bluuebunny/crossref_metadata_2025 huggingface dataset:
A Troublesome Statistic: Traders and Coastal Shipments in the Westward Movement of Slaves
Authors: Steckel Richard H. , Ziebarth Nicolas
Published: August 2013

We analyze all slave manifests housed at the National Archives—some 24,400 documents involving approximately 135,000 slaves who were transported in the coastwise trade from 1810 to 1861. The manifests list the name of the owner or shipper, which allows us to match names with traders found in other sources. We also utilize demographic characteristics of the manifests to estimate the probability that a trader organized the shipment. Commercial transactions increased over the antebellum period, and on average were responsible for approximately 55 percent of slaves who migrated from Atlantic to Gulf coast ports.

“No one has ever suggested a method for finding what proportion of the slaves transported from one state to another were taken by their original masters or their heirs for their own use.”

Bancroft 1931, p. 397
Law, Politics, and Financial Development: The Great Reversal of the U.K. Corporate Debt Market
Authors: Coyle Christopher , Turner John D.
Published: August 2013

This article examines the role of creditor protection in the development of the U.K. corporate bond market. This market grew rapidly in the late nineteenth century, but in the twentieth century it experienced a reversal, albeit with a short-lived post-1945 renaissance. Such was the extent of the reversal that the market from the 1970s onwards was smaller than it had been in 1870. We find that law does not explain the variation in the size of this market over time. Alternatively, our evidence suggests that inflation and taxation policies were major drivers of this market in the post-1945 era.
Theoretical investigations on the effect of different plasmas on growth and field emission properties of a spherical carbon nanotube (CNT) tip placed over cylindrical surfaces
Authors: TEWARI AARTI , SHARMA SURESH C.
Published: August 2013

The theoretical investigations on the effect of different plasmas on the growth and field emission properties of a spherical carbon nanotube (CNT) tip placed over cylindrical CNT surfaces have been carried out for the typical glow discharge plasma parameters. Different plasmas such as H2, Ar, CH4 and CF4 have been considered, and the growth of the CNT in the presence of various plasmas has been estimated in the present investigation. This study suggests that the field emission from the CNT grown in the presence of the H2 plasma is largest. It is also found that amongst the plasmas considered, the CF4 plasma is the most favourable for the growth of the large radius CNT, since the radius achieved in the CF4 plasma is the largest.
An electromagnetic gamma-ray free electron laser
Authors: ELIASSON BENGT , LIU CHUAN SHENG
Published: August 2013

We present a theoretical model for the generation of coherent gamma rays by a free electron laser, where a high-energy electron beam interacts with an electromagnetic wiggler. By replacing the static undulator with a 1-μm laser wiggler, the resulting radiation would go from X-rays currently observed in experiments, to gamma rays. Coherent light in the gamma-ray range would have wide-ranging applications in the probing of matter on sub-atomic scales.
Drift instability in a positive ion–negative ion plasma
Authors: ROSENBERG M. , MERLINO R. L.
Published: August 2013

Drift wave instability in a magnetized plasma composed of positive ions and negative ions is considered using linear kinetic theory in the local approximation. We consider the case where the mass (temperature) of the negative ions is much larger (smaller) than that of the positive ions, and where the gyroradii of the two ion species are comparable. Weak collisional effects are taken into account. Application to possible laboratory parameters is discussed.
Relativistic cross-focusing of extraordinary and ordinary modes in a magnetoactive plasma
Authors: VARSHNEY MEENU ASTHANA , SHUKLA SHALINI , SEN SONU , VARSHNEY DINESH
Published: August 2013

