bluuebunny/crossref_metadata_2025 huggingface dataset:
Analyzing factors associated with major complications after adenotonsillectomy in 4776 patients: Comparing three tonsillectomy techniques
Authors: Gallagher Thomas Q. , Wilcox Lyndy , McGuire Erin , Derkay Craig S.
Published: May 2010

Objective

To compare the rates of major complications (postoperative hemorrhage requiring return to the operating room or cauterization in the emergency department and dehydration requiring intravenous fluids or readmission) in a large cohort of children undergoing adenotonsillectomy by three different techniques.

Study Design

Case series with chart review, case‐controlled study.

Setting

Regional children's hospital.

Subjects and Methods

Subjects comprised patients aged 1 to 18 years undergoing adenoidectomy, tonsillectomy, or adenotonsillectomy by microdebrider, coblator, or Bovie over a 36‐month period. Major complications identified were compared to two case‐matched controls to try to identify patients at risk for major postoperative complications.

Results

The overall complication rate was 80 of 4776 (1.7 ± 0.4% [percent ± 95% confidence interval]). Of the 3362 patients who received either an adenotonsillectomy or tonsillectomy alone, 80 had a complication (2.3 ± 0.5%). Major complication rates differed among tonsil removal techniques: 34 of 1235 (2.8 ± 0.9%) coblation; 40 of 1289 (3.1 ± 0.9%) electrocautery; six of 824 (0.7 ± 0.7%) microdebrider (P < 0.001). Postoperative hemorrhage occurred in older children (8.5 vs 5.5 years; P < 0.001), while age did not influence postsurgical dehydration (5.33 vs 5.49 years). The case‐control portion of the study did not find any reliable way to identify patients at risk for complications during adenotonsillectomy. Identity of the surgeon was not a confounding independent variable, nor was participation by resident surgeons.

Conclusion

In this “real life” teaching hospital surgical setting in which three different techniques of tonsillectomy are routinely performed by a variety of resident and attending surgeons, microdebrider intracapsular tonsillectomy is associated with lower rates of post‐tonsillectomy hemorrhage and dehydration when compared to coblation and electrocautery complete tonsillectomy technique.
Lymphatic malformations: Review of current treatment
Authors: Perkins Jonathan A. , Manning Scott C. , Tempero Richard M. , Cunningham Michael J. , Edmonds Joseph L. , Hoffer Fredric A. , Egbert Mark A.
Published: May 2010

Objective

Summarize current knowledge of lymphatic malformation medical, sclerotherapy, and surgical treatment; and highlight areas of treatment controversy and treatment difficulty that need improvement.

Methods

Panel presentation of various aspects of lymphatic malformation treatment.

Results

The mainstay of lymphatic malformation treatment has been surgical resection, which has been refined through lesion staging and radiographic characterization. Intralesional sclerotherapy in macrocystic lymphatic malformations is effective. Suprahyoid microcystic lymphatic malformations are more difficult to treat than macrocystic lymphatic malformations in the infrahyoid and posterior cervical regions. Bilateral suprahyoid lymphatic malformations require staged treatment to prevent complications. Lymphatic malformation treatment planning is primarily determined by the presence or possibility of functional compromise. Problematic areas include chronic lymphatic malformation inflammation, dental health maintenance, macroglossia, airway obstruction, and dental malocclusion.

Conclusions

Lymphatic malformation treatment improvements have been made through radiographic characterization and staging of lymphatic malformations. Direct malformation involvement of the upper aerodigestive tract can cause significant functional compromise that is difficult to treat.
A study of resident proficiency with thyroid surgery: Creation of a thyroid‐specific tool
Authors: Stack Brendan C. , Siegel Eric , Bodenner Donald , Carr Michelle M.
Published: May 2010

Objective

Creation and testing of a tool, Hemithyroidectomy‐Specific Scale (HSS), to evaluate performance of a hemithyroidectomy.

Study Design

Prospective, multi‐center study of our HSS tool versus a Global Scale (GS).

Setting

Two tertiary care academic medical centers.

Subjects and Methods

Sixteen unique residents (postgraduate years [PGY] 2‐5) evaluated a total of 97 times with a performance tool by a single endocrine surgeon evaluator (B.C.S.).

Results

Overall, the reliability of both evaluation instruments was good. Cronbach's alpha was 0.972 for the GS and 0.959 for the HSS. This indicates high internal consistency of each instrument. In general, the scores increased with increasing PGY level, indicating reasonable construct validity.

Conclusion

This study describes a new HSS checklist type of evaluation instrument for hemithyroidectomy and compares it to a validated GS. HSS offers advantages to GS. Most residents reached competence in hemithyroidectomy by the PGY4 level. A large, multi‐institutional study would be required for adequate evaluation of our tool prior to its routine use in resident evaluations.
Treatment of auricular hematoma by OK‐432
Authors: Kubota Toshinori , Ohta Nobuo , Fukase Shigeru , Kon Yoshihisa , Aoyagi Masaru
Published: May 2010

Objectives

Intralesional injection therapy with OK‐432 was developed as a therapy for operatively difficult lymphangioma (cystic hygroma) and is currently becoming a first‐choice treatment for this disease. The aim of this article was to evaluate the outcome and complications of the treatment of patients with auricular hematoma by OK‐432 therapy.

Study Design

Case series with planned data collection.

Setting

Yamagata University School of Medicine.

