bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultratrace Emission Spectroscopy
Authors: Morrison George H. , Rupp R. L.
Published: September 2009

As a consequence of the increased emphasis in recent years on materials research and the preparation of high-purity semiconductors, metals, and compounds, highest interest has been aroused in the powerful field of direct detection and determination of trace elements.
Development and Performance of the Portable Skid-Resistance Tester
Authors: Giles C G , Sabey B E , Cardew KH F
Published: September 2009

The portable skid-resistance tester can carry out a wide variety of measurements on the road and in the laboratory. This paper outlines the basic principles underlying the design of the tester and describes the laboratory and field trials conducted during the development of the instrument. The factors influencing its performance are emphasized.

In its performance, the instrument behaves as a patterned tire skidding at 30 mph. It is particularly well suited for testing rough-textured surfaces, and readings are independent of gradient, camber, or crossfall on the test surface.
Application of Fracture Mechanics to Adhesive Joints
Authors: Ripling E. J. , Mostovoy S. , Patrick R. L.
Published: September 2009

Fracture mechanics is a relatively new topic that makes it possible to define toughness of material in the presence of flaws. The effect of joint geometry, section size, strain rate, and fracture mode on fracture toughness are discussed. The overriding factor in establishing the toughness of any joint is the speed with which the crack moves along the glueline. Slow-moving cracks result in high toughness, while cracks that abruptly jump along the glueline result in low toughness. Changing the fracturing mode from tensile to forward shear results in an order of magnitude increase in toughness.
Adhesion and Cleavage Stress at Interfaces Between Solids and a Pressure-Sensitive Adhesive
Authors: Dahlquist C. A.
Published: September 2009

The surface-free energies of several solids, including a series of alkyl esters of cellulose, were estimated using recent theories of Zisman, Fowkes, Girifalco, Good, and Kraus. Using these values, the relative works of adhesion between a pressure-sensitive adhesive and the solids were estimated. The work of adhesion is directly proportional to the critical surface energy of the solid. Assuming a covariance between the critical surface energy and the boundary cleavage stress, it was shown that the change in peel force was explained reasonably well by the change in work of adhesion. The possibility of accounting for the trend in peel force by the variation in tensile strength of the cellulose esters is discounted, but the adhesion data for the cellulose esters can be explained qualitatively by the theory of Sharpe and Schonhorn.
Chemical Nature of Polymer to Metal Adhesion
Authors: Lewis A. F. , Forrestal L. J.
Published: September 2009

Irradiation grafting of bis(2-chloroethyl) vinyl phosphonate onto polypropylene is found to be a very effective way of improving its adhesionability toward metals (aluminum, steel, copper). At low grafting levels representing small radiation doses, a condition of greatly enhanced adhesion with small change in bulk mechanical properties of the polymer is achieved. This enables one to study the interfacial aspects of adhesion practically independent of gross changes in the mechanical properties of the bulk polymer. The results indicate that interfacial properties influence adhesive joint strength up to a critical “minimal value.” At and above this critical degree of surface attachment, the adhesive joint strength is optimized, and a condition is reached where the bulk mechanical (rheological) properties of the adhesive polymer (in both the bulk and boundary layer) become the sole determinant of the adhesive joint strength.

The effectiveness of other functional groups is shown by presenting polymermetal adhesion test results obtained by using polypropylene grafted with other monomers. Empirically, it is found that acids (electron accepting groups) are conducive to strong interfacial adhesion to metals while other functional groups exhibit specificity.
Adhesive Requirements for the Automotive Industry
Authors: Twiss S. B.
Published: September 2009

The automotive industry uses a wide range of adhesives and sealants in the construction of an automobile. Some of these are an integral part of the body, others are used for attachment of auxiliary parts, and still others are used in the assembly of parts that are occasionally replaced during the average 12-year life of a car. As a result, the requirements for adhesives in the automotive industry vary considerably, but all must be capable of being handled on a production basis with assurance of consistent results. Further, without exception, they are expected to last the life of a car or subassembly without failure or significant change in properties.

The functional requirements and the production requirements of adhesives are discussed. Products approved for automotive use are specification products required to meet specifications peculiar to the automotive industry, and which in many cases vary from one manufacturer to another. The minimum specifications for adhesives and sealants are discussed. A classification of automotive adhesives and sealants is given, and a compilation of the material base, special properties, and use or application for each product is outlined in an Appendix. Brief descriptions and photographs are used to describe typical products and their application in the automobile.