This paper presents the effect of self-focusing on a circularly polarized beam propagating along the static magnetic field when the extraordinary and ordinary modes are present simultaneously for relativistic intensities. The nonlinearity in the dielectric function arises on account of the relativistic variation of mass, which leads to the mutual coupling of the two modes that support the self-focusing of each other. The propagation and focusing of the first mode affects the propagation and focusing of the second mode. The fact that the two modes are laser-intensity dependent leads to cross-focusing. Dynamics of one laser beam affects the dynamics of the second laser beam. When both the beams or modes are strong, the nonlinearities introduced by the relativistic effect in the presence of the magnetic field are additive in nature, such that one beam can undergo oscillatory self-focusing and other beam simultaneously defocusing and vice versa. The dynamical equation governing the cross-focusing has been set up and a numerical solution has been presented for typical relativistic laser–plasma parameters from a slightly underdense to overdense plasma.
Anisotropic model for resonant heating of ions by Alfvén waves
Authors: ZHANG T. X.
Published: August 2013

Anisotropic heating of ions by Alfvén waves with frequency in the ion–cyclotron frequency range and propagation parallel to the magnetic field lines is investigated. First, particle–Alfvén wave interactions are quasilinearly examined from the kinetic theory in a hot multi-ion-magnetized plasma. As a result, the parallel and perpendicular heating rates of ions are derived analytically. Then, in terms of this anisotropic heating model and the dispersion relation of magnetic field-aligned left-hand polarized electromagnetic ion–cyclotron–Alfvén (EMICA) waves, the resonant heating of H,2H,3H,3He, and4He ions in a typical preheated laboratory plasma is numerically studied. It is shown that the EMICA waves can efficiently heat ions through cyclotron resonances primarily in the perpendicular direction. The perpendicular temperatures of H,2H,3H,3He, and4He increase much faster than the parallel ones. In comparison with the result from the previously developed isotropic heating model, the parallel heating by the EMICA waves is about much weaker, while the perpendicular heating is more efficient. Parameters such as density, temperature, magnetic field, wave-energy density, and ion species can affect the efficiency of the Alfvén wave heating in a similar way as shown in the isotropic heating model. The anisotropic model can be applied to explain the measurements of why O+5and Mg+9are heated extreme perpendicularly in solar coronal holes.
Seabird and dolphin associations: do seabirds benefit from feeding in association with dusky dolphins in Patagonia?
Authors: Degrati Mariana , Dans Silvana L. , Garaffo Griselda V. , Crespo Enrique A.
Published: August 2013

The objective of this study was to describe associations between several species of seabirds and dusky dolphins. We investigated during what dolphin activities seabirds were most commonly associated, and the size of flock in relation to the number of dolphins in a group. Since both seabirds and dolphins may display different feeding strategies, we also investigated if benefits differed among seabird species. Data were collected in Golfo Nuevo (42°20′S65°00′W) on-board a research vessel between 2001 and 2008. A total of 224 mixed groups of seabirds were encountered during this study. The seabird–dolphin associations were mainly observed during dusky dolphin surface feeding. Shearwaters and kelp gulls were mainly observed in flocks that were associated with dolphins, while Magellanic penguins and cormorants were mainly observed without dolphins. Seabirds may be conditioned to the foraging strategy of dolphins, since birds are associated with dolphins only during dolphin surface feeding. This association probably helped seabirds to find prey, but there were no obvious benefits to dolphins.
Neural substrates of behavioral variability in attention deficit hyperactivity disorder: based on ex-Gaussian reaction time distribution and diffusion spectrum imaging tractography
Authors: Lin H.-Y. , Gau S. S.-F. , Huang-Gu S. L. , Shang C.-Y. , Wu Y.-H. , Tseng W.-Y. I.
Published: August 2013

Background

Increased intra-individual variability (IIV) in reaction time (RT) across various tasks is one ubiquitous neuropsychological finding in attention deficit hyperactivity disorder (ADHD). However, neurobiological underpinnings of IIV in individuals with ADHD have not yet been fully delineated. The ex-Gaussian distribution has been proved to capture IIV in RT. The authors explored the three parameters [μ(mu),σ(sigma),τ(tau)] of an ex-Gaussian RT distribution derived from the Conners' continuous performance test (CCPT) and their correlations with the microstructural integrity of the frontostriatal–caudate tracts and the cingulum bundles.