Subjects and Methods

We tried this therapy in 21 patients with auricular hematoma between January 2001 and February 2009. We injected OK‐432 solution into the lesion with a 27‐gauge needle to prevent the leak of the agent out of the hematoma. We performed this treatment on an outpatient basis without hospitalization.

Results

Disappearance or marked reduction of the lesion were observed in all patients who had this therapy, and local scarring and deformity of the auricle did not occur in any patients. As for side effects, local pain at the injection site and fever (37°C‐38°C) were observed in a few of the patients who had this therapy, but such problems resolved within a few days.

Conclusion

These results may allow us to speculate that intralesional injection therapy with OK‐432 is simple, easy, safe, and effective and can be used as a substitute for surgery in the treatment of auricular hematoma.
Gustatory itching: an unusual complication following superficial parotidectomy
Authors: Ricks R , Banga R , Porter M
Published: May 2010

Objective:

We report the previously undocumented complication of gustatory itching following superficial parotidectomy.

Method:

Case report and review of the English literature concerning Frey's syndrome, complications of superficial parotidectomy and the pathophysiology of itching.

Results:

A 49-year-old woman developed gustatory itching following a superficial parotidectomy. Her symptoms were satisfactorily managed with topical and oral antihistamine preparations. We propose a neurophysiological pathway involving acetylcholine and histamine to explain this phenomenon.

Conclusion:

To our knowledge, this is the first documented case of gustatory itching following superficial parotidectomy. The use of antihistamine preparations appears to effectively manage this symptom, without the need for invasive procedures.
Psychopathic personality in children: genetic and environmental contributions
Authors: Bezdjian S. , Raine A. , Baker L. A. , Lynam D. R.
Published: May 2010

Background

The current study investigates whether the underlying factor structure of psychopathic personality traits found in adults is similar to that in children and what the extent of the genetic and environmental influences are on these psychopathic traits.

Method

Psychopathic personality traits were assessed in a community sample of 1219 twins and triplets (age 9–10 years) through caregiver reports of each child's behavior using the Child Psychopathy Scale (CPS).

Results

Confirmatory factor analyses revealed an optimal two-factor solution (callous/disinhibited and manipulative/deceitful) to the CPS subscales. Bivariate genetic modeling of the two computed factor scores revealed significant genetic as well as unique environmental influences on psychopathic personality traits in both boys and girls, with heritability estimates of 0.64 and 0.46, respectively, in boys and 0.49 and 0.58, respectively, in girls. No shared environmental influences on psychopathic personality traits were found.

Conclusions

The relationship between the two factors was mediated by both genetic and unique environmental factors common to both traits.
An Improved Bound for k-Sets in Four Dimensions
Authors: SHARIR MICHA
Published: May 2010

We show that the number of halving sets of a set of n points in ℝ4 is O(n4−1/18), improving the previous bound of [10] with a simpler (albeit similar) proof.
THE GETTIER PROBLEM AND LEGAL PROOF
Authors: Pardo Michael S.
Published: May 2010

This article explores the relationships between legal proof and fundamental epistemic concepts such as knowledge and justification. A survey of the legal literature reveals a confusing array of seemingly inconsistent proposals and presuppositions regarding these relationships. This article makes two contributions. First, it reconciles a number of apparent inconsistencies and tensions in accounts of the epistemology of legal proof. Second, it argues that there is a deeper connection between knowledge and legal proof than is typically argued for or presupposed in the legal literature. This connection is illustrated through a discussion of the Gettier problem in epistemology. It is argued that the gap or disconnect between truth and justification that undermines knowledge in Gettier cases also potentially undermines the success of legal verdicts.
Inductive Logic Programming in Databases: From Datalog to
Authors: LISI FRANCESCA A.
Published: May 2010

In this paper we address an issue that has been brought to the attention of the database community with the advent of the Semantic Web, i.e., the issue of how ontologies (and semantics conveyed by them) can help solving typical database problems, through a better understanding of Knowledge Representation (KR) aspects related to databases. In particular, we investigate this issue from the ILP perspective by considering two database problems, (i) the definition of views and (ii) the definition of constraints, for a database whose schema is represented also by means of an ontology. Both can be reformulated as ILP problems and can benefit from the expressive and deductive power of the KR framework $\mathcal{DL}+log}^{\neg\vee}$. We illustrate the application scenarios by means of examples.
Asset commitment, constitutional governance and the nature of the firm
Authors: GRANDORI ANNA
Published: May 2010

Integrating organization theory, organizational economics, and organizational law considerations, it is argued that the ‘nature of the firm’ can be more completely understood if it is considered a complete society-establishing contract, including constitutional pacts on procedures for the selection of actions, rather than a nexus of incomplete transactional contracts complemented by authority, power, or relational norms. The explanation is more general since firm-establishing contracts are a sub-set of those society-establishing contracts that are capable of regulating any venture in condition of high uncertainty and potential conflict, and because the constitutional regime adopted (authority-based, democratic, or other) becomes a specification of particular types of firms rather than part of the explanation of the firm. Evidence from published studies, as well as from newly gathered data on firm-founding contracts and other partnership establishing contracts (500 record database on large multi-party projects), document that actual contracts under uncertainty do fit the hypothesized pattern.
Equatorial paleomagnetic time‐averaged field results from 0–5 Ma lavas from Kenya and the latitudinal variation of angular dispersion
Authors: Opdyke Neil D. , Kent Dennis V. , Huang Kainian , Foster David A. , Patel J. P.
Published: May 2010

