cssi/SciSciGPT-SciSciNet huggingface dataset:
On Process Temperature in Powder-Bed Electron Beam Additive Manufacturing: Process Parameter Effects

Build part certification has been one of the primary roadblocks for effective usage and broader applications of metal additive manufacturing (AM) technologies including powder-bed electron beam additive manufacturing (EBAM). Process sensitivity to operating parameters, among others such as powder stock variations, is one major source of property scattering in EBAM parts. Thus, it is important to establish quantitative relations between the process parameters and process thermal characteristics that are closely correlated with the AM part properties. In this study, the experimental techniques, fabrications, and temperature measurements, developed in recent work (Cheng et al., 2014, "On Process Temperature in Powder-Bed Electron Beam Additive Manufacturing: Model Development and Experimental Validation," ASME J. Manuf. Sci. Eng., (in press)) were applied to investigate the process parameter effects on the thermal characteristics in EBAM with Ti-6Al-4 V powder, using the system-specific setting called “speed function (SF)” index that controls the beam speed and the beam current during a build. EBAM parts were fabricated using different levels of SF index (20–65) and examined in the part surface morphology and microstructures. In addition, process temperatures were measured by near infrared (NIR) thermography with further analysis of the temperature profiles and the melt pool size. The thermal model, also developed in recent work, was further employed for EBAM temperature predictions, and then compared with the experimental results. The major results are summarized as follows. SF index noticeably affects the thermal characteristics in EBAM, e.g., a melt pool length of 1.72 mm and 1.26 mm for SF20 and SF65, respectively, at 24.43 mm build height. SF setting also strongly affects the EBAM part quality including the surface morphology, surface roughness and part microstructures. In general, a higher SF index tends to produce parts of rougher surfaces with more pore features and large β grain columnar widths. Increasing the beam speed will reduce the peak temperatures, also reduce the melt pool sizes. Simulations conducted to evaluate the beam speed effects are in reasonable agreement compared to the experimental measurements in temperatures and melt pools sizes. However, the results of a lower SF case, SF20, show larger differences between the simulations and the experiments, about 58% for the melt pool size. Moreover, the higher the beam current, the higher the peak process temperatures, also the larger the melt pool. On the other hand, increasing the beam diameter monotonically decreases the peak temperature and the melt pool length.
Neural Network Implementations Of Data Association Algorithms For Sensor Fusion

The paper is concerned with locating a time varying set of entities in a fixed field when the entities are sensed at discrete time instances. At a given time instant a collection of bivariate Gaussian sensor reports is produced, and these reports estimate the location of a subset of the entities present in the field. A database of reports is maintained, which ideally should contain one report for each entity sensed. Whenever a collection of sensor reports is received, the database must be updated to reflect the new information. This updating requires association processing between the database reports and the new sensor reports to determine which pairs of sensor and database reports correspond to the same entity. Algorithms for performing this association processing are presented. Neural network implementation of the algorithms, along with simulation results comparing the approaches are provided.
The immune system

Objective: To explain the role of the immune system in cancer control and its response to environmental and perceived stressors. Data sources: Review articles, research studies, and book chapters related to immunology and the immune system. Conclusions: The immune system responds to foreign pathogens and cancer cells by activating specific and nonspecific immune responses. The goal of immunotherapy is to enhance these responses to control the growth of cancer cells. Knowledge of the influence of stress on immune and cytokine response is evolving. Implications for nursing practice: Knowledge of the principles of immunology, the immune response to cancer, the role of cytokines in mediating immune response, and the influence of stress on immune and cytokine response will help nurses provide quality care to patients receiving biological agents.
String variable grammar: A logic grammar formalism for the biological language of DNA☆

Abstract Building upon Definite Clause Grammar (DCG), a number of logic grammar systems have been developed that are well-suited to phenomena in natural language. We have proposed an extension called String Variable Grammar (SVG), specifically tailored to the biological language of DNA. We here rigorously define and characterize this formalism, showing that it specifies a class of languages that properly contains the context-free languages, but is properly contained in the indexed languages. We give a number of mathematical and biological examples, and use an SVG variant to propose a new abstraction of the process of gene expression. A practical implementation called GenLang is described, and some recent results in parsing genes and other high-level features of DNA sequences are summarized.
Budget balance or voluntary participation? Incentivizing investments in interdependent security games

In a system of interdependent users, all entities are affected by the security decisions of one another. These users benefit from the improved health of the system when their neighbors invest in security measures; an effect known as positive externality. The externality of these decisions make security a public good, the optimal provision of which in a system of self-interested users requires regulation/incentives through an external mechanism. In this paper we first show that due to the non-excludable nature of security, no mechanism can achieve social optimality and ensure voluntary participation, while maintaining a balanced budget, for all instances of a security game. We then compare two incentive mechanisms in this context for improving security investment among users, namely the Pivotal mechanism and the Externality mechanism. We show that even though both mechanisms incentivize socially optimal investments, they differ in terms of budget requirements and participation. The Pivotal mechanism guarantees users' participation; however, although (weakly) budget balanced in many game environments, it runs a budget deficit in security games. The Externality mechanism on the other hand is a budget balanced mechanism, but fails to incentivize voluntary participation. We further study the effects of the information available to the mechanism designer on the budget deficit of the Pivotal mechanism.
The interpretation of children's needs at home and in school