Method

We assessed 28 youths with ADHD (8–17 years; 25 males) and 28 age-, sex-, IQ- and handedness-matched typically developing (TD) youths using the CCPT, Wechsler Intelligence Scale for Children, 3rd edition and magnetic resonance imaging (MRI). Microstructural integrity, indexed by generalized fractional anisotropy (GFA), was measured by diffusion spectrum imaging tractrography on a 3-T MRI system.

Results

Youths with ADHD had largerσ(s.d.of Gaussian distribution) andτ(mean of exponential distribution) and reduced GFA in four bilateral frontostriatal tracts. With increased inter-stimulus intervals of CCPT, the magnitude of greaterτin ADHD than TD increased. In ADHD youths, the cingulum bundles and frontostriatal integrity were associated with three ex-Gaussian parameters and withμ(mean of Gaussian distribution) andτ, respectively; while only frontostriatal GFA was associated withμandτin TD youths.

Conclusions

Our findings suggest the crucial role of the integrity of the cingulum bundles in accounting for IIV in ADHD. Involvement of different brain systems in mediating IIV may relate to a distinctive pathophysiological processing and/or adaptive compensatory mechanism.
Sovereign debt in Latin America, 1820-1913
Authors: della Paolera Gerardo , Taylor Alan M.
Published: August 2013

This paper examines sovereign lending to Latin America and the Caribbean from 1820 to 1913. We examine four waves of capital flows where defaults were followed by a return to market access. In spite of extended default, countries kept promising high returns that attracted international investors again and again: financial autarky thus gave way to eras of high integration to global markets as measured by sovereign risk pricing. We discuss imperfections of the sovereign debt institutional context in the region and discuss a menu of options that some countries used to seek funds in the global financial markets after defaults. The parallel with the modern Latin American and Caribbean sovereign bond market experience is striking.
A snake-based scheme for path planning and control with constraints by distributed visual sensors
Authors: Cheng Y. , Jiang P. , Hu Y. F.
Published: August 2013

This paper proposes a robot navigation scheme using wireless visual sensors deployed in an environment. Different from the conventional autonomous robot approaches, the scheme intends to relieve massive on-board information processing required by a robot to its environment so that a robot or a vehicle with less intelligence can exhibit sophisticated mobility. A three-state snake mechanism is developed for coordinating a series of sensors to form a reference path. Wireless visual sensors communicate internal forces with each other along the reference snake for dynamic adjustment, react to repulsive forces from obstacles, and activate a state change in the snake body from a flexible state to a rigid or even to a broken state due to kinematic or environmental constraints. A control snake is further proposed as a tracker of the reference path, taking into account the robot's non-holonomic constraint and limited steering power. A predictive control algorithm is developed to have an optimal velocity profile under robot dynamic constraints for the snake tracking. They together form a unified solution for robot navigation by distributed sensors to deal with the kinematic and dynamic constraints of a robot and to react to dynamic changes in advance. Simulations and experiments demonstrate the capability of a wireless sensor network to carry out low-level control activities for a vehicle.
The risk of acquiring bacterial meningitis following surgery in Denmark, 1996–2009: a nationwide retrospective cohort study with emphasis on ear, nose and throat (ENT) and neurosurgery
Authors: HOWITZ M. F. , HOMØE P.
Published: August 2013

This paper estimates the risk of bacterial meningitis following surgery between 1996 and 2009 in Denmark. We conducted two retrospective nationwide cohort studies; first by linking notified bacterial meningitis cases to the National Patient Registry to see how many had undergone a surgical procedure; second, we scrutinized notified bacterial meningitis cases to see if the clinician suspected a surgical procedure to be the aetiology. We found that ear, nose and throat surgery had an 11-fold, and neurosurgery a sevenfold, increased risk compared to the reference group in the first 10 days following surgery. Streptococcus pneumoniae was the pathogen most often involved. Operation procedures involving penetration of dura mater was associated with increased risk for post-operative bacterial meningitis. In absolute numbers we found few bacterial meningitis cases after surgery; however, patients undergoing certain surgical procedures are at-risk and should be considered when national vaccination guidelines are revised.
Paternal fibrillin-1 mutation transmitted to an affected son with neonatal marfan syndrome: the importance of early recognition
Authors: Elshershari Huda , Harris Catharine
Published: August 2013

