bluuebunny/crossref_metadata_2025 huggingface dataset:
Two Parties, Two Types of Nominees, Two Paths to Winning a Presidential Nomination, 1972‐2004
Authors: BERGGREN D. JASON
Published: April 2007

Contrary to findings that show the contemporary nomination process, regardless of party, favoring early frontrunners, this article shows that the eventual Democratic nominee is typically different from and often travels a different path to victory than the eventual Republican nominee. Since 1972, the eventual Democratic winners began as relatively unknown candidates with single‐digit support who emerge as the frontrunner late in the process, sometimes just before the voting begins in Iowa and New Hampshire and sometimes just after the first votes are cast. John Kerry is only the latest Democratic example. In contrast, Republican winners have been national figures and have consistently been the early favorites a year before any votes were cast or large sums of money raised. To date, the accuracy of partyless models is driven largely by Republican successes. These models may be better at predicting Republican nominees than predicting Democratic nominees.
Agreeable Administrators? Analyzing the Public Positions of Cabinet Secretaries and Presidents
Authors: BERTELLI ANTHONY M. , GROSE CHRISTIAN R.
Published: April 2007

Cabinet secretaries represent their departments when testifying before Congress on a broad range of legislation. Do they also represent the president's views on such legislation? Consistent with institutional theories of the presidency, we posit that, in some instances, cabinet secretaries take public positions contrary to those of the president, suggesting ideological distinctions between presidents and their appointed secretaries. We examine all congressional testimonies of secretaries of labor, commerce, and agriculture from 1991 to 2002, coding their positions taken on legislation considered on the floor of the Senate. Though these public disagreements are infrequent, our evidence suggests that agreement is more likely as support for the president's position among oversight committee members increases, yet less likely as secretaries’ tenure in office increases.
Policy Speech in the Nineteenth Century Rhetorical Presidency: The Case of Zachary Taylor's 1849 Tour
Authors: ELLIS RICHARD J. , WALKER ALEXIS
Published: April 2007

Jeffrey Tulis's The Rhetorical Presidency (1987) is among the most influential accounts of the historical development of the American presidency. According to Tulis, the nineteenth‐century presidency embodied the founders' proscriptions against the rhetorical presidency in several ways. Chief among these were that “unofficial” speeches were generally few in number and limited to vague, innocuous utterances that avoided specific policies or partisan debates. In this article we test Tulis's portrayal of the nineteenth‐century “Old Way” by focusing on the presidential tour taken by Zachary Taylor in the summer of 1849. Taylor's speeches on tour, according to Tulis, were limited to the purpose of acknowledging greetings and expressing thanks for a town's welcome. Taylor's speaking tour was thus an archetype of the “laconic” style characteristic of the nineteenth‐century Old Way. Our research indicates that Tulis's characterization of Taylor's tour is mistaken. We find that not only did Taylor discuss public policy throughout his tour but that the issue positions he staked out were harnessed to a strategic partisan agenda. These findings raise larger questions about the accuracy of Tulis's portrayal of a nineteenth‐century Old Way governed by settled norms or an agreed upon rhetorical doctrine. Our research suggests instead that mid‐nineteenth‐century presidents were buffeted by competing expectations. On the one hand were the expectations and constraints that stemmed from the founders' plan for a president above party, and on the other hand were the expectations and demands that stemmed from the president's role as a party leader. Taylor's speeches reveal a president trying to navigate between these colliding expectations.
An Evaluation of the Bush Administration Reforms to the Regulatory Process
Authors: SHAPIRO STUART
Published: April 2007

The Bush administration has implemented more reforms to the regulatory process than any of its predecessors. These reforms are often stereotyped as anti‐regulatory. This article examines the reforms as a whole and asks which interests have been empowered by the Bush administration regulatory reforms. I believe this method is a more effective way of assessing the impact of the reforms. I find that, in addition to adding potential costs to the regulatory process, the reforms are likely to empower powerful interest groups and the presidency. Whether the impact of these reforms is pro‐regulation or anti‐regulation will depend on how a future administration more dedicated to regulatory protections uses them. I also lay out a research agenda to better empirically assess the impact of these regulatory reforms.
The “Hidden Hand” and White House Roll‐Call Predictions: Legislative Liaison in the Eisenhower White House, 83d‐84th Congresses
Authors: CONLEY RICHARD S. , YON RICHARD M.
Published: April 2007

This article offers a fresh perspective into the Eisenhower administration's attempts to predict and influence roll‐call outcomes in Congress during the transition from Republican to Democratic control following the midterm elections of 1954. Analysis of archival data uncovered at the Eisenhower Presidential Library in Abilene, Kansas, provides insight into a different facet of Eisenhower's “hidden‐hand presidency” and early efforts to systematize congressional liaison. Using headcount data assembled by the Legislative Liaison Unit, this research assesses the accuracy of forecasts of presidential legislative support in the House of Representatives. A multinomial logit model is developed to account for the basis of successful and unsuccessful White House estimates of members' positions. On the subset of votes the White House found difficult to predict, the empirical model highlights that the least accurate forecasts of individual members' positions are best explained by constituency factors, partisan politicking, and disunity in the Republican House Conference.
The Contemporary President: Should the Senate Take a Floor Vote on a Presidential Judicial Nominee?
Authors: CROCKETT DAVID A.
Published: April 2007

