bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of High Pressure on the Allosteric Properties of Phosphofructokinase from Escherlchia coli
Authors: Johnson Jason L. , Reinhart Gregory D.
Published: November 2020

Phosphofructokinase (PFK) from Escherichia coli is subject to allosteric regulation by phosphoenolpyruvate (PEP) and MgADP. These ligands inhibit and activate, respectively, by binding to a single allosteric binding domain and thereby altering the affinity the enzyme displays for its substrate, fructose-6-phosphate (Fru-6-P). The effect of hydrostatic pressure of up to 1.4 kbar on the binding of each of these ligands to PFK has been evaluated. This pressure range is insufficient to cause significant dissociation of the PFK tetramers. However, the logarithm of the equilibrium constant for each ligand binding to free enzyme decreases in a linear manner, and to virtually the same extent, when pressure is increased from 1 to 700 bar. Consequently, the ΔV associated with the binding of the inhibitor ligand PEP is virtually identical to the ΔV for the binding of the activator ligand MgADP or the substrate Fru-6-P, which falls within the range of 40–45 ml mol−1. The apparent ΔV for Fru-6-P binding decreases with increasing concentration of PEP until it is equal to +18 ml mol when PEP is fully saturating. Similarly, ΔV for Fru-6-P binding decreases to +26 ml mol−1 when MgADP is fully saturating. These data are interpreted as implying that both PEP and MgADP improve the “fit” of Fru-6-P to its binding domain despite the fact that the ligands have opposing effects on Fru-6-P binding affinity. Phosphofructokinase (PFK) from E. coli is a prototypical allosteric enzyme which was one of the first to be studied in depth (Blangy & Buc, 1967; Blangy et al., 1968) after Monod et al. (1965) published their famous proposal that allosteric behavior results from the concerted transition between discrete functional states of a protein (the MWC two-state model). PFK from E. coli is a tetrameric enzyme with a single allosteric binding domain that can bind either the activator MgADP or the inhibitor PEP. Under many circumstances the substrate, fructose 6-phosphate (Fru-6-P), binds to the enzyme with positive cooperativity, and the affinity and cooperativity that Fru-6-P exhibits is modulated by the allosteric ligands in classic K-type fashion.
Membrane-Free Volume Variation with Bulky Lipid Concentration by Regular Distribution: A Functionally Important Membrane Property Explored by Pressure Studies of Phosphatidylcholine Bilayers
Authors: Chong Parkson Lee-Gau
Published: November 2020

We have used the dips in the ratio of excimer to monomer fluorescence intensity (E/M) as the index of lipid regular distribution to examine the effect of pressure on lipid lateral organization in the liquid-crystalline state of dimyristoylphosphatidylcholine (DMPC)/1-palmitoyl-2-(10-pyrenyl)decanoyl)-sn-glyceroI-3-phosphatidylcholine (Pyr-PC) bilayers. In the pressure range of 0.001-0.7 kbar at 30 °C, E/M dips remain discernible, suggesting that lipid regular distribution appears favorably in the liquid-crystalline state. In the same pressure range, E/M decreases steadily with increasing pressure at noncritical mole fractions; in contrast, E/M changes little with pressure at critical mole fractions. This result reveals an important physical principle underlying lipid regular distribution—that is, that membrane free volume reaches a local minimum at critical mole fractions of bulky lipids (for example, cholesterol and Pyr-PC). Using the activity of phospholipase A2 and the membrane fluidity inferred from diphenylhexatriene fluorescence polarization, we demonstrate that regular distribution of bulky lipids has a regulatory role in membrane properties or functions. Our data show that the activity of snake venom phospholipase A2 can be significantly modulated by minute changes (for example, 0.5 mol%) in the concentration of bulky lipids on either side of a critical mole fraction as a result of membrane free volume variation. The approach employed in this study illustrates the usefulness of high-pressure fluorescence methodology for obtaining new information about membranes at ambient conditions. High-pressure fluorescence spectroscopy has emerged as a powerful tool in biophysical research during the past 15 years (Paladini & Weber, 1981; Weber, 1992). Previous fluorescence studies of membranes at high pressure were focused on dynamic aspects, particularly on membrane fluidity. These dynamic studies have included probe rotations in lipid membranes (Chong & Weber, 1983; Chong et al., 1983; Mateo et al, 1993 and references cited therein), probe lateral diffusion (Flamm et al, 1982; Muller & Galla, 1983, 1987; Turley & Offen, 1985, 1986; Eisinger & Scarlata, 1987; Macdonald et al., 1988; Kao et al., 1992), spontaneous intermembrane transfer (Mantulin et al., 1984), and the relationship of membrane dynamics to the activity of membrane-bound proteins (Chong et al, 1985; Verjovski-Almeida et al, 1986; Jona & Martonosi, 1991).
Pressure- and Temperature-Induced Inactivation of Microorganisms
Authors: Ludwig Horst , Scigalla Wilhelm
Published: November 2020

