Improving and elucidating factors regulating black walnut (Juglans nigra L.) clonal propagation

Black walnut (Juglans nigra L.) is a fine hardwood tree species native to the central hardwood region of the United States. High-quality black walnut timber is highly desirable. Traded in both regional and global markets, it has been used for veneer, and the manufacture of high-end products such as cabinets, furniture, and gunstocks. As a result of its high economic value, black walnut has been commercially cultivated for many years, and breeding programs have generated superior timber genotypes with improved marketable traits. Once elite genotypes were developed, it was quickly recognized that black walnut was recalcitrant to clonal propagation techniques. Current black walnut propagation techniques such as grafting are time and labor intensive, and are less than optimal for commercial clonal black walnut production. Reports on black walnut propagation are limited, and successful protocols were often genotype dependent and difficult to replicate. The inability of black walnut to predictably and reliably produce adventitious roots is often the greatest hurdle to successful propagation protocols. The objective of this research was to develop a reproducible and dependable clonal propagation protocol for black walnut, as well as to study the mechanisms controlling adventitious root formation in black walnut. Clonal propagation systems are ideal to rapidly replicate elite genotypes, assist conservation efforts, and act to complement tree improvement programs. These goals were achieved using a multi-faceted approach. First, an in vitro propagation protocol was developed for elite black walnut genotypes 55 and 189. Nodal cutting explants were aseptically cultured on semi-solid Driver and Kuniyuki walnut (DKW) medium supplemented with 8.9 µM benzyladenine (BA), 0.005 µM indole-3-butryic acid (IBA), 200 mg L-1 casein hydrolysate (CH), 50 mg L-1adenine hemisulfate (AS), 2 ml L-1 Plant Preservative Mixture™ (PPM), and 4.1 µM meta-topolin. This medium resulted in the greatest shoot growth after 8 weeks for both genotypes, 1.7 and 1.3 cm respectively. Long-term survival and proliferation of microshoots was achieved when nodal segments of in vitro grown shoots were cultured in liquid initiation medium in 3 L polycarbonate Fernbach-style flasks on a rotary shaker (100 rpm) under a 16 h photoperiod at 25°C. Elongated microshoots (5–7 cm in length) were rooted (40%) in a slurry-like medium composed of half-strength DKW medium with 0.11% (w/v) Phytagel™ and coarse vermiculite (2:1, v/v) supplemented with 50 µM IBA for 5 weeks. Rooted microshoots shoots were acclimatized to ambient culture room conditions, but did not survive acclimatization to the greenhouse. Softwood cuttings were used to improve ex vitro propagation and to develop a spatial and temporal timeline of the stages of adventitious root formation. Softwood cuttings (15–20 cm) that were collected from juvenile sources of elite genotypes, dipped for 60 s in 93.2 mM indole-3-butyric acid-potassium salt (K-IBA), and then inserted into a moist medium consisting of 3 perlite: 1 coarse vermiculite (v/v) rooted at a 72% frequency. Rooted cuttings were successfully acclimatized to ambient conditions and continued to grow normally. To visualize anatomical changes during root formation, stems were fixed in formaldehyde, embedded in paraffin, serially sectioned, and stained on sequential days throughout root development. Anatomical analysis revealed adventitious root initials by day 16 and root primordia formation by day 18. Rooted cuttings survived acclimatization to the greenhouse, and continued to grow normally. Using this timeline as a reference for the when and where the stages of root formation were occurring, gene expression assays of genes known to participate in adventitious root formation were conducted. The basal end (1–3 cm) of shoots from juvenile and mature origin, were collected on days 0, 8, 16, and 16; and 26 from mature shoots after treatment with 93.3 K-IBA or deionized water (control) and immediately frozen in liquid nitrogen. Shoots were serially sectioned using a Cryostat microtome, and cortical, phloem fiber, or phloem parenchyma tissues were isolated using a laser capture microdissection system. RNA was extracted from the samples, and quantitative real-time polymerase chain reaction (qRT-PCR) analysis was performed to characterize relative changes during root development. Rooting-related genes displayed a distinct, localized expression pattern during depending on treatment and age. These findings elucidated the factors contributing to the recalcitrance of adventitious root formation in this economically valuable hardwood species, and may contribute to the improvement of clonal propagation of elite black walnut timber genotypes

Justice as a Rounding Error?: Evidence of Subconscious Bias in Second-Degree Murder Sentences in Canada

