Frontiers, Opportunities, and Challenges in Biochemical and Chemical Catalysis of CO_2 Fixation

Two major energy-related problems confront the world in the next 50 years. First, increased worldwide competition for gradually depleting fossil fuel reserves (derived from past photosynthesis) will lead to higher costs, both monetarily and politically. Second, atmospheric CO_2 levels are at their highest recorded level since records began. Further increases are predicted to produce large and uncontrollable impacts on the world climate. These projected impacts extend beyond climate to ocean acidification, because the ocean is a major sink for atmospheric CO2.1 Providing a future energy supply that is secure and CO_2-neutral will require switching to nonfossil energy sources such as wind, solar, nuclear, and geothermal energy and developing methods for transforming the energy produced by these new sources into forms that can be stored, transported, and used upon demand

Links Between Hydrothermal Environments, Pyrophosphate, Na+, and Early Evolution

The discovery that photosynthetic bacterial membrane-bound inorganic pyrophosphatase (PPase) catalyzed light-induced phosphorylation of orthophosphate (Pi) to pyrophosphate (PPi) and the capability of PPi to drive energy requiring dark reactions supported PPi as a possible early alternative to ATP. Like the proton-pumping ATPase, the corresponding membrane-bound PPase also is a H+-pump, and like the Na+-pumping ATPase, it can be a Na+-pump, both in archaeal and bacterial membranes. We suggest that PPi and Na+ transport preceded ATP and H+ transport in association with geochemistry of the Earth at the time of the origin and early evolution of life. Life may have started in connection with early plate tectonic processes coupled to alkaline hydrothermal activity. A hydrothermal environment in which Na+ is abundant exists in sediment-starved subduction zones, like the Mariana forearc in the W Pacific Ocean. It is considered to mimic the Archean Earth. The forearc pore fluids have a pH up to 12.6, a Na+-concentration of 0.7 mol/kg seawater. PPi could have been formed during early subduction of oceanic lithosphere by dehydration of protonated orthophosphates. A key to PPi formation in these geological environments is a low local activity of water

Downloaded from

This paper presents the design of a robot wrist with zero hand length and unlimited mutually orthogonal joints. This design is an improvement over existing ones. When equipped with this type of wrist, a robot’s entire reachable workspace becomes the dexterous workspace. Because some wrist joint limitations may need to be imposed under practical consideration, to better assess this new wrist design, kinematics on robot point accessibility is derived. An algorithm and a software package are developed that enable the plotting of the point accessibility throughout the robot’s entire workspace. Examples for demonstration are also included. KEY WORDS—robot wrist, zero-dimension, design, accessibilit

Age Dependence of Spiral Grain in White Oaks (Quercus Alba L.) in Southwestern Illinois

Dendrochronologists have used the presence of spiral grain as an indicator of old trees for most of the history of the field, although this relationship has been little studied. We examined cross-sections from dead trees and used a 12-mm Haglof Swedish Increment borer to collect cores from living white oak (Quercus alba L.) trees in an Eastern Deciduous Forest stand in southwestern Illinois. Spiral grain is the alignment of wood fibers to the longitudinal axis of trees and is driven by patterns of initial cambial cell division. In this study, we examine environmental factors that may affect spiral grain severity, the usefulness of non-destructive sampling methods (using the 12-mm increment borer), and the relationship between tree age and spiral grain. We tested Brazier’s method (1965) of averaging the spiral grain angle from two radii taken 180 degrees apart (i.e. one diameter in the tree) to get representative grain angles for the whole circumference of a tree at a certain height. The 12-mm increment borer did not produce consistent results in this study; therefore, the collection of cross-sections is advised for the study of spiral grain in white oaks. Brazier’s method should not be used in white oaks and should not be applied universally to all tree species. The severity of spiral grain is expressed in the xylem and may not be expressed in the bark of the tree. Left spiral grain does generally increase in white oaks with age, although this relationship is not always consistent, so a tree without severe spiral grain is not necessarily young.This item is part of the Tree-Ring Research (formerly Tree-Ring Bulletin) archive. It was digitized from a physical copy provided by the Laboratory of Tree-Ring Research at The University of Arizona. For more information about this peer-reviewed scholarly journal, please email the Editor of Tree-Ring Research at [email protected]

Veränderung von Aminosäuren und Aktivität bei Röntgenbestrahlung von krystallisiertem Lysozym / Transformation of amino acids and activity in roentgen irradiation of crystallized lysozyme

