Pennsylvania State University

About: Pennsylvania State University is a education organization based out in State College, Pennsylvania, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 79763 authors who have published 196876 publications receiving 8318601 citations. The organization is also known as: Penn State & PSU.

Classification and Comparison of Small RNAs from Plants

Abstract: Regulatory small RNAs, which range in size from 20 to 24 nucleotides, are ubiquitous components of endogenous plant transcriptomes, as well as common responses to exogenous viral infections and introduced double-stranded RNA (dsRNA). Endogenous small RNAs derive from the processing of helical RNA precursors and can be categorized into several groups based on differences in biogenesis and function. A major distinction can be observed between small RNAs derived from singlestranded precursors with a hairpin structure [referred to here as hairpin RNAs (hpRNAs)] and those derived from dsRNA precursors [small interfering RNAs (siRNAs)]. hpRNAs in plants can be divided into two secondary groups: microRNAs and those that are not microRNAs. The currently known siRNAs fall mostly into one of three secondary groups: heterochromatic siRNAs, secondary siRNAs, and natural antisense transcript siRNAs. Tertiary subdivisions can be identified within many of the secondary classifications as well. Comparisons between the different classes of plant small RNAs help to illuminate key goals for future research.

Positive feedbacks in the fire dynamic of closed canopy tropical forests

Abstract: The incidence and importance of fire in the Amazon have increased substantially during the past decade, but the effects of this disturbance force are still poorly understood. The forest fire dynamics in two regions of the eastern Amazon were studied. Accidental fires have affected nearly 50 percent of the remaining forests and have caused more deforestation than has intentional clearing in recent years. Forest fires create positive feedbacks in future fire susceptibility, fuel loading, and fire intensity. Unless current land use and fire use practices are changed, fire has the potential to transform large areas of tropical forest into scrub or savanna.

Autocratic breakdown and regime transitions: A new data set

Abstract: When the leader of an autocratic regime loses power, one of three things happens. The incumbent leadership group is replaced by democratically elected leaders. Someone from the incumbent leadership group replaces him, and the regime persists. Or the incumbent leadership group loses control to a different group that replaces it with a new autocracy. Much scholarship exists on the first kind of transition, but little on transitions from one autocracy to another, though they make up about half of all regime changes. We introduce a new data set that facilitates the investigation of all three kinds of transition. It provides transition information for the 280 autocratic regimes in existence from 1946 to 2010. The data identify how regimes exit power, how much violence occurs during transitions, and whether the regimes that precede and succeed them are autocratic. We explain the data set and show how it differs from currently available data. The new data identify autocratic regime breakdowns regardless of whether the country democratizes, which makes possible the investigation of why the ouster of dictators sometimes leads to democracy but often does not, and many other questions. We present a number of examples to highlight how the new data can be used to explore questions about why dictators start wars and why autocratic breakdown sometimes results in the establishment of a new autocratic regime rather than democratization. We discuss the implications of these findings for the Arab Spring.

Pre‐Sowing Seed Treatment—A Shotgun Approach to Improve Germination, Plant Growth, and Crop Yield Under Saline and Non‐Saline Conditions

Abstract: Rapid seed germination and stand establishment are critical factors to crop production under salt‐stress conditions. In many crop species, seed germination and early seedling growth are the most sensitive stages to salinity stress. Salinity may delay the onset, reduce the rate, and increase the dispersion of germination events, leading to reductions in plant growth and final crop yield. The adverse effects of salt‐stress can be alleviated by various measures, including seed priming (a.k.a. pre‐sowing seed treatment). The general purpose of seed priming is to partially hydrate the seed to a point where germination processes are begun but not completed. Most priming treatments involve imbibing seed with restricted amounts of water to allow sufficient hydration and advancement of metabolic processes but preventing germination or loss of desiccation tolerance. Treated seeds are usually redried before use, but they would exhibit rapid germination when re‐imbibed under normal or stress conditions. Various seed priming techniques have been developed, including hydropriming (soaking in water), halopriming (soaking in inorganic salt solutions), osmopriming (soaking in solutions of different organic osmotica), thermopriming (treatment of seed with low or high temperatures), solid matrix priming (treatment of seed with solid matrices), and biopriming (hydration using biological compounds). Each treatment has advantages and disadvantages and may have varying effects depending upon plant species, stage of plant development, concentration/dose of priming agent, and incubation period. In this article, we review, evaluate, and compare effects of various methods of seed priming in improving germination of different plant species under saline and non‐saline conditions. We also discuss the known metabolic and ultra‐structural changes that occur during seed priming and subsequent germination. To maximize the utility of various seed priming techniques, factors affecting their efficiency must be examined and potential benefits and drawbacks determined. For example, quality of the seed before treatment, concentration/dose of priming agent, time period for priming, and storage quality of the seed following priming treatment must be carefully determined. Furthermore, such assessments must be based on large‐scale experiments if seed priming is to be used for large‐scale field planting. A better understanding of the metabolic events that take place in the seed during priming and subsequent germination will improve the effective application of this technology. The incorporation of advanced molecular biology techniques in seed research is vital to the understanding and integration of multiple metabolic processes that can lead to enhanced seed germination, and consequently to improved stand establishment and crop yield under saline and non‐saline conditions.

On-chip manipulation of single microparticles, cells, and organisms using surface acoustic waves

Abstract: Techniques that can dexterously manipulate single particles, cells, and organisms are invaluable for many applications in biology, chemistry, engineering, and physics. Here, we demonstrate standing surface acoustic wave based “acoustic tweezers” that can trap and manipulate single microparticles, cells, and entire organisms (i.e., Caenorhabditis elegans) in a single-layer microfluidic chip. Our acoustic tweezers utilize the wide resonance band of chirped interdigital transducers to achieve real-time control of a standing surface acoustic wave field, which enables flexible manipulation of most known microparticles. The power density required by our acoustic device is significantly lower than its optical counterparts (10,000,000 times less than optical tweezers and 100 times less than optoelectronic tweezers), which renders the technique more biocompatible and amenable to miniaturization. Cell-viability tests were conducted to verify the tweezers’ compatibility with biological objects. With its advantages in biocompatibility, miniaturization, and versatility, the acoustic tweezers presented here will become a powerful tool for many disciplines of science and engineering.