Lavas of Pliocene‐Pleistocene age were sampled in two regions in Kenya: Mount Kenya on the equator and the Loiyangalani region, east of Lake Turkana, at about 3°N. We sampled 100 sites distributed around the Mount Kenya Massif and to the northeast along the Nyambini Range. The equator bisects Mount Kenya, and all sites were sampled within 40′ of the equator. Thirty‐two sites were sampled in the Loiyangalani area, making a total of 132 sites. Many sites from the Mount Kenya study were severely affected by lightning; however, after progressive AF demagnetization 69 sites yielded directions with α95 equal to or less than 10°. Normal polarity sites dominate (N = 58 and a mean of declination (dec) = 1.2°, inclination (inc) = −0.7°, and α95 = 3.6°) with only 11 reverse polarity sites (mean of dec = 182.3°, inc = 0.6°, and α95 = 7.2°); no transitional directions were identified. Inverting the reverse sites yields a combined mean direction of dec = l.4°, inc = −0.7°, and α95 = 3.2°. This result is not significantly different from what is expected from the geocentric axial dipole for the mean locality (dec = 0° and inc = 0°); a quadrupole component was not resolved. The samples from the Loiyangalani region were not seriously affected by lightning, and all 32 sites gave satisfactory data with α95 less than 10° (17 reverse sites, dec = 183.4°, inc = 0.8°, and α95 = 6.7°; 15 normal sites, dec = 358.6°, inc = −1.1°, and α95 = 4.7°); after inverting the reverse sites the combined mean was dec = 1.1°, inc = −1.0°, and α95 = 4.1°. Altogether, we had a total of 101 successful sites. A virtual geomagnetic pole (VGP) was calculated from each site mean; the VGP dispersion is low, with Sb = 10.9° for Mount Kenya and 9.8° for the Loiyangalani region. This dispersion agrees with updated Model G of McElhinny and McFadden (1997) and model TK03 of Tauxe and Kent (2004) that was tuned to the compilation of McElhinny and McFadden (1997) but disagrees with the higher dispersion near the equator and the smaller latitudinal gradient in dispersion estimated by Johnson et al. (2008). A new database is presented, and the included studies support a systematic decrease of dispersion from high to low latitudes.
On the origins of water masses exported along both sides of Greenland: A Lagrangian model analysis
Authors: Lique C. , Treguier A. M. , Blanke B. , Grima N.
Published: May 2010

The origin of the water masses exported from the Arctic to the North Atlantic along both sides of Greenland is investigated using an original numerical method. A quantitative Lagrangian analysis is applied to the monthly climatological 3‐D output of a global ocean/sea ice high‐resolution model. It allows quantification of the different branches of the export to the North Atlantic, as well as related timescales and water mass transformations. In the model, the outflow through Davis Strait consists in equal parts of Pacific and Atlantic water, whilst the export through Fram Strait consists almost fully of Atlantic water (contrary to observations). Pacific water is transferred quickly (O(10 years)) to the North Atlantic through the Beaufort Gyre, where gradual warming and salinification occur. Atlantic water exiting in the surface layer along both sides of Greenland remains about 10 years in the Arctic Basin and undergoes cooling and significant freshening. Below the surface water, Atlantic water exiting through the intermediate and deep layers in Fram Strait follows different pathways in the Arctic, with trajectories being subject to topography constraints. The travel time depends strongly on the pathway (from 1 to 1000 years). The intermediate outflow consists mainly of water entering the Arctic at Fram Strait, while half the deep outflow is composed of water from the Barents Sea. We find that the Barents Sea Branch, which contributes to both the outflows at Fram and Davis straits, is almost fully transformed after a year due to heat exchanges with the very cold atmosphere (in the Barents Sea).
Synthesis of SiO2 spheres with magnetic cores: Implications for the primary accretion in the solar nebula
Authors: Wang Mingsheng , Chen Qianwang , Ding Qiang
Published: May 2010

Current models used to explain how floating nebular dust accretes to planetesimals still encounter different kinds of problems. Since the magnetic force induced accretion model was first proposed by Nuth et al. (1994), it has been considered as an important route via which nebular dust accretes. In this paper, a system analogous to the primitive solar nebula has been created. A magnetic iron compound and silica were evenly dispersed in this system at high temperatures and their accretion behavior was investigated. Experimental results show that microspheres with magnetite and iron silicate cores and amorphous silica shells were formed. By analyzing the formation mechanism, we find that if the local temperature is under its Curie point, magnetite can aggregate spontaneously by magnetic interactions and can further attract charged silicon‐bearing radicals via the Lorentz force. We have also found that the oxidation of iron to magnetite does not hinder the magnetic aggregation process, but facilitates the formation of widespread iron silicate. Therefore, our model provides an alternative view of “primary accretion” in the protoplanetary nebula.
Mystery of ice multiplication in warm‐based precipitating shallow cumulus clouds
Authors: Sun Jiming , Ariya Parisa A. , Leighton Henry G. , Yau M. K.
Published: May 2010

