Application of recombinant DNA methods to restructure metabolic networks can improve production of metabolite and protein products by altering pathway distributions and rates. Recruitment of heterologous proteins enables extension of existing pathways to obtain new chemical products, alter posttranslational protein processing, and degrade recalcitrant wastes. Although some of the experimental and mathematical tools required for rational metabolic engineering are available, complex cellular responses to genetic perturbations can complicate predictive design.

https://science.sciencemag.org/content/sci/252/5013/1668.full.pdf

Toward a science of metabolic engineering

Life on Earth is sustained by a small volume of soil surrounding roots, called the rhizosphere. The soil is where most of the biodiversity on Earth exists, and the rhizosphere probably represents the most dynamic habitat on Earth; and certainly is the most important zone in terms of defining the quality and quantity of the Human terrestrial food resource. Despite its central importance to all life, we know very little about rhizosphere functioning, and have an extraordinary ignorance about how best we can manipulate it to our advantage. A major issue in research on rhizosphere processes is the intimate connection between the biology, physics and chemistry of the system which exhibits astonishing spatial and temporal heterogeneities. This review considers the unique biophysical and biogeochemical properties of the rhizosphere and draws some connections between them. Particular emphasis is put on how underlying processes affect rhizosphere ecology, to generate highly heterogeneous microenvironments. Rhizosphere ecology is driven by a combination of the physical architecture of the soil matrix, coupled with the spatial and temporal distribution of rhizodeposits, protons, gases, and the role of roots as sinks for water and nutrients. Consequences for plant growth and whole-system ecology are considered. The first sections address the physical architecture and soil strength of the rhizosphere, drawing their relationship with key functions such as the movement and storage of elements and water as well as the ability of roots to explore the soil and the definition of diverse habitats for soil microorganisms. The distribution of water and its accessibility in the rhizosphere is considered in detail, with a special emphasis on spatial and temporal dynamics and heterogeneities. The physical architecture and water content play a key role in determining the biogeochemical ambience of the rhizosphere, via their effect on partial pressures of O2 and CO2, and thereby on redox potential and pH of the rhizosphere, respectively. We address the various mechanisms by which roots and associated microorganisms alter these major drivers of soil biogeochemistry. Finally, we consider the distribution of nutrients, their accessibility in the rhizosphere, and their functional relevance for plant and microbial ecology. Gradients of nutrients in the rhizosphere, and their spatial patterns or temporal dynamics are discussed in the light of current knowledge of rhizosphere biophysics and biogeochemistry. Priorities for future research are identified as well as new methodological developments which might help to advance a comprehensive understanding of the co-occurring processes in the rhizosphere.

Rhizosphere: biophysics, biogeochemistry and ecological relevance

Working memory has been proposed as an important component of reading and arithmetic skills. The development of working memory was studied in normally achieving and subtypes of learning disabled children. The performance of reading disabled (RD), arithmetic disabled (ARITHD), and attentional deficit disordered (ADD) children, age 7-13, was compared to normal achievers (NA) on 2 working memory tasks, 1 involving sentences and the other involving counting. There was a significant growth of working memory as a function of age. In addition, the RD children had significantly lower scores on both tasks. The ARITHD children had significantly lower scores only on the Working Memory--Counting task, and the ADD group had scores similar to the normally achieving children except at the youngest age level in the Working Memory--Sentences task. Thus, a reading disability appears to involve a generalized deficit in working memory. Children with an arithmetic disability do not have a generalized language deficit but have a specific working memory deficit in relation to processing numerical information. As children with ADD did not have deficits in these tasks, working memory may not have significant attentional components. An important component of the development of reading and computational arithmetic skills appears to be the growth of working memory for language and numerical information.

The development of working memory in normally achieving and subtypes of learning disabled children.

Various bacterial species accumulate intracellular polyhydroxyalkanoates (PHAs) granules as energy and carbon reserves inside their cells. PHAs are biodegradable, environmentally friendly and biocompatible thermoplastics. Varying in toughness and flexibility, depending on their formulation, they can be used in various ways similar to many nonbiodegradable petrochemical plastics currently in use. They can be used either in pure form or as additives to oil-derived plastics such as polyethylene. However, these bioplastics are currently far more expensive than petrochemically based plastics and are therefore used mostly in applications that conventional plastics cannot perform, such as medical applications. PHAs are immunologically inert and are only slowly degraded in human tissue, which means they can be used as devices inside the body. Recent research has focused on the use of alternative substrates, novel extraction methods, genetically enhanced species and mixed cultures with a view to make PHAs more commercially attractive.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2672.2007.03335.x

Bacterial synthesis of biodegradable polyhydroxyalkanoates

An integrated biomechanical analysis of normal stair ascent and descent

A mathematical model for decompression is presented. It includes a first-order linear differential equation, which models the diffusion of gases within the body, as well as initial conditions and a nonlinear constraint inequality which insures safety from decom- pression sickness. The model is solved (numerically and/or analytically) under various hypotheses, and the results are compared with the U.S. Navy Dive Table. which changes in pressure on the body may result in a buildup of air bubbles in the tissues. This condition is known as decompression sickness or, more commonly, the "bends." Scuba diving is a popular sport in which participants subject themselves to changes in pressure. Other examples are provided by the man-in-space program and certain tunnelling operations in which air pressure on the body is alternately increased and decreased. During respiration, air is inspired into the lungs, from which it enters the blood. The air in solution in the blood is then carried to the body tissues where it is released by the blood into the tissues. The driving force for the exchange of gas at either the lungs or the body tissues is the difference in the partial pressures of the different gases on either side of the transaction site. In the normal situation in which the pressure on the body is decreased, the pressure of the air that is breathed is less than that in solution in the body tissues. When this happens, the body will act to relieve the difference in pressure. The blood will pick up excess gas in solution in the tissues and transfer it to the lungs from which it is exhaled. A dangerous situation occurs when the outside pressure is decreased so much that the tissue-blood-lung transfer of excess gas cannot take place rapidly enough. In this case, the gas pressure in the tissues will force the excess gas out of solution, resulting in the formation of gas bubbles in the tissues. The diffusion of a gas between lungs and blood and between blood and tissues can be modeled mathematically. Henry's Law is a linearized pressure law which guarantees that a gas will flow from a higher pressure region to a lower pressure region at a rate which is proportional to the difference in the partial pressure of the gas in the two different regions. In what follows, we shall be concerned mainly with the effect of nitrogen and carbon

https://www.divetable.info/workshop/Math_Model.pdf

Gilbert N. Lewis

Papers

A mathematical model for