We describe a case of neonatal Marfan syndrome diagnosed because of a family history, dysmorphic features, and cardiac abnormality. The echocardiogram showed aortic root dilatation. Molecular genetic studies showed a mutation in exon 31 of the FBN1 gene in the infant and father. The infant was treated with losartan, which significantly slowed the rate of enlargement of the aorta.
Urbanicity, Persecutory Delusions, and Clinical Intervention: The Development of a Brief CBT Module for Helping Patients with Persecutory Delusions Enter Social Urban Environments
Authors: Freeman Daniel , Waller Helen , Harpur-Lewis Ruth Ann , Moore Rosanna , Garety Philippa , Bebbington Paul , Kuipers Elizabeth , Emsley Richard , Dunn Graham , Fowler David , Jolley Suzanne
Published: August 2013

Background: Substantial epidemiological research has shown that psychotic experiences are more common in densely populated areas. Many patients with persecutory delusions find it difficult to enter busy social urban settings. The stress and anxiety caused by being outside lead many patients to remain in-doors. We therefore developed a brief CBT intervention, based upon a formulation of the way urban environments cause stress and anxiety, to help patients with paranoid thoughts to feel less distressed when outside in busy streets. Aims: The aim was to pilot the new intervention for feasibility and acceptability and gather preliminary outcome data. Method: Fifteen patients with persecutory delusions in the context of a schizophrenia diagnosis took part. All patients first went outside to test their reactions, received the intervention, and then went outside again. Results: The intervention was considered useful by the patients. There was evidence that going outside after the intervention led to less paranoid responses than the initial exposure, but this was only statistically significant for levels of distress. Conclusions: Initial evidence was obtained that a brief CBT module specifically focused on helping patients with paranoia go outside is feasible, acceptable, and may have clinical benefits. However, it could not be determined from this small feasibility study that any observed improvements were due to the CBT intervention. Challenges in this area and future work required are outlined.
REAL-TIME, ADAPTIVE LEARNING VIA PARAMETERIZED EXPECTATIONS
Authors: Berardi Michele , Duffy John
Published: August 2013

We explore real-time adaptive nonlinear learning dynamics in stochastic macroeconomic systems. Rather than linearizing nonlinear Euler equations where expectations play a role around a steady state, we instead approximate the nonlinear expected values using the method of parameterized expectations. Further, we assume that these approximated expectations are updated in real time as new data become available. We argue that this method of real-time parameterized expectations learning provides a plausible alternative to real-time adaptive learning dynamics under linearized versions of the same nonlinear system, and we provide a comparison of the two approaches.
Ultrastructure of Lymphatic Stomata in the Tunica Vaginalis of Humans
Authors: Wang Jiaxiong , Ping Zepeng , Jiang Tingting , Yu Hongyuan , Wang Chong , Chen Zhongliang , Zhang Xing , Xu Dandan , Wang Li , Li Zhongjie , Li Ji-Cheng
Published: August 2013

Lymphatic stomata are small openings of lymphatic capillaries on the surface of the mesothelium that lines the serous cavity and have the function of active absorption. They play an important role in physiological and pathological conditions. The cavity of the tunica vaginalis is a typical serous cavity of the testis, but the lymphatic stomata of the tunica vaginalis of humans have never been reported. Here, we studied their ultrastructure by scanning and transmission electron microscopy. The submesothelial connective tissue with foramina was investigated after the mesothelial cells were digested using NaOH solution. We found the lymphatic stomata in cuboidal mesothelial cell regions of the parietal layer of the tunica vaginalis of humans with a diameter of about 1–2 μm. Sometimes, closed lymphatic stomata could be observed. Our study is the first to report the existence of lymphatic stomata of the tunica vaginalis of humans. We found that the tunica vaginalis cavity is connected with the lymphatic system through the stomata, which might provide a morphological basis for the drainage of hydrocele and tumor metastasis of the tunica vaginalis of humans.
The Determination of Rotation Axis in the Rotation Electron Diffraction Technique
Authors: Buxhuku Mika , Hansen Vidar , Oleynikov Peter , Gjønnes Jon
Published: August 2013