Crystallized lysozyme was X-irradiated with doses between 1 and 100 Mrads. Doses of a few Mrads have no measurable effect on activity and quantitative amino acid composition of lysozyme. However, increasing doses successively convert the original protein into a large number of modified proteins showing more or less lysozyme activity. These processes are of a complex nature. Consequently can the inactivation not be described in terms of the classical target theory. Only X-ray doses of the order of magnitude of 100 Mrads produce amino acid changes which can clearly be determined with an automatic amino acid analyzer. The G-values for the destruction of the various constituent amino acids are between 3 and 13. The larger sensitivities have the S-containing and aromatic amino acids as well as the long chain aliphatic amino acids. A comparison with other results shows that the radiation sensitivity of the constituent amino acids of solid proteins is little influenced by other factors (O2-pressure, water content, protein structure etc.). / Kristallisiertes Lysozym wurde mit Dosen zwischen 1 und 100 Mrad Röntgenstrahlen bestrahlt. Die kleineren Dosen haben keine meßbare Wirkung auf Aktivität oder quantitative Aminosäurezusammensetzung. Da das Molekül durch größere Strahlendosen in andere Modifikationen umgewandelt wird und die entsprechenden Vorgänge komplex sind, läßt sich die ⌞naktivierung“des Enzyms nicht ohne weiteres durch die „lassische“ Treffertheorie interpretieren. Hiermit zusammenhängende Probleme werden diskutiert. Erst Strahlendosen von der Größenordnung 100 Mrad erzeugen in einem automatischen Aminosäureanalysator sicher analysierbare Aminosäureveränderungen. Die G-Werte liegen zwischen 3 und 13. Die größere Strahlenempfindlichkeit haben vor allem die aromatischen und die schwefelhaltigen Aminosäuren. Vergleiche mit anderen Ergebnissen führen zu dem Schluß, daß diese Strahlenempfindlichkeit der Aminosäuren durch Milieufaktoren nur wenig beeinflußt wird

Complex Incisional Hernias

Incisional hernias are the most frequent “late complications” after laparotomy. They develop in more than 10% of patients and their incidence is related to numerous risk factors (Table 1). The most important risk factors are obesity, impaired wound healing of the laparotomy wound, malnutrition and tobacco smoking. Regarding the multifactorial pathogenesis of the disease local tissue ischemia is one of the most important risk factors. This causes weakness of the fascia and finally incisional hernia [4,5]. In addition, there are more rare causes, such as immunosuppression, diseases of the collagen metabolism and connective tissue diseases (e.g. patients with aneurysms, Ehlers-Danlos-syndrome). Any factors which are characterized by a persistent or frequent high intra-abdominal pressure (e.g. chronic cough) contribute to the development of an incisional hernia. An important risk factor is the surgeon her/himself, i.e. the quality of the abdominal closure and this is not sufficiently considered in the scientific literature. The pathogenesis of an incisional hernia is in general multifactorial.</p

Dendroecological Analysis of Spruce Budworm Outbreaks and Their Relation to Climate near the Prairie–Forest Border in Northwestern Minnesota.

This paper investigates the effects of spruce budworm (Choristoneura fumiferana) on balsam fir (Abies balsamea) and white spruce (Picea glauca) at Itasca State Park in northwestern Minnesota. We studied the species composition, age structure, and radial growth patterns in tree rings along five belt transects at sites infested with spruce budworm. Our objectives were to: (1) discover when the latest spruce budworm outbreak started; (2) determine whether tree growth was similarly reduced in earlier decades, suggesting earlier spruce budworm outbreaks; and (3) test whether radial tree growth and the start of the outbreak(s) were correlated with climate. We used the computer program OUTBREAK to determine that the current spruce budworm infestation began to reduce tree growth in the 1990s, before it was detected by park officials in 2001. The tree-ring record indicated that growth of the host-species trees was periodically reduced at all sites prior to the 1990s. We found no consistent relationship between temperature/precipitation and the initiation of spruce budworm outbreaks, as reconstructed by the OUTBREAK program, at the southwestern edge of the distribution of balsam fir. The Palmer Drought Severity Index, however, was positive (i.e., wetter-than-normal conditions) before increased spruce budworm activity at all sites. Outbreaks are related to climatic conditions, but they also depend on other factors such as the availability of sufficient food for the spruce budworm