Bacteria are unstable when the temperature or pressure is sufficiently high. Their inactivation by pressure is the result of a complicated interplay of both temperature and pressure effects. The p-T stability diagram of bacteria is similar to that of proteins. But inactivation kinetics of bacteria indicate that the lethal event cannot be the denaturation of the most sensitive proteins in the cell. For in that case one would expect a lag time followed by a sudden inactivation when the last copy of those sensitive proteins was destroyed. On the contrary, it appears as if the kinetics is caused by a single damage mechanism. In addition, some evidence suggests that the membrane is involved. Therefore, it seems that membrane-associated proteins play a major role in the activation of bacteria. The inactivation of bacterial spores shows an even more complex T-p interrelationship. The reason is that two different processes are combined in spore inactivation: the germination of dormant spores at comparatively low pressures and the inactivation of the germinated specimens at high pressures. Thus, special procedures are needed for effective spore inactivation. Microorganisms are killed when the surrounding hydrostatic pressure is sufficiently high. This finding provides the basis for developing a physical sterilization method for drugs and food. Initial experiments in this area were carried out nearly 100 years ago (Hite, 1899), but technical shortcomings and incomplete scientific knowledge impeded their utilization at that time. Recently, the application of high pressure in food preservation and processing has garnered new interest (Hayashi 1989; Balny et al, 1992). To collect precise kinetic data for pressure-induced degermination, we constructed a device which consisted of 10 pressure vessels that could be thermostated in two groups of five each. Each vessel had an inner diameter of 1.2cm and an inner length of 12 cm. The samples were separated from the pressure medium, water, by polyethylene tubes or bags. The maximum pressure was 7 kbar. The vegetative bacteria were always freshly cultured from one single organism before each experimental run. The preparations were allowed to grow to the exponential phase and were used in experiments just before the stationary phase had been reached.
Coordination Adsorption of Anions
Authors: Zhang G. Y. , Yu T. R.
Published: November 2020

In Chapter 4, when the electrostatic adsorption of anions by variable charge soils is discussed, another type of adsorption, specific adsorption, has already been mentioned, although it is not very remarkable for chloride ions and nitrate ions. For some other anions, specific adsorption can be very important. Specific adsorption is determined by the nature of the anions and is also related to the kind of functional groups on the surface of soils. In general, this type of adsorption is more pronounced in soils containing large amounts of iron and aluminum oxides. Therefore, specific adsorption of anions is one of the important characteristics of variable charge soils. Specific adsorption is a common term. For anions, the mechanism of specific adsorption is ligand exchange between these ions and some groups that have already been coordinately linked on the surface of soil particles. Therefore, the term coordination adsorption may be more appropriate than the term specific adsorption. For variable charge soils, phosphate is the strongest specifically adsorbed anion species. Phosphate adsorption is also the most intensively studied anion adsorption in soil science. However, the valence status of phosphate ions is apt to change with the change in environmental conditions. In the adsorption of phosphate by soils, in addition to ligand exchange, other mechanisms, such as chemical precipitation, may also be involved. Therefore, the phenomenon of phosphate adsorption is rather complex, and it is often difficult to make definitive interpretations of experimental results. In the present chapter, the coordination adsorption of anions will be discussed, mainly taking sulfate as the example, because sulfate is only secondary to phosphate in importance for agricultural production among anions capable of undergoing coordination adsorption. For the purpose of comparison, the adsorption of fluoride ions will also be mentioned. On the surface of soil particles there are functional groups such as hydroxyl groups (M-OH) and water molecules (M-OH2) that can participate in ligand exchange with anions. Al-OH, Fe-OH, Al-OH2, and Fe-OH2 groups on the surface of soil particles are the important sites for coordination adsorption of anions. Therefore, when a soil contains large amounts of iron and aluminum oxides, the phenomenon of coordination adsorption of anions will be more pronounced.
Electric Conductance
Authors: Li C. B.
Published: November 2020