High concentrations of ice crystals exceeding those of background ice nuclei have often been observed in warm‐based precipitating shallow cumulus clouds. Laboratory experiments reveal that such ice multiplication can occur when large ice particles collide with cloud droplets (Hallett‐Mossop mechanism). Further studies suggested that this mechanism is unable to account for the exceedingly high ice concentrations in those kinds of clouds. However, the results of our numerical simulations show that the ice multiplication phenomena can be explained by the Hallett‐Mossop mechanism with the freezing of a narrow band of supercooled raindrops which act as rimers playing a crucial role.
Hierarchical asperity model for multiscale characteristic earthquakes: A numerical study for the off‐Kamaishi earthquake sequence in the NE Japan subduction zone
Authors: Hori Takane , Miyazaki Shin'ichi
Published: May 2010

We develop a numerical model to simulate the occurrence of multiscale characteristic earthquakes in the off‐Kamaishi area of the northeast Japan subduction zone. A notable feature of these earthquake sequences is that microearthquakes occur during the later half of interseismic period between two successive M ∼ 4.9 characteristic earthquakes, which we call moderate earthquakes. We introduce a microasperity, the rupture area of the microearthquakes, with a significantly smaller nucleation size than the size of a hyper‐asperity, the rupture area for moderate earthquakes. In contrast, the nucleation size in the rest of the hyper‐asperity, which we call a conditional asperity, is set to be comparable to the spatial size of the hyper‐asperity. Such a hierarchical asperity model successfully reproduces the observed earthquake sequences. The simulation results show that both microearthquakes and moderate earthquakes nucleate at the microasperity. The stress level in the conditional asperity determines whether a rupture terminates just outside the microasperity or propagates out into the conditional asperity.
Reservoir fluid substitution effects on seismic profile interpretation: A physical modeling experiment
Authors: Wang Shangxu , Li Xiang‐Yang , Di Bangrang , Booth David
Published: May 2010

P‐wave seismic surveys are performed on realistic physical models of a reservoir formed of interbedded sand and shale layers and filled with gas, water, and oil. They show characteristic behaviour which can be used to distinguish between fluids, with significant implications for the interpretation of time‐lapse experiments. Discontinuous reflections originate in gas‐filled reservoirs, with widely varying amplitude compared to oil‐ or water‐filled reservoirs. Anomalous changes in seismic amplitude difference attributes for reflections within the reservoir are seen for gas/oil substitution. Oil/water substitution results in only weak variations of reservoir elastic properties, thus amplitude difference attributes may be unsuitable for monitoring changes in oil/water saturation. However, direct differences between the time traces are strong. On time‐lapse sections, strong amplitude difference anomalies do not necessarily correspond to the region where the fluid variations occur; this is significant for monitoring oil field development by water injection.
Unusual extremes in the negative phase of the Arctic Oscillation during 2009
Authors: L'Heureux Michelle , Butler Amy , Jha Bhaskar , Kumar Arun , Wang Wanqiu
Published: May 2010

During 2009, the Arctic Oscillation (AO) index was exceptionally negative during four months, which was unprecedented in a 60‐year record extending back to 1950. The negative phase of the AO corresponded to a nearly zonally symmetric anomaly of temperature and pressure over the middle‐to‐high latitudes of the Northern Hemisphere. Consistent with the strong negative phase of the AO, below‐average temperatures were also observed over North America and parts of Eurasia during June, July, October, and December 2009. Although the impact of the AO on 2‐meter temperatures was near zero when averaged over the entire hemisphere (20°–90°N), positive anomalies were evident in the residual pattern of observed temperature. The residual, along with observed below‐average stratospheric temperatures, are consistent with anthropogenic climate projections. The possible implication of the recent negative values on the long‐term AO trend is also discussed.
Posttranslational modification and sequence variation of redox-active proteins correlate with biofilm life cycle in natural microbial communities
Authors: Singer Steven W , Erickson Brian K , VerBerkmoes Nathan C , Hwang Mona , Shah Manesh B , Hettich Robert L , Banfield Jillian F , Thelen Michael P
Published: May 2010

Characterizing proteins recovered from natural microbial communities affords the opportunity to correlate protein expression and modification with environmental factors, including species composition and successional stage. Proteogenomic and biochemical studies of pellicle biofilms from subsurface acid mine drainage streams have shown abundant cytochromes from the dominant organism, Leptospirillum Group II. These cytochromes are proposed to be key proteins in aerobic Fe(II) oxidation, the dominant mode of cellular energy generation by the biofilms. In this study, we determined that posttranslational modification and expression of amino-acid sequence variants change as a function of biofilm maturation. For Cytochrome579 (Cyt579), the most abundant cytochrome in the biofilms, late developmental-stage biofilms differed from early-stage biofilms in N-terminal truncations and decreased redox potentials. Expression of sequence variants of two monoheme c-type cytochromes also depended on biofilm development. For Cyt572, an abundant membrane-bound cytochrome, the expression of multiple sequence variants was observed in both early and late developmental-stage biofilms; however, redox potentials of Cyt572 from these different sources did not vary significantly. These cytochrome analyses show a complex response of the Leptospirillum Group II electron transport chain to growth within a microbial community and illustrate the power of multiple proteomics techniques to define biochemistry in natural systems.
Links between viral and prokaryotic communities throughout the water column in the (sub)tropical Atlantic Ocean
Authors: De Corte Daniele , Sintes Eva , Winter Christian , Yokokawa Taichi , Reinthaler Thomas , Herndl Gerhard J
Published: May 2010