Statements of need are used promiscuously by caretakers and children. The term may refer to mere wants (desire), to wants that have become socialized into secondary needs, to needs inferred by adults based on interpretations of future adaptive requirements, as well as to fundamental needs required for a child's well-being. It is important to distinguish the various uses of the term, first, because need carries an imperative–it would be unethical to frustrate a child's basic needs. Second, when confounding meanings, there is the risk that what appears as an expression of concern–‘you need to’–is more arbitrarily coercive than benevolent. Because even genuine needs are multiple and often in tension (protection and independence), separating meanings does not necessarily determine appropriate responses. Caretakers are advised to critically refine and reflect their need statements and, when balancing, remain faithful to the fundamental human need for autonomy.
Evidence on extracellular dopamine level in rat striatum: implications for the validity of quantitative microdialysis.

Microdialysis zero-net-flux (ZNF) method is commonly used to monitor drug-induced changes in neurotransmitter baseline and release/uptake processes. Recent studies in this field suggest that microdialysis ZNF method seriously underestimates the resting concentration of extracellular dopamine in the rat neostriatum because probe implantation preferentially damages nearby dopamine release sites and that dopamine uptake inhibition increases the relative recovery of dopamine by microdialysis. This study assessed the validity of these claims by examining current data on extracellular dopamine levels at rest and after drug application obtained by voltammetry, a technique thought to induce less tissue disruption than microdialysis. To obtain the extracellular baseline value for dopamine from the evoked overflow data, we modified the existing dopamine kinetic model to suit both the resting and stimulated circumstances. It was found that dopamine uptake inhibition did in fact decrease the microdialysis relative recovery of dopamine, implying that the average basal extracellular dopamine level is within the range of 7‐20 nM in rat striatum. This study concludes that the microdialysis ZNF method indeed underestimates the extracellular dopamine concentration, although not by as much as had been thought. Chronic microdialysis damages both neurotransmitter release and uptake, but it does so in a somewhat relative and proportional way for both processes. Thus the validity of the microdialysis ZNF method is not seriously undermined.
Biaxial Flexure Strength and Dynamic Fatigue of Soda–Lime–Silica Float Glass

The strength and dynamic fatigue behavior of float glass was investigated using biaxial flexure tests. The samples were tested using the ring-on-ring (ROR) biaxial flexure test geometry, and the data analyzed using a conventional two-parameter Weibull distribution. The as-received samples revealed that the air side exhibits a higher characteristic strength (243 MPa) compared with the tin side (114 MPa); fractographic analysis confirmed the presence of significantly larger flaws on the tin side of the specimens, presumably due to contact damage by the rollers in the float glass process. Dynamic fatigue results for as-received and indented samples were performed to assess whether differences in the stress corrosion behavior of float glass exist because of tin penetration. No statistical difference in the stress corrosion exponent was found between the air (n= 21.7) and tin (n= 21.6) sides of the float glass. This indicates either that the tin penetration (which extends ∼25 μm) plays no role in altering the stress corrosion susceptibility of float glasses because the native flaw size is larger than the tin penetration depth or that the tests do not have the required sensitivity to distinguish the effect of the tin. Alternative test methods for direct observation of slow crack growth in tin-doped bulk glasses are planned to investigate this in the future.
Electronic Creativity Techniques for Organizational Innovation

Innovation is the key to survival. Domestic and international competitions, changing government regulations, and rapidly evolving global market conditions demand constant and visionary innovation. The aim of this paper is to explore ways of using advance electronic and communication technology to improve innovation in organizations. This paper proposes that two group creativity techniques, PMI and synectics, should be implemented electronically in Group Support Systems to complement electronic brainstorming and support group idea generation. Not only are these two group creativity techniques well-developed and popular in the industry, their electronic counterparts have the added capability of transcending space and time constraints. A comparison of electronic brainstorming, PMI, synectics, and their verbal counterparts is discussed in the paper.
Application of displacement principle for detecting heavy metal ions and EDTA using microcantilevers