The migration of colloidal soil particles in an applied electric field has been discussed in Chapter 7. Soil particles carrying electric charges invariably adsorb equivalent amounts of ions of the opposite charge. Generally there is a certain amount of free ions present in soil solution. When an electric field is applied to a soil system, a phenomenon known as electric conductance occurs. As in the case for electrolyte solutions, soil particles and various ions interact with one another during their migration, and these interactions can affect the electric conductance of the system. Variable charge soils carry both positive and negative surface charges, and it can be expected that their interactions with various ions would be rather complicated during conductance. On the other hand, this makes the measurement of electric conductance an effective means in elucidating the mechanisms of interactions between variable charge soils and ions. Both direct-current (DC) electric fields and alternating-current (AC) electric fields can induce the migration of charged particles. In the latter case, the migration of these particles should be related to the frequency of the applied AC electric field. Therefore, in this chapter, after describing the principles of electric conductance of ions and colloids and the factors that affect the conductance of a soil, emphasis shall be placed on the interaction between variable charge soils and various ions as reflected by the frequency effect in electric conductance. For a colloidal suspension, the electric conductance may be regarded as the contribution of conductances of both charged colloidal particles and ions. These two parts may be called the electric conductance of colloidal panicles and the electric conductance of ions, respectively. However, in actual cases it is difficult to distinguish between these two parts. Therefore, it is a general practice to distinguish the electric conductance as that caused by colloidal particles plus their counterions from that caused by ions of the free solution. These may be called electric conductance of the colloid and electric conductance of the free solution. The former conductance is the difference between the electric conductance of the suspension and that of the free solution.
The Development of 13C Labeling and 13C NMR Spectroscopy Techniques to Study the Interaction of Pollutants with Humic Substances
Authors: Bortiatynski Jacqueline M. , Hatcher Patrick G.
Published: November 2020

Modern agricultural practices have contributed to the accumulation of herbicides, pesticides and their decomposition products in the soil. These pollutants are known to interact with soil organic matter to form covalent and/or noncovalent bonding associations. The covalent bonds are thought to result from addition or oxidative coupling reactions, some of which may be catalyzed by oxidoreductive enzymes. Noncovalent associations include such interactions as ion exchange, hydrogen bonding, protonation, charge transfer, ligand exchange, coordination through metal ions, van der Waals forces, and hydrophobic bonding. The association of pollutants with soil organic matter is an area of study that is of extreme interest for two reasons. First, dissolved organic matter present in lakes and streams is known to enhance the solubility of pollutants, which poses a real threat to the quality of fresh water supplies. Therefore, if we are to predict the movement of pollutants in the water table we need to have a mechanistic understanding of their interactions with dissolved humic materials. Second, early studies had indicated that some pollutants chemically bind to humic materials, thus reducing the risk of further transport and dispersion. If this chemical binding of the pollutants is irreversible, then this process may serve as a natural means for their detoxification. Regardless of the type of association, the first task in any mechanistic study is to characterize the reaction products structurally. In the case of noncovalent binding mechanisms, studies have focused on the physical characteristics of the process and not on the structure of the associated pollutant. Association studies are used to determine the sorption kinetics and transport of pollutants as well as their association constants. These types of studies utilize various techniques such as batch sorption, gas-purge desorption, column adsorption, and miscible displacement. All of these techniques are only capable of providing quantitative information on the amount of pollutant sorbed by a substrate. The study of the covalent binding of pollutants to humic substances has utilized 14C labeling in addition to various spectrometric techniques such as ultraviolet (UV) difference, fluorescence polarization and infrared (IR) spectroscopy.
NMR Studies of the Reaction of Amino Acids with Aqueous Chlorine
Authors: Scully, Jr Frank E. , Conyers Barbara
Published: November 2020

Over the past 20 years, gas chromatography/mass spectroscopy (GC/MS) has been widely used to identify trace organic environmental contaminants and to study the mechanisms of the formation or transformation of organic compounds either by natural or man-made processes. In the area of water and wastewater disinfection, GC/MS has been highly successful in identifying numerous volatile organic chlorination by-products, some of which may pose undesirable health risks to humans and aquatic organisms at concentrations found in some waters. However, despite a considerable amount of research in this area much of the chemistry continues to be poorly understood. Analysis of trace organics by GC/MS relies on the assumption that the compounds to be analyzed are (1) volatile and (2) thermally stable to GC temperatures as high as 300 °C. Because nuclear magnetic resonance spectroscopy (NMR) is a mild and nondestructive method of analysis, it can reveal reactions that occur in water that cannot be observed by GC/MS. Until recently the reactions of amino acids with two or more equivalents of aqueous chlorine were believed to produce aldehydes and nitriles according to equation (1). LeCloirec and Martin have reported that the formation of nitriles in such situations may come in part from the reaction of monochloramine with aldehydes (equation (2)). Because reaction (2) may affect the distribution of products in reaction (1), it was important to determine the relationship between these two reactions. This chapter will review the applications of NMR we have used in studies of the products formed upon chlorination of amino acids.
Cation and Water Interactions in the Interlamellae of a Smectite Clay
Authors: Labouriau Andrea , Johnston Cliff T.
Published: November 2020