President George W. Bush has argued that the Senate ought to hold final up‐or‐down floor votes on all of his judicial nominations rather than use various parliamentary procedures to prevent such action. Some scholars argue that there is no traditional mandate for such a demand, and that the Senate is well within its prerogatives to deny the president's request. This article revisits the question of Senate parliamentary procedures and the president's function to nominate individuals to the judicial branch. The article examines Founding‐era debates to determine whether current practice comports with the logic and design of the system. By focusing on similar constitutional procedures from a separation‐of‐powers perspective, the article argues that filibusters of judicial nominations are not well founded in constitutional logic. The article concludes by evaluating whether such a change would lead to excessive presidential influence in staffing the judiciary.
Elections: Debating the 1976 Debates: Establishing a Tradition of Negotiations
Authors: SELF JOHN W.
Published: April 2007

The 1976 presidential campaign brought televised presidential debates back to the presidential campaign after a 16‐year absence. Like every presidential campaign debate, the 1976 debates were carefully planned and negotiated before they aired in the fall. The negotiators, much like the negotiators in 1960, gained control of the negotiations as well as the debates. This article culls together information from many sources to reveal how the 1976 debates were negotiated between the Ford and Carter campaigns as well as the League of Women Voters. This article is part of a larger project to develop a theory of presidential debate negotiation.
The Law: Unilaterally Shaping U.S. National Security Policy: The Role of National Security Directives
Authors: GORDON VIKKI
Published: April 2007

In recent times, some scholars have discussed a new way in which to view presidential power, one that considers the president's ability to effect policy change unilaterally without the consent of Congress or the courts. The limits of presidential power can still be defined essentially by the ability and willingness of Congress and the courts to constrain it. However, the use of national security directives poses particular challenges to the abilities of both Congress and the courts to constrain effectively the president's power to act unilaterally in setting public policy. Drawing upon continuing research, this article offers some preliminary observations and insights into the role of national security directives and how they have contributed to shaping U.S. national security policy.
Vadose Zone–Attenuated Artificial Recharge for Input to a Ground Water Model
Authors: Nichols William E. , Wurstner Signe K. , Eslinger Paul W.
Published: April 2007

Accurate representation of artificial recharge is requisite to calibration of a ground water model of an unconfined aquifer for a semiarid or arid site with a vadose zone that imparts significant attenuation of liquid transmission and substantial anthropogenic liquid discharges. Under such circumstances, artificial recharge occurs in response to liquid disposal to the vadose zone in areas that are small relative to the ground water model domain. Natural recharge, in contrast, is spatially variable and occurs over the entire upper boundary of a typical unconfined ground water model. An improved technique for partitioning artificial recharge from simulated total recharge for inclusion in a ground water model is presented. The improved technique is applied using data from the semiarid Hanford Site. From 1944 until the late 1980s, when Hanford’s mission was the production of nuclear materials, the quantities of liquid discharged from production facilities to the ground vastly exceeded natural recharge. Nearly all hydraulic head data available for use in calibrating a ground water model at this site were collected during this period or later, when the aquifer was under the diminishing influence of the massive water disposals. The vadose zone is typically 80 to 90 m thick at the Central Plateau where most production facilities were located at this semiarid site, and its attenuation of liquid transmission to the aquifer can be significant. The new technique is shown to improve the representation of artificial recharge and thereby contribute to improvement in the calibration of a site‐wide ground water model.
Using PHREEQC to Simulate Solute Transport in Fractured Bedrock
Authors: Lipson David S. , McCray John E. , Thyne Geoffrey D.
Published: April 2007

The geochemical computer model PHREEQC can simulate solute transport in fractured bedrock aquifers that can be conceptualized as dual‐porosity flow systems subject to one‐dimensional advective‐dispersive transport in the bedrock fractures and diffusive transport in the bedrock matrix. This article demonstrates how the physical characteristics of such flow systems can be parameterized for use in PHREEQC, it provides a method for minimizing numerical dispersion in PHREEQC simulations, and it compares PHREEQC simulations with results of an analytical solution. The simulations assumed a dual‐porosity conceptual model involving advective‐reactive‐dispersive transport in the mobile zone (bedrock fracture) and diffusive‐reactive transport in the immobile zone (bedrock matrix). The results from the PHREEQC dual‐porosity transport model that uses a finite‐difference approach showed excellent agreement compared with an analytical solution.
An Experimental Investigation of Nitrogen Gas Produced during Denitrification
Authors: Istok J.D. , Park M. M. , Peacock A. D. , Oostrom M. , Wietsma T. W.
Published: April 2007