There are few areas of law that grant judges as much discretion as the sentencing of criminal offenders. This discretion necessarily leads to concerns about the influence of biases, including those that result from subconscious processes associated with human cognition; that is to say, heuristics. In this article, the authors explore one heuristic—number preference—through an examination of all reported second degree murder parole ineligibility decisions between 1990 and 2012. Number preference leads individuals to predictably round off measurements to certain favoured numbers. The authors identify a tendency for parole ineligibility decisions to cluster around even numbers and multiples of five, without any obvious, legally-justifiable reason for such rounding. The authors propose that the phenomenon should cause concern not least because it suggests that other, less easily measurable but no less powerful, heuristics may also be at work in judicial decisions

Re-examining rates of lithium-ion battery technology improvement and cost decline

Lithium-ion technologies are increasingly employed to electrify transportation and provide stationary energy storage for electrical grids, and as such their development has garnered much attention. However, their deployment is still relatively limited, and their broader adoption will depend on their potential for cost reduction and performance improvement. Understanding this potential can inform critical climate change mitigation strategies, including public policies and technology development efforts. However, many existing models of past cost decline, which often serve as starting points for forecasting models, rely on limited data series and measures of technological progress. Here we systematically collect, harmonize, and combine various data series of price, market size, research and development, and performance of lithium-ion technologies. We then develop representative series for these measures and employ performance curve models to estimate improvement rates. We also develop a method to incorporate additional performance characteristics into these models, including energy density and specific energy performance metrics. When energy density is incorporated into the definition of service provided by a lithium-ion cell, estimated technological improvement rates increase considerably, suggesting that previously reported improvement rates might underestimate the rate of lithium-ion technologies' change. Moreover, our estimates suggest the degree to which lithium-ion technologies' price decline might have been limited by performance requirements other than cost per energy capacity. These rates also suggest that battery technologies developed for stationary applications, where restrictions on volume and mass are relaxed, might achieve faster cost declines, though engineering-based mechanistic cost modeling is required to further characterize this potential.Comment: 37 pages, 11 figure

Imaging the Mott Insulator Shells using Atomic Clock Shifts

Microwave spectroscopy was used to probe the superfluid-Mott Insulator transition of a Bose-Einstein condensate in a 3D optical lattice. Using density dependent transition frequency shifts we were able to spectroscopically distinguish sites with different occupation numbers, and to directly image sites with occupation number n=1 to n=5 revealing the shell structure of the Mott Insulator phase. We use this spectroscopy to determine the onsite interaction and lifetime for individual shells

Continuous and Pulsed Quantum Zeno Effect

Continuous and pulsed quantum Zeno effects were observed using a $^{87}$Rb Bose-Einstein condensate(BEC). Oscillations between two ground hyperfine states of a magnetically trapped condensate, externally driven at a transition rate $\omega_R$, were suppressed by destructively measuring the population in one of the states with resonant light. The suppression of the transition rate in the two level system was quantified for pulsed measurements with a time interval $\delta t$ between pulses and continuous measurements with a scattering rate $\gamma$. We observe that the continuous measurements exhibit the same suppression in the transition rate as the pulsed measurements when $\gamma\delta t=3.60(0.43)$, in agreement with the predicted value of 4. Increasing the measurement rate suppressed the transition rate down to $0.005\omega_R$.Comment: 5 pages, 4 figure

Atom trapping with a thin magnetic film

We have created a $^{87}$Rb Bose-Einstein condensate in a magnetic trapping potential produced by a hard disk platter written with a periodic pattern. Cold atoms were loaded from an optical dipole trap and then cooled to BEC on the surface with radiofrequency evaporation. Fragmentation of the atomic cloud due to imperfections in the magnetic structure was observed at distances closer than 40 $\mu$m from the surface. Attempts to use the disk as an atom mirror showed dispersive effects after reflection.Comment: 4 pages, 5 figure

THE INFORMATION-THEORETIC APPROACH TO MODEL SELECTION: DESCRIPTION AND CASE STUDY

In the wildlife literature there has been some recent criticism of statistical significance testing. In the past few years, both the Journal of ·Wildlife Management and the Wildlife Society Bulletin have published articles criticizing the overuse and misuse of hypothesis tests. One alternative to using hypothesis tests for model selection is the information-theoretic approach, proposed by Burnham and Anderson (1998). This technique uses values such as the Akaike Information Criterion and others to choose a set of plausible models from a set of a prioTi candidate models. Inferences are based on the set of plausible models, rather than on a single selected best model, and model-averaged point estimates of parameters may be used for prediction. The Burnham and Anderson method is gaining popularity in the wildlife science community, and statisticians who work with wildlife scientists should be aware of this analysis technique and how to use it properly. This paper will introduce statisticians to the information-theoretic approach to model selection and the statistical theory underlying it, as well as demonstrate the technique using data on bird species richness and abundance in riparian areas in southeastern Nebraska