bluuebunny/crossref_metadata_2025 huggingface dataset:
A discourse of silence: professional carers reasoning about death and dying in nursing homes
Authors: ÖSTERLIND JANE , HANSEBO GÖREL , ANDERSSON JANICKE , TERNESTEDT BRITT-MARIE , HELLSTRÖM INGRID
Published: January 2011

Nursing homes are a setting in which death and dying is common. How death and dying is articulated and the actions that take place in a nursing home constitute a discourse that guides the staff in their work. The aim of this study was to explore the discourse of death and dying in nursing homes from the perspective and understanding of the staff. The study draws on Foucault's discourse analysis. Data are from five focus-group discussions held with 28 staff of four different nursing homes in Sweden. The findings show that the discourse had three characteristics: (a) dying was silent and silenced, (b) emotions were pushed into the background, and (c) attentiveness to death arose after the moment of the elderly person's death. The structure of the discourse was characterised by a movement between two positions, avoiding and confronting death, the main focus being on avoidance. The articulation and practices of silence highlight a need to regard dying as a process that requires attention. One way to ensure appropriate attention could be to instil the philosophy of palliative care in nursing homes, including training and support for the staff in their work. The study demonstrates that nursing-home staff need more knowledge and support to enable them to feel that they do a good job.
Considerable Life Extension and Three Views on the Meaning of Life
Authors: HÄYRY MATTI
Published: January 2011

Picture this. You are having your regular medical checkup, when, all of a sudden, the physician turns to you and says: “Oh, did I remember to mention that you can now live forever?” You look at the doctor enquiringly and she goes on: “Well, it’s not actual immortality, you know, but they’ve invented this treatment—I don’t have the full details—that stops aging, getting physically older. It might not be for everyone, but you seem to be a suitable candidate. You could still die of accidents and illness, of course, but they’ve calculated that with care and any luck you should live to be a thousand, as opposed to the hundred or so that you would now have. And in a millennium, techniques will advance further, so there could be more in store for you after that.”
The Double Effect Effect
Authors: FOSTER CHARLES , HERRING JONATHAN , MELHAM KAREN , HOPE TONY
Published: January 2011

The “doctrine of double effect” has a pleasing ring to it. It is regarded by some as the cornerstone of any sound approach to end-of-life issues and by others as religious mumbo jumbo. Discussions about “the doctrine” often generate more heat than light. They are often conducted at cross-purposes and laced with footnotes from Leviticus.
Ideology and Politicization in Public Bioethics
Authors: McGEE SUMMER
Published: January 2011

Recently, concern has been raised regarding the politicization of public bioethics. Party politics has increasingly influenced public debate on ethical issues like stem cell research, human cloning, and end-of-life care. These debates have put bioethics “smack in the middle” of the culture wars. These recent events confirm Daniel Callahan’s prescient claim made in 1996 that “bioethical debates are beginning to reflect those culture wars … the larger moral struggles of our society.”
Justice and the Fetus: Rawls, Children, and Abortion
Authors: SHAW DAVID M.
Published: January 2011

In a footnote to the first edition of Political Liberalism, John Rawls introduced an example of how public reason could deal with controversial issues. He intended this example to show that his system of political liberalism could deal with such problems by considering only political values, without the introduction of comprehensive moral doctrines. Unfortunately, Rawls chose “the troubled question of abortion” as the issue that would illustrate this. In the case of abortion, Rawls argued, “the equality of women as equal citizens” overrides both “the ordered reproduction of political society over time” and also “the due respect for human life.” It seems fair to say that this was not the best choice of example and also that Rawls did not argue for his example particularly well: a whole subset of the Rawlsian literature concerns this question alone.
The Moral Basis for Healthcare Reform in the United States
Authors: TROTTER GRIFFIN
Published: January 2011

In speculating on the motives for government, English philosopher Thomas Hobbes identified the pervasive role of fear and the danger of violent death, holding famously that where no government prevails to secure physical safety and property, there can also be no enduring knowledge, art, or civilization—leaving human lives “solitary, poore [sic], nasty, brutish and short.”
The Rapid Ethical Decisionmaking Model: Critical Medical Interventions in Resource-Poor Environments
Authors: ISERSON KENNETH V.
Published: January 2011

Applying bioethical principles can be difficult in resource-poor environments, particularly for Western doctors unfamiliar with these limitations. The challenges become even greater when clinicians must make rapid critical decisions. As the following case in Zambia illustrates, the Rapid Ethical Decisionmaking Model, long used in emergency medicine, is a useful tool in such circumstances.
The Case of the Criminal Liver
Authors: MISHRA RUCHIKA
Published: January 2011

Mr. C was a 62-year-old Chinese-American man suffering from end stage liver disease secondary to Hepatitis C. While on the waiting list for a liver, he was told that his current condition and MELD score were not advanced enough to expect a liver transplant for several years. Because of his chronic fatigue, he asked if there was any way to speed up the process but was told that was not possible.
Improving TEM Fixation with Additives
Authors: Landers Stephen C.
Published: January 2011