Abstract A microcantilever sensor based on a reversible displacement reaction was developed. The demonstration was performed with the Ni–NTA–EDTA sample system. Ni ions, a typical heavy metal, were injected and adsorbed onto a NTA-functionalized AFM cantilever in a fluid cell. This adsorption resulted in tensile stress which was detected by monitoring the corresponding deflection of the microcantilever. In the next step, EDTA was injected into the cell to release the adsorbed Ni ions from the surface of the cantilever. Since EDTA molecules have a stronger affinity for Ni ions compared to NTA, they compete with and eventually replace the NTA molecules and take over the binding positions on Ni. The displacement of Ni ions from the cantilever by EDTA, followed by water flow removes the tensile stress and restores the cantilever deflection to its original value. In this way, both heavy metal ions and EDTA can be specifically recognized. From the cantilever deflection, the concentration of Ni ions and EDTA can be quantified. The detection limits are presently at the micromolar level. Another weaker Ni ion binder, imidazole, was unable to dissociate Ni ions from NTA and produce similar effects. The demonstrated principle can be used for microcantilever sensors which are capable of regeneration for multiple uses. The method presented can be generalized to detect other reactants.
Footprints: A Visual Search Tool that Supports Discovery and Coverage Tracking

Searching a large document collection to learn about a broad subject involves the iterative process of figuring out what to ask, filtering the results, identifying useful documents, and deciding when one has covered enough material to stop searching. We are calling this activity "discoverage," discovery of relevant material and tracking coverage of that material. We built a visual analytic tool called Footprints that uses multiple coordinated visualizations to help users navigate through the discoverage process. To support discovery, Footprints displays topics extracted from documents that provide an overview of the search space and are used to construct searches visuospatially. Footprints allows users to triage their search results by assigning a status to each document (To Read, Read, Useful), and those status markings are shown on interactive histograms depicting the user's coverage through the documents across dates, sources, and topics. Coverage histograms help users notice biases in their search and fill any gaps in their analytic process. To create Footprints, we used a highly iterative, user-centered approach in which we conducted many evaluations during both the design and implementation stages and continually modified the design in response to feedback.
Advanced practice registered nurses: Addressing emerging needs in emergency care

An advanced practice registered nurse (APRN) is a registered nurse with advanced specialized clinical knowledge and skills to provide healthcare to diverse populations. The role of the APRN is emerging worldwide to improve access to, quality, and cost-effective healthcare services. APRNs with expanded capabilities are now working in a variety of healthcare settings including emergency centres. This paper will provide a brief overview of APRN roles in the United States followed by a discussion of how APRNs can meet the healthcare needs of patients seeking emergency care. An example from a paediatric specialty practice will demonstrate how the APRN role can be implemented in the emergency centre. Finally, implications for initiating APRNs in emergency care across Africa will be addressed.
Effect of Infarct Artery Patency on Prognosis After Acute Myocardial Infarction

Background In patients with acute myocardial infarction (MI), early restoration of patency of the infarct-related artery (IRA) leads to preservation of left ventricular function and improved clinical outcome. However, there is evidence that the benefits associated with a patent IRA are out of proportion to the observed improvement in ventricular function and may result not only from salvage of ischemic myocardium but also from the opening of the IRA beyond a narrow postinfarct time window. The objectives of this study were (1) to assess the effect of IRA patency on outcome of patients after acute MI with left ventricular dysfunction while controlling for differences in left ventricular ejection fraction and the extent of coronary disease and (2) to determine the effect of angiotensin-converting enzyme (ACE) inhibitor therapy on patients with patent as well as occluded infarct arteries. Methods and Results The Survival and Ventricular Enlargement (SAVE) study consisted of 2231 patients with a documented MI...
HERBIVORE‐MEDIATED APPARENT COMPETITION BETWEEN TWO SALT MARSH FORBS

Indirect negative interactions between prey species that share a predator, referred to as apparent competition, have been modeled extensively. However, experimental studies examining the importance of apparent competition in the field are sparse, especially in plant–herbivore systems. In this study, I examined the role of a beetle herbivore, Erynephala maritima, in mediating the indirect effects of an abundant host plant, Salicornia europaea, on a less common host species, Atriplex patula var. hastata, in New England salt marshes. To examine these relationships, I manipulated plant density (plants with vs. without neighbors) and composition (conspecific neighbors vs. Salicornia neighbors) surrounding focal Atriplex plants, as well as the presence or absence of herbivores in a field experiment. Densities of both beetle eggs and larvae were significantly greater in plots with Salicornia, suggesting that its presence increases patch location or selection by herbivores. Higher insect densities resulted in sig...
Effects of genotype and age on mixed-function oxidase activities in adult Drosophila melanogaster

Abstract The mixed-function oxidases that metabolize dimethylnitrosamine, aminopyrine, benzphetamine, 7-ethoxycoumarin and benzo[a]pyrene were measured in adults of the Canton-S, Oregon-R and Hikone-R strains of Drosophila melanogaster. The expression of these activities is both genotype and age dependent.
The Influence of Orbital Forcing of Tropical Insolation on the Climate and Isotopic Composition of Precipitation in South America

