Nondestructive SEM for surface and subsurface wafer imaging

The scanning electron microscope (SEM) is considered as a tool for both failure analysis as well as device characterization. A survey is made of various operational SEM modes and their applicability to image processing methods on semiconductor devices

Structure of the Proline Utilization A Proline Dehydrogenase Domain Inactivated by \u3ci\u3eN\u3c/i\u3e-propargylglycine Provides Insight into Conformational Changes Induced by Substrate Binding and Flavin Reduction

Proline utilization A (PutA) from Escherichia coli is a flavoprotein that has mutually exclusive roles as a transcriptional repressor of the put regulon and a membrane-associated enzyme that catalyzes the oxidation of proline to glutamate. Previous studies have shown that the binding of proline in the proline dehydrogenase (PRODH) active site and subsequent reduction of the FAD trigger global conformational changes that enhance PutA-membrane affinity. These events cause PutA to switch from its repressor to enzymatic role, but the mechanism by which this signal is propagated from the active site to the distal membrane-binding domain is largely unknown. Here, it is shown that N-propargylglycine irreversibly inactivates PutA by covalently linking the flavin N(5) atom to the ε-amino of Lys329. Furthermore, inactivation locks PutA into a conformation that may mimic the proline reduced, membrane-associated form. The 2.15 Å resolution structure of the inactivated PRODH domain suggests that the initial events involved in broadcasting the reduced flavin state to the distal membrane binding domain include major reorganization of the flavin ribityl chain, severe (35 degree) butterfly bending of the isoalloxazine ring, and disruption of an electrostatic network involving the flavin N(5), Arg431, and Asp370. The structure also provides information about conformational changes associated with substrate binding. This analysis suggests that the active site is incompletely assembled in the absence of the substrate, and the binding of proline draws together conserved residues in helix 8 and the β1-αl loop to complete the active site

Economic Growth and Agricultural Trade of Less-Developed Countries: Technical Report

The United States has an extensive assistance program for less developed countries (LDCs), although its contribution is the lowest among the developed market economies in percent of allocated GNP (OECD 1988). On average for 1985/86, about 11.2 percent or $1.05 billion (1985 prices and exchange rates) of U.S. official development assistance was related directly to agricultural production (OECD 1988). The impact of agricultural development assistance on U.S. agricultural export markets is a concern of the U.S. government and agricultural producers, especially in periods of excess supplies of agricultural commodities. Specifically, U.S. policy makers and producers ask whether development assistance emphasizing agriculture in LDCs is consistent with policies to promote or enhance exports of U.S. agricultural commodities and increase income to the domestic agricultural sector

3-D Structural Modeling of Humic Acids through Experimental Characterization, Computer Assisted Structure Elucidation and Atomistic Simulations. 1. Chelsea Soil Humic Acid

This paper describes an integrated experimental and computational framework for developing 3-D structural models for humic acids (HAs). This approach combines experimental characterization, computer assisted structure elucidation (CASE), and atomistic simulations to generate all 3-D structural models or a representative sample of these models consistent with the analytical data and bulk thermodynamic/structural properties of HAs. To illustrate this methodology, structural data derived from elemental analysis, diffuse reflectance FT-IR spectroscopy, 1-D/2-D ^1H and ^(13)C solution NMR spectroscopy, and electrospray ionization quadrupole time-of-flight mass spectrometry (ESI QqTOF MS) are employed as input to the CASE program SIGNATURE to generate all 3-D structural models for Chelsea soil humic acid (HA). These models are subsequently used as starting 3-D structures to carry out constant temperature-constant pressure molecular dynamics simulations to estimate their bulk densities and Hildebrand solubility parameters. Surprisingly, only a few model isomers are found to exhibit molecular compositions and bulk thermodynamic properties consistent with the experimental data. The simulated ^(13)C NMR spectrum of an equimolar mixture of these model isomers compares favorably with the measured spectrum of Chelsea soil HA