Finally, the future applications of these products in automobile manufacturing is discussed with an indication of the adhesive requirements to meet the suggested uses. Joining of dissimilar materials, improved vibration dampening, replacement of spot welding, attachment of exterior trim, and structural bonding of subassemblies are all areas of future growth of adhesives if the rigorous requirements of both performance and manufacturing are met.
Tolerances and Variations of Highway Materials from Specification Limits
Authors: Warden W. B. , Sandvig L. D.
Published: September 2009

The application of statistical quality control techniques has proved to be a valuable management tool in the control of highway materials. The large masses of test data being collected daily by highway departments, when checked for reliability and properly analyzed statistically, can provide valuable information to specification writers. An enforceable specification must be realistic statistically, in the sense that the required tolerance limits reasonably reflect (1) the random variation inherent in the material itself and (2) the error of measurement (sampling and testing). In addition, each specification requirement should satisfy some useful engineering or control purpose: there should be a good reason for its existence. The comparison of the results of the analysis of actual test data with existing specification requirements can provide a measure of how well a specification is being met and can indicate the suitability and practicality of the required limits or tolerances. This paper discusses and illustrates methods of comparing specification limits with actual variation of the properties of selected materials and mixtures as shown by the results of field and laboratory tests. The data used were obtained from the results of tests made in various States on bituminous paving mixtures, on asphalt cement and aggregate for flexible pavement, and on subbase material.
Motivation for and Implementation of Grading Asphalt Cement by Viscosity at 140 F
Authors: Hawthorne H. R.
Published: September 2009

A method of grading asphalt cements on the basis of viscosity at 140 F and characterizing the materials by means of absolute viscosity values at other temperatures is described. It is believed that this procedure will substantially eliminate the field problems resulting from variations in the properties of asphalt when supplied by different manufacturers. It will also lead into a better understanding and control of the properties of asphalt as they may relate to pavement performance.
Chromium-Base Alloys
Authors: Parke Robert M. , Bens Frederick P.
Published: September 2009

The creation of superior heat-resistant materials is one part of the classical problem of efficiently converting thermal energy into ordered kinetic energy and will remain an important part so long as the Second Law of Thermodynamics is a guiding principle in the improvement of heat engines.

This paper describes an investigation of chromium-base alloys, a class of heat-resistant materials not well known. The investigation was supervised during its entirety—a period of 3½ yr.—by the War Metallurgy Committee of the National Defense Research Committee, through contract with Climax Molybdenum Co. It was part of a project entitled “Development of Heat-Resistant Metals for Gas Turbine Parts.” In particular, the heat-resistant metals being sought were for use as gas-turbine blades rotating in an oxidizing atmosphere at temperatures up to 1600 F. (870 C.). During the final year of the investigation, the alloys were applied experimentally as erosion-resistant materials for ordnance uses under the supervision of Division One, NDRC.

This paper, therefore, is based in whole or in part on work done for the Office of Scientific Research and Development under Contracts OEMsr-457 and OEMsr-1273.
Compressive Properties of Aluminum Alloy Sheet at Elevated Temperatures
Authors: Flanigan Alan E. , Tedsen Leslie F. , Dorn John E.
Published: September 2009

Apparatus has been developed to allow the compression testing of sheet materials at elevated temperatures. It includes a testing fixture, a special extensometer, and an oil-bath furnace which are described in detail. The short-time compressive properties of five high-strength aluminum alloy sheet materials have been determined at temperatures up to 300 F. after exposures ranging from ½ to 1000 hr. The materials include 24S-T, 24S-T81, 24S-T86, R301-T, and 75S-T. The effects of temperature and time on compressive yield strength are compared with those for the corresponding tensile properties and it is found that approximate values of compressive yield strength may be derived from calculations based upon the tension values. Of the materials tested, the members of the 24S-T8 series appear to offer the best possibilities for elevated-temperature service.
Tensile and Creep Strengths of Some Magnesium-Base Alloys at Elevated Temperature
Authors: Moore A. A. , McDonald J. C.
Published: September 2009

Creep tests up to and including rupture were carried out for periods of 1000 hr. Several commercial alloys, as well as some experimental cerium-containing alloys, were studied.

At room temperature it was observed for many of the alloys that the yield strength was an adequate criterion for design of parts to be loaded steadily for long periods. At the maximum temperature of test, 300 F., this is true of cerium-containing alloys, but the commercial alloys have strengths-to-rupture less than the yield strength. The magnesium-manganese alloy, M, is the best of the commercial alloys in respect to creep properties at elevated temperature.

Magnesium-base alloys do not lose ductility at rupture under long-time conditions of loading.
Thermal Properties of Thirteen Metals
Authors: Lucks C. F. , Deem H. W.
Published: September 2009

Thermal-conductivity, linear-thermal-expansion, specific-heat, density, and thermal-diffusivity values are reported over the temperature ranges shown for the following metals: 2024-T4 and 7075-T6 aluminum from −250 to 800 F, chromium from 75 to 3000 F (thermal conductivity and diffusivity 400 to 1800 F), copper from 75 to 1900 F (density from 75 to 3000 F), Inconel and Inconel “X” from −250 to 1800 F, AN-M-29 magnesium from −250 to 600 F, molybdenum from 75 to 3000 F (thermal conductivity and diffusivity from 400 to 1600 F), “K” monel from −250 to 1800 F, SAE 1010 steel from −250 to 1650 F, stainless steels types 301, 316, and 347 from −250 to 1800 F.
Use of a TG/DTA/Raman System to Monitor Dehydration and Phase Conversions
Authors: Bigalow Kern Adrienne S. , Collins Wendy J. , Cambron R. Thomas , Redman-Furey Nancy L.
Published: September 2009