In situ denitrification relies on indigenous microorganisms to reduce nitrate to N2 gas. However, when initial nitrate concentrations are large, produced gas volumes also can be very large, potentially resulting in reduced water saturation and hydraulic conductivity in the treatment zone. In this study, we investigated the fate of N2 and other gases produced during denitrification in a laboratory flow cell containing packed sediment. Denitrifying activity was stimulated by additions of nitrate and ethanol. Microbial activity was monitored by measuring nitrate, nitrite, and ethanol concentrations; gas saturations were measured during the experiment using a gamma imaging system. Biomass was measured using phospholipid fatty acid analysis of sediment samples. Bioenergetic calculations calibrated to measured nitrate consumed and biomass produced predicted that 1.2 L N2 gas/L water should have been produced following the addition of 100 mM nitrate. However, the maximum measured gas saturation was only 23%, indicating substantial gas loss from the sediment pack. Temporal gamma images and visual observations confirm that small gas bubbles formed in the sediment pack coalesced into larger bubbles and migrated upward through gas‐filled channels to the sediment pack surface. Although gas saturations increased, there was no significant change in sediment pack hydraulic conductivity. These results suggest that in permeable reactive barriers used for in situ denitrification, gas production will not necessarily lead to unlimited gas accumulation in the pore space and that the effects of gas production on water saturation and hydraulic conductivity may be relatively minor.
Predicting the Tails of Breakthrough Curves in Regional‐Scale Alluvial Systems
Authors: Zhang Yong , Benson David A. , Baeumer Boris
Published: April 2007

The late tail of the breakthrough curve (BTC) of a conservative tracer in a regional‐scale alluvial system is explored using Monte Carlo simulations. The ensemble numerical BTC, for an instantaneous point source injected into the mobile domain, has a heavy late tail transforming from power law to exponential due to a maximum thickness of clayey material. Haggerty et al.’s (2000) multiple‐rate mass transfer (MRMT) method is used to predict the numerical late‐time BTCs for solutes in the mobile phase. We use a simple analysis of the thicknesses of fine‐grained units noted in boring logs to construct the memory function that describes the slow decline of concentrations at very late time. The good fit between the predictions and the numerical results indicates that the late‐time BTC can be approximated by a summation of a small number of exponential functions, and its shape depends primarily on the thicknesses and the associated volume fractions of immobile water in “blocks” of fine‐grained material. The prediction of the late‐time BTC using the MRMT method relies on an estimate of the average advective residence time,tad. The predictions are not sensitive to estimation errors intad, which can be approximated by, whereis the arithmetic mean ground water velocity andLis the transport distance. This is the first example of deriving an analytical MRMT model from measured hydrofacies properties to predict the late‐time BTC. The parsimonious model directly and quantitatively relates the observable subsurface heterogeneity to nonlocal transport parameters.
Preoperative patient preparation for enhanced recovery after surgery
Authors: LJUNGQVIST OLLE , HAUSEL JONATAN , NYGREN JONAS , THORELL ANDERS , SOOP MATTIAS ,   IN COLLABORATION WITH THE ERAS STUDY GROUP
Published: May 2007

Enhanced recovery after surgery begins before the onset of surgery with detailed and structured preparation of the patient for the surgery they are about to go through. Detailed information to the patient and their kin at a separate occasion in advance of the admission is an important beginning. This ensures that the patient knows what they can do to enhance recovery and what to expect postoperatively including when to go home. Avoiding bowel preparation as a routine avoids unnecessary fasting and fluid derangements before the onset of surgery. Instead of the traditional overnight fasting routine that has no scientific support, modern fasting guidelines should be applied. In these, patients are recommended to take clear fluids ad libitum up until 2 hours before anesthesia. A further improved preparation can be achieved by having the patient take a carbohydrate‐rich clear drink 2 hours before anesthesia. This changes the overnight fasted state of metabolism into a fed state, improves well‐being perioperatively, and markedly reduces the metabolic derangement and the risk for hyperglycemia in the postoperative phase.
Application of Peracetic Acid and Quarternary Ammonium Disinfectants as a Part of Sanitary Treatment in a Poultry House and Poultry Processing Plant
Authors: Kašková A. , Ondrašovičová O. , Vargová M. , Ondrašovič M. , Venglovský J.
Published: May 2007

Hygiene and sanitation play a major role in any effective disease control programme for poultry production and processing premises. Various deficiencies in disinfection may induce that chains of infections are not broken from one stock to another. The present study investigated the efficacy of disinfection on a broiler farm and in a plant processing poultry from the investigated farm. Besides inspection of disinfection, the influence of contamination on broiler carcasses and consequences of this contamination on sanitation of the processing lines were studied. Swabs from surfaces coming into contact with the handled raw material were taken and evaluated. The results obtained by a standard microbiological swab method were evaluated and compared with an ATP‐bioluminescence method. The investigations included determination of total counts of microorganisms, coliform bacteria and moulds. When employing the standard plate‐count method, the total counts of microorganisms (TCM) reached <1, 1–100 and >100 CFU in 0, 12 and 88% swabs on poultry farm and in 22%, 36% and 42% swabs in the processing plant, respectively. The bioluminescence method was used only in the processing plant and contamination corresponding to <100, 100–300 and >300 relative light units (RLU) was detected in 80%, 10% and 10% swabs respectively.
Long‐Lasting Stability of Vaccinia Virus (Orthopoxvirus) in Food and Environmental Samples
Authors: Essbauer S. , Meyer H. , Porsch‐Özcürümez M. , Pfeffer M.
Published: May 2007