Viral and prokaryotic abundance, production and diversity were determined throughout the water column of the subtropical Atlantic Ocean to assess potential variations in the relation between viruses and prokaryotes. Prokaryotic abundance and heterotrophic activity decreased by one and three orders of magnitude, respectively, from the epi- to the abyssopelagic layer. Although the lytic viral production (VP) decreased with depth, lysogenic VP was variable throughout the water column and did not show any trend with depth. The bacterial, archaeal and viral community composition were depth-stratified as determined by the automated ribosomal intergenic spacer analysis, terminal-restriction fragment length polymorphism and randomly amplified polymorphic DNA-PCR, respectively. Generally, the number of operational taxonomic units (OTUs) did not reveal consistent trends throughout the water column. Viral and prokaryotic abundance were strongly related to heterotrophic prokaryotic production, suggesting similar linkage strength between the viral and prokaryotic communities from the lower epi- to the abyssopelagic layer in the Atlantic Ocean. Strikingly, the prokaryotic and viral parameters exhibited a similar variability throughout the water column down to the abyssopelagic layers, suggesting that the dark ocean is as dynamic a system as is the lower epipelagic layer. It also indicates that viruses are apparently having a similar role for prokaryotic mortality in the dark oceanic realm as in surface waters. The more than twofold increase in bacterial OTUs from 2750 m depth to >5000 m depth and the concurrent decrease in viral OTUs, however, suggests that viruses might exhibit a wider host range in deep waters than in surface waters.
Characterization of two dimensional self-organized Au nanoparticles embedded in Si3N4
Authors: Céspedes Eva , Babonneau David , Lyon Olivier , Sánchez-Marcos Jorge , Rouzière Stéphan , Prieto Carlos , Olivi Luca , Traverse Agnès
Published: May 2010

Au / Si 3 N 4 films have been prepared by gold and silicon nitride sequential sputtering with different Au thicknesses. The goal is to investigate the Au growth mode and to identify the regime where Au nanoparticles (NPs) can be prepared. The number of Au atoms, the bilayer thickness, the Au environment, the size, and the organization of the particles have been determined. Gold appears in metallic form. The thickest Au layer (8 nm) is continuous whereas the thinnest ones (with average values of 1–3 nm) are formed by nearly spherical Au NPs with diameters in the 5–7 nm range. Au NPs spatial self-organization is observed for average thickness of tAu=2.9 nm. These growth modes are discussed and compared with those observed for other metal/Si3N4 systems prepared in similar conditions.
First-principles study of structural stability and electronic structure of La-doped Sr1.9375La0.0625TiO3.968 75
Authors: Yun J. N. , Zhang Z. Y. , Yan J. F. , Zhao W.
Published: May 2010

The stability, structural geometry, and electronic structure of the La-doped Sr1.9375La0.0625TiO3.968 75 are investigated by first-principles calculations based on the density functional theory. The calculated results reveal that the oxygen vacancies have a tendency to distribute in the ab planes of the perovskite SrTiO3 layer. The structural stability of Sr1.9375La0.0625TiO3.968 75 is weakened by the simultaneous substitution of La for Sr and the introduction of oxygen vacancies. After electron doping, the lattice parameter a increases while the lattice parameter c decreases. The corner-shared TiO6 octahedra dominate the main electronic properties of Sr2TiO4 and the Sr1.9375La0.0625TiO3.968 75 system shows n-type degenerate semiconductor features. There is an incipient localization of some of the doped electrons being trapped in the oxygen vacancy. The introduction of oxygen vacancy in Sr2TiO4 makes little contribution to the electrical activity of Sr1.9375La0.0625TiO3.968 75.
Bogomolny-Prasad-Sommerfeld state counting in local obstructed curves from quiver theory and Seiberg duality
Authors: Chuang Wu-Yen , Pan Guang
Published: May 2010

In this paper, we study the Bogomolny-Prasad-Sommerfeld (BPS) state counting in the geometry of local obstructed curve with normal bundle O⊕O(−2). We find that the BPS states have a framed quiver description. Using this quiver description along with the Seiberg duality and the localization techniques, we can compute the BPS state indices in different chambers dictated by stability parameter assignments. This provides a well-defined method to compute the generalized Donaldson–Thomas invariants. This method can be generalized to other affine ADE quiver theories.
Thermal stability of copper nitride thin films: The role of nitrogen migration
Authors: Gonzalez-Arrabal R. , Gordillo N. , Martin-Gonzalez M. S. , Ruiz-Bustos R. , Agulló-López F.
Published: May 2010

The atomic composition, structural, morphological, and optical properties of N-rich copper nitride thin films have been investigated prior to and after annealing them in vacuum at temperatures up to 300 °C. Films were characterized by means of ion-beam analysis (IBMA), X-ray diffraction (XRD), atomic force microscopy (AFM), and spectroscopic ellipsometry techniques (SE). The data reveal that even when the total (integrated over the whole thickness) atomic composition of the films remains constant, nitrogen starts to migrate from the bulk to the film surface, without out-diffusing, at temperatures as low as 100 °C. This migration leads to two chemical phases with different atomic concentration of nitrogen, lattice parameters, and crystallographic orientation but with the same crystal structure. XRD experimental and Rietveld refined data seem to confirm that nitrogen excess accommodates in interstitial locations within the anti-ReO3 crystal lattice forming a solid solution. The influence of nitrogen migration on the optical (electronic) properties of the films will be discussed.
Two-dimensional spatially periodic electron flow in various emission regimes
Authors: Rokhlenko A , Lebowitz J. L.
Published: May 2010