Advances in NMR instrumentation and availability have led to increased application to mineral systems and to environmental problems. The sensitivity of high-field NMR systems is nearly sufficient to work at real environmental concentrations. Even with limited sensitivity, the amount of chemical information obtained through NMR spectroscopy makes it a very valuable technique in many model systems. The application of NMR spectroscopy in mineral systems has been primarily limited to studies of the structural metals aluminum and silicon. However, in recent years there have been several publications on mobile cations in minerals, including work on the exchangeable cations in clays. Our interests lie in understanding the sorption of cations in clays, the structural sites available for that sorption, and the role of water in cation–clay interactions. Our goal is to eventually understand the molecular interactions that determine the adsorption and diffusion of cations in clays and, thus, the role of clays in determining cation transport through the geosphere. This fundamental understanding has applications in the fate of heavy metals, radionuclides, and even the mobility of nutrients for plants. It is well known that there are very strong interactions between metals and humic materials and these are also strong contributors to cation mobility. However, for simplicity, we have chosen to focus on the interactions of mobile metal ions with well-characterized clays. An NMR-based approach to this problem can take two complementary directions: first, studies of the structural components of clays such as 29Si and 27Al NMR as a function of cation or hydration; second, NMR studies of probe molecules—which in this case are the cations themselves. High magnetic field, multinuclear NMR spectrometers make it quite possible to study various “uncommon” nuclei with relative ease. It is our experience that using the cations as probe nuclei for studying sorption phenomena yields more information than studies of structural nuclei. This chapter is basically a report of work in progress on several systems that are starting to yield interesting results, which it is hoped will lead to a general understanding of these complex systems.
2H NMR and Gel Formation of the Ultrafine Solids Fraction Associated with the Athabasca Oil Sands Fine Tails
Authors: Ripmeester John A. , Kotlyar L. S.
Published: November 2020

The two oil sands plants operated by Syncrude Canada Ltd. and Suncor Canada Ltd. near Fort MacMurray, Alberta, use a hot water process for the separation of bitumen from oil sands. In brief, hot water and oil sands, with caustic soda as dispersing agent, are mixed thoroughly, and bitumen is floated to the top of the resulting slurry by streams of air. After secondary bitumen recovery, the remaining tailings are carried to ponds, where the coarse sands are used to form dikes, the fine tails are left to settle, and freed water is recycled. Typical production figures for the Syncrude plant are 390 000 barrels of diluted bitumen per day produced from 325 000 tonnes of oil sand. One complicating factor is that the fine tails dewater only to a solids content of ~30%, requiring ponds of ever increasing size (the Syncrude pond is 22km2) to store the resulting sludge. As the ponded material is toxic to wildlife, it poses a considerable local environmental hazard. In addition, there is the potential hazard of contamination of surface water and a major river system as a result of seepage or potential dike failure. The work reported here was carried out as part of a major project initiated to address the problem of the existing tailings ponds, and also to modify the currently used separation process so as not to produce sludge. Starting with the recognition that the very stable fine tails, consisting of water, silt, clay and residual bitumen, have gel-like properties, we employed the strategy of fractionating the fine tails with the hope of identifying a specific fraction which might show gel-forming propensity. This was done by breaking the gel, and collecting fractions according to sedimentation behavior during centrifugation. Fractions consisting of the coarser solids (>0.5μm) settled rapidly, whereas fractions with smaller particle sizes (termed ultrafines) gave suspensions which set into stiff, thixotropic gels on standing. Gel formation and the sol-gel transition in colloidal clay suspensions are classical problems which have received much attention over the years; however, much remains to be learned. NMR techniques have shown considerable promise in understanding clay-water interactions at a microscopic level.
Acquisition and Interpretation of Liquid-state 1H NMR Spectra of Humic and Fulvic Acids
Authors: Leenheer Jerry A. , Noyes T. I.
Published: November 2020