Attempts to fix the gregarinePterospora floridiensis(a protozoan parasite found in marine bristle worms) for TEM using a conventional glutaraldehyde and osmium protocol produced poor preservation of the outer pellicular membranes and internal membranous structures. However, fixation success was achieved using the well-known fixative additives tannic acid and potassium ferrocyanide, which improved membrane preservation, cytoplasmic integrity, and contrast in both the unencysted feeding stage ofP. floridiensisas well as the difficult-to-fix cyst stage. The longer fixation times (24 hours) needed for the cysts were compatible with the modified fixatives. Interestingly,bothadditives were needed to improve fixation.
Getting Started with NIST DTSA-II
Authors: Ritchie Nicholas W. M.
Published: January 2011

Since its introduction in 2007, DTSA-II has been adopted by numerous researchers, and it has been integrated into numerous educational programs. This is the first of a series of articles in Microscopy Today that will appear in the upcoming months to provide an introduction to use of the product. These articles also will provide details of how DTSA-II can be used to implement best practices for microanalysis in your laboratory or in your teaching environment. These articles will demonstrate how to form the most accurate type of spectrum quantification—standards-base quantification—as well as how to use simulation to optimize various types of measurement problems. They will focus on using DTSA-II to understand the physical process including the interaction of energetic electrons with your sample and the propagation of x-rays through matter and to the detector.
What Caused Recent Acceleration of the North Magnetic Pole Drift?
Authors: Chulliat Arnaud , Hulot Gauthier , Newitt Lawrence R. , Orgeval Jean‐Jacques
Published: January 2011

The north magnetic pole (NMP) is the point at the Earth's surface where the geomagnetic field is directed vertically downward. It drifts in time as a result of core convection, which sustains the Earth's main magnetic field through the geodynamo process. During the 1990s the NMP drift speed suddenly increased from 15 kilometers per year at the start of the decade to 55 kilometers per year by the decade's end. This acceleration was all the more surprising given that the NMP drift speed had remained less than 15 kilometers per year over the previous 150 years of observation.
Eos Interviews John Holdren, President Obama's Science Advisor
Authors: Showstack Randy
Published: January 2011

With the Obama administration about to face a Republican‐led House of Representatives in January, presidential science advisor John Holdren sat down with Eos for an exclusive and wide‐ranging interview following a policy speech he delivered on 13 December at the AGU Fall Meeting in San Francisco. During the interview, Holdren, who also is director of the White House Office of Science and Technology Policy (OSTP), focused on the challenging congressional and budgetary environment, the administration's priorities related to the Earth sciences, and the responsibility of scientists in helping to communicate the societal benefits of science, educate the public, and improve science education and literacy.

Holdren said the Obama administration's top priorities related to the Earth sciences include improving observations of the Earth, making progress in dealing with climate change, and rebalancing NASA's focus.
Report calls for transforming the U.S. energy system
Authors: Showstack Randy , Tretkoff Ernie
Published: January 2011

The United States should develop a coordinated, government‐wide, federal energy policy to transform the nation's energy system within 1–2 decades, according to a 29 November report by the President's Council of Advisors on Science and Technology (PCAST). A key recommendation is for the president to establish a quadrennial energy review process to provide a road map for short‐ and long‐term energy objectives, to outline legislative proposals, to put forward anticipated executive branch actions, and to identify resource requirements for research and development programs.

Entitled “Report to the president on accelerating the pace of change in energy technologies through an integrated federal energy policy,” the report also calls for the government to invest $16 billion per year for clean energy innovation. The report indicates that this would be an approximate tripling of current Department of Energy investments in energy science and technology. Stating that “the discretionary budget is under severe pressure,” the report recommends that the president engage the private sector and Congress to generate about $10 billion per year of funding through new revenue streams. A small charge on electricity and transportation fuel could be “well within the normal fluctuations in price seen by consumers” and generate billions of dollars for research.
Melting glaciers
Authors: Showstack Randy , Tretkoff Ernie
Published: January 2011

Glaciers in Patagonia and Alaska have been losing their mass, and for longer than glaciers elsewhere in the world, according to a 7 December report compiled by the United Nations Environment Programme (UNEP). “Climate change is causing significant mass loss of glaciers in high mountains worldwide,” notes the report, which calls for accelerated research, monitoring, and modeling of glaciers and snow and their role in water supplies. The report “also highlights the vulnerability and exposure of people dependent upon [glacier‐fed] rivers to floods, droughts and eventually shortages as a result of changes in the melting and freezing cycles linked with climate change and other pollution impacts,” according to UNEP executive director Achim Steiner.
Modeling Earth Dynamics: Complexity, Uncertainty, and Validation 28th IUGG Conference on Mathematical Geophysics; Pisa, Italy, 7–11 June 2010
Authors: Neri A.
Published: January 2011

The capabilities and limits of mathematical models applied to a variety of geophysical processes were discussed during the 28th international Conference on Mathematical Geophysics, held in Italy (see the conference Web site (http://cmg2010.pi.ingv.it), which includes abstracts). The conference was organized by the International Union of Geodesy and Geophysics (IUGG) Commission on Mathematical Geophysics (CMG) and the Istituto Nazionale di Geofisica e Vulcanologia and was cosponsored by the U.S. National Science Foundation. The meeting was attended by more than 160 researchers from 26 countries and was dedicated to the theme “Modelling Earth Dynamics: Complexity, Uncertainty, and Validation.”