Use of a TG/DTA/Raman system enabled real time collection of Raman spectra during the dehydration of Risedronate, the active pharmaceutical ingredient in the osteoporosis drug Actonel. Raman spectra collected during the dehydration of this material show a crystal lattice adjustment below the boiling point of water facilitating interpretation of the TG/DTA thermal profile. Raman spectra also revealed recrystallization processes subsequent to loss of lattice water that were not evident in the thermal analysis profile. Spectral evidence showing the formation and disappearance of a second hydrate form are observed during the dehydration of this material. In addition, spectral evidence indicating the presence of an anhydrate form of this material are observed prior to thermal induced degradation of this material.
Characterizing Fatigue Response of Nickel-Titanium Alloys by Rotary Beam Testing
Authors: Patel Mitesh M.
Published: September 2009

Fatigue information has been reliable in predicting wire critical structural integrity. The aim of this study is to expound on the characterization technique of rotary beam fatigue testing (RBT). By alternating tension and compression stress states through RBT, it is possible to determine the life expectancy of Nitinol monofilament round wires. Fatigue testing has been employed to characterize the influence of subtle changes in inclusion content, chemistry variations of raw material, ingot transformation temperatures of Nitinol (NiTi), and surface finish conditions for implant grade wires. Currently, an ASTM standard does not exist that concentrates solely on fatigue testing shape memory alloys. By exploiting part geometry, this testing technique serves to compliment other characterization methods. Evaluation of fracture surfaces has proven useful in diagnosing the factors influencing failures. The utilization of fatigue data and fracture mechanics compliments tensile testing in providing information to the design engineer. Results from studying flexural endurance, statistical Weibull life assessment analysis, fracture analysis, and a determination of stress/strain levels at the site of failure have proven useful in determining desired material properties for next generation medical devices.
Improved Suction Technique for the Characterization of Construction Materials
Authors: Thygesen Lisbeth G. , Hansen Kurt K.
Published: September 2009

The suction technique is a method from soil science that is used for the study of moisture storage capacity in porous construction materials at high relative humidity levels (above approximately 93 %). The samples to be studied are placed in a pressurized container (an extractor) on a water saturated ceramic disk or membrane. The pressure corresponding to a certain relative humidity level is established and moisture is expelled from the samples until moisture equilibrium is reached. This paper presents two adjustments to this method and their applicability. The first adjustment is a new procedure for determining the equilibrium moisture content of samples during the experiment. The method (referred to as the balance method) is to simply keep track of all water entering and leaving the system and use these data to estimate the moisture content of the samples. The advantage of this approach is that the experiment does not need to be stopped and restarted for each relative humidity level tested. The main disadvantage of the method is that the estimation of the moisture content in the samples depends on a correct estimation of the moisture content of the ceramic disk. The second adjustment is the development of a pressure regulation system that keeps the pressure constant (±0.015 bar) within an extractor for weeks.
Moisture Buffer Value of Building Materials
Authors: Rode Carsten , Peuhkuri Ruut , Time Berit , Svennberg Kaisa , Ojanen Tuomo
Published: September 2009

When building materials are in contact with indoor air they have some capacity to moderate the variations of indoor humidity in occupied buildings. But, so far, there has been a lack of a standardized quantity to characterize the moisture buffering capability of materials. It has been the objective of a recent Nordic project to define such a quantity, and to declare it in the form of a NORDTEST method. The Moisture Buffer Value is the figure that has been developed in the project as a way to appraise the moisture buffer effect of materials, and the value is described in the paper. Also explained is a test protocol which expresses how materials should be tested for determination of their Moisture Buffer Value. Finally, the paper presents some of the results of a round robin test on various typical building materials that has been carried out in the project.
Evaluation of Functional Approaches to Describe the Moisture Diffusivity of Building Materials
Authors: Scheffler Gregor , Grunewald John , Plagge Rudolf
Published: September 2009

With a set of material parameters and a material model called engineering model of hygrothermal material characteristics, both proposed in (Scheffler, 2004), the material functions used for input to hygrothermal building component simulation programs can be adjusted. Using inverse identification of functional parameters by simulation of laboratory experiments, the model is calibrated to reproduce measured water uptake and drying curves. The developed material functions contain an approach to describe the liquid water conductivity of building materials. In addition, moisture storage data approximated by a GAUSSian functional approach, showing sufficient flexibility in the whole moisture range, is available. There with the derivative of the moisture retention curve is known at high precision and the liquid water diffusivity can be derived, too. There exists a wide interest in applicable material functions based on literature data. But literature reviews of hygrothermal material parameters often yield incomplete datasets and experimentally determined curves are lacking or are available at lower accuracy only. Different authors introduced several diffusivity approaches requiring less input parameters for description of liquid water transport in building materials. These models are evaluated by means of diffusivity data derived from the calibrated liquid water conductivity function of the engineering model. A selection of four accurately measured materials is used for this investigation. The investigation is based on controlled laboratory data of high resolution. With the knowledge gained from this study, the uncertainties in interpretation of incomplete datasets frequently encountered in literature reviews shall be reduced.
Inputs and Analyses: An End User's Perspective of Heat-Air-Moisture Data
Authors: Decareau Christopher P. , Kan Liyen , Piñon Joseph P.
Published: September 2009