AbstractThe δ18O of calcite (δ18Oc) in speleothems from South America is fairly well correlated with austral summer [December–February (DJF)] insolation, indicating the role of orbitally paced changes in insolation in changing the climate of South America. Using an isotope-enabled atmospheric general circulation model (ECHAM4.6) coupled to a slab ocean model, the authors study how orbitally paced variations in insolation change climate and the isotopic composition of precipitation (δ18Op) of South America. Compared with times of high summertime insolation, times of low insolation feature (i) a decrease in precipitation inland of tropical South America as a result of an anomalous cooling of the South American continent and hence a weakening of the South American summer monsoon and (ii) an increase in precipitation in eastern Brazil that is associated with the intensification and southward movement of the Atlantic intertropical convergence zone, which is caused by the strengthening of African winter monsoon...
Viscosity of concentrated colloidal suspensions: comparison of bidisperse models

In this paper, recent advances in the study of rheological behavior of concentrated bimodal suspensions are briefly reviewed. The predictive models are divided into two categories, namely, the effective volume fraction (or hard sphere scaling) approach and the separation of contributions approach. Predictions of both approaches are compared with experimental data of electrostatically and sterically stabilized suspensions. It is shown that the predictions of both hard sphere scaling and the scaling method of Zaman and Moudgil (J. Colloid Interface Sci. 212 (1999) 167) to separate the contributions of fine and coarse particles are in good agreement with the experimentally observed results. The approach by Dames, Morrison, Wilenbacher (Rheol. Acta 40 (2001) 434) to separate the hard-sphere and non-hard-sphere contributions is investigated using the aqueous silica and polystyrene suspensions respectively. A good agreement is shown for aqueous silica suspensions. However, significant differences between the predictions and experimental data are found for the sterically stabilized polystyrene suspensions, suggesting a more generalized expression is needed. As an attempt to classify the models on the viscosity of colloidal suspensions, the present study will provide guidelines for interpretation of experimental results and for the development of more comprehensive predictive methodologies for polydispersed colloidal dispersions.
Amylase activity and growth in internodes of deepwater rice

Isoelectrofocusing, product analysis, thermal denaturation studies and affinity chromatography on cycloheptaamylose-Sephadex were used to identify the amylolytic enzymes in internodes of deepwater rice (Oryza sativa L.). Amylolytic activity in internodes of deepwater rice consists of α-amylase (sometimes separated into two isoforms) and of β-amylase. During submergence of whole plants, α-amylase activity increases in young, growing internodes, but β-amylase activity declines. Although non-growing, mature internodes contain higher levels of β-amylase than do the elongating younger internodes, the effect of submergence on amylase activities in both tissues follows the same trend. Submergence, gibberellic acid (GA3) and ethylene all promote α-amylase activity in growing and non-growing internodes of excised deepwater-rice stem sections. Inhibitor studies showed that submergence and ethylene promote α-amylase activity in the absence of endogenous gibberellin (GA), and GA3 enhances α-amylase activity when ethylene action is inhibited. Therefore, ethylene and GA appear to increase α-amylase activity independently of each other. Enhanced α-amylase activities are probably responsible for the mobilization of carbohydrates which are needed to support internode elongation during submergence of deepwater rice.
Quantitative assessment of collagen assembly by live cells.

Changes in supramolecular assembly of matrix, specifically collagen, have important functional consequences, especially for tissues requiring high mechanical strength. Thus modulation of collagen assembly could be used as a therapeutic intervention or to control the development of tissue-engineered constructs containing natural matrix. Quantitative methods that monitor such effects currently are lacking. Using live cultured cells, we developed a convenient way either to visualize by fluorescence microscopy or to measure directly, using a high throughput fluorescence assay, the supramolecular assembly of FITC-labeled collagen monomers. The wide applicability of this assay was confirmed by testing the assay using two major collagen sources, rat tail and bovine skin, and vascular smooth muscle cells from two different origins, mouse aorta and human saphenous vein. We further determined that treatments that interfere with the function of the cytoskeleton modulate collagen assembly. Use of positive and negative regulators of lysyl-oxidase indicated that while the assay does not require active production of endogenous collagen, it can be used to monitor the incorporation of such de novo synthesized collagen into labeled fibrils. Thus we have designed a novel quantitative assay that can monitor assembly of exogenous and endogenous collagen by live cells and reveal the effects of various interventions upon this process.
Unusual Reactivity of Molecular Oxygen with π-Allylnickel(N-heterocyclic carbene) Chloride Complexes

One-pot preparation and characterization of the first reported nickel(II) complexes containing a single imidazol-2-ylidene ligand are reported. Subsequent treatment of these complexes with molecular oxygen at room temperature results in rapid formation of a μ-hydroxo dimer and α,β-unsaturated carbonyl compounds. Mechanistic investigations indicate that this reaction proceeds via reversible oxygen binding followed by rate-limiting decomposition of the resulting metal−oxygen species.
Impact Jetting of Geological Materials