The Ursinus Weekly, April 28, 1941

Causes of cancer told to pre-meds by Pfahler • Manchester to sub for Wallace May 6 • Besse Howard will speak at forum Wednesday on topic, Spring, 1941 • Sub-frosh to view Ursinus this Saturday • May hop to feature music of Woody Leh • \u27Unity in diversity\u27 will be conference theme on May 7 • The Ursinus weekend travelogue around the circuit • Play \u27Lightnin\u27 centers around Calivada Hotel • Sixteen visit medical centers on excursion to New York • Five attend chemistry conference at Villanova • Powers of God are subject of vespers • Herber is pre-legal prexy • Meistersingers plan spring concert, May 1 • French Club to hear talk on prestige of French tongue • Debaters elect Lownes prexy; mixed team meets Drexel • Kriebel, Hartman to present reviews of Hilton and Brittain • Class of 1940 makes the grade in business and graduate work • IRC elects Byron president; discusses plans for next year • Local draft boards to weigh claims of students for deferment • Baseballers lose to Mules 3-2; trounce Dickinson 12-2 • Irvin paces track squad to victory over Delaware clan by 65-61 score • Netmen blank Lions in season opener • Co-ed net squad defeats Penn and Albright lassies • Zulick and Baberick win as Moravian beats golfers 3-2 • Freshman girls lead race in class softball league • Doc Baker heads old English game at Ursinus • Carter\u27s articles appear in historical dictionary • Hobos and bums to have poverty ball Saturday • Y officers to be inducted in service on Sundayhttps://digitalcommons.ursinus.edu/weekly/1816/thumbnail.jp

Analysis of boundary layer sounding data from the FIRE Marine Stratocumulus Project

October 1987.FIRE volume 2 on cover.Includes bibliographical references.We present an analysis of the boundary layer thermodynamic data obtained by the CLASS radiosonde system during the marine boundary layer experiment on San Nicolas Island in the summer of 1987. The analysis procedure retains the highest possible vertical resolution in the data. Plots of temperature, dew point temperature, potential temperature, equivalent potential temperature and saturation equivalent potential temperature are presented for each of the sixty-nine soundings taken during FIRE. Conditions were mostly cloudy with fifty-five of the sixty-nine soundings being released with stratocumulus overhead. For the fifty-live cloudy soundings, cloud top Jumps of equivalent potential temperature i, and total water mixing ratio r were also determined. Each of these soundings is then represented by a point in the (~11., ~r) plane. Fifteen of these soundings are on the unstable aide of the evaporative instability line, and there appears to be some tendency for break-up under these conditions

Dendritic Anion Hosts: Perchlorate Uptake by G5-NH_2 Poly(propyleneimine) Dendrimer in Water and Model Electrolyte Solutions

Perchlorate (ClO_4^-) has emerged as a major groundwater and surface water contaminant in the United States. Ion exchange (IX) is the most widely used technology for treating water containing lower concentrations of perchlorate (<100 ppb). However, a major drawback of IX is the need for frequent regeneration or disposal of the perchlorate-laden resins. As a first step toward the development of high-capacity, selective and recyclable dendritic ligands for the recovery of perchlorate from aqueous solutions by dendrimer filtration, we tested the hypothesis that dendrimers with hydrophobic cavities and positively charged internal groups should selectively bind ClO_4^- over more hydrophilic anions such as Cl^-, NO_3^-, SO_4^(2-), and HCO_3^-. We measured the uptake of ClO_4^- by the fifth generation (G5-NH_2) poly(propyleneimine) (PPI) dendrimer with a diaminobutane core and terminal NH_2 groups in deonized water and model electrolyte solutions as a function of (i) anion−dendrimer loading, (ii) solution pH, (iii) background electrolyte concentration, and (iv) reaction time. The ClO_4^- binding capacity of this dendrimer is comparable to those of perchlorate-selective IX resins. However, its ClO_4^- binding kinetics is faster and reaches equilibrium in ∼1 h. Note also that only a high pH (∼9.0) aqueous solution is needed to release more than 90% of the bound ClO_4^- anions by deprotonation of the dendrimer tertiary amine groups. The overall results of this study suggest that dendritic macromolecules such as the G5-PPI NH_2 dendrimer provide ideal building blocks for the development of high-capacity, selective and recyclable ligands for the recovery of anions such as perchlorate from aqueous solutions by dendrimer enhanced filtration