Many talks were dedicated to illustration of the complexities affecting geophysical processes. Novel applications of geophysical fluid dynamics were presented, with specific reference to volcanological and subsurface/surface flow processes. In most cases, investigations highlighted the need for multidimensional and multiphase flow models able to describe the nonlinear effects associated with the nonhomogeneous nature of the matter. Fluid dynamic models of atmospheric, oceanic, and environmental systems also illustrated the fundamental role of nonlinear couplings between the different subsystems. Similarly, solid Earth models have made it possible to obtain the first tomographies of the planet; to formulate nonlocal and dynamic damage models of rocks; to investigate statistically the triggering, clustering, and synchronization of faults; and to develop realistic simulators of the planetary dynamo, plate tectonics, and gravity and magnetic fields.
CXCR3 ligands: redundant, collaborative and antagonistic functions
Authors: Groom Joanna R , Luster Andrew D
Published: January 2011

CXCR3 is a chemokine receptor that is rapidly induced on naïve T cells following activation, and preferentially remains highly expressed on type‐1 helper (Th1)‐type CD4+ T cells, effector CD8+ T cells and innate‐type lymphocytes, such as natural killer (NK) and NKT cells. CXCR3 is activated by three interferon (IFN)‐γ‐inducible ligands CXCL9 (monokine induced by gamma‐interferon), CXCL10 (interferon‐induced protein‐10) and CXCL11 (interferon‐inducible T‐cell alpha chemoattractant). Although some studies have revealed that these ligands have redundant functions in vivo, other studies have demonstrated that the three CXCR3 ligands can also collaborate and even compete with each other. Differential regulation of the three ligands at specific times in defined anatomically restricted locations in vivo likely participates in the fine control of T‐cell trafficking over the course of an immune response. Among the differences in regulation, CXCL10 is induced by a variety of innate stimuli that induce IFN‐α/β as well as the adaptive immune cell cytokine IFN‐γ, whereas CXCL9 induction is restricted to IFN‐γ. In this review, we will discuss how the balance, timing and pattern of CXCR3 ligand expression appears to regulate the generation of effector T cells in the lymphoid compartment and subsequent migration into peripheral sites of Th1‐type inflammation in which the CXCR3 ligands also then regulate the interactions and migratory behavior of effector T cells in an inflamed peripheral tissue.
Polycomb group protein Bmi1 negatively regulates IL‐10 expression in activated macrophages
Authors: Sienerth Arnold R , Scheuermann Christian , Galmiche Antoine , Rapp Ulf R , Becker Matthias
Published: January 2011

Macrophages exert a wide variety of functions, which necessitate a high level of plasticity on the chromatin level. In the work presented here, we analyzed the role of the polycomb group protein Bmi1 during the acute response of bone marrow derived macrophages (BMDM) to lipopolysaccharide (LPS). Unexpectedly, we observed that Bmi1 was rapidly induced at the protein level and transiently phosphorylated upon LPS treatment. The induction of Bmi1 was dependent on MAP‐kinase signaling. LPS treatment of BMDM in the absence of Bmi1 resulted in a pronounced increase in expression of the anti‐inflammatory cytokine interleukin‐10 (IL‐10). Our results identify Bmi1 as a repressor of IL‐10 expression during macrophage activation.
Role of TLR4 in ethanol effects on innate and adaptive immune responses in peritoneal macrophages
Authors: Pascual María , Fernández‐Lizarbe Sara , Guerri Consuelo
Published: January 2011

Toll‐like receptors (TLRs) play an important role in the innate immune response and these receptors link innate and adaptive responses. We have reported that ethanol modulates TLR4 receptors by activating or inhibiting its response. However, the role of TLRs in the effects of ethanol on the innate and adaptive responses during acute or chronic treatment is presently unknown. Peritoneal macrophages of wild‐type and TLR4‐deficient mice treated with acute ethanol (4 g kg−1, intraperitoneally) or chronic ethanol consumption (5 months) were used. Here we report how acute ethanol dose induces inflammatory cytokines (tumor necrosis factor‐α, interleukin (IL)‐1β, macrophage inflammatory protein 1α (MIP‐1α), interferon β1 and IL‐12β) and chemokines (monocyte chemoattractant protein ‐1α and MIP‐1α), and upregulates major histocompatibility complexes class I and II (MHC‐I and ‐II), but inhibits the activation of the costimulatory molecules (CD86 and CD40), leading to the suppression of the CD4+ T‐cell proliferation in the macrophages of wild‐type mice. Chronic ethanol consumption downregulates the number of F4/80+ cells expressing MHC‐I and ‐II and decreases CD4+ T‐cell activation in wild‐type mice. Interestingly, elimination of TLR4 abolishes the effects of ethanol on the innate and the adaptive inflammatory response induced by both ethanol treatments in macrophages. Taken together, our findings support the role of TLR4 in the effects of ethanol on the immune system, and suggest that alterations in the function of this receptor might modulate the immune response induced by alcohol abuse.
Bleaching versus poling: Comparison of electric field induced phenomena in glasses and glass-metal nanocomposites
Authors: Lipovskii A. A. , Melehin V. G. , Petrov M. I. , Svirko Yu. P. , Zhurikhina V. V.
Published: January 2011