Hygrothermal simulation programs (HSPs) have the potential to help the way building enclosures are designed if end users are convinced the results are reliable. However, HSPs suffer from a lack of manufacturer-specific material data. HSP users often “create” materials by scouring multiple sources for hygrothermal properties. To the less familiar HSP user, significant error can be introduced into simulations by using properties that are calculated from variable sources. Through a series of case studies, this paper illustrates how material properties can make a difference in hygrothermal calculations and, ultimately, material specification.
Energy Savings with Multigraded Diesel Lubricants — An Experimental Test Design in Winter,Urban Bus Operation
Authors: Farnsworth G. R. , Bachman H. E. , Overton R.
Published: September 2009

This paper illustrates how experimental design techniques can be employed to obtain an accurate assessment of multigrade Heavy Duty (HD) performance in the field. Compared to monograde (SAE 40) oil, the use of SAE 15W/40 oil was found to improve vehicle fuel mileage (MPG) as well as oil economy (MPQ). The demonstration, conducted in two groups of 10 city buses each in regular service, was structured to dampen out the effect of numerous incidental variables. Statistical data analysis indicate a “most probable” improvement in fuel mileage of 2.7% as well as a 47% increase on multigraded oil economy.
The Use of Time/Temperature Additive Release Package in the Automotive Lubrication System
Authors: Bethell Michael R. , Browne Paul S. , Hegel Robert W.
Published: September 2009

A system combining an oil filter with a supplementary time/temperature additive release package has been developed which provides a non-conventional but very effective means of maintaining the viscosity level in the operating engine. Simultaniously, the system introduces certain other additives important to the engine oil performance. Studies of this system have been conducted to better understand the additive delivery rate as a function of operating conditions in the engine. This data shows that the system is generally beneficial and effective in actual field performance as well as in stationary engine test sequences.
Friction Power Loss of Mineral and Synthetic Lubricants in a Running Engine
Authors: Badiali F. L. , Cassiani Ingoni A. A. , Pusateri G.
Published: September 2009

The performance of single grade and multigrade oils and synthetic oils, has been eva luated in terms of friction power loss using an engine running on the test bed according to a modified Morse procedure. The results obtained show a good correlation between the engine performance and the Theological proper ties of the lubricants. The very low friction power loss experiern ced when using lubricants containing polymer can be explained by introducing the concept of anisotropic effective viscosity. Based on the good correlation between the measured and calculated friction generated in main bearings, a method has been devised for evaluating the temporary viscosity losses of multigrade oils by measuring the en gine friction power loss and bearing temperatures.
European Activity Concerning Engine Oil Viscosity Classification—Part II
Authors: Eberan-Eberhorst C. G.A. , Di Lelio G. F. , Cassiani Ingoni A. A.
Published: September 2009

This paper is a follow-up to Part 1 of the review on European work in the field of engine oil viscosity relevant to the revision of SAE J 300 classification. The European activity covers both low and high temperature aspects and is coordinated within C.E.C., Investigation Groups IGL-8 and IGL-9 respectively. The IGL-8 activity is well under way and results have already been generated in three main areas: — the replies of the European engine builders to the SAE Questionnaire on low temperature practices and experience have indicated that there is quite a scatter in the low temperature viscometric requirements of different engines similar to that shown in the U.S.A. — the Borderline Pumping Temperatures determined with four ASTM pumpability reference oils on eight different European engines have shown a wide spectrum of engine sensitivity although the average results are similar to the data generated by ASTM. — regarding metrication of SAE J 300, European opinion expressed through the C.E.C. National organisations is strongly of the opinion that the 15W grade should be incorporated into the main body of the table and that minimum viscosity values should be assigned to the W grades in order to avoid confusion. The IGL-9 work on high temperature aspects has concentrated on the viscosity measurements of seven multigrade oils in laboratory apparatus at different temperatures and rates of shear, and the results look encouraging. The next immediate step will concern engine testing of the same reference oils in an attempt to generate information on the behaviour of these lubricants in several high temperature engine performance areas. The completion of this work is necessary before attempting any correlation between practical experience and oil viscosity characteristics as defined in one or more laboratory test methods.
The Effect of Polymeric, Ammonium Sulfate-Based Adjuvants on the Deposition of Glyphosate Spray Solutions
Authors: Rose Simon A. H. , Lyons Lynn , Whitehead Mark
Published: September 2009