Methods to determine the rotation axis using the rotation electron diffraction technique are described. A combination of rotation axis tilt, beam tilt, and simulated experimental diffraction patterns with nonintegers zone axis has been used. Accurate knowledge of the crystallographic direction of the incident beam for deducing the excitation error of reflections simultaneously near Bragg positions is essential in quantitative electron diffraction. Experimental patterns from CoP3 are used as examples.
A Comparative Scanning Electron Microscopy Evaluation of Smear Layer Removal from Teeth with Different Irrigation Solutions and Lasers
Authors: Kalyoncuoğlu Elif , Demiryürek Ebru Özsezer
Published: August 2013

The aim of this study was to evaluate the efficacy of smear layer removal from teeth following root canals using lasers (Er:YAG and Nd:YAG), NaOCl, 17% EDTA, and MTAD by scanning electron microscopy (SEM). Root canals were irrigated with 3 mL of 5.25% NaOCl after each file. Teeth were randomly divided into five groups. In the final irrigation, canals were irrigated with 5.25% NaOCl (Group 1, control), 17% EDTA (Group 2), or BioPure MTAD (Group 3). Laser groups were irradiated with Er:YAG laser (1.8 W, 120 mJ, 15 Hz) (Group 4) or Nd:YAG laser (1 W, 100 mJ, 15 Hz) (Group 5). The smear layer at the apical, middle, and coronal thirds of each root canal was imaged using SEM. Smear layer removal by EDTA was the most effective in all regions. The difference between EDTA and MTAD was statistically significant in the coronal and middle (p < 0.05), but not the apical (p > 0.05), regions. The difference between the control and laser groups was not statistically significant (p > 0.05). In all regions, the difference between 17% EDTA–MTAD and the control–laser groups was statistically significant (p < 0.05). Although improvement was observed in removal of the smear layer using alternative materials and techniques, application of a combination of EDTA and NaOCl remains an effective technique.
Liver Alterations in Two Freshwater Fish Species (Carassius auratusandDanio rerio) Following Exposure to Different TiO2Nanoparticle Concentrations
Authors: Diniz Mário S. , de Matos António P. Alves , Lourenço Joana , Castro Luísa , Peres Isabel , Mendonça Elsa , Picado Ana
Published: August 2013

The toxicity of titanium dioxide nanoparticles (TIO2NPs) and oxidative stress effects were studied in two freshwater fish species (Carassius auratusandDanio rerio) exposed for 21 days to different concentrations (0.01, 0.1, 1, 10, 100/mgL) of TiO2NPs and to a control (tap water). Additional fish were transferred to clean water for 14 days to assess the ability to recover from exposure to TiO2NPs. Activities of the enzyme glutathione-S-transferase (GST) and lipid peroxidation (LPO) (malondialdheyde) were measured as indicators of oxidative stress. Histological and ultra-structural changes in livers from bothspecies of fish were evaluated by light and electron microscopy. Results show a general GST activity increase according to TiO2NPs concentrations, which is in agreement with data from LPO. After 21 days, GST activities decreased possibly caused by suppression of GST synthesis as a result of severe stress. Histological and ultra-structural analysis of livers from exposed fish show degeneration of the hepatic tissue and alterations in hepatocytes such as glycogen depletion and an increase in lipofucsin lysosome-like granules. After a depuration period a partial recovery for biochemical markers and cells was observed. The results suggest that TiO2promotes alterations in hepatic tissues compatible with oxidative stress.
Human P-glycoprotein differentially affects antidepressant drug transport: relevance to blood–brain barrier permeability
Authors: O'Brien Fionn E. , Clarke Gerard , Dinan Timothy G. , Cryan John F. , Griffin Brendan T.
Published: August 2013