Poxviruses are known to remain infectious in the scabs of patients for months to years. The aim of this study was to investigate viral stability in storm water, food or gauze spiked with vaccinia virus strain Munich 1 (VACV M1). Storm water, storm water supplemented with either fetal calf serum (FCS) or potting soil was stored at two different temperatures (refrigerator, room temperature; 4°C/25°C). In addition, we analysed the viability of VACV M1 on the surface of bread, salad, sausages and gauze bandages stored at 4°C. Samples were titrated in MA 104 cells and the presence of viral DNA was demonstrated by orthopoxvirus‐specific PCRs. After 2 weeks, reisolation of VACV M1 from all kinds of food, bandage and water samples except for storm water supplemented with potting soil was possible. Viral DNA was detected in almost all samples by PCR. Prolonged experiments with VACV M1‐spiked storm water and storm water supplemented with FCS revealed that samples kept at 4.5°C are infectious for up to 166 days. Our data demonstrate that VACV M1 has a longlasting stability in water and food. The results obtained during this study should be taken into account for risk assessment calculations for poxvirus transmission. Implying that variola virus and vaccinia virus behave in a similar way, our data call for sophisticated countermeasures in cases of a variola release in biological warfare.
Dynamic and differential regulation of NKCC1 by calcium and cAMP in the native human colonic epithelium
Authors: Reynolds Amy , Parris Alyson , Evans Luke A. , Lindqvist Susanne , Sharp Paul , Lewis Michael , Tighe Richard , Williams Mark R.
Published: May 2007

The capacity of the intestine to secrete fluid is dependent on the basolateral Na+–K+–2Cl− co‐transporter (NKCC1). Given that cAMP and Ca2+ signals promote sustained and transient episodes of fluid secretion, respectively, this study investigated the differential regulation of functional NKCC1 membrane expression in the native human colonic epithelium. Tissue sections and colonic crypts were obtained from sigmoid rectal biopsy tissue samples. Cellular location of NKCC1, Na+–K+‐ATPase, M3 muscarinic acetylcholine receptor (M3AChR) and lysosomes was examined by immunolabelling techniques. NKCC1 activity (i.e. bumetanide‐sensitive uptake), intracellular Ca2+ and cell volume were assessed by 2′,7′‐bis(2‐carboxyethyl)‐5‐(and‐6)‐carboxyfluorescein (BCECF), Fura‐2 and differential interference contrast/calcein imaging. Unstimulated NKCC1 was expressed on basolateral membranes and exhibited a topological expression gradient, predominant at the crypt base. Cholinergic Ca2+ signals initiated at the crypt base and spread along the crypt axis. In response, NKCC1 underwent a Ca2+‐dependent 4 h cycle of recruitment to basolateral membranes, activation, internalization, degradation and re‐expression. Internalization was prevented by the epidermal growth factor receptor kinase inhibitor tyrphostin‐AG1478, and re‐expression was prohibited by the protein synthesis inhibitor cylcoheximide; the lysosome inhibitor chloroquine promoted accumulation of NKCC1 vesicles. NKCC1 internalization and re‐expression were accompanied by secretory volume decrease and bumetanide‐sensitive regulatory volume increase, respectively. In contrast, forskolin (i.e. cAMP elevation)‐stimulated NKCC1 activity was sustained, and membrane expression and cell volume remained constant. Co‐stimulation with forskolin and acetylcholine promoted dramatic recruitment of NKCC1 to basolateral membranes and prolonged the cycle of co‐transporter activation, internalization and re‐expression. In conclusion, persistent NKCC1 activation by cAMP is constrained by a Ca2+‐dependent cycle of co‐transporter internalization, degradation and re‐expression; this is a novel mechanism to limit intestinal fluid loss.
The effects of hypo‐ and hyperglycaemia on the hypoxic ventilatory response in humans
Authors: Ward Denham S. , Voter William A. , Karan Suzanne
Published: May 2007

Animal and tissue studies have indicated that the carotid bodies are sensitive to glucose concentrations within the physiological range. This glucose sensitivity may modulate the ventilatory response to hypoxia, with hyperglycaemia suppressing the hypoxic response and hypoglycaemia stimulating it. This study was designed to determine whether hypo‐ and hyperglycaemia modulate the hypoxic ventilatory response in humans. In 11 normal research participants, glucose levels were clamped at 2.8 and 11.2 mmol l−1 for 30 min. At the start and end of each clamp, blood was drawn for hormone measurement and the isocapnic hypoxic ventilatory response was measured. Because generation of reactive oxygen species may be a common pathway for the interaction between glucose and oxygen levels, the experiments were repeated with and without pretreatment for 1 week with vitamins C and E. Hypoglycaemia caused an increase in the counter‐regulatory hormones, a 54% increase in isocapnic ventilation, and a 108% increase in the hypoxic ventilatory response. By contrast, hyperglycaemia resulted in small but significant increases in both ventilation and the hypoxic ventilatory response. Antioxidant vitamin pretreatment altered neither response. In conclusion, the stimulant effect of hypoglycaemia on the hypoxic ventilatory response is consistent with a direct effect on the carotid body, but an indirect effect through the activation of the counter‐regulatory response cannot be excluded. The mechanisms behind the mild stimulating effect of hyperglycaemia remain to be elucidated.
Macroendocytosis and endosome processing in snake motor boutons
Authors: Teng Haibing , Lin Michael Y. , Wilkinson Robert S.
Published: May 2007