High molecular weight polymers have been shown to improve the efficacy of systemic herbicides such as glyphosate. The mode of activity of these polymeric adjuvants is not well understood. In this study a commercial polymer/ammonium sulfate (AMS)-based adjuvant was tested with commercial glyphosate formulations. The effect of the various treatments on the mass of spray deposited, droplet bounce, and droplet run-off was determined. The polymeric/AMS adjuvant was found to improve the deposition of the commercial glyphosate formulations in that: the loss of active due to spray drift was reduced, i.e., the mass of spray deposited was increased; droplet bounce of the spray solutions was reduced, i.e., droplet retention was improved; the polymeric/AMS adjuvant did not significantly affect the angle at which droplets were detached from leaves, therefore the adjuvant should not affect droplet run-off.
Nozzle-Adjuvant Formulation Interactions: Implications on Herbicide Efficacy
Authors: McMullan Patrick M. , Thurman Steve , McManic Greg , Brigance Mickey
Published: September 2009

A series of adjuvants were developed to improve herbicide performance when applied through air induction nozzles. A series of research trials were conducted in 2004 and 2005 with clethodim, foramsulfuron, and glyphosate. Efficacy of these herbicides was reduced in over 30 % of all cases when applied through air induction nozzles compared to conventional flatfan nozzles. However, when modified forms of the adjuvants were used, efficacy increased approximately 25 % of cases with glyphosate, 40 % of cases with clethodim, and 90 % of cases with foramsulfuron when using air induction nozzles. A separate series of oil-based adjuvants developed had over 20 % air entrapment whereas conventional oil-based adjuvants had 5 % or less air entrapment when using air induction nozzles. Research conducted in the field in 2005 indicated that these novel formulations may improve herbicide efficacy.
Impact of Adjuvants on Droplet Spreading and Droplet Deposit Area After Spray Application
Authors: Baur Peter
Published: September 2009

The effects of adjuvants on spreading of small droplets after spray application and of larger drops with volumes in the microliter range was studied. The characterization of spreading as affected by adjuvants is done often with lab tests on artificial surfaces. In these tests much larger drops in the microliter range are used and plant factors such as the presence of hairs or crystalline waxes and spray related factors such as rapid evaporation, a different drop size magnitude, a drop size distribution in reality, and effects of adjuvants on drop size are not considered. For a set of test compounds from different chemical classes we evaluated stepwise the approximation to real systems with plant surfaces representing the major surface features. With larger drops of 10 and 20 µl we obtained a surprisingly good correlation of spreading on Parafilm® M and the mature leaves of Chlorophytum, tomato, rape, and corn. With good wetters better spreading was observed on leaves than on Parafilm M. The correlation of spread diameters with real spray (flat fan nozzle, 300 l/ha) on an easily wettable plant and drops on Parafilm M was very good as well though with the best spreaders the gravimetric momentum on spreading and longer times for evaporation overestimated spreading of the larger droplets on Parafilm M. If the mean spread diameters of real spray was plotted vs. the logtransformed spread diameter on Parafilm M a linear correlation was obtained (r2=0.92).
Spray Adjuvant Effects on Droplet Size Spectra Measured by Three Laser-Based Systems in a High-Speed Wind Tunnel
Authors: Hoffmann W. Clint , Hewitt A. J. , Ross J. B. , Bagley W. E. , Martin D. E. , Fritz B. K.
Published: September 2009

Spray droplet size has long been recognized as the most important variable that aerial applicators can influence to mitigate spray drift from the application site. There are several different technologies that are used by researchers to measure droplet size from spray nozzles. The objective of these studies was to determine the influence of eight spray adjuvants on the droplet size spectrum produced by two nozzles in a high-speed wind tunnel when characterized using three different droplet size measurement systems. The adjuvant, nozzles, and airspeeds used in these studies are commonly used by aerial applicators. Three droplet sizing systems (Malvern laser diffraction, PMS optical array probe, and LaVision laser imaging) were simultaneously operated to measure the spray droplet size spectra for each adjuvant, airspeed, and nozzle combination. Two spray nozzles (a D6-46 nozzle and a D2 straight stream nozzle) were evaluated in a high-speed wind tunnel at airspeeds of 45 and 58 m/sec. There were significant differences in the droplet size spectra produced by the eight spray adjuvants tested. There were also significant differences between the droplet size values reported by the three measurement systems (Malvern, LaVision, and PMS) evaluated; however, there was considerable agreement trendwise. In general, the Malvern reported smaller spray droplet size spectra values than the LaVision, while the PMS system generally reported the largest spray droplet size spectra values. These tests are the first reported studies where all three droplet sizing systems were operated simultaneously.
Part I—Measurement of Earth Pressure and Deflection Along the Embedded Portion of a 40-ft Steel Pile
Authors: Mason H. G. , Bishop J. A.
Published: September 2009