To understand jetting of earth materials, gabbro slabs (5 mm thick) were accelerated to 1.5-2 km sec^(-1) and impacted gabbro (5-10 mm thick), novaculite (10 mm thick), and porous sandstone (12 mm thick) targets at inclination angles of 30°-60°. The ejecta were collected using a catcher box filled with styrofoam and the particles are extracted using chloroform. Jetting angles are determined by the relative positions of the target and the crater produced by the ejecta. The mass of the ejected particles per unit area (∼50 mg cm^(-2)) of the impactor remains almost independent of the impact velocity, inclination angle, thickness of the target and sample mineralogy, and density. Hydrodynamic models are used to calculate the jetting mass, angle, and velocity. Theoretical models predict ∼6 times more ejecta than the experimentally measured as the inclination angle increases. X-ray diffraction of the recovered ejecta shows that it is still in crystalline form, which agrees with thermodynamic calculations. Because the experimental results indicate that the theoretical jetting model for thin metal plates provides a poor description of the experiments, the application of metal plate theory to planet-sized objects appears to be questionable.
Analysis of Omnidirectional Dual-Reflector Antenna and Feeding Horn Using Method of Moments

A hybrid numerical technique is applied for the analysis of circularly symmetric dual reflector antenna fed by TEM coaxial horn to generate an omnidirectional radiation pattern. By following the steps of a technique developed for the analysis of horn antennas, it employs a stepped-waveguide method to analyze the interior surfaces of the TEM coaxial horn transition and the electric field integral equation (EFIE) is applied on the outer surfaces of the TEM coaxial horn including the radiating aperture and the reflectors. Simultaneously, the magnetic field integral equation (MFIE) is employed on the aperture to relate the aperture fields and those in the horn transition. Method of moments (MoM) is employed to numerically solve the resultant hybrid field integral equation. The technique is applied for electromagnetic analysis of a coaxial TEM horn antenna and an omnidirectional dual reflector antenna. Results for the antenna return loss at the input port and for the vertical radiation pattern are given and compared with measurements and with commercial software results.
Evolution of monolithological breccia deposits in supradetachment basins, Whipple Mountains, California

Extensive sheets of monolithological breccia (megabreccia) within detachment-fault systems of the North American Cordillera have been identified as large landslides. Although the origin of the megabreccia deposits is controversial, their spatial and temporal association with detachment-fault systems implies a causal relationship between the initiation of such landslides and motion along detachment faults. Emplacement may have been catastrophic following seismic activity, or slow, as the result of gravity gliding. Nevertheless, comprehensive analysis of these deposits provides important constraints on the evolution of supradetachment basins by detailing the unroofing history, palaeotopography and palaeoseismicity of detachment-fault systems. An extensive Miocene landslide deposit, the War Eagle landslide, in the north-eastern Whipple Mountains, provides an opportunity for such an endeavour to elucidate: (1) the cause and timing of its initiation; (2) mechanism for its emplacement; (3) nature of the apparent association of the landslide with detachment-fault development; and (4) role of the megabreccia in the development of supradetachment basins. Cross-sections were drawn through the deposit to determine the geometry and kinematic development of the landslide. Additionally, a simple mechanical model based on limit equilibrium force balance was designed to explore physical mechanisms that controlled its creation. The results of this model combined with field relationships suggest that the Whipple detachment fault was active at an angle of less than 30° with displacement most likely accompanied by the release of seismic energy. Continued extensional evolution of the Whipple detachment fault caused tilting of the upper-plate strata and the formation of numerous half and full grabens as well as roll-over structures. Rocks from the lower plate were brought to the surface during the later stages of detachment-fault activity thereby producing sufficient topographic relief for large landslides to be seismically activated. Increased pore-fluid pressure in the footwall subjacent to the Whipple detachment fault probably aided landslide initiation. The landslide was emplaced onto the upper plate of the detachment fault, providing a significant amount of material into the evolving supradetachment basin. Although the rate of emplacement of the megabreccia remains uncertain, penetrative fracturing throughout the breccia sheet is evidence that emplacement occurred catastrophically. The results of this study indicate that Tertiary megabreccias were emplaced during continued detachment-fault evolution, implying oversteepened topography and seismicity of these low-angle systems.
The impossibility of a bouncing universe

Petrosian1 has recently discussed the possibility that the restoration of symmetry at grand unification in a closed contracting Robertson–Walker universe could slow down and halt the contraction, causing the universe to bounce. He then went on to discuss the possibility that our universe has undergone a series of such bounces. We disagree with this analysis. One of us (M.S.) has already shown2 that if a contracting universe is dominated by radiation, then a bounce is impossible. We will show here two further results: (1) entropy considerations imply that the quantity S (defined in ref. 1 and below), which must decrease by ∼1075 to allow the present Universe to bounce, can in fact decrease by no more than a factor of ∼2; (2) if the true vacuum state has zero energy density, then a universe which is contracting in its low temperature phase can never complete a phase transition soon enough to cause a bounce.
Low-Cost Analog/RF IC Testing Through Combined Intra- and Inter-Die Correlation Models