We have examined the processing of endosomes formed by macroendocytosis (ME), or bulk membrane retrieval, in active motor terminal boutons at the snake nerve–muscle synapse. Endocytic probes were imaged at light (FM1–43) and electron (horseradish peroxidase (HRP)) levels over stimulus frequencies representing low, intermediate and high levels of use. Endosomes formed rapidly (1–2 s) at all frequencies, concomitant with clathrin‐mediated vesicular endocytosis (CME). Endosomes dissipated rapidly into vesicles (∼10 s). The dissipation rate was not influenced by activity. Many endosomes split into clusters of 2–20 smaller endosomes of varying size. Vesicles budded from these smaller endosomes, from large endosomes that had not undergone fission into smaller ones, and from precursor membrane infoldings that had not yet internalized. In snake, exocytosed vesicular membrane is not competent for reuse until after a delay (> 3 min). We found that time required for endosome processing is not responsible for this delay. Endosome processing might, however, limit availability of some vesicles for release at very high levels of use. Generally, endosome processing paralleled that of vesicles internalized directly from the plasma membrane via CME, regardless of stimulus frequency. There was no evidence for differential recruitment of ME versus CME depending upon level of use.
Fatty acid binding protein facilitates sarcolemmal fatty acid transport but not mitochondrial oxidation in rat and human skeletal muscle
Authors: Holloway Graham P. , Lally Jamie , Nickerson James G. , Alkhateeb Hakam , Snook Laelie A. , Heigenhauser George J. F. , Calles‐Escandon Jorge , Glatz Jan F. C. , Luiken Joost J. F. P. , Spriet Lawrence L. , Bonen Arend
Published: May 2007

The transport of long‐chain fatty acids (LCFAs) across mitochondrial membranes is regulated by carnitine palmitoyltransferase I (CPTI) activity. However, it appears that additional fatty acid transport proteins, such as fatty acid translocase (FAT)/CD36, influence not only LCFA transport across the plasma membrane, but also LCFA transport into mitochondria. Plasma membrane‐associated fatty acid binding protein (FABPpm) is also known to be involved in sacrolemmal LCFA transport, and it is also present on the mitochondria. At this location, it has been identified as mitochondrial aspartate amino transferase (mAspAT), despite being structurally identical to FABPpm. Whether this protein is also involved in mitochondrial LCFA transport and oxidation remains unknown. Therefore, we have examined the ability of FABPpm/mAspAT to alter mitochondrial fatty acid oxidation. Muscle contraction increased (P < 0.05) the mitochondrial FAT/CD36 content in rat (+22%) and human skeletal muscle (+33%). By contrast, muscle contraction did not alter the content of mitochondrial FABPpm/mAspAT protein in either rat or human muscles. Electrotransfecting rat soleus muscles, in vivo, with FABPpm cDNA increased FABPpm protein in whole muscle (+150%; P < 0.05), at the plasma membrane (+117%; P < 0.05) and in mitochondria (+80%; P < 0.05). In these FABPpm‐transfected muscles, palmitate transport into giant vesicles was increased by +73% (P < 0.05), and fatty acid oxidation in intact muscle was increased by +18% (P < 0.05). By contrast, despite the marked increase in mitochondrial FABPpm/mAspAT protein content (+80%), the rate of mitochondrial palmitate oxidation was not altered (P > 0.05). However, electrotransfection increased mAspAT activity by +70% (P < 0.05), and the mitochondrial FABPpm/mAspAT protein content was significantly correlated with mAspAT activity (r= 0.75). It is concluded that FABPpm has two distinct functions depending on its subcellular location: (a) it contributes to increasing sarcolemmal LCFA transport while not contributing directly to LCFA transport into mitochondria; and (b) its primary role at the mitochondria level is to transport reducing equivalents into the matrix.
Reactive and anisotropic etching of magnetic tunnel junction films using pulse-time-modulated plasma
Authors: Mukai Tomonori , Ohshima Norikazu , Hada Hiromitsu , Samukawa Seiji
Published: May 2007

Reactive and anisotropic etching of magnetic tunnel junction (MTJ) stacked films has been achieved using pulse-time-modulated (TM) plasma. While corrosion and delamination of MTJs are observed in continuous wave discharge plasma, a chlorine pulse-time-modulated plasma achieved a high MTJ etching rate without corrosion or delamination. The authors think that the negative ions enhance the chemical reactions on the surface of magnetic films. The magnetic characteristics are also significantly improved by using TM plasma because of reduced residues and improved tapered profiles. Accordingly, TM plasma etching is a promising candidate for high-rate and damage-free MTJ etching for magnetoresistive random access memory devices.
Fluorine content of SiOF films as determined by IR spectroscopy and resonant nuclear reaction analysis
Authors: Alonso J. C. , Díaz-Bucio X. M. , Ortiz A. , Benami A. , Cheang-Wong J. C. , Rodríguez-Fernández L.
Published: May 2007