The pharmacological concept that inhibition of the drug efflux pump P-glycoprotein (P-gp) enhances brain distribution of the antidepressant imipramine in the rat has recently been demonstrated. To determine if these findings are relevant to humans, the present study investigated if imipramine is a transported substrate of human P-gp. Furthermore, additional experiments were carried out to determine if findings in relation to imipramine and human P-gp would apply to other antidepressants from a range of different classes. To this end, bidirectional transport experiments were carried out in the ABCB1-transfected MDCKII-MDR1 cell line. Transported substrates of human P-gp are subjected to net efflux in this system, exhibiting a transport ratio (TR) ⩾ 1.5, and directional efflux is attenuated by co-incubation of a P-gp inhibitor. Imipramine was identified as a transported substrate of human P-gp (TR = 1.68, attenuated by P-gp inhibition). However, the antidepressants amitriptyline, duloxetine, fluoxetine and mirtazapine were not transported substrates of human P-gp (TR ⩽ 1.16 in all cases). These results offer insight into the role of P-gp in the distribution of antidepressants, revealing that rodent findings pertaining to imipramine may translate to humans. Moreover, the present results highlight that other antidepressants may not be transported substrates of human P-gp.
Isolated Congenital Hereditary Cataract in a Dizygotic Twin: Prenatal Ultrasonographic Diagnosis
Authors: Lee Kyung A , Park Mi-Hye , Kim Young Ju , Chun Sun Hee
Published: August 2013

Cataract, defined as opacity of the lens in one or both eyes, is a major cause of blindness throughout the world, and not uncommon, particularly in the elderly population. However, congenital cataracts are rare and occur with a frequency of 30 cases in 100,000 births. About one-third of the cases fall into the group inherited without systemic abnormality. Importantly, congenital cataracts produce deprivation amblyopia, refractive amblyopia, and retinal detachment, leading to lifelong visual impairment. Successful management is dependent on early diagnosis and referral for surgery when indicated. Here we present a case of hereditary bilateral cataracts in a dizygotic twin detected on prenatal ultrasound examinations and postnatally confirmed as congenital cataracts associated with posterior lenticonus.
The delicate balance of melanoma immunotherapy
Authors: Gyorki David E , Callahan Margaret , Wolchok Jedd D , Ariyan Charlotte E
Published: August 2013

The strategy of immune modulation for the treatment of cancer is being refined with the introduction of multiple new therapeutic agents into the clinic. Melanoma is a disease where many of these agents have demonstrated efficacy. The mechanisms of action of these agents exploit the counter‐regulatory mechanisms of the immune response. However, these agents are also associated with immune‐related adverse events (IRAEs), which represent tissue‐specific inflammatory responses. These IRAEs highlight the delicate balance of immunologic homeostasis and, with some interventions, may occur more frequently in patients who sustain a therapeutic response. This review will discuss melanoma immunogenicity and immunotherapy. Furthermore, the spectrum and distinction between a reversible immune adverse event and autoimmunity will be highlighted.
Association of telomere shortening in myocardium with heart weight gain and cause of death
Authors: Terai Masanori , Izumiyama-Shimomura Naotaka , Aida Junko , Ishikawa Naoshi , Sawabe Motoji , Arai Tomio , Fujiwara Mutsunori , Ishii Akio , Nakamura Ken-ichi , Takubo Kaiyo
Published: August 2013

We attempted to clarify myocardial telomere dynamics using samples from 530 autopsied patients using Southern blot analysis. Overall regression analysis demonstrated yearly telomere reduction rate of 20 base pairs in the myocardium. There was a significant correlation between myocardial telomere and aging. Moreover, regression analyses of telomere and heart weight yielded a telomere reduction rate of 3 base pairs per gram and a small but significant correlation between telomere reduction and heart weight was demonstrated. Hearts of autopsied patients who had died of heart disease were significantly heavier than those of patients who had died of cancer or other diseases and heart disease was significantly more correlated with myocardial telomere shortening than cancer or other diseases. Here we show that telomeres in myocardial tissue become shortened with aging and heart disease and that heart disease was associated with a gain of heart weight and telomere shortening in the myocardium.
Molecular design for enhanced sensitivity of a FRET aptasensor built on the graphene oxide surface
Authors: Ueno Yuko , Furukawa Kazuaki , Matsuo Kota , Inoue Suzuyo , Hayashi Katsuyoshi , Hibino Hiroki
Published: August 2013