Fourier Transform nuclear magnetic resonance (NMR) spectrometers have become available to many researchers studying humic substances over the last decade. As a result, liquid-state proton (1H) NMR spectrometry has been commonly used to determine the nonexchangeable proton distribution in humic and fulvic acids. The high sensitivity of the 1H nucleus to NMR spectrometry allows spectra to be obtained on a relatively small quantity of sample (10-100 mg) in a short time (10-30 min). 1H NMR spectrometric profiles of humic substances are useful to environmental scientists in determining the source, properties, and degree of transformation (humification) of organic matter that is operationally classified as humic substances. These 1H NMR spectrometric profiles, which provide information about hydrogen distributions in humic substances, are more useful for structural and biogeochemical studies when combined with 13C NMR spectra, which provide information on carbon distributions, and infrared spectra, which provide information on oxygen distributions. These three spectra, in conjunction with elemental composition, molecular weight, and titrimetric data, can then be synthesized to provide average structural characteristics that can be related to source, properties, and degree of humification of the organic material being studied. Special challenges, that are not met when obtaining the spectra of pure compounds, are encountered in obtaining 'H NMR spectra of natural humic substances. These challenges include (1) lack of complete dissolution of macromolecular humic substances at the high concentrations required for NMR studies; (2) significant concentrations of exchangeable protons giving broad peaks that obscure portions of the spectrum; (3) broad peaks of non-exchangeable protons over the entire spectrum that cause difficulties in correct phasing; (4) unstable structures that oxidize, hydrolyze, and structurally rearrange at the high pH conditions under which humic substances are the most soluble; and (5) the presence of unusual structures that complicate straightforward assignment of structure from handbook data. The purposes of this chapter are to describe methods of sample preparation and to provide generally applicable structural assignments whereby 1H NMR spectra suitable for quantitative studies of humic substance structure may be obtained and interpreted.
An Orientation to Principles-in-Action
Authors: Bartlett Leslee , Turkanis Carolyn Goodman
Published: November 2020

As mentioned at the beginning of this book, the key principle for learning as a school community is to build instruction on children’s interests in a collaborative way—learning activities are planned by children as well as adults, and adults learn from their own involvement as they foster children’s learning. Children are natural learners as long as they can be deeply involved in activities which they help to devise and for which they see a purpose—”minds-on” activities. At the OC, children participate in setting their learning goals and deciding how to use their time and resources, with the aid of the adults. Discussion, conversation, and enjoyment are a valued part of the learning process. The children learn not only the academic subjects but also how to make responsible choices for their own learning and how to solve problems ranging from mathematics and writing to interpersonal frictions at recess. The children learn to lead others (including adults) in school activities and to build on their own interests at the same time that they contribute to the learning of others in the classroom. Much of the day is planned flexibly, to build the curriculum around student contributions, staying open to the serendipitous “learning moments” that naturally emerge as interested people discuss ideas and issues and organize projects for children’s learning. Small groups of children work at an activity with a parent volunteer (a “co-oper”), the classroom teacher, or a child who has organized an activity for the others. Most children stay with the same teacher for two years in blended grade-level classes, creating a supportive classroom environment in which people of differing skills and interests contribute to each others’ learning and learn from teaching others. The children plan their day, choosing among some required activities and some optional ones. The whole class also meets several times each day for planning and for whole-group instruction connected with the learning activities. The principles of learning as a community are not easy even for seasoned teachers and co-oping parents to summarize, since they are generally enacted in everyday situations rather than spoken.
A New Teacher Learning to Share Responsibility with Children
Authors: Seaman Jessica
Published: November 2020

As a first-year teacher, I sometimes felt that I was learning more than my students. I learned more about teaching and how people learn in my first year of teaching than I had in my five years of college education. Maybe that’s because some of my training at two different universities actually conflicted with OC philosophy. My training had taught me that my students really couldn’t learn unless I was in total control of my classroom, but the more control I used in my classroom, the less my students learned (and the less fun we all had). I remember giving a lesson that I thought went really well during my student teaching at another school. Later, an experienced teacher told me that I had not been strict enough in enforcing the classroom rules, because some of the students were reaching into their desks or fidgeting with things while I was up in front teaching. So I put into practice the “listening position,” an idea I had heard about in my management class. The “listening position” had four rules that every student had to follow while anyone was up in front of the class. First, everyone needed to be sitting flat on their bottom on their chair, with the chair on all four legs and under the desk as far as it would go. Second, the tops of the desks had to be completely clear, leaving no room for distractions. Third, everyone’s hands had to remain on the desk at all times. If a student needed an item in his desk (even a pencil or text book), he needed to raise his hand and ask permission. Fourth, all eyes had to be looking forward. A very natural way to learn, don’t you think? I am sure it felt more like being in a prison. The consequence for not being in “listening position” was getting your name on the board. As subsequent infractions occurred and checks were added to your name, things started to happen— phone calls to your parents, being removed from class, being taken to the principal’s office, and so on.
Qualifying to Help People Learn: Becoming a Beginner
Authors: Bradshaw Pamela
Published: November 2020