We study the effects of cathode surface curvature on the space charge limited current emitted by a two-dimensional periodic array of field emitters. Each of these emitters has a shape described by a simple analytic function. Linear, quadratic, and Fowler–Nordheim current-field dependences of the cathode emissivity as well as the infinite emissivity Child–Langmuir model are considered. We develop a mathematical anzatz to capture the main features of the potential field structure of this system and supplement it with a set of correction functions with free parameters. A special least square procedure is used for an approximate solution of this nonlinear problem. We find that even a smooth curved cathode can yield significant spatial variations in the current density but for the cases considered it does not change substantially the total current (properly adjusted). When the cathode emissivity and/or the applied voltage are high enough the current density from the top of the cathode bump (where the curvature is maximal) exceeds the current density produced by a flat cathode with infinite emissivity placed at the same distance from the anode. An explanation of this effect is given. The spatial pattern of emission is determined almost solely by the cathode curvature no matter how strong the current is.
Quantization by cochain twists and nonassociative differentials
Authors: Beggs E. J. , Majid S.
Published: May 2010

We show that several standard associative quantizations in mathematical physics can be expressed as cochain module-algebra twists in the spirit of Moyal products at least to O(ℏ3), but to achieve this we twist not by a 2-cocycle but by a 2-cochain. This implies a hidden nonassociativity not visible in the algebra itself but present in its deeper noncommutative differential geometry, a phenomenon first seen in our previous work on semiclassicalization of differential structures. The quantizations are induced by a classical group covariance and include enveloping algebras U(g) as quantizations of g∗, a Fedosov-type quantization of the sphere S2 under a Lorentz group covariance, the Mackey quantization of homogeneous spaces, and the standard quantum groups Cq[G]. We also consider the differential quantization of Rn for a given symplectic connection as part of our semiclassical analysis and we outline a proposal for the Dirac operator.
Adhesion-driven buckling of single-walled carbon nanotube bundles
Authors: Ke Changhong , Zheng Meng , Bae In-Tae , Zhou Guangwen
Published: May 2010

Buckling of a thin single-walled carbon nanotube (SWNT) bundle that is partially bound on another straight free-standing SWNT bundle is reported. The buckling of the SWNT bundle is purely due to the adhesion interaction between two SWNT bundles. The deformation curvature of the buckled SWNT bundle is experimentally measured by transmission electron microscopy, and is theoretically modeled by a continuum model based on nonlinear elastica theory. Our results reveal that the binding strength of the bundle interface and the bulk elastic modulus of the SWNT bundle can be associated by its buckling curvature. Our results show that the bulk elastic moduli of the tested SWNT bundles are significantly lower than the Young’s modulus of individual SWNTs. The reported adhesion-driven nanotube buckling provides a potential new approach to quantify the elastic modulus and the binding strength of bundled nanotubes.
Effect of local solid reaction on diffusion-induced stress
Authors: Yang Fuqian
Published: May 2010

Incorporating the volumetric change due to local solid reaction in the theory of diffusion-induced stress, a general relation is derived among concentration of solute atoms, local reaction product, and mechanical stress. This relation describes the dependence of local stress on the local dilatation created by diffusion of solute atoms and local solid reaction. Assuming that the elastic properties of an isotropic thin plate are constants independent of reaction product and concentration of solute atoms, closed-form solutions of the diffusion-induced deformation fields in the plate are obtained when the plate is free of external stress and subjected to a constant concentration of solute atoms on surface. Local solid reaction significantly increases the stress on the surface of the plate, which can potentially cause structural degradation.
A heat kernel approach to the stability of exponential equation in distributions and hyperfunctions
Authors: Chung Jae-Young
Published: May 2010

Let f,g,h:G×(0,∞)→C with G an Abelian group. We consider the stability of the Pexiderized exponential equation, |f(x+y,t+s)−g(x,t)h(y,s)|≤H(t,s),x,y∊G, t,s>0, where H:(0,∞)2→(0,∞) is a decreasing function. As an application we establish the stability problem of the Pexiderized exponential equation, u∘A−v⊗w∊D′L∞(R2n), in some spaces of generalized functions, where D′L∞(R2n) denotes the space of bounded distributions.
Composition dependence of band alignment and dielectric constant for Hf1−xTixO2 thin films on Si (100)
Authors: Ye Cong , Wang Hao , Zhang Jun , Ye Yun , Wang Yi , Wang Baoyuan , Jin Yingchun
Published: May 2010

Composition-dependent band alignment and dielectric constant for Hf1−xTixO2 thin films on Si (100) have been investigated. It was found with increasing Ti content, the band gap and band offsets (ΔEv and ΔEc) of Hf1−xTixO2 films against Si all decrease and the optimal Ti content in the films should be no higher than 21%, at which ΔEc is 1.06 eV. The dielectric constant of the films not only can increase up to 31.3, but show a linear increase with increasing TiO2 content. Compared with HfO2 thin film with similar equivalent oxide thickness, low leakage currents were obtained.
Properties of nitrogen implanted and electron beam annealed bulk ZnO
Authors: Kennedy J. , Carder D. A. , Markwitz A. , Reeves R. J.
Published: May 2010