This paper presents statistical methods to identify and take advantage of correlations in the test methods and wafer-level spatial correlations among devices. The result, shown for industrial designs, is a far more optimized test suite.
Thermal isomerizations of vinylcyclopropanes to cyclopentenes

The thermal isomerization of vinylcyclopropane to cyclopentene was discovered in 1960 and soon recognized as the simplest known example of a [1,3] sigmatropic shift. Experimental observations for the parent rearrangement and for isomerizations shown by substituted systems suggest that diradical transition structures are involved; recent theoretical treatments of the reaction find no minima corresponding to diradical intermediates. The common dichotomy opposing concerted versus diradical and thus necessarily stepwise mechanisms appears inappropriate. The reaction of vinylcyclopropane may involve four energetically concerted paths traversed by different conformational forms of nearly isoenergetic diradical species leading through four isometric diradical transition structures to cyclopentene. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 222–231, 1998
Mutagenicity of 4-aminoantipyrine and 4-nitrosoantipyrine, the C-nitroso derivative of antipyrine

The drug antipyrine and its 4-substituted analogs, 4-aminoantipyrine, 4-dimethylaminoantipyrine (aminopyrine) and 4-nitrosoantipyrine were tested for mutagenicity against the screening array of Salmonella typhimurium tester strains TA100, TA98, TA97, TA102 and TA104. Antipyrine and aminopyrine were nonmutagenic to all 5 tester strains even in the presence of S9. 4-Aminoantipyrine was directly mutagenic to TA97 only and the presence of S9 slightly increased its activity. 4-Nitrosoantipyrine was directly mutagenic to all tester strains used and S9 decreased its activity except with strain TA102. The possible long-term hazards of C-nitroso compounds derived from drugs and dietary constituents are discussed in view of their pluripotent direct genotoxicity.
Tyrosine kinase signaling at fertilization.

Abstract The unfertilized egg is a highly differentiated cell that retains unlimited developmental potential. The execution of that potential requires signal transduction pathways that release the egg from its quiescent metabolic state, direct the union of the maternal and paternal genome, and initiate a developmental program that will guide embryogenesis. The egg is equipped with an array of cytosolic as well as cell surface receptor protein tyrosine kinases as part of a pre-assembled signal transduction mechanism. These protein tyrosine kinases have been found to act at several points during this egg activation process, beginning as early as the initial sperm-egg interaction. While many of these kinase functions are common to all cells, several functions unique to fertilization demonstrate the versatility of this class of protein kinases.
Breadth or depth in introductory computer courses: A controlled experiment

A controlled experiment comparing the first-year approaches of in-depth study of programming methodology to breadth of experience in programming and languages is described. The experiment involves two groups of students who will follow different paths in the freshman year which converge in the sophomore year. Performance of students from each group in the common sophomore courses will be analyzed. The efforts to reduce bias and the methods of measurement and analysis are described in detail.
Xanthan: effect of molecular conformation on surface tension properties

Abstract The effect of ionic strength, xanthan concentration and temperature on the molecular conformation of xanthan in aqueous solutions was determined by Potentiometrie titration. The surface tension of these aqueous xanthan solutions was determined by the drop weight and the Wilhelmy plate methods. The degree of xanthan ionization affected its molecular conformation with a transition point at ~0.85; below 0.85 the conformation was that of a helix, while above 0.85 that of a random coil. The ordered conformation was disrupted by increasing the electrostatic potential of the molecule. Temperature increases also disrupted the helix conformation; this effect was reduced by added salt. As expected, the surface tension properties of aqueous xanthan solutions were affected by its molecular conformation. Xanthan in the random coil conformation was more surface active than xanthan in the helix conformation. Wilhelmy plate determinations showed that the surface tension of xanthan solutions is time dependent. The equilibrium surface tension decreased and the adsorption rate increased significantly by increasing the xanthan concentration and by adding 0.1 N NaCl. Surface excess values calculated by the Gibbs equation suggested that the surface tension was affected by the proportion of molecular segments absorbed at the interface. The implications of these findings to industrial applications are discussed with particular reference to food emulsions.
Clinical trial investigating success rates for polyether and vinyl polysiloxane impressions made with full-arch and dual-arch plastic trays