In this article, the authors compare the fluorine concentrations obtained from the strength of the infrared-absorption band due to Si–F bonds, with the absolute concentrations determined from F19(p,αγ)O16 resonant nuclear reaction analysis, for a series of fluorinated silicon oxide (SiOF) films prepared by remote plasma-enhanced chemical-vapor deposition with different flow rates of H2 in SiF4∕O2∕He mixtures. The authors use this comparison to calibrate the proportionality constant between the strength (integrated absorption) of the infrared-absorption band due to Si–F bonds and the concentration of these bonds in the films. The authors found that (under the Gentzel and Martin approach [Surf. Sci. 34, 33 (1973)]) this calibration requires the correction of the “fudge” factor, to a new value, γ=1.28, which is more consistent with the small correction to the local field expected for porous SiOF films. The authors also found that the changes in the refractive index and density of the films introduce less significant corrections in the quantification process of fluorine by the infrared method.
Reduction of thin oxidized copper films using a hot-filament hydrogen radical source
Authors: Kondoh E. , Fukasawa M. , Ojimi T.
Published: May 2007

This article aims to provide practical information on the performance of a hot-filament radical source, with which it becomes feasible for metallization in ultralarge-scale integrated circuits, which has not been studied in detail thus far. A very simple arrangement using this technique allows the highly efficient generation of hydrogen radicals and a quick recovery of oxidized Cu surfaces to their original metallic state. The amount of CuO reduction was evaluated by measuring sheet resistance and also by transmission microscopy. The reduction started when the specimen temperature exceeded 100°C, and several tens of nanometers Cu of film was formed without resulting in a serious increase in the specimen temperature. The amount of reduction was found to increase almost proportionately to the hydrogen radical flux. The Cu layer had a very flat surface topography showing no trace of self-agglomeration of Cu. The reduction of a thermally oxidized Cu specimen was also demonstrated.
Influence of the positive ion composition on the ion-assisted chemical etch yield of SrTiO3 films in Ar∕SF6 plasmas
Authors: Stafford L. , Langlois O. , Margot J. , Gaidi M. , Chaker M.
Published: May 2007

Langlois et al. [Appl. Phys. Lett. 87, 131503 (2005)] have demonstrated that the etch yield of SrTiO3 films in Ar∕SF6 plasmas decreases as the concentration fraction of molecular ions in the plasma increases. Introducing the concept of effective mass for both ions and SrTiO3, these experimental results have quantitatively been explained in the framework of a well-established model originally developed to describe the sputtering of single-atom materials by nonreactive monoatomic ions. This model has, however, ignored the dissociation of molecular ions occurring as these particles impact the material surface. In the present article, the influence of the positive ion composition on the ion-assisted chemical etch yield of SrTiO3 films in Ar∕SF6 plasmas is reexamined to the light of this consideration. A rate model accounting for the dissociation of the various molecular ions is proposed and validated using experimental data. It is found that even though a specific ion species may not be the most important charge carrier in the plasma, its contribution to the plasma etching dynamics may still be the most significant.
Effects of the deposition parameters on the growth of ultrathin and thin SiO2 films
Authors: Quartarone E. , Mustarelli P. , Grandi S. , Marabelli F. , Bontempi E.
Published: May 2007

Si O 2 ultrathin and thin films have been deposited on single-crystal Si substrates by means of nonreactive radio frequency magnetron sputtering. The temperature of the substrate and the deposition times have been varied in the range of 200–500°C and 60–14400s, respectively. The average deposition rate has a range of 0.5–5nm∕min and tends to decrease with the increase of the substrate temperature. Two different growth regimes may be observed for ultrathin and thin films, the transition taking place in the range of 5–10nm depending on the substrate temperature. The roughness of the film surface and the grain dimensions do increase with the substrate temperature for short deposition times (t⩽300s), whereas their behavior is less defined for intermediate ones (300s<t<1800s). Finally, for long deposition times (t>1800s) the roughness increases again with T, and its slope is higher, the higher the substrate temperature is.
Structural and electrical characteristics of microcrystalline silicon prepared by hot-wire chemical vapor deposition using a graphite filament
Authors: Adachi Michael M. , Kavanagh Karen L. , Karim Karim S.
Published: May 2007

Intrinsic hydrogenated microcrystalline silicon (μc-Si:H) films were prepared on Corning glass substrates by hot-wire chemical vapor deposition using a graphite filament. The advantage of the graphite filament is its longer lifetime and greater chemical stability as compared to the commonly used Ta and W wires, particularly at lower filament temperatures at which silicides are known to form on Ta and W. This study examines the deposition of μc-Si:H at the lower filament temperature of 1525°C. A low substrate temperature of 210°C was used for all μc-Si:H depositions with resulting deposition rates of up to 2.0±0.2Å∕s. Raman spectroscopy and electrical conductivity measurements showed that μc-Si:H growth occurred only for silane concentrations below 1.5% dilution in hydrogen. The average grain size was found to be 25nm measured by transmission electron microscopy.
Residence times of water molecules on stainless steel and aluminum surfaces in vacuum and atmosphere
Authors: Dobrozemsky R. , Menhart S. , Buchtela K.
Published: May 2007