When I taught kindergarten at the OC, I would finish the first parent letter of the year with a quote by Rainer Maria Rilke: “If the angel deigns to come, it will be because you have convinced him, not by tears, but by your humble resolve to be always beginning: to be a beginner.” In kindergarten there were many families completely new to the OC, and the first parent letter found people at various stages of comfort with the whole system. The quote was certainly comforting to me as I approached a new group. It helped me to remember that no matter what I felt my qualifications were, a humble resolve to be always a beginner, along with a deep breath, cleared an emotional path that allowed me to venture into the unknown. The “unknown,” in fact, is the catch. To examine qualifications for parents’ success in teaching in the OC, I need to indicate the task that the qualifications are for. The expected tasks that parents perform within the OC can be described, such as bringing in activities, inviting children into groups, and supporting responsibility and decision making. But the tasks that are unanticipated are much harder to classify or define. These include problematic moments when a parent might desperately want a “how to” list of instructions. But “how to’s”—and qualifications such as college degrees—might fail someone who is limited to any such well-worn tools. In fact, a difficult situation might be much better met by someone who is willing to shrug her shoulders and just be a beginner. Something powerful happens for me when I realize I am handling something I’ve never seen before, something for which I am neither prepared nor qualified, when none of my tricks work. As soon as I acknowledge my “beginner” status, then I open the door for my own learning. The OC was surely a community that supported my learning by providing me with many opportunities to fall flat on my qualified face—to get up, shrug my shoulders, and admit to myself that I needed to think again, to be a beginner.
Restructuring for the Twenty-First Century
Authors: Katz Stanley N.
Published: November 2020

Today, as the demographics and culture of America change, the demands made on any number of social, cultural, and educational institutions that had their origins in the traditions of Europe and earlier American history seem almost impossible to reconcile. The current demand that these institutions serve all members of American society—people of a multitude of backgrounds, cultures, and interests—and at a higher technological level than ever before, gathers increasing weight, weight that threatens these institutions. At the same time, those with a vested interest in universities, museums, social services, and arts organizations desperately try to shore up their beloved institutions from within, with the result that no one is pleased. Reform attempts seem to lead to the creation of yet more bureaucracy, further stifling institutional ability to respond to the new needs. Goals apparently so simple and clear as "We must better educate our youth to compete in the new world economy" become complicated and muddled. To complicate all the more this process of "change"—to use the current buzzword—we are coming to realize that in tinkering with our traditional institutions, we no longer have confidence in the traditional ways of passing along our values, nor is there a strong consensus on what those values are. William E. Brock, chairman of the Wingspread Group, which was convened to study higher education, states that we must pass along to the next generation the "critical importance of honesty, decency, integrity, compassion, and personal responsibility in a democratic society." Who could disagree? The problem is that people of goodwill no longer necessarily define terms such as "integrity" and "personal responsibility" the same way. So while everyone of every political persuasion is able to agree that something must be done, it has become almost impossible to agree on what to do. Goals become either so idealistic that they are laughable or so watered down, in order not to offend any interest group, that they are useless. In today's political climate, it is clear that to call for "major reform" plays well in the press but can actually forestall any needed change.
Electron Density Studies of Molecular Crystals
Authors: Coppens Philip
Published: November 2020

Small molecules consisting of light-, few-electron atoms were the first species beyond atoms to yield to quantum-mechanical methods. Similarly, crystals of small light-atom molecules have served as most useful test cases of charge density mapping. The small number of core electrons in first-row atoms enhances the relative contribution of valence electron scattering to the diffraction pattern. Early studies, done just after automated diffractometers became widely available, were concerned with molecular crystals such as uracil (Stewart and Jensen 1967), s-triazine (Coppens 1967), oxalic acid dihydrate (Coppens et al. 1969), decaborane (Dietrich and Scheringer 1978), fumaramic acid (Hirshfeld 1971), glycine (Almlof et al. 1973), and tetraphenylbutatriene (Berkovitch-Yellin and Leiserowitz 1976). While thermal motion is often pronounced in molecular crystals, advances in low-temperature data collection have done much to alleviate this disadvantage. In recent years, subliquid-nitrogen cooling techniques have been increasingly applied. Among the most interesting aspects of molecular crystals are the influence of intermolecular interactions on the electronic structure. Physically meaningful Coulombic parameters pertinent to a molecule in a condensed environment can be obtained from the diffraction analysis, and can be used in the modeling of macromolecules. The enhancement of the electrostatic moments relative to those of the isolated species has been noted in chapter 7. But, beyond these considerations, molecular crystals are important in their own right. For example, crystals of aromatic molecules substituted with π-electron donor and acceptor groups are among the most strongly nonlinear optical solids known, considerably exceeding the nonlinearity of inorganic crystals such as potassium titanyl phosphate (KTP); while mixed-valence organic components of low-dimensional solids can become superconducting at low temperatures. The relation between such properties of molecular crystals and their charge distribution provides a continuing impetus for further study. The suitability of light-atom crystals for charge density analysis can be understood in terms of the relative importance of core electron scattering. As the perturbation of the core electrons by the chemical environment is beyond the reach of practically all experimental studies, the frozen-core approximation is routinely used. It assumes the intensity of the core electron scattering to be invariable, while the valence scattering is affected by the chemical environment, as discussed in chapter 3.
Awaking to the Organizational Challenge
Authors: Gleason Philip
Published: November 2020

