On the morning of January 24, 1848, James W. Marshall discovered gold in California. The news spread across the continent, launching hundreds of ships and hitching a thousand prairie schooners filled ...with adventurers in search of heretofore unimagined wealth. Those who joined the procession—soon called 49ers—included the wealthy and the poor from every state and territory, including slaves brought by their owners. In numbers, they represented the greatest mass migration in the history of the Republic.
In this first comprehensive history of the Gold Rush, Malcolm J. Rohrbough demonstrates that in its far-reaching repercussions, it was the most significant event in the first half of the nineteenth century. No other series of events between the Louisiana Purchase and the Civil War produced such a vast movement of people; called into question basic values of marriage, family, work, wealth, and leisure; led to so many varied consequences; and left such vivid memories among its participants.
Through extensive research in diaries, letters, and other archival sources, Rohrbough uncovers the personal dilemmas and confusion that the Gold Rush brought. His engaging narrative depicts the complexity of human motivation behind the event and reveals the effects of the Gold Rush as it spread outward in ever-widening circles to touch the lives of families and communities everywhere in the United States. For those who joined the 49ers, the decision to go raised questions about marital obligations and family responsibilities. For those men—and women, whose experiences of being left behind have been largely ignored until now—who remained on the farm or in the shop, the absences of tens of thousands of men over a period of years had a profound impact, reshaping a thousand communities across the breadth of the American nation.
All crops require nitrogen (N) for the production of a photosynthetically active canopy, whose functionality will strongly influence yield. Cereal crops also require N for storage proteins in the ...grain, an important quality attribute. Optimal efficiency is achieved by the controlled remobilization of canopy-N to the developing grain during crop maturation. Whilst N will always be required for crop production, targeting efficient capture and use will optimise consumption of this valuable macronutrient. Efficient management of N through agronomic practice and use of appropriate germplasm are essential for sustainability of agricultural production. Both the economic demands of agriculture and the need to avoid negative environmental impacts of N-pollutants, such as nitrate in water courses or release of N-containing greenhouse gases, are important drivers to seek the most efficient use of this critical agronomic input. New cultivars optimised for traits relating to N-use efficiency rather than yield alone will be required. Targets for genetic improvement involve maximising capture, partitioning and remobilization in the canopy and to the grain, and yield per se. Whilst there is existing genetic diversity amongst modern cultivars, substantial improvements may require exploitation of a wider germplasm pool, utilizing land races and ancestral germplasm.
•Trends in yields, NUE and N fertilizer application are described.•NUE terms are explained.•Specific traits for improvement are listed.•Existing variation is outlined.•An overview for the scope for improvement is presented.
Crop nutrient and especially nitrogen use efficiency (NUE) is both an economically and an environmentally highly desirable trait. It has been estimated that only a third of nitrogen inputs to cereal ...crop worldwide are recovered in grain for consumption, resulting in a huge waste of resource with major negative impacts on the environment. Most measures of NUE in wheat and other cereals are based on field assessments of crop yields at given N inputs, performance responses to added N fertilizer, or by quantifying N fertilizer recovery rates. However, NUE is a complex trait comprising two key major components, N uptake and N utilization efficiency, both also complex traits in themselves, each involving many physiological processes and biochemical pathways. A deeper understanding of the processes involved in NUE has been a target of the UK Wheat Genetic Improvement Network project (http://www.wgin.org.uk/). This has enabled the breakdown of characteristics contributing to NUE and an assessment of the variation present in those characteristics, predominantly in modern cultivars; a total of 13 years of data have been obtained to date. Significant but limited variation suggests a requirement for broader germplasm screening such as older varieties, landraces, and wild relatives.
A
bstract
It is shown that black hole spacetimes in classical Einstein gravity are characterized by, in addition to their ADM mass
M
, momentum
P
→
, angular momentum
J
→
and boost charge
K
→
, an ...infinite head of supertranslation hair. The distinct black holes are distinguished by classical superrotation charges measured at infinity. Solutions with super-translation hair are diffeomorphic to the Schwarzschild spacetime, but the diffeomorphisms are part of the BMS subgroup and act nontrivially on the physical phase space. It is shown that a black hole can be supertranslated by throwing in an asymmetric shock wave. A leading-order Bondi-gauge expression is derived for the linearized horizon supertranslation charge and shown to generate, via the Dirac bracket, supertranslations on the linearized phase space of gravitational excitations of the horizon. The considerations of this paper are largely classical augmented by comments on their implications for the quantum theory.
Black hole entropy and soft hair Haco, Sasha; Hawking, Stephen W.; Perry, Malcolm J. ...