The adsorption and desorption phenomena of water molecules on stainless steel and aluminum surfaces have been studied by means of tritium tracer technique (TTT) with special emphasis on potential differences in the residence times in atmosphere and vacuum. Samples with a geometrical surface area of about 2cm2 have been exposed in an atmospheric environment loaded with a vapor pressure of HTO (tritium-labeled water) of known specific activity, and the adsorbed amount of water has been determined by liquid-scintillation counting technique. In previous studies it was found that, in atmosphere, adsorbed water quantities and their reproducibility depend significantly on the cleanliness of the surfaces. Furthermore, it was observed that desorption into atmosphere (or exchange with atmospheric humidity) is a rather slow process with a few percent of the adsorbed water molecules staying even for several days and with the water coverage versus time t characterized approximately by a 1∕tα law with α≈0.4. In this work, TTT measurements of water desorption have been extended into high vacuum. HTO-covered specimens have been transferred into a vacuum chamber soon after HTO exposure and have been kept under high vacuum for a certain vacuum desorption time which was varied from minutes to several days. It was found that water desorption from stainless steel and aluminum surfaces in vacuum is slower than in atmosphere with the residual coverage again described approximately by a 1∕tα law but now with α≈0.14 (stainless steel) and α≈0.17 (Al). Water desorption rates calculated from coverage versus time are within the range of outgassing data reported in literature, indicating that the TTT method can be a powerful tool for the characterization of potential new vacuum materials even if just small specimens are available.
Coverage dependent reaction of yttrium on silicon and the oxidation of yttrium silicide investigated by x-ray photoelectron spectroscopy
Authors: Chiam S. Y. , Chim W. K. , Huan A. C. H. , Zhang J. , Pan J. S.
Published: May 2007

The reaction of yttrium (Y) on (001) silicon (Si) with low temperature annealing is investigated for different coverages of Y using in situ x-ray photoelectron spectroscopy. The authors have also performed oxidation studies for Y on Si in the formation of yttrium silicate by a two-step process. This consists of an ex situ oxidation of Y–Si film, which is formed from low temperature annealing in vacuum. These films were then probed with depth profiling x-ray photoelectron spectroscopy. They report on three general reaction phases of Y on Si that are coverage dependent. Different coverages show differences in Si mixing and selective ultrahigh vacuum oxidation. They also report on the self-limiting formation of yttrium silicate at room temperature and low annealing temperature, which is insensitive to the annealing ambient. They also highlight the importance of oxygen partial pressure in both initial silicate formation and the extent of oxidation at different annealing temperatures. Finally, the authors also show that a high oxygen diffusion barrier prevents the oxidation of the entire Y–Si film.
Spectral behavior of the optical constants in the visible∕near infrared of GeSbSe chalcogenide thin films grown at glancing angle
Authors: Martín-Palma R. J. , Ryan J. V. , Pantano C. G.
Published: May 2007

GeSbSe chalcogenide thin films were deposited using glancing angle deposition onto transparent glass substrates for the determination of the spectral behavior of the optical constants (index of refraction n and extinction coefficient k) in the visible and near infrared ranges (400–2500nm) as a function of the deposition angle. Computational simulations based on the matrix method were employed to determine the values of the optical constants of the different films from the experimental reflectance and transmittance spectra. A significant dependence of the overall optical behavior on the deposition angle is found. Furthermore, the band gap of the GeSbSe thin films was calculated. The accurate determination of the optical constants of films grown at glancing angle will enable the development of sculptured thin film fiber-optic chemical sensors and biosensors.
Measurement and prediction of H2O outgassing kinetics from silica-filled polydimethylsiloxane TR55 and S5370
Authors: Dinh L. N. , Burnham A. K. , Schildbach M. A. , Smith R. A. , Maxwell R. S. , Balazs B. , McLean W.
Published: May 2007

The isoconversional technique was employed for the measurement and prediction of H2O outgassing kinetics from silica-filled polydimethylsiloxane TR55 and S5370 in a vacuum or dry environment. Isoconversional analysis indicates that the energy barrier for H2O release from TR55 and S5370 is an increasing function of the fractional H2O release. This can be interpreted as the release of H2O from physisorbed water and then chemisorbed water with decreasing OH density from the surfaces of the embedded silica particles. Model-independent predictions of H2O outgassing based on the measured kinetics follow the trend of actual isothermal outgassing at elevated temperatures and suggest gradual outgassing in dry/vacuum storage over many decades at low temperatures for both TR55 and S5370.
Measurement and modeling of time- and spatial-resolved wafer surface temperature in inductively coupled plasmas
Authors: Hsu C. C. , Titus M. J. , Graves D. B.
Published: May 2007

The transient temperature profile across a commercial wafer temperature sensor device in an inductively coupled Ar plasma is reported. The measured temperatures are compared to model predictions, based on a coupled plasma-wafer model. The radial temperature profile is the result of the radial profile in the ion energy flux. The ion energy flux profile is obtained by combining the Langmuir probe measurement, the ion wall flux probe measurement, and a plasma model. A methodology to estimate the ion flux profile using the sensor measurements has been validated by combining the plasma measurements, the wafer temperature measurements, and the plasma-wafer model. It is shown that with minimal heat transfer between the wafer and the chuck, the initial transient wafer temperature profile after plasma ignition can be used to estimate the ion energy flux profile across the wafer.
Extracting the Green’s function of attenuating heterogeneous acoustic media from uncorrelated waves
Authors: Snieder Roel
Published: May 2007