Statement of problem Success rates for making fixed prosthodontic impressions based on material and tray selection are not known. Purpose The purpose of this clinical study was to compare first impression success rates for 2 types of impression material and 2 impression tray systems. Material and methods Dual-viscosity impressions were made with a vinyl polysiloxane (VPS) (Aquasil Ultra Monophase/Aquasil Ultra XLV) and a polyether (PE) (Impregum Penta Soft HB/Impregum Garant Soft LB) impression material. The first impression made was evaluated for success or failure using developed criteria. Fifty senior dental students participated. The type of impression material alternated for each new patient. A full-arch perforated plastic (President Tray) or a plastic dual-arch impression tray (Tri-Bite) was used based on clinical guidelines. Impression success rates were compared using logistic regression, fitted using the method of generalized estimating equations (α=.05). Results One hundred ninety-one impressions were evaluated, and the overall success rate was 61% for VPS and 54% for PE ( P =.39). Additional regression analyses, adjusted for potential confounders, did not indicate a difference between the 2 systems ( P =.35). There was little difference in success rates between the 2 materials when a full-arch tray was used (50% versus 49% success, P =.89), whereas a larger difference was apparent with the use of dual-arch trays (70% success with VPS versus 58% success with PE, P =.21). The most common critical defect was located on the preparation finish line (94%), and the most common operator error was inadequate gingival displacement (15%). Conclusions There was little difference in success rates between VPS and PE when full-arch impression trays were used, but there was greater success when using VPS with dual-arch trays. For single teeth, the trend favored VPS, but when more than one prepared tooth per impression was involved, the success rate was higher for PE.
Constant heating rate analysis of simultaneous sintering mechanisms in alumina

Constant heating rate sintering experiments were conducted on a submicron alumina powder during the initial stage. Shrinkage was measured by precision dilatometry and surface area reduction was monitored with gas adsorption measurements. Furthermore, grain size and pore size results were collected using X-ray line broadening and mercury porosimetry. Analysis of the shrinkage and surface area reduction data showed excellent correlation with a computer simulation based on simultaneous surface diffusion and grain boundary diffusion mechanisms. A comparison of the simulated and the experimental sintering paths on a plot of surface area reduction versus shrinkage indicated the combination of mechanisms and activations energies which best describe this sintering behaviour. From this analysis the estimated activation energies for grain boundary and surface diffusion are 440 and 508 kJ mol−1, respectively.
The interaction of the macrophage and the osteoblast in the pathophysiology of aseptic loosening of joint replacements.

Macrophage phagocytosis of cement particles with production of inflammatory mediators is a component of the underlying mechanism of aseptic loosening of joint prostheses. Prostaglandin E2 (PGE2), a bone resorbing mediator, has been implicated in the loosening process. Investigations have shown that macrophage phagocytosis of cement particles leads to production of bone-resorbing mediators other than PGE2. In this study, conditioned medium from macrophages exposed to crushed simplex cement particles stimulated osteoblasts to release radiolabeled arachidonic acid and metabolites. Incubation of osteoblasts in conditioned medium from macrophages exposed to cement particles small enough to be phagocytized increased PGE2 release 80-fold over unexposed osteoblasts (P<0.001). Incubation of osteoblasts in conditioned medium from macrophages exposed to particles too large to be phagocytized, or to bone cement filtrate, did not stimulate PGE2 release. We propose that the role of the macrophage in aseptic loosening is primarily to recognize the mechanical failure of the cement mantle by phagocytosis of cement particles and subsequent production of small amounts of specific mediators. These mediators stimulate surrounding osteoblasts to secrete PGE2, which then amplifies the inflammatory response and ultimately results in bone resorption and aseptic loosening.
Pharmaceutical intervention for myopia control

Myopia is the result of a mismatch between the optical power and the length of the eye, with the latter being too long. Driving the research in this field is the need to develop myopia treatments that can limit axial elongation. When axial elongation is excessive, as in high myopia, there is an increased risk of visual impairment and blindness due to ensuing pathologies such as retinal detachments. This article covers both clinical studies involving myopic children, and studies involving animal models for myopia. Atropine, a nonselective muscarinic antagonist, has been studied most extensively in both contexts. Because it remains the only drug used in a clinical setting, it is a major focus of the first part of this article, which also covers the many shortcomings of topical ophthalmic atropine. The second part of this article focuses on in vitro and animal-based drug studies, which encompass a range of drug targets including the retina, retinal pigment epithelium and sclera. While the latter studies have contributed to a better understanding of how eye growth is regulated, no new antimyopia drug treatments have reached the clinical setting. Less conservative approaches in research, and in particular, the exploration of new bioengineering approaches for drug delivery, are needed to advance this field.
Effects of maternal calorie-restricted diet on development of the foetal heart, as evaluated in primary cultures of rat myocardial cells.