The journal of high energy physics,
12/2018, Letnik:
2018, Številka:
12
Journal Article
Recenzirano
Odprti dostop
A
bstract
A set of infinitesimal Virasoro
L
⊗ Virasoro
R
diffeomorphisms are presented which act non-trivially on the horizon of a generic Kerr black hole with spin J. The covariant phase space ...formalism provides a formula for the Virasoro charges as surface integrals on the horizon. Integrability and associativity of the charge algebra are shown to require the inclusion of ‘Wald-Zoupas’ counterterms. A counterterm satisfying the known consistency requirement is constructed and yields central charges
c
L
=
c
R
= 12
J
. Assuming the existence of a quantum Hilbert space on which these charges generate the symmetries, as well as the applicability of the Cardy formula, the central charges reproduce the macroscopic area-entropy law for generic Kerr black holes.
Soft Hair on Black Holes Hawking, Stephen W; Perry, Malcolm J; Strominger, Andrew
Physical review letters,
2016-Jun-10, Letnik:
116, Številka:
23
Journal Article
Recenzirano
Odprti dostop
It has recently been shown that Bondi-van der Burg-Metzner-Sachs supertranslation symmetries imply an infinite number of conservation laws for all gravitational theories in asymptotically Minkowskian ...spacetimes. These laws require black holes to carry a large amount of soft (i.e., zero-energy) supertranslation hair. The presence of a Maxwell field similarly implies soft electric hair. This Letter gives an explicit description of soft hair in terms of soft gravitons or photons on the black hole horizon, and shows that complete information about their quantum state is stored on a holographic plate at the future boundary of the horizon. Charge conservation is used to give an infinite number of exact relations between the evaporation products of black holes which have different soft hair but are otherwise identical. It is further argued that soft hair which is spatially localized to much less than a Planck length cannot be excited in a physically realizable process, giving an effective number of soft degrees of freedom proportional to the horizon area in Planck units.
Near-infrared (NIR) spectroscopy has increasingly been adopted as an analytical tool in various fields, such as the petrochemical, pharmaceutical, environmental, clinical, agricultural, food and ...biomedical sectors during the past 15 years. A NIR spectrum of a sample is typically measured by modern scanning instruments at hundreds of equally spaced wavelengths. The large number of spectral variables in most data sets encountered in NIR spectral chemometrics often renders the prediction of a dependent variable unreliable. Recently, considerable effort has been directed towards developing and evaluating different procedures that objectively identify variables which contribute useful information and/or eliminate variables containing mostly noise. This review focuses on the variable selection methods in NIR spectroscopy. Selection methods include some classical approaches, such as manual approach (knowledge based selection), “Univariate” and “Sequential” selection methods; sophisticated methods such as successive projections algorithm (SPA) and uninformative variable elimination (UVE), elaborate search-based strategies such as simulated annealing (SA), artificial neural networks (ANN) and genetic algorithms (GAs) and interval base algorithms such as interval partial least squares (
iPLS), windows PLS and iterative PLS. Wavelength selection with B-spline, Kalman filtering, Fisher's weights and Bayesian are also mentioned. Finally, the websites of some variable selection software and toolboxes for non-commercial use are given.
•A statement on the critical importance of this area of plant science in terms of food security and sustainability.•An outline of the critical NUE processes and example studies of identified ...variation in the complex trait of nitrogen use efficiency.•Reference to number of critical single key genes/alleles which have major impacts on NUE.•A description of the most useful genetic approaches being utilised to breed for NUE in cereals.•Future prospects on the most important areas and approaches likely to have impact.
Cereals are the most important sources of calories and nutrition for the human population, and are an essential animal feed. Food security depends on adequate production and demands are predicted to rise as the global population rises. The need for increased yields will have to be coupled to the efficient use of resources including fertilisers such as nitrogen to underpin the sustainability of food production. Although optimally performing crops with high yields require a balanced mineral nutrition, nitrogen fundamentally drives growth and yield as well as requirements for other nutrients. It is estimated that globally only 33% of applied nitrogen fertiliser is recovered in the harvested grain, indicative of a huge waste of resource and potential major pollutant and is thus a major target for crop improvement. Both agronomy and breeding will contribute to improved nitrogen use efficiency (NUE) and an important component of the latter is harnessing germplasm variation. This review will consider the key traits involved in NUE, the potential to exploit genetic variation for these specific traits, and the approaches to be utilised.
Pancreatic adenocarcinoma is the most lethal of the solid tumors and the fourth leading cause of cancer-related death in North America. Most patients present with locally advanced or metastatic ...disease that precludes curative resection. These patients have an extremely poor prognosis. In the absence of effective screening methods, considerable efforts have been made during the past decade to identify better systemic treatments. Unfortunately most trials have not shown a survival advantage for most therapies. In tandem with this increased clinical research, there has also been an expansion of preclinical laboratory investigation. These preclinical studies revealed many of the molecular mechanisms involved in pancreatic cancer development, which has provided insights into why current therapies are ineffective. These new discoveries provide some optimism that new agents inhibiting specific targets will improve outcome and overcome the resistance of pancreatic cancer to most standard treatments. We review the current standards of care for patients with locally advanced and metastatic pancreatic carcinoma and outline some future directions for the development of new treatment strategies.
PDF