The Green’s function of acoustic or elastic wave propagation can, for loss-less media, be retrieved by correlating the wave field that is excited by random sources and is recorded at two locations. Here the generalization of this idea to attenuating acoustic waves in an inhomogeneous medium is addressed, and it is shown that the Green’s function can be retrieved from waves that are excited throughout the volume by spatially uncorrelated injection sources with a power spectrum that is proportional to the local dissipation rate. For a finite volume, one needs both volume sources and sources at the bounding surface for the extraction of the Green’s functions. For the special case of a homogeneous attenuating medium defined over a finite volume, the phase and geometrical spreading of the Green’s function is correctly retrieved when the volume sources are ignored, but the attenuation is not.
Ultrasonic oil-film thickness measurement: An angular spectrum approach to assess performance limits
Authors: Zhang Jie , Drinkwater Bruce W. , Dwyer-Joyce Rob S.
Published: May 2007

The performance of ultrasonic oil-film thickness measurement in a ball bearing is quantified. A range of different viscosity oils (Shell T68, VG15, and VG5) are used to explore the lowest reflection coefficient and hence the thinnest oil-film thickness that the system can measure. The results show a minimum reflection coefficient of 0.07 for both oil VG15 and VG5 and 0.09 for oil T68 at 50MHz. This corresponds to an oil-film thickness of 0.4μm for T68 oil. An angular spectrum (or Fourier decomposition) approach is used to analyze the performance of this configuration. This models the interaction of component plane waves with the measurement system and quantifies the effect of the key parameters (transducer aperture, focal length, and center frequency). The simulation shows that for a focused transducer the reflection coefficient tends to a limiting value at small oil-film thickness. For the transducer used in this paper it is shown that the limiting reflection coefficient is 0.05 and the oil-film measurement errors increase as the reflection coefficient approaches this value. The implications for improved measurement systems are then discussed.
Generation of shock-free pressure waves in shaped resonators by boundary driving
Authors: Luo C. , Huang X. Y. , Nguyen N. T.
Published: May 2007

Investigation of high amplitude pressure oscillations generated by boundary driving in shaped resonators has been carried out both theoretically and experimentally. In the theoretical modeling, the acoustic resonance in an axisymmetric resonator is studied by the Galerkin method. The resonator is exponentially expanded and the boundary driving is provided by a piston at one end. The pressure wave forms, amplitudes, resonance frequencies, and ratio of pressures at the two ends of the resonator are calculated for various expansion flare constants and driving strengths. These results are partially compared with those generated by shaking the resonator. They are also verified in the experiment, in which an exponentially expanded resonator is connected to a speaker box functioning as the piston. The experiment is further extended to a horn-shaped resonator with a rectangular cross section. The boundary driving in this case is generated by a circular piezoelectric disk, which forms one sidewall of the resonator cavity. The characteristics of axisymmetric resonators, such as the resonance frequency and amplitude ratio of pressures at the two ends, are observed in this low aspect ratio rectangular resonator with the sidewall driving.
Frequency- and time-domain asymptotic fields near the critical cone in fluid-fluid configuration
Authors: Lihh Won-seok
Published: May 2007

Near the critical cone of a point source placed at the interface between two half-space fluid media, investigation is made of the asymptotic fields in the frequency domain and their synthetic wave forms in the time domain. While the leading-order (and the head-wave) components give a good description of the true fields well off the critical cone, the uniform asymptotic (UA) analysis has to be made for the approximation near the critical cone. The UA analysis splits into two cases, depending on the medium densities and wave speeds. For Case 1, the UA1 approximation is employed that takes into account the proximity of the stationary-phase point to the branch point. In Case 2, the UA2 approximation is employed in which consideration is also given to the proximity of the stationary point to the pole and to the combined effect of the stationary point, the branch point, and the pole. The validities of the asymptotic fields are checked in the time domain by comparing the asymptotic field wave forms against the wave-number-synthetic wave forms. The UA fields show good accuracy and causal behaviors, with the causality of the UA2 fields previously unreported in the literature.
Discomfort from sinusoidal oscillation in the roll and lateral axes at frequencies between 0.2 and 1.6Hz
Authors: Wyllie I. H. , Griffin M. J.
Published: May 2007

Discomfort caused by low frequency lateral and roll oscillations is often predicted from lateral acceleration in the plane of the seat, irrespective of whether it comes from horizontal motion or a component of gravity arising from roll. This study investigated discomfort from lateral and roll oscillation and whether acceleration in the plane of a seat predicts discomfort. Twelve subjects, sitting with and without backrest, used magnitude estimation to judge sinusoidal oscillations in the roll and lateral axes at ten frequencies between 0.2 and 1.6Hz at magnitudes between 0.063 and 0.63ms−2 root mean square. The rate of growth of vibration discomfort with increasing magnitude reduced with increasing frequency, so the frequency-dependence of discomfort varied with magnitude. Acceleration in the plane of the seat predicted discomfort from both lateral and roll oscillation at frequencies less than 0.4Hz. At higher frequencies, acceleration produced by roll oscillation resulted in greater discomfort than the same acceleration produced by lateral oscillation. At frequencies greater than 0.4Hz, a full height backrest increased discomfort with both lateral and roll oscillation. The prediction of discomfort caused by low frequency lateral and roll oscillation requires that both components are measured and assessed according to their separate effects.