By examining the electric field induced processes in glasses and glass-metal nanocomposites (GMN) we propose mechanism of the electric field assisted dissolution (EFAD) of metal nanoparticles in glass. We show that in both glass poling and EFAD processes, the strong (up to 1 V/nm) local electric field in the subanodic region is due to the presence of “slow” hydrogen ions bonded to nonbridging oxygen atoms in glass matrix. However, the origin of these hydrogen ions in glass and GMN is different. Specifically, when we apply the electric field to a virgin glass, the enrichment of the glass with hydrogen species takes place in the course of the poling. In GMN, the hydrogen ions have been incorporated into the glass matrix during metal nanoparticles formation via reduction in a metal by hydrogen, i.e., before the electric field was applied. The EFAD of metal nanoparticles resembles the electric field stimulated diffusion of metal film in glass (the important difference however is that in GMN, there is no direct contact of dissolving metal entity with anodic electrode). This similarity makes it possible to estimate the energy of thermal activated transition of silver atoms from a nanoparticle to glass matrix as ∼1.3 eV. Electroneutrality of the GMN requires emission of electrons from nanoparticles. Photoconductivity spectra of soda-lime glasses and the results of numerical calculations of band structure of fused silica, sodium disilicate and sodium-calcium-silicate glass enable us to evaluate the bandgap and the position of electron mobility edge in soda-lime glass. The evaluated values are ∼6 eV and ∼1.2 eV below vacuum level, respectively. The bent of the glass band structure in strong electric field permits a direct tunneling of Fermi electrons from silver nanoparticle (4.6 eV below the vacuum level) to the glass conductivity band. Evaluated in accordance with the Fowler–Nordheim equation the magnitude of electric field necessary to establish comparable electron emission and ion ejection rates is ∼0.27 V/nm, although other phenomena including polarization of the nanoparticles and tunneling of electrons thermally distributed above Fermi level, decreases this magnitude. We believe that the different mechanisms of ejection for electrons and ions should result in charging nanoparticles in EFAD process. The electron tunneling to localized OH− states and glass matrix relaxation process are also discussed.
Joint analysis of ESR lineshapes and 1H NMRD profiles of DOTA-Gd derivatives by means of the slow motion theory
Authors: Kruk D. , Kowalewski J. , Tipikin D. S. , Freed J. H. , Mościcki M. , Mielczarek A. , Port M.
Published: January 2011

The “Swedish slow motion theory” [Nilsson and Kowalewski, J. Magn. Reson. 146, 345 (2000)] applied so far to Nuclear Magnetic Relaxation Dispersion (NMRD) profiles for solutions of transition metal ion complexes has been extended to ESR spectral analysis, including in addition g-tensor anisotropy effects. The extended theory has been applied to interpret in a consistent way (within one set of parameters) NMRD profiles and ESR spectra at 95 and 237 GHz for two Gd(III) complexes denoted as P760 and P792 (hydrophilic derivatives of DOTA-Gd, with molecular masses of 5.6 and 6.5 kDa, respectively). The goal is to verify the applicability of the commonly used pseudorotational model of the transient zero field splitting (ZFS). According to this model the transient ZFS is described by a tensor of a constant amplitude, defined in its own principal axes system, which changes its orientation with respect to the laboratory frame according to the isotropic diffusion equation with a characteristic time constant (correlation time) reflecting the time scale of the distortional motion. This unified interpretation of the ESR and NMRD leads to reasonable agreement with the experimental data, indicating that the pseudorotational model indeed captures the essential features of the electron spin dynamics.
Magnetism of substitutional Fe impurities in graphene nanoribbons
Authors: Longo R. C. , Carrete J. , Gallego L. J.
Published: January 2011

Using the generalized gradient approximation to exchange and correlation, we perform density functional calculations on an Fe atom at a single vacancy of graphene nanoribbons. Our results show that, after relaxation, the Fe atom is magnetic, in contrast to the behavior recently found for Fe at a single vacancy of the graphene sheet.
Application of Brewster angle microscopy and fractal analysis in investigations of compressibility of Langmuir monolayers
Authors: Risović Dubravko , Frka Sanja , Kozarac Zlatica
Published: January 2011

The aim of this study was to investigate the connection between the lipid/amphiphile monolayer structure at the interface and its macroscopic/rheological properties, in particular, to establish the link between the fractality of the monolayer structure and its compressibility modulus. To that purpose we have used fractal analysis of images obtained by Brewster angle microscopy to infer the fractal dimension of the monolayer structure and relate its change to the corresponding changes in compressibility derived from a simultaneously measured π-A isotherm. The results of the study confirmed the starting assumption based on theoretical considerations that the fractal dimension of an amphiphilic monolayer and its compressibility should be correlated. We have shown that there exists a strong correlation between the fractal dimension and the corresponding compressibility modulus of different amphiphilic materials. Thus, confirming the link between the short ordered structure on the molecular level and the macroscopic property—compressibility of the monolayer. The established correlation between the fractal dynamics and compressibility modulus of the monolayer enabled identification of onset of percolation—a second-order phase transition that is otherwise not easy and unambiguously detectable. We have found that the signature of percolation in a monolayer, regardless of its composition, is the occurrence of a sharp increase (a jump) of compressibility modulus (at macroscopic level) at the characteristic value of the corresponding fractal dimension D = 1.89. This is the result of the abrupt establishment of a connected structure on the molecular level, consequently involving a change in the elastic properties of the monolayer on a macroscopic scale. The results of this investigation provide means for unambiguous identification of the onset of percolation in the Langmuir layer and should facilitate a more efficient application of the percolation theory in further study of processes and structures at the interface during the monolayer compression.
Dependence of the localized surface plasmon resonance of noble metal quasispherical nanoparticles on their crystallinity-related morphologies
Authors: Yang Peng , Portalès Hervé , Pileni Marie-Paule
Published: January 2011