Even while they were distracted by the ideological fireworks of the 1890s, Catholic educators began to realize that changes in the organizational realm presented a more immediate challenge than did the conflict over broad issues of ecclesiastical policy. The most important features of this organizational challenge were: the emergence of the free public high school as the characteristic agency of secondary education; the marked increase in collegiate enrollments, which included unprecedented numbers of women attending both coeducational institutions and women’s colleges; the breakdown of the classical curriculum and the proliferation of new fields of study; the rise of the research university as the dominant institution, which was accompanied by a general professionalization of learning and the beginnings of a vast expansion of employment opportunities in the “knowledge industry”; and the development of voluntary associations of educators which acted as quality-control agencies by establishing and enforcing standards of performance at every level of education. Taken together, these and related developments constituted a veritable revolution which reshaped American higher education in the last quarter of the nineteenth century and the first two decades of the twentieth. The Catholic response to these developments constituted a form of modernization, since what Catholic colleges had to do was bring themselves into line with contemporary norms in respect to institutional structure, curricular organization, and articulation between secondary, collegiate, and graduate levels of education. This organizational modernization took place unevenly over a span of several decades. The establishment of the Catholic University of America was a decisive early event, but the general movement did not get under way till around 1900. Thus the first quarter of the twentieth century saw American Catholic collegiate education assume the modernized shape it still retains. Graduate education, too, was being introduced in Catholic institutions; but consideration of its development is best postponed for a later chapter. Catholic educators did not, of course, undertake this organizational modernization simply because they wanted to be up-to-date. On the contrary, most of them were deeply conservative on matters methodological and curricular; they certainly did not regard being modern as a virtue to be sought for its own sake.
The Beginnings of the Catholic Renaissance
Authors: Gleason Philip
Published: November 2020

The beginnings of the Catholic Renaissance in the United States were closely linked to the experience of American Catholics in the First World War. As we saw in Chapter 3, mobilization of Catholic energies to meet the wartime crisis led to the creation of the National Catholic War Council. The NCWC’s success in coordinating Catholic participation in the war effort, and the recognition it gained as the representative agency of the church in matters of broad national interest persuaded Catholic leaders that it should be perpetuated after the war. That was accomplished in 1919, when the War Council was transformed into the National Catholic Welfare Council (later National Catholic Welfare Conference). The creation of a national headquarters and staff not only gave the church a more effective voice in public affairs, it also enhanced Catholic visibility and served notice that a new era of purposeful Catholic participation in American life was about to begin. These developments had a tonic effect on Catholic morale and reinforced the sense of emotional solidarity with, and responsibility to, the nation that had grown out of the shared experience of wartime mobilization. The earliest manifestations of the Catholic Revival in the United States emerged from this matrix and took the form of a new kind of Catholic Americanism. There were, of course, certain points of similarity between the Americanism of the war and postwar years and that of the 1890s. Both versions, for example, reflected intense patriotic feeling, and both urged Catholics to identify with, and participate in, American life. Moreover, Cardinal Gibbons, who presided over the creation of the War Council and its transformation into the permanent NCWC, constituted a living link between the two eras. Yet no real effort was made to portray the new Americanism as a continuation of the earlier version. Reticence on this point made good sense tactically, since in 1899 Pope Leo XIII had condemned the opinions that “some comprise under the head of Americanism.”
Ab Initio Calculations of Amino Acids and Peptides
Authors: Schäfer Lothar , Newton Susan Q.
Published: November 2020