The details of a test installation in which a full scale pile was embedded in an earth fill and subjected to lateral loads are outlined. The authors describe the instrumentation, including means of measuring pressures and deflections at intervals along the entire pile length. An example of the pressures and deflections obtained is presented and a comparison is made between measured and theoretical values. Two methods of solving simultaneous difference equations such as those involved in the analysis of the problem of computing lateral earth pressures, deflections, shears, and moments along the embedded length of a pile are introduced.
Part II—Analysis of Pressure Deflection, Moment, and Shear by the Method of Difference Equations
Authors: Palmer L. A. , Brown P. P.
Published: September 2009

Part II utilizes the earth-pressure and pile-deflection data contained in Part I to show the effect of different variables, particularly the parameters, k and n, on the magnitude of the maximum bending moment in the pile and the depth at which it occurs. This part also outlines applications of the data and their analyses in engineering design and presents a concise system for defining the expressions used in the method of differences as applied to the problems. The data presented in Part I are used in Part II for computing moments and shears along the embedded pile length and to evaluate the separate variables, stiffness factor of pile, width of pile pushed against soil, the height of thrust above the ground line and the parameters, k and n, with respect to their effects on earth pressures, pile deflections, and shears and moments at all depths of pile embedment. The following conclusions are restricted to the conditions of tests as described in Part I: (1) There is good agreement between the measured and theoretical earth pressures and pile deflections. (2) The most realistic earth-pressure-distribution curves are obtained with n values that are between zero and unity. (3) Laboratory tests have thus far not been adequate for determining suitable values for k and n. Those values can be determined from lateral load tests. (4) The variables, stiffness factor, height of thrust above grade, width of pile, and depth of pile embedment, have surprisingly small effects on the magnitude of the maximum moment and its location in the pile. (5) The magnitude of the maximum bending moment is much less than usually supposed and as usually computed. (6) The depth below grade of the maximum moment is much less than is commonly supposed. (7) The magnitude of the peak earth pressure far exceeds the passive earth pressure as computed from classical earth pressure theories.
A Genome-Wide Screen for Spatially Restricted Expression Patterns Identifies Transcription Factors That Regulate Glial Development
Authors: Fu Hui , Cai Jun , Clevers Hans , Fast Eva , Gray Susan , Greenberg Rachel , Jain Mukesh K. , Ma Qiufu , Qiu Mengsheng , Rowitch David H. , Taylor Christopher M. , Stiles Charles D.
Published: September 2009

Forward genetic screens in genetically accessible invertebrate organisms such asDrosophila melanogasterhave shed light on transcription factors that specify formation of neurons in the vertebrate CNS. However, invertebrate models have, to date, been uninformative with respect to genes that specify formation of the vertebrate glial lineages. All recent insights into specification of vertebrate glia have come via monitoring the spatial and temporal expression patterns of individual transcription factors during development. In studies described here, we have taken this approach to the genome scale with anin silicoscreen of the Mahoney pictorial atlas of transcription factor expression in the developing CNS. From the population of 1445 known or probable transcription factors encoded in the mouse genome, we identify 12 novel transcription factors that are expressed in glial lineage progenitor cells. Entry-level screens for biological function establish one of these transcription factors, Klf15, as sufficient for genesis of precocious GFAP-positive astrocytes in spinal cord explants. Another transcription factor, Tcf4, plays an important role in maturation of oligodendrocyte progenitors.
Brain-Derived Neurotrophic Factor Controls Activity-Dependent Maturation of CA1 Synapses by Downregulating Tonic Activationof Presynaptic Kainate Receptors
Authors: Sallert Marko , Rantamäki Tomi , Vesikansa Aino , Anthoni Heidi , Harju Kirsi , Yli-Kauhaluoma Jari , Taira Tomi , Castren Eero , Lauri Sari E.
Published: September 2009

Immature hippocampal synapses express presynaptic kainate receptors (KARs), which tonically inhibit glutamate release. Presynaptic maturation involves activity-dependent downregulation of the tonic KAR activity and consequent increase in release probability; however, the molecular mechanisms underlying this developmental process are unknown. Here, we have investigated whether brain derived neurotrophic factor (BDNF), a secreted protein implicated in developmental plasticity in several areas of the brain, controls presynaptic maturation by regulating KARs.

Application of BDNF in neonate hippocampal slices resulted in increase in synaptic transmission that fully occluded the immature-type KAR activity in area CA1. Conversely, genetic ablation of BDNF was associated with delayed synaptic maturation and persistent presynaptic KAR activity, suggesting a role for endogenous BDNF in the developmental regulation of KAR function. In addition, our data suggests a critical role for BDNF TrkB signaling in fast activity-dependent regulation of KARs. Selective acute inhibition of TrkB receptors using a chemical–genetic approach prevented rapid change in synapse dynamics and loss of tonic KAR activity that is typically seen in response to induction of LTP at immature synapses.