The absorption spectra of 5 nm noble metal nanoparticles (Ag, Au, and Cu) with typical morphologies of multiply twinned particles (MTPs) and single crystals are calculated by using the discrete dipole approximation method. Among the considered morphologies, it is found that icosahedral, cuboctahedral and truncated octahedral particles behave like quasispherical particles whereas the optical response of the decahedral particles significantly differs from the others. This result, which originates from the shape anisotropy of the decahedron, points out the capacity to discriminate decahedral MTPs from a population of particles with mixed crystallinities and related quasispherical shapes.
Autoionization widths by Stieltjes imaging applied to Lanczos pseudospectra
Authors: Kopelke S. , Gokhberg K. , Cederbaum L. S. , Tarantelli F. , Averbukh V.
Published: January 2011

Excited states of atoms and molecules lying above the ionization threshold can decay by electron emission in a process commonly known as autoionization. The autoionization widths can be calculated conveniently using Fano formalism and discretized atomic and molecular spectra by a standard procedure referred to as Stieltjes imaging. The Stieltjes imaging procedure requires the use of the full discretized spectrum of the final states of the autoionization, making its use for poly-atomic systems described by high-quality basis sets impractical. Following our previous work on photoionization cross-sections, here we show that also in the case of autoionization widths, the full diagonalization bottleneck can be overcome by the use of Lanczos pseudospectra. We test the proposed method by calculating the well-documented autoionization widths of inner-valence-excited neon and apply the new technique to autoionizing states of hydrofluoric acid and benzene.
A quantitative model for doping contrast in the scanning electron microscope using calculated potential distributions and Monte Carlo simulations
Authors: Chee Augustus K. W. , Broom Ronald F. , Humphreys Colin J. , Bosch Eric G. T.
Published: January 2011

This paper describes the use of a Monte Carlo model incorporating a finite-element method computing the electrostatic fields inside and outside a semiconductor, plus a ray-tracing algorithm for determining the doping contrast observed in a scanning electron microscope (SEM). This combined numerical method also enables the effects on the doping contrast of surface band-bending to be distinguished from those of external patch fields outside the specimen, as well as any applied macroscopic external fields from the detection system in the SEM. Good agreement of our new theory with experiment is obtained. The contrast characteristics in energy-filtered secondary electron images are also explained. The results of this work lead to a more advanced understanding of the doping contrast mechanisms, thereby enabling quantitative dopant profiling using the SEM.
Multiwalled carbon nanotubes and dispersed nanodiamond novel hybrids: Microscopic structure evolution, physical properties, and radiation resilience
Authors: Gupta S. , Farmer J.
Published: January 2011

We report the structure and physical properties of novel hybrids of multiwalled carbon nanotubes (MWCNTs) and ultradispersed diamond (UDD) forming nanocomposite ensemble that were subjected to 50, 100, and 103 kGy gamma ray doses and characterized using various analytical tools to investigate hierarchical defects evolution. This work is prompted by recent work on single-walled CNTs and UDD ensemble [Gupta et al., J. Appl. Phys. 107, 104308 (2010)] where radiation-induced microscopic defects seem to be stabilized by UDD. The present experiments show similar effects where these hybrids display only a minimal structural modification under the maximum dose. Quantitative analyses of multiwavelength Raman spectra revealed lattice defects induced by irradiation assessed through the variation in prominent D, G, and 2D bands. A minimal change in the position of D, G, and 2D bands and a marginal increase in intensity of the defect-induced double resonant Raman scattered D and 2D bands are some of the implications suggesting the radiation coupling. The in-plane correlation length (La) was also determined following Tunistra–Koenig relation from the ratio of D to G band (ID/IG) besides microscopic stress. However, we also suggest the following taking into account of intrinsic defects of the constituents: (a) charge transfer arising at the interface due to the difference in electronegativity of MWCNT C sp2 and UDD core (C sp3) leading to phonon and electron energy renormalization; (b) misorientation of C sp2 at the interface of MWCNT and UDD shell (C sp2) resulting in structural disorder; (c) softening or violation of the q∼0 selection rule leading to D band broadening and a minimal change in G band intensity; and (d) normalized intensity of D and G bands with 2D band help to distinguish defect-induced double resonance phenomena. The MWCNT when combined with nanodiamond showed a slight decrease in their conductance further affected by irradiation pointing at relatively good interfacial contact. Furthermore, owing to high thermal and electrical conductivity properties, they can facilitate potentially efficient heat-transfer applications and some results deduced using Nielsen’s model is provided.
Self-consistent electrothermal analysis of nanotube network transistors
Authors: Kumar S. , Pimparkar N. , Murthy J. Y. , Alam M. A.
Published: January 2011