In the late seventies and early eighties, a small number of researchers who had the requisite resources at their disposal made the first systematic attempts to employ the newly emerging quantum-chemical computational tools in experimental studies of molecular structures (for reviews see Boggs 1983G, 1988G; Schäfer et al. 1983G, 1987G, 1988aG; and Geise et al. 1988G). In this process, which provided an important testing ground for the evolution of computational chemistry, the ab initio geometric optimizations of glycine (Sellers et al. 1978AA) represent a special landmark. In a sequence of events unprecedented in conformational chemistry, the results of the optimizations first suggested the existence of a hidden conformation that had remained undetected in two independent microwave spectroscopic studies of the compound (Brown et al. 1978G; Suenram et al. 1978G), and then guided new experiments that led to the detection of the missing state (Suenram et al. 1980G; Schafer et al. 1980AA). In the first microwave investigations of glycine (Brown et al. 1978G; Guenram et al. 1978G)—experiments whose success represent a considerable achievement because glycine is difficult to work with in the vapor phase—the observed transitions were assigned to the cyclic form, C, of the compound. In both studies, it was emphasized that other conformers of glycine could have been present but were not detected in the microwave spectra because their line intensities were weaker than those of C. Nevertheless, since C was observed but not the stretched form, S, Brown et al. concluded that “the most likely conformation of glycine in the vapor state” is C and that the experimental result was in conflict with ab initio calculations of glycine by Vishveshwara and Pople (1977AA) in which S was found more stable than C. Brown et al. (1978G): “The microwave spectrum of glycine vapor has been measured and analyzed; it is in the molecular form with a dipole moment of 4.5–4.6D and probably having conformation (C), which is in conflict with a recent theoretical study that implies that conformation (S) is more stable.” In the sixties and seventies, theoretical chemistry had developed a somewhat uncertain reputation.
Historical Records
Authors: Polyak Ilya
Published: November 2020

In this chapter, the historical records of annual surface air temperature, pressure, and precipitation with the longest observational time series will be studied. The analysis of the statistically significant systematic variations, as well as random fluctuations of such records, provides important empirical information for climate change studies or for statistical modeling and long-range climate forecasting. Of course, compared with the possible temporal scales of climatic variations, the interval of instrumental observations of meteorological elements proves to be very small. For this reason, in spite of the great value of such records, they basically characterize the climatic features of a particular interval of instrumental observations, and only some statistics, obtained with their aid, can have more general meaning. Because each annual or monthly value of such records is obtained by averaging a large number of daily observations, the corresponding central limit theorem of the probability theory can guarantee their approximate normality. In spite of this, we computed the sample distribution functions for each time series analyzed below and evaluated their closeness to the normal distribution by the Kolmogorov- Smirnov criterion. As expected, the probability of the hypothesis that each of the climatic time series (annual or monthly) has a normal distribution is equal to one with three or four zeros after the decimal point. As seen in this section, the straight line least squares approximation of the climatic time series enables us to obtain very simple and easy-to-interpret information about the power of the long period climate variability. Carrying out such an approximation, we assume that the fluctuation with a period several times greater than the observational interval will become apparent as a gradual increase or decrease of the observed values. Using only a small sample, it is impossible to determine accurately the amplitude and frequency of such long-period climate fluctuation. Consequently, the straight-line model is the simplest approach in this case. Let us begin with an analysis of the annual surface air temperature time series, the observations of which are published in Bider et al., (1959), Bider and Schiiepp, (1961), Lebrijn (1954), Manlcy (1974), and in the World Weather Records (1975).
The Nineteenth-Century Perspective
Authors: Verschuur Gerrit L.
Published: November 2020

If comets and asteroids have a habit of wandering dangerously close to the earth, why wasn’t the danger recognized a long time ago? It was. In fact, before the beginning of the twentieth century the threat of comets was taken for granted (asteroids had not yet entered the picture). Most astronomers in the nineteenth century accepted that the danger of collision was so obvious that it hardly warranted argument. How they elaborated on the danger varied from the understated, as in the case of Sir John Herschel who in 1835 said that the experience of passing through a comet’s tail might not be “unattended by danger,” to the dramatic, as we shall see. In 1840, Thomas Dick, a well-known popularizer of astronomy, wrote a wonderful book entitled The Sidereal Heavens. In it he reviewed all that was known about the heavens, and did so from a theologian’s perspective. This meant that he repeatedly reminded his readers that the splendor of the night skies was largely the responsibility of the “Divine.” But then, if the existence of planets, comets, nebulae, stars, the sun and moon could be attributed to God, this raised a difficult issue for Dick. If comets were also part of God’s plan, why did the threat of impact exist? Surely God would never allow his creation to be destroyed. Dick did not shy from his predicament and began to search for an answer by conceding that little was known about the nature and origin of comets. At the time it was thought that the head of a comet probably consisted of “something analogous to globular masses of vapor, slightly condensed towards the center, and shining either by inherent light or by the reflected rays of the sun.” The reason he could not be sure as to why the head glowed was because the means to study the properties of light had not yet been invented. That required the development of the spectroscope decades later, a device that breaks light into its various colors, which, when examined closely, can reveal the chemical signature of the object from which the light arrives.