Introducing a DNA spacer between an aptamer and a dye enhances the sensitivity for protein detection.
Photo-reactive nanogels as a means to tune properties during polymer network formation
Authors: Liu JianCheng , Rad Ima Y. , Sun Fang , Stansbury Jeffrey W.
Published: August 2013

Delay of gelation in a matrix was achieved by incorporation of a secondary photo-reactive nanogel functionalized with RAFT groups.
Direct and indirect core–shell inversion of block copolymer micelles
Authors: Lin Mingchang , Chen Guosong , Jiang Ming
Published: August 2013

A novel block copolymer PNIPAm-b-PBOB is reported where denaturation of PNIPAm and PBOB is switched by independent, controllable stimuli. Core–shell inversion may be realized via different pathways, indirect and direct, by adjusting the program of imposing the stimuli.
Recovering the spectrum of a low level signal from two noisy measurements using the cross power spectral density
Authors: Fleming Andrew J. , Ninness Brett , Wills Adrian
Published: August 2013

The article describes a method for estimating the spectrum or RMS value of a low-level signal corrupted by noise. If two identical sensors can be employed simultaneously and the additive noise sources are uncorrelated, the cross power spectrum can recover the power spectrum of the underlying signal. When using the Welch method to estimate the cross power spectrum, the estimation process is shown to be biased but consistent, with a variance that is inversely proportional to the number of data sets. The proposed technique is demonstrated experimentally to recover the vibration spectrum of a piezoelectric cantilever. The dual sensor method reduces the effective noise floor by three orders of magnitude and recovers spectral features that were otherwise lost in noise.
Kinetics of swelling under constraint
Authors: Liu Qihan , Robisson Agathe , Lou Yucun , Suo Zhigang
Published: August 2013

Swellable elastomers are used to seal flow channels in oilfield operations. After sealing, the elastomers are constrained triaxially, and a contact load builds up between the elastomers and surrounding rigid materials. For these applications, the ability to predict the evolution of the contact load is important. This work introduces an experimental setup to measure the contact load as a function of time. The experimental data are well represented by a simple time-relaxation equation derived from the linear poroelastic theory, enabling a determination of the effective diffusivity of solvent inside the elastomers.
How do high pressures change the Debye process of 4-methyl-3-heptanol?
Authors: Pawlus S. , Wikarek M. , Gainaru C. , Paluch M. , Böhmer R.
Published: August 2013

4-methyl-3-heptanol, a monohydroxy alcohol with a relatively small dielectric Debye process, is studied in wide ranges of temperature (143 K < T < 308 K) and pressure (0.1 MPa < p < 864 MPa). When monitored under isochronous conditions, i.e., focusing on constant relaxation times, as well as under isothermal conditions, the Debye process gains significant intensity upon pressure application. This behavior contrasts with that of the previously studied octanol 2-ethyl-1-hexanol, which features a large Debye process. These experimentally observed, clearly distinguishable pressure evolutions are discussed to reflect differences in the formation of hydrogen-bonded supramolecular structures.
Anthrax toxin-induced rupture of artificial lipid bilayer membranes
Authors: Nablo Brian J. , Panchal Rekha G. , Bavari Sina , Nguyen Tam L. , Gussio Rick , Ribot Wil , Friedlander Art , Chabot Donald , Reiner Joseph E. , Robertson Joseph W. F. , Balijepalli Arvind , Halverson Kelly M. , Kasianowicz John J.
Published: August 2013