We develop an electrothermal transport model for nanocomposite thin films based on self-consistent solution of drift-diffusion and Poisson equations for electrons coupled with diffusive transport of heat. This model is used to analyze the performance of an electronic display the pixels of which are controlled by carbon nanotube (CNT) network thin-film transistors (TFTs). The effect of electrothermal coupling on device performance and steady state temperature rise is analyzed as a function of key device parameters such as channel length, network density, tube-to-substrate thermal conductance, and tube-to-substrate thermal conductivity ratio. Our analysis suggests that device on-current Ion may reduce by 30% for a 1 μm channel length devices due to self-heating. The temperature rise in such devices can be as high as 500 K in extreme cases due to the thermally insulating substrate and the low tube-to-substrate thermal conductance. These results suggest that an appropriate combination of network density, channel length and width should be selected for CNT-TFTs to avoid device temperature rise above acceptable limits. We analyze the effectiveness of active cooling in reducing the temperature and enhancing the performance of the device. We find that the high thermal spreading resistance between the CNT device and the electronic display reduces the effectiveness of forced convective cooling, necessitating the exploration of alternative designs for viable CNT-FET based display technology.
Temperature and injection level dependencies and impact of thermal oxidation on carrier lifetimes in p-type and n-type 4H–SiC epilayers
Authors: Hayashi T. , Asano K. , Suda J. , Kimoto T.
Published: January 2011

Dependencies of temperature and injection level on carrier lifetimes in 50 μm thick p-type and n-type 4H–SiC epilayers have been investigated. The carrier lifetimes have been measured by differential microwave photoconductance decay measurements at various injection levels and temperatures. In both p-type and n-type epilayers, the carrier lifetimes gradually increased with increasing the injection level, which were naturally expected from the Shockley-Read-Hall (SRH) model, and after taking a maximum, the lifetimes dropped at the very high-injection level. In contrast, the carrier lifetimes exhibited continuous increase with elevating the temperature for both epilayers. In addition, the impact of thermal oxidation process on the carrier lifetimes has been also investigated. The thermal oxidation process, by which the Z1/2 and EH6/7 centers were remarkably reduced that had been observed in n-type 4H–SiC in our previous work, led to the improvement of the carrier lifetimes especially for n-type epilayers. The carrier lifetime reached 4.1 μs in p-type and 6.1 μs in n-type epilayers at 250 °C with an injection level of 1.8×1016 cm−3 through the thermal oxidation processing.
Fourier-based magnetic induction tomography for mapping resistivity
Authors: Puwal Steffan , Roth Bradley J.
Published: January 2011

Magnetic induction tomography is used as an experimental tool for mapping the passive electromagnetic properties of conductors, with the potential for imaging biological tissues. Our numerical approach to solving the inverse problem is to obtain a Fourier expansion of the resistivity and the stream functions of the magnetic fields and eddy current density. Thus, we are able to solve the inverse problem of determining the resistivity from the applied and measured magnetic fields for a two-dimensional conducting plane. When we add noise to the measured magnetic field, we find the fidelity of the measured to the true resistivity is quite robust for increasing levels of noise and increasing distances of the applied and measured field coils from the conducting plane, when properly filtered. We conclude that Fourier methods provide a reliable alternative for solving the inverse problem.
Vibrational transitions of the $^7$7LiH$^+$+ ion calculated without the Born–Oppenheimer approximation and with leading relativistic corrections
Authors: Bubin Sergiy , Stanke Monika , Adamowicz Ludwik
Published: January 2011

We recently presented very accurate calculations of the fundamental vibrational frequency of the \documentclass[12pt]{minimal}\begin{document}$^7$\end{document}7LiH\documentclass[12pt]{minimal}\begin{document}$^+$\end{document}+ and \documentclass[12pt]{minimal}\begin{document}$^3$\end{document}3He\documentclass[12pt]{minimal}\begin{document}$^4$\end{document}4He\documentclass[12pt]{minimal}\begin{document}$^+$\end{document}+ ions [Stanke et al. Phys. Rev. A 79, 060501(R) (2009)] performed without the Born–Oppenheimer approximation and included leading relativistic corrections. The accuracy of those calculations was estimated to be of the order of 0.06 cm\documentclass[12pt]{minimal}\begin{document}$^{-1}$\end{document}−1. In the present work we extend the calculations to the remaining pure vibrational states of \documentclass[12pt]{minimal}\begin{document}$^7$\end{document}7LiH\documentclass[12pt]{minimal}\begin{document}$^+$\end{document}+ and similarly accurate results are generated. They may lead to the experimental search for still unidentified lines corresponding to those transitions.
Photodissociation of thioglycolic acid studied by femtosecond time-resolved transient absorption spectroscopy
Authors: Attar Andrew R. , Blumling Daniel E. , Knappenberger Kenneth L.
Published: January 2011