Very-low-calorie diets have been implicated in causing ventricular arrhythmias and sudden cardiac death. Furthermore, studies indicate that maternal carbohydrate-restricted diets consumed during pregnancy and lactation reduce foetal growth, parturition and postnatal survival of rat pups. In this study, Sprague-Dawley rats were maintained on a semi-purified full-calorie or 50% carbohydrate-calorie-restricted diet throughout pregnancy. The function and integrity of myocardial cell cultures obtained from 3–5-day-old offspring from both groups of dams were evaluated after a drug-induced toxic challenge. After the myocytes had been in culture for 4 days, they were exposed to various concentrations of amitriptyline (1 × 10−3 to 1 × 10−5 m). Morphology, beating activity, lactate dehydrogenase release, glucose utilization, β-adrenergic receptor [125I]iodopindolol binding, and cellular adenosine triphosphate content were evaluated for 24 hr after drug exposure. There were no significant differences in morphology, beating activity or glucose utilization between the full-calorie and calorie-restricted groups. When compared with the full-calorie group, lactate dehydrogenase release from the calorie-restricted group was significantly lower at 8 hr for the untreated controls and those cells exposed to 1 × 10−4 and 1 × 10−5 m-amitriptyline. Adenosine triphosphate levels were lower in untreated controls from the calorie-restricted group when compared with the full-calorie group at 4 hr. Within the calorie-restricted group, those cultures exposed to 1 × 10−4 m-amitriptyline had significantly depressed adenosine triphosphate levels after 8 hr of drug treatment when compared with their respective untreated controls. Finally, the calorie-restricted group had significantly increased binding affinities of β-receptors. Thus, maternal consumption of calorie-restricted diets during pregnancy may affect the myocardial functional capacity and integrity of the offspring.
HIRISE: a ground-based high-resolution imaging spectrograph using echelle grating for measuring daytime airglow=auroral emissions

Abstract We discuss a new optical technique for measuring daytime optical emissions. We elucidate the method of analysis for retrieving the daytime airglow and auroral emissions using this instrument and explain the procedure used to account for the Ring effect contribution. Finally, we show sample results of thermospheric oxygen dayglow emissions obtained by this instrument.
In vitro studies on the metabolism and co valent binding of [14C]1,1-dichloroethylene by mouse liver, kidney and lung

Abstract The metabolism and covalent binding of 1,1-dichloro[1,2-14C]ethylene (DCE) to subcellular fractions of liver, kidney and lung of C57BL/6N mice have been investigated in vitro. Covalent binding was NADPH- and cytochrome P-450-dependent. The microsomal fraction bound more radiolabel than any other subcellular fraction, and the levels of covalent binding in cell fractions correlated well with their cytochrome P-450 content. Covalent binding by mouse liver and lung microsomes also reflected their cytochrome P-450 content. However, although mouse kidney microsomes contained twice as much total cytochrome P-450 as the lung, no detectable covalent binding of DCE-derived radioactivity occurred in kidney. Omission of NADPH, heat inactivation of microsomes, carbon monoxide, addition of SKF-525A, piperonyl butoxide or reduced glutathione (GSH), all inhibited (40–90%) covalent binding of radiolabel to liver and lung microsomes. The absence of O2 (incubation under N2) did not greatly affect the metabolism and covalent binding. Pretreatment of mice with various inducers, phenobarbital (PB),β-naphthoflavone (β-NF), pregnenolone 16α-carbonitrile (PCN) and 3-methylcholanthrene (3-MC), evoked increases in total liver microsomal cytochrome P-450 content (2-fold) and corresponding increases in covalent binding (3-fold). However, microsomes from PCN-treated mice showed only a 50% increase in DCE binding. Kidney microsomes from control, PB-, and β-NF-pretreated mice were incapable of covalent binding of radiolabel but those from PCN- and 3-MC-pretreated mice showed levels of binding similar to untreated mouse lung microsomes. It is proposed that the nephrotoxicity of DCE may be due to translocation of reactive metabolites from the liver to the kidney.
The effect of medroxyprogesterone acetate on premature labor in the sheep

Abstract The ability of medroxyprogesterone acetate to delay premature delivery was investigated in nine chronically catheterized pregnant sheep (125 to 130 days' gestation). Catheters were placed for measurement of intrauterine pressure and uterine vein concentrations of progesterone, 17β-estradiol, and 15-keto-13,14-dihydroxyprostaglandin F2α. Premature parturition was induced in all animals by infusion of dexamethasone (1 mg/24 hours) to the fetus. Three ewes served as controls, three ewes received oral medroxyprogesterone acetate (5 mg/kg/day) 48 hours prior to the start of and during dexamethasone early medroxyprogesterone acetate), and the remaining three animals received oral medroxyprogesterone acetate 12 hours after the onset of dexamethasone infusion (late medroxyprogesterone acetate). The engths of time from dexamethasone until the onset of labor and from dexamethasone until delivery were compared, and were significantly longer for each group compared to control times. Of all endocrine events analyzed, the fall in plasma progesterone was the most consistent in all groups, showing that animals with rapid falls in progesterone levels (control group) tended to deliver earlier. These results demonstrate that medroxyprogesterone acetate can delay premature parturition in the sheep. Also medroxyprogesterone acetate appears to delay the endocrinologic events that normally occur at this time.