Together, these data show that BDNF–TrkB-dependent maturation of glutamatergic synapses is tightly associated with a loss of endogenous KAR activity. The coordinated action of these two receptor mechanisms has immediate physiological relevance in controlling presynaptic efficacy and transmission dynamics at CA3–CA1 synapses at a stage of development when functional contact already exists but transmission is weak.
Aberrant Frontoparietal Function during Recognition Memory in Schizophrenia: A Multimodal Neuroimaging Investigation
Authors: Weiss Anthony P. , Ellis Cameron B. , Roffman Joshua L. , Stufflebeam Steven , Hamalainen Matti S. , Duff Margaret , Goff Donald C. , Schacter Daniel L.
Published: September 2009

Prefrontal–parietal networks are essential to many cognitive processes, including the ability to differentiate new from previously presented items. As patients with schizophrenia exhibit structural abnormalities in these areas along with well documented decrements in recognition memory, we hypothesized that these patients would demonstrate memory-related abnormalities in prefrontal and parietal physiology as measured by both functional magnetic resonance imaging and magnetoencephalography (MEG). Medicated outpatients with schizophrenia (n= 18) and age-matched healthy control subjects (n= 18) performed an old–new recognition memory task while physiological data were obtained. Whereas controls exhibited strong, bilateral activation of prefrontal and posterior parietal regions during successful identification of old versus new items, patients exhibited greatly attenuated activation of the right prefrontal and parietal cortices. However, within the patient group, there was strong correlation between memory performance and activation of these right-sided regions as well as a tight correlation between old–new effect-related activations in frontal and parietal regions, a pattern not seen in control subjects. Using MEG, control subjects—but not patients—exhibited a sequential pattern of old > new activity in the left posterior parietal cortex and then right prefrontal cortex; however, patients uniquely exhibited old > new activity in right temporal cortex. Collectively, these findings point to markedly different distributions of regional specialization necessary to complete the old–new item recognition task in patients versus controls. Inefficient utilization of prefrontal–parietal networks, with compensatory activation in temporal regions, may thus contribute to deficient old–new item recognition in schizophrenia.
KV7/M Channels Mediate Osmotic Modulation of Intrinsic Neuronal Excitability
Authors: Caspi Anna , Benninger Felix , Yaari Yoel
Published: September 2009

Modest decreases in extracellular osmolarity induce brain hyperexcitability that may culminate in epileptic seizures. At the cellular level, moderate hyposmolarity markedly potentiates the intrinsic neuronal excitability of principal cortical neurons without significantly affecting their volume. The most conspicuous cellular effect of hyposmolarity is converting regular firing neurons to burst-firing mode. This effect is underlain by hyposmotic facilitation of the spike afterdepolarization (ADP), but its ionic mechanism is unknown. Because blockers of KV7 (KCNQ) channels underlying neuronal M-type K+currents (KV7/M channels) also cause spike ADP facilitation and bursting, we hypothesized that lowering osmolarity inhibits these channels. Using current- and voltage-clamp recordings in CA1 pyramidal cellsin situ, we have confirmed this hypothesis. Furthermore, we show that hyposmotic inhibition of KV7/M channels is mediated by an increase in intracellular Ca2+concentration via release from internal stores but not via influx of extracellular Ca2+. Finally, we show that interfering with internal Ca2+-mediated inhibition of KV7/M channels entirely protects against hyposmotic ADP facilitation and bursting, indicating the exclusivity of this novel mechanism in producing intrinsic neuronal hyperexcitability in hyposmotic conditions.
Short Trains of Theta Frequency Stimulation Enhance CA1 Pyramidal Neuron Excitability in the Absence of Synaptic Potentiation
Authors: Fink Ann E. , O'Dell Thomas J.
Published: September 2009

Although plasticity at excitatory synapses is widely studied as a mechanism for memory formation, less is known about the properties and mechanisms underlying activity-dependent changes in excitability. Using extracellular and intracellular recordings in hippocampal slices, we find that short trains (2–3 s) of Schaffer collateral fiber stimulation delivered at 5 Hz induce a robust and persistent increase in the excitability of CA1 pyramidal cells in the absence of synaptic potentiation. This change in excitability is input specific, NMDA receptor dependent, and is not accompanied by lasting changes in either inhibitory synaptic transmission or somatic excitability. Although many of these properties are similar to those seen in synaptic long-term potentiation (LTP), the increase in CA1 pyramidal cell excitability was not blocked by inhibitors of several protein kinases required for the induction of LTP by theta frequency stimulation. Instead, 5 Hz stimulation-induced changes in neuronal excitability were blocked by inhibitors of the protein phosphatase calcineurin. Together, our results suggest that very brief bouts of theta frequency synaptic activity induce a selective, persistent, and dendritically localized increase in CA1 pyramidal cell excitability that might have an important role in both information storage and metaplasticity.
Dopamine Is Necessary for Cue-Dependent Fear Conditioning
Authors: Fadok Jonathan P. , Dickerson Tavis M. K. , Palmiter Richard D.
Published: September 2009