Steady-state and time-resolved spectroscopies were employed to study the photodissociation of both the neutral (HS-CH2-COOH) and doubly deprotonated (−S-CH2-COO−) forms of thioglycolic acid (TGA), a common surface-passivating ligand used in the aqueous synthesis and organization of semiconducting nanostructures. Room temperature UV-Vis absorption spectroscopy indicated strong absorption by the S1 and S2 excited states at 250 nm and 185 nm, respectively. The spectrum also contained a weaker absorption band that extended to approximately 550 nm, which was assigned to the $\pi ^ * _{CO} \leftarrow n_O$πCO*←nO transition. Femtosecond time-resolved transient absorption spectroscopy was performed on TGA using 400 nm excitation and a white-light continuum probe to provide the temporally and spectrally resolved data. Both forms of TGA underwent a photoinduced dissociation from the excited state to form an α-thiol-substituted acyl radical (α-TAR, S-CH2-CO•). For the acidic form of TGA, radical formation occurred with an apparent time constant of 60 ± 5 fs; subsequent unimolecular decay took 400 ± 60 fs. Similar kinetics were observed for the deprotonated form of TGA (70 ± 10 fs radical formation; 420 ± 40 fs decay). The production of the α-TAR was corroborated by the observation of its characteristic optical absorption. Time-resolved data indicated that the photoinduced dissociation of TGA via cleavage of the C-OH bond occurred rapidly (≤100 fs). The prevalence of TGA in aqueous semiconducting nanoparticles makes its absorption in the visible spectral region and subsequent dissociation key to understanding the behavior of nanoscale systems.
Controllability of the subband occupation of InAs quantum dots on a delta-doped GaAsSb barrier
Authors: Ban Keun-Yong , Hong Woong-Ki , Bremner Stephen P. , Dahal Som N. , McFelea Heather , Honsberg Christiana B.
Published: January 2011

Optical properties of InAs quantum dots (QDs) embedded in GaAsSb barriers with delta-doping levels equivalent to 0, 2, 4, and 6 electrons per dot (e/dot) are studied using time-integrated photoluminescence (PL). When the PL excitation power is increased the full width at half maximum (FWHM) of the 4 and 6 e/dot samples is found to increase at a much greater rate than the FWHMs for the 0 and 2 e/dot samples. PL spectra of the 4 e/dot sample show a high energy peak attributed to emission from the first excited states of the QDs, a result deduced to be due to preoccupation of states by electrons supplied by the delta-doping plane. When temperature dependent PL results are fitted using an Arrhenius function, the thermal activation energies for the 4 and 6 e/dot samples are similar and greater than the thermal activation energies for the 0 and 2 e/dot samples (which are similar to each other). This increased thermal activation energy is attributed to the enhanced Coulombic interaction in the InAs QD area by the delta-doping plane for higher doping levels. It is concluded that delta-doping of the barrier in QD systems is a feasible method for controlling the level of carrier occupation in a QD mediated intermediate band.
Distinguishing magnetic blocking and surface spin-glass freezing in nickel ferrite nanoparticles
Authors: Nadeem K. , Krenn H. , Traussing T. , Letofsky-Papst I.
Published: January 2011

Nickel ferrite nanoparticles dispersed in SiO2 matrix have been synthesized by sol-gel method. Structural analysis has been performed by using x-ray diffraction and transmission electron microscopy. Magnetic properties have been investigated by using superconducting quantum interference device magnetometry. In addition to the average blocking temperature peak at TB=120 K measured by a zero field cooled temperature scan of the dc susceptibility, an additional hump near 15 K is observed. Temperature dependent out-of-phase ac susceptibility shows the same features: one broad peak at high temperature and a second narrow peak at low temperature. The high temperature peak corresponds to magnetic blocking of individual nanoparticles, while the low temperature peak is attributed to surface spin-glass freezing which becomes dominant for decreasing particle diameter. To prove the dynamics of the spin (dis)order in both regimes of freezing and blocking, the frequency dependent ac susceptibility is investigated under a biasing dc field. The frequency shift in the “frozen” low-temperature ac susceptibility peak is fitted to a dynamic scaling law with a critical exponent zv=7.5, which indicates a spin-glass phase. Exchange bias is turned on at low temperature which signifies the existence of a strong core-shell interaction. Aging and memory effects are further unique fingerprints of a spin-glass freezing on the surface of isolated magnetic nanoparticles.
Shape transformation of lipid vesicles induced by diffusing macromolecules
Authors: Góźdź W. T.
Published: January 2011

The attachment of macromolecules to the surface of a lipid vesicle may cause its deformations such as budding or creation of cylindrical protrusions. Diffusion of the macromolecules in the membranes may cause its shape transformations. The process of shrinking the protrusions due to diffusion of the macromolecules is investigated. It is assumed that macromolecules modify locally the spontaneous curvature and bending rigidity of the lipid membrane. Both spontaneous curvature and bending rigidities depend on the concentration of membrane components. It has been shown that cylindrical protrusions are created when the macromolecules which induce large spontaneous curvature are accumulated at a piece of the vesicle surface. It has been observed that here the elastic constants influence very little the evolution of the vesicle shape caused by diffusing macromolecules and the most important is the value the spontaneous curvature imposed by the macromolecules.
Mathematical model of vortex penetration phenomenon
Authors: Ma Rongchao
Published: January 2011

Vortex penetration affects the stability of a superconducting system and limits the possible application of the system. However, the mathematical description to this phenomenon is currently unavailable. Here, I presented a mathematical model in which I considered the effects of bulk pinning and internal field repulsive force on vortex hopping. Thereafter, I proposed a series expansion to the activation energy and derived a general formula to describe the time dependence of the vortex penetration process. With these formulas, I can analyze the experimental data and calculate the activation energy of the vortex penetration phenomenon. The results are accurate for the time dependence of the internal field measurements in a Bi2Sr2CaCu2O8+x superconductor.
Coherent transport description of the dual-wavelength ambipolar terahertz quantum cascade laser
Authors: Beji G. , Ikonić Z. , Evans C. A. , Indjin D. , Harrison P.
Published: January 2011

