to some extent decreased by intraspecific aggregation. Although statistically not significant, effects of intrafamily aggregations tended to be rather negative in Capsella but positive in Stachys. Our results confirmed that spatial patterns affect growth and reproduction of plant species promoting coexistence in plant communities. Although, we could not provide strong evidence for sibling competition or kin selection, our results suggested that competition among relatives was more severe for Capsella (lighter seeds) compared to Stachys (heavier seeds).     

Fumaric acid: an overlooked form of fixed carbon in Arabidopsis and other plant species

Photoassimilates are used by plants for production of energy, as carbon skeletons and in transport of fixed carbon between different plant organs. Many studies have been devoted to characterizing the factors that regulate photoassimilate concentrations in different plant species. Most studies examining photoassimilate concentrations in C₃ plants have focused on analyzing starch and soluble sugars. However, work presented here demonstrates that a number of C₃ plants, including the popular model organism Arabidopsis thaliana (L.) Heynh., and agriculturally important plants, such as soybean, Glycine max (L.) Merr., contain significant quantities of fumaric acid. In fact, fumaric acid can accumulate to levels of several milligrams per gram fresh weight in Arabidopsis leaves, often exceeding those of starch and soluble sugars. Fumaric acid is a component of the tricarboxylic acid cycle and, like starch and soluble sugars, can be metabolized to yield energy and carbon skeletons for production of other compounds. Fumaric acid concentrations increase with plant age and light intensity in Arabidopsis leaves. Moreover, Arabidopsis phloem exudates contain significant quantities of fumaric acid, raising the possibility that fumaric acid may function in carbon transport. Received: 11 February 2000 / Accepted: 1 April 2000     

Semi-continuous biohydrogen production as an approach to generate electricity

In this work, a semi-continuous biological system was established to produce hydrogen and generate electricity by coupling the bioreactor to a fuel cell. Heat and acid pretreatments (at 35 and 55 °C) of a seed sludge used as inoculum were performed in order to increase hydrogen producers. Different initial glucose concentrations (IGC) were tested for heat pretreated inoculum at 35 °C to determine the optimum concentration of glucose that supported the highest hydrogen production. Results showed that the heat pretreated inoculums (35 °C) reached the highest hydrogen molar yield of 2.85 mol H₂/mol glucose (0.014 L/h), which corresponds to the acetic acid pathway. At the optimum IGC (10 g/L, 35 °C) the hydrogen molar yield was 3.6 mol H₂/mol glucose (0.023 L/h). The coupled bioreactor-fuel cell system yielded an output voltage of 1.06 V, power of 0.1 W (25 °C) and a current of 68 mA. The overall results suggest that high hydrogen molar yields can be obtained through the acetic acid pathway and that is feasible to generate electricity using hydrogen from the semi- continuous bioreactor.     

Mechanisms of stimulation of olfactory neurons: an essay

It is widely believed that the mechanism by which olfactoryneurons are stimulated by odorants is via specific receptorproteins located on or in the apical cell membranes of the neurons.In this review alternative mechanisms are explored and a modelis presented in which sensitivity and specificity can be accountedfor by the general irritability of cells to chemicals. The premiseson which the model is based are: (i) Groups of olfactory nerves fire action potentials whichare summated at the first synapse, in the olfactory bulb. Theseneurons fire spontaneously because their resting potentialsare unstable. (ii) What we call olfactory quality is encoded in patterns offiring of different olfactory neurons. (iii) Olfactory neurons are not identical. The sources of theirindividuality include differences in their age, spatial locationin the plane of the tissue, depth within the tissue and distancefrom the nearest capillary. The heterogeneity will be reflectedas differences in their metabolism and chemical composition. (iv) Most of the surface area of olfactory neurons is bathedin mucus that is secreted by Bowman's glands and sustentacularcells. Therefore, the resting potential and firing frequencyof each will depend upon the composition of the mucus. It follows from these premises that alterations in the mucuscomposition, extracellular fluid composition, metabolic stateor properties of neuronal membranes will alter the resting potentialand, therefore, the firing frequency of each neuron. The effectswill vary among neurons because of their individuality evenif the stimulus is distributed uniformly across the olfactorymucosa, different regions will be exposed to different patternsof stimulus concentration because odorants are differentiallyadsorbed and metabolized. According to this scheme qualitativelydifferent patterns of neural activity will result from differentodorants, the firing of some neurons being inhibited and thatof others being stimulated in each case. This will be true independentlyof the existence of specific receptor proteins, the effectsof which must be superimposed upon the general effects of nonspecificirritability.     

Niche theory and plant growth form

Plant growth form diversity (GFD) is high in the vegetation of North American deserts, and increases from north (Great Basin Desert) to south (Sonoran Desert). While abiotic features (annual temperature, precipitation, and seasonality) appear to limit the range of desert plant GFD, biotic features associated with the coexisting plants at a site, and their GF distribution, add further constraints. Climate may constrain the GF options at certain sites and select for some degree of GF convergence there, but within sites other species in the vegetation select for GF segregation that fosters the local coexistence of species. In this paper GF variation is viewed along structural niche axes, and related to classical niche theory; several corollaries of the theory are examined in the light of plant GF patterns. These are: a) regular spacing of species on the structural niche axis, and the concept of limiting similarity; b) niche axis complementarity, such that species dissimilar in position on one axis, e.g. GF, are similar in position on other axes, e.g. habitat or substrate, and vice versa; c) niche shifts in GF within species are expected, and occur, as the suite of coexisting species varies among sites with similar climate; d) in some desert plant guilds species with very similar GF do not coexist at a site, but act as geographical replacements in different sites.