Dopamine (DA) is implicated in many behaviors, including motor function, cognition, and reward processing; however, the role of DA in fear processing remains equivocal. To examine the role of DA in fear-related learning, dopamine-deficient (DD) mice were tested in a fear-potentiated startle paradigm. DA synthesis can be restored in DD mice through administration of 3, 4-dihydroxy-l-phenylalanine (l-Dopa), thereby permitting the assessment of fear processing in either a DA-depleted or -replete state. Fear-potentiated startle was absent in DD mice but could be restored byl-Dopa administration immediately after fear conditioning. Selective viral-mediated restoration of DA synthesis within the ventral tegmental area fully restored fear learning in DD mice, and restoration of DA synthesis to DA neurons projecting to the basolateral amygdala restored short-term memory but not long-term memory or shock sensitization. We also demonstrate that the DA D1receptor (D1R) and D2-like receptors are necessary for cue-dependent fear learning. These findings indicate that DA acting on multiple receptor subtypes within multiple target regions facilitates the stabilization of fear memory.
Differential Engagement of the Ventromedial Prefrontal Cortex by Goal-Directed and Habitual Behavior toward Food Pictures in Humans
Authors: de Wit Sanne , Corlett Philip R. , Aitken Mike R. , Dickinson Anthony , Fletcher Paul C.
Published: September 2009

According to dual-system accounts, instrumental learning is supported by both a goal-directed and a habitual system. Although behavioral control by the goal-directed system, through outcome–action associations, dominates with moderate training, stimulus–response associations are thought to form concurrently in the habit system. It is therefore challenging to isolate the neural substrate of the goal-directed system in neuroimaging research with healthy human volunteers. Recently, however, de Wit et al. (2007) developed an instrumental discrimination task that distinguishes between goal-directed and habit-based responding. In this task, cues are congruent, unrelated, or incongruent with subsequent outcomes. Whereas performance on congruent and control trials can be supported by both the goal-directed and habitual system, performance on the incongruent discrimination relies solely on the habit system. In the present study, we used this task with healthy participants undergoing functional magnetic resonance imaging to demonstrate that engagement of the goal-directed system during learning is reflected in increased activity in the ventromedial prefrontal cortex. Moreover, using a subsequent outcome devaluation manipulation, we show that this area is involved in guiding decision making when goal values change, even in the absence of external cues to guide performance. We can therefore exclude a purely Pavlovian account of ventromedial prefrontal function and unequivocally demonstrate its involvement in the acquisition as well as deployment of goal-directed knowledge.
Does Retinotopy Influence Cortical Folding in Primate Visual Cortex?
Authors: Rajimehr Reza , Tootell Roger B. H.
Published: September 2009

In humans and other Old World primates, much of visual cortex comprises a set of retinotopic maps, embedded in a cortical sheet with well known, identifiable folding patterns. However, the relationship between these two prominent cortical variables has not been comprehensively studied. Here, we quantitatively tested this relationship using functional and structural magnetic resonance imaging in monkeys and humans. We found that the vertical meridian of the visual field tends to be represented on gyri (convex folds), whereas the horizontal meridian is preferentially represented in sulci (concave folds), throughout visual cortex in both primate species. This relationship suggests that the retinotopic maps may constrain the pattern of cortical folding during development.
Reward Modulates Attention Independently of Action Value in Posterior Parietal Cortex
Authors: Peck Christopher J. , Jangraw David C. , Suzuki Mototaka , Efem Richard , Gottlieb Jacqueline
Published: September 2009

While numerous studies have explored the mechanisms of reward-based decisions (the choice of action based on expected gain), few have asked how reward influences attention (the selection of information relevant for a decision). Here we show that a powerful determinant of attentional priority is the association between a stimulus and an appetitive reward. A peripheral cue heralded the delivery of reward or no reward (these cues are termed herein RC+ and RC−, respectively); to experience the predicted outcome, monkeys made a saccade to a target that appeared unpredictably at the same or opposite location relative to the cue. Although the RC had no operant associations (did not specify the required saccade), they automatically biased attention, such that an RC+ attracted attention and an RC− repelled attention from its location. Neurons in the lateral intraparietal area (LIP) encoded these attentional biases, maintaining sustained excitation at the location of an RC+ and inhibition at the location of an RC−. Contrary to the hypothesis that LIP encodes action value, neurons did not encode the expected reward of the saccade. Moreover, at odds with an adaptive decision process, the cue-evoked biases interfered with the required saccade, and these biases increased rather than abating with training. After prolonged training, valence selectivity appeared at shorter latencies and automatically transferred to a novel task context, suggesting that training produced visual plasticity. The results suggest that reward predictors gain automatic attentional priority regardless of their operant associations, and this valence-specific priority is encoded in LIP independently of the expected reward of an action.