A transport and gain model is developed for the recently realized ambipolar dual-wavelength terahertz quantum cascade laser. The model is based on the simplified density matrix formalism, describing the population and coherence terms of five relevant states per period, which includes the laser optical field and single-temperature thermal balance. Using the measured current densities under forward and reverse bias for calibration, a good theoretical/experimental agreement is found for the current-optical power characteristics and the laser dynamic range. This shows that the model is a reliable analyzer, if not yet a fully predictive tool, for quantum cascade laser simulation.
Convective instability in inhomogeneous media: Impulse response in the subcritical cylinder wake
Authors: Marais C. , Godoy-Diana R. , Barkley D. , Wesfreid J. E.
Published: January 2011

We study experimentally the impulse response of a cylinder wake below the critical Reynolds number of the Bénard–von Kármán instability. In this subcritical regime, a localized inhomogeneous region of convective instability exists which causes initial perturbations to be transiently amplified. The aim of this work is to quantify the evolution resulting from this convective instability using two-dimensional particle image velocimetry in a hydrodynamic tunnel experiment. The velocity fields allow us to describe the evolution of wave packets in terms of two control parameters: the Reynolds number and the magnitude of the imposed perturbation. The temporal evolution of energy exhibits a transient algebraic growth at short times followed by an exponential decay.
Structural, optical, and photoluminescence characterization of electron beam evaporated ZnS/CdSe nanoparticles thin films
Authors: Mohamed S. H. , Ali H. M.
Published: January 2011

Structural, optical, and photoluminescence investigations of ZnS capped with CdSe films prepared by electron beam evaporation are presented. X-ray diffraction analysis revealed that the ZnS/CdSe nanoparticles films contain cubic cadmium selenide and hexagonal zinc sulfide crystals and the ZnS grain sizes increased with increasing ZnS thickness. The refractive index was evaluated in terms of envelope method, which has been suggested by Swanepoel in the transparent region. The refractive index values were found to increase with increasing ZnS thickness. However, the optical band gap and the extinction coefficient were decreased with increasing ZnS thickness. Photoluminescence (PL) investigations revealed the presence of two broad emission bands. The ZnS thickness significantly influenced the PL intensities.
Fourier transformation infrared spectrum studies on the role of fluorine in SnO2:F films
Authors: Zhang B. , Tian Y. , Zhang J. X. , Cai W.
Published: January 2011

In this letter we employed Fourier transform infrared spectroscopy (FTIR) to study fluorine-doped SnO2 films deposited by spray pyrolysis. The role of oxygen vacancy and substitution of fluorine for oxygen are demonstrated by FTIR. It is found that at low doping levels, fluorine ions prefer to occupy oxygen positions in SnO2 lattice. While beyond a certain doping level, fluorine ions start to occupy interstitial positions, which has a negative effect on carrier concentration that, in turn, affects the infrared reflectivity of SnO2 films. FTIR also shows the increase of the disorder of SnO2 films with increasing fluorine doping.
Ferroelectric, piezoelectric, and leakage current properties of (K0.48Na0.48Li0.04)(Nb0.775Ta0.225)O3 thin films grown by pulsed laser deposition
Authors: Wang D. Y. , Lin D. M. , Kwok K. W. , Chan N. Y. , Dai J. Y. , Li S. , Chan H. L. W.
Published: January 2011

Lead-free (K0.48Na0.48Li0.04)(Nb0.775Ta0.225)O3 (KNLNT) thin films were deposited on Pt(111)/Ti/SiO2/Si(001) substrates using pulsed laser deposition. The film exhibited a well-defined ferroelectric hysteresis loop with a remnant polarization 2Pr of 22.6 μC/cm2 and a coercive field Ec of 10.3 kV/mm. The effective piezoelectric coefficient d33,f of the KNLNT thin films was found to be about 49 pm/V by piezoelectric force microscope. The dominant conduction mechanisms of Au/KNLNT/Pt thin film capacitor were determined to be bulk-limited space-charge-limited-current and Poole–Frenkle emission at low and high electric field strengths, respectively, within a measured temperature range of 130–370 K.
Deformation-immunized optical deposition of graphene for ultrafast pulsed lasers
Authors: Kim Hyungseok , Cho Junhyun , Jang Sung-Yeon , Song Yong-Won
Published: January 2011

We demonstrate deformation-suppressed optical deposition of graphene onto an optical fiber by forming a graphene/polyvinyl acetate (PVAc) composite for ultrafast nonlinear photonics. With pure graphene, its nonlinear operation threshold is elevated by the optical deposition that cannot guarantee the intact two-dimensional nanoshape of graphene. The role of PVAc that provides immunity to graphene against deleterious degradation of morphology and optical nonlinearity is elucidated via electron microscope analysis, Raman characterization, and realizing passive mode-locking operation of fiber lasers. Resultant center wavelength, spectral width, and repetition rate of the laser pulses are 1572.6 nm, 0.6 nm, and 91.5 MHz, respectively.