The optical properties of bulk ZnO ion implanted with nitrogen ions, at an energy of 23 keV have been studied as a function of implantation fluence and electron beam (EB) annealing conditions. Nuclear reaction analysis and Raman results have revealed the implanted N concentration and its structural changes with respect to various nitrogen ion fluences. The optical properties of nitrogen implanted bulk ZnO were investigated by low temperature photoluminescence measurements. An enhanced peak at 3.235 eV has been attributed to donor-accepter pair (DAP) emission involving the implanted N acceptor in ZnO. The emission near 3.3085 eV is attributed to a free electron to acceptor transition. We also report a broad band emission feature at ∼3.09 eV in the nitrogen implanted with 1–2×1015 ions cm−2 and EB annealed at 800–900 °C. This is assigned to a thermally activated nitrogen acceptor transition as it is unique only to nitrogen implanted samples. An ionization energy of 377 meV indicates that this line may correspond to a significantly less shallow acceptor level. In addition an increase in the intensity and dominance of this DAP line in nitrogen implanted samples over the other acceptor transitions was observed with increasing annealing time and temperatures. It is shown that EB annealing offers a method of enhanced nitrogen activation when compared to a more conventional furnace approach.
Novel nanocarbon hybrids of single-walled carbon nanotubes and dispersed nanodiamond: Structure and hierarchical defects evolution irradiated with gamma rays
Authors: Gupta S. , Scuttler A. M. , Farmer J.
Published: May 2010

We report the structure and physical properties of novel nanocarbon hybrids of single-walled carbon nanotubes (SWCNT) and ultradispersed diamond (UDD) forming truly tetragonal-trigonal nanocomposite ensemble with and without gamma irradiation. They were subjected to 50, 100, and 103 kGy doses and were characterized using analytical tools including electron microscopy, x-ray diffraction, resonance Raman spectroscopy (RS), and electrical measurements. Experiments showed that irradiation generates microscopic defects (the most likely vacancies) in a hierarchical manner much below amorphization threshold (≥103 kGy) and that nanocomposites tend to be radiation resilient, elucidated through the intensity, bandwidth, and position variation in prominent RS signatures. In the interpretation of findings the possibilities for these complex system are: (1) defect-mediated double-resonance mechanism may not explain intensity variation; (2) softening or violation of the q=0 selection rule; (3) difference in electronegativity of sp2 C (SWCNT) and sp3 C (UDD) can result in charge transfer and bond misalignment at the interface; and (4) the nanotubes are stabilized by nanodiamond particles. Furthermore, an attempt was made to identify the nature of defects (charged versus residual) through in-plane correlation length or sp2 C cluster size (La). The decreasing trend of La for both SWCNT and nanocompo sites with gamma irradiation implies charging defects described in terms of dangling bonds in contrast to passivating residual or neutral defects. Moreover, the electrical properties were relatively more labile to irradiation than structural and vibrational properties.
Interfacial engineering and coupling of electric and magnetic properties in Pb(Zr0.53Ti0.47)O3/CoFe2O4 multiferroic epitaxial multilayers
Authors: Zhang J. X. , Dai J. Y. , Chan H. L. W.
Published: May 2010

Epitaxial magnetoelectric (ME) Pb(Zr0.53Ti0.47)O3(PZT)/CoFe2O4(CFO) multilayer nanocomposite thin films with up to 11 alternative layers are grown on Nb doped SrTiO3 (STO) substrates by pulsed-laser deposition. X-ray diffraction and high resolution transmission electron microscopy studies reveal a good epitaxial relationship between the PZT and CFO layers without interfacial reaction at their interfaces. These epitaxial composite films exhibit strong ferroelectric and magnetic responses simultaneously at room temperature, and the interfacial-coupling-modulated dielectric behavior, polarization, and magnetic properties are observed and analyzed systematically. These results suggest that the magnetic, electric, and ME coupling effect may be tuned by the “strain engineering” in ferroelectric/magnetic or other multiferroic superlattice.
Extended temperature tuning of an ultraviolet diode laser for trapping and cooling single Yb+ ions
Authors: Nguyen A.-T. , Wang L.-B. , Schauer M. M. , Torgerson J. R.
Published: May 2010

We describe an ultraviolet (uv) diode laser system for cooling trapped Yb+ ions. Using four stages of thermoelectric cooling, 10 mW of light at 369.5 nm is obtained by cooling a 373.4-nm uv diode to approximately −20 °C. Frequency stabilization is provided by a diffraction grating mounted in the Littrow configuration which allows for a mode-hop free tuning range of ∼25 GHz. In order to avoid water condensation, the diode laser and associated optics are placed inside an evacuated chamber. Saturated absorption spectroscopy utilizing an Yb hollow cathode lamp is performed. This laser system is currently being used to cool single ions in an experiment whose ultimate goal is to look for modern variation of the fine-structure constant.
Material-dependent smoothing of periodic rippled structures by pulsed laser deposition
Authors: Röder Johanna , Liese Tobias , Krebs Hans-Ulrich
Published: May 2010

Any kind of processing of materials like thin film deposition, ion beam treatment or polishing often creates structures, which have lateral length scales of 20–200 nm. For many applications an efficient smoothing of such roughened surfaces is needed. To study smoothing on this length-scale, in this work periodic rippled structures with wavelengths of 55 nm and an average height of 4.5 nm were systematically covered by thin films of different material classes by pulsed laser deposition. All materials used possess a low intrinsic roughness on smooth substrates. As studied by atomic force microscopy, the surface roughness is continuously smoothed out with increasing layer thickness. In all cases, the whole process is strongly frequency dependent as expected from theoretical predictions. The dominant smoothing mechanisms have been identified as surface diffusion for small structures below a critical lateral size and sputter erosion or downhill currents for larger structures.
Coherent transport of armchair graphene constrictions
Authors: Yin HuiQiong , Li Wei , Hu Xiao , Tao Ruibao
Published: May 2010

The coherent transport properties of armchair graphene nanoconstrictions (GNC) are studied using tight-binding approach and Green’s function method. We find a nonbonding state at zero Fermi energy which results in a zero conductance valley, when a single vacancy locates at y=3n±1 of a perfect metallic armchair graphene nanoribbon (aGNR). However, the nonbonding state does not exist when a vacancy locates at y=3n, and the conductance behavior of lowest conducting channel will not be affected by the vacancy. For the square-shaped armchair GNC consisting of three metallic aGNR segments, resonant tunneling behavior is observed in the single channel energy region. We find that the presence of localized edge state locating at the zigzag boundary can affect the resonant tunneling severely. A simplified one dimensional model is put forward at last, which explains the resonant tunneling behavior of armchair GNC very well.
Experimental verification of tomographic phase-space imaging for beams with space-charge using a pinhole-scan
Authors: Stratakis D. , Kishek R. A. , Haber I. , Fiorito R. B. , Reiser M. , O’Shea P. G.
Published: May 2010

A model is described for tomographic phase-space mapping and emittance measurement in beams with space-charge. The tomographic results of an experiment with a 10 keV space-charge dominated electron beam are presented. The data are compared against a direct experimental sampling of the phase-space using a pinhole scan. It is found that the accuracy of the tomographic method is within 10% for beams with space-charge intensity less than 90%. With the aid of numerical simulation the observed similarities and differences between the tomography method and pinhole scan are discussed.
dc and high frequency magnetic properties of nanopatterned CoFe2O4 arrays fabricated using sol-gel precursors
Authors: Sheet Goutam , Cunliffe Alexandra R. , Offerman Erik J. , Folkman Chad M. , Eom Chang-Beom , Chandrasekhar Venkat
Published: May 2010

Nanostructures of ferromagnetic oxides having Curie temperatures above room temperature have potential for applications in memory devices and future spin-based electronic applications. In this article, we report on the dc and high frequency magnetic properties of arrays of elliptical CoFe2O4 nanopillars, covering a large area, fabricated by combined electron beam lithography, and a sol-gel based chemical route. The nanopillars were successfully fabricated on insulating oxidized silicon substrates and on epitaxial thin films of ferroelectric BiFeO3. We performed magnetic force microscopy and ferromagnetic resonance spectroscopy on the arrays to probe their magnetic properties. Due to the possible existence of dominant pinning sites, the CoFe2O4 nanopillars are not single-domain even at nanometer size scales.
Lithium and electrical properties of ZnO
Authors: Vines L. , Monakhov E. V. , Schifano R. , Mtangi W. , Auret F. D. , Svensson B. G.
Published: May 2010

Hydrothermal grown n-type ZnO samples have been investigated by deep level transient spectroscopy (DLTS), thermal admittance spectroscopy (TAS), temperature dependent Hall effect (TDH) measurements, and secondary ion mass spectrometry (SIMS) after thermal treatments up to 1500 °C, in order to study the electrical properties of samples with different lithium content. The SIMS results showed that the most pronounced impurities were Li, Al, Si, Mg, Ni, and Fe with concentrations up to ∼5×1017 cm−3. The Li concentration was reduced from ∼1017 cm−3 in as-grown samples to ∼1015 cm−3 for samples treated at 1500 °C, while the concentration of all the other major impurities appeared stable. The results from DLTS and TAS displayed at least five different levels having energy positions of Ec−20 meV, Ec−55 meV, Ec−0.22 eV, Ec−0.30 eV, and Ec−0.57 eV (Ec denotes the conduction band edge), where the Ec−55 meV level is the dominant freeze out level for conduction electrons in samples treated at temperatures <1300 °C, while higher annealing temperatures revealed the shallower (Ec−20 meV) level. The TDH measurements showed a pronounced increase in the electron mobility for the heat treated samples, where a peak mobility of 1180 cm2/V s was reached for a sample treated at 1300 °C. The results provide strong evidence that Li in hydrothermal ZnO is almost exclusively in the substitutional configuration (LiZn), supporting theoretical predictions that the formation of LiZn prevails over Li on the interstitial site for Fermi level positions at and above the middle of the band gap.
Laser excitation of electrostatic eigenmode of a plasma in azimuthal magnetic field and electron acceleration
Authors: Kumar K K Magesh , Tripathi V. K.
Published: May 2010

The localized electrostatic eigenmodes of a plasma with parabolic density profile in the presence of azimuthal magnetic field are investigated in the slab model by taking stepwise variations in plasma density and magnetic field. The mode amplitude is maximum where magnetic field is maximum. A mode can be resonant by beating two collinear lasers with frequency difference equal to the frequency of the eigenmode. Such a mode efficiently accelerates energetic electrons, executing bounce motion in the azimuthal field to high energies. At dimensionless mode plasma wave amplitude ap=eϕp0/m0c2=0.55, 10 keV electrons in a plasma of density n=1017/cm3 can be accelerated to 30 MeV energy.