We demonstrate experimentally that anthrax toxin complexes rupture artificial lipid bilayer membranes when isolated from the blood of infected animals. When the solution pH is temporally acidified to mimic that process in endosomes, recombinant anthrax toxin forms an irreversibly bound complex, which also destabilizes membranes. The results suggest an alternative mechanism for the translocation of anthrax toxin into the cytoplasm.
Understanding the relationship between molecular order and charge transport properties in conjugated polymer based organic blend photovoltaic devices
Authors: Wood Sebastian , Kim Jong Soo , James David T. , Tsoi Wing C. , Murphy Craig E. , Kim Ji-Seon
Published: August 2013

We report a detailed characterization of the thin film morphology of all-polymer blend devices by applying a combined analysis of physical, chemical, optical, and charge transport properties. This is exemplified by considering a model system comprising poly(3-hexylthiophene) (P3HT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT). We show that the interactions between the two conjugated polymer components can be controlled by pre-forming the P3HT into highly ordered nanowire structures prior to blending with F8BT, and by varying the molecular weight of the F8BT. As a result, it is possible to produce films containing highly ordered P3HT with hole mobilities enhanced by three orders of magnitude over the pristine blends. Raman spectroscopy under resonant excitation conditions is used to probe the molecular order of both P3HT and F8BT phases within the blend films and these morphological studies are complemented by measurements of photocurrent generation. The resultant increase in photocurrent is associated with the enhanced charge carrier mobilities. The complementary analytical method demonstrated here is applicable to a wide range of polymer blend systems for all applications where the relationships between morphology and device performance are of interest.
Assessing the phase retardation in corneal tissues using a femtosecond laser
Authors: Calhoun William , Weiblinger Richard , Beylin Alexander , Ilev Ilko K.
Published: August 2013

We developed and validated a versatile test method for precise quantification of phase retardation in corneal tissues using a femtosecond laser. It is based on an experimental system for direct measurement of corneal phase rotation due to corneal birefringence effects using a dual-polarizer, computer-controlled, femtosecond laser design. It also includes a comprehensive analytical model using Jones matrices. The test method presented is used for quantification of phase retardation in corneal tissues by employing the experimental data obtained from corneal phase rotation measurements and using analytical model assessments. The experimental and theoretical results obtained, and thus, the system's high accuracy and repeatability potential for assessing the corneal phase retardation are validated using control phase retardation evaluation.
Theoretical characterization of C7, C7−, and C7+
Authors: Mogren Al-Mogren M. , Senent M. L. , Hochlaf M.
Published: August 2013

We present a theoretical investigation of neutral and ionic C7 molecules. Since carbon chains present isomerism and the number of possible structures increases fast with the number of carbon atoms, a B3LYP/aug-cc-pVTZ search of stationary points has been achieved. For C7, we found twelve minimal structures. Among these forms, eleven C7 isomers are located into the lowest singlet hyper potential energy surface. The most stable form of C7 is linear and possesses a 1Σg+ symmetry species. For C7−, we characterized fifteen stable forms, where twelve are of doublet spin-multiplicity. The global minimum of C7− is a 2Πg doubly degenerate Renner-Teller structure. For C7+ cation, we found eleven doublet and three quartet isomers with a 7-atom cycle, C7+ (X2A1) ground state. For the most stable forms, explicitly correlated (R)CCSD(T)-F12 calculations have been performed for the determination of equilibrium geometries and for the spectroscopic characterization of C7, C7−, and C7+, providing accurate rotational constants and harmonic frequencies. Vertical excitation energies to the lowest electronic states have been computed at the CASSCF/MRCI/aug-cc-pVTZ level. Thirty five electronic states of C7, suitable of being involved in reactive processes, lie below 7 eV. Fourteen metastable electronic states of C7− have been found below 3.5 eV. For linear-C7, we compute the electron affinity and the ionization energy to be 3.38 eV and 10.42 eV, respectively.
Properties of Alfvén eigenmodes in the Toroidal Alfvén Eigenmode range on the National Spherical Torus Experiment-Upgrade
Authors: Podestà M. , Gorelenkov N. N. , White R. B. , Fredrickson E. D. , Gerhardt S. P. , Kramer G. J.
Published: August 2013

A second Neutral Beam (NB) injection line is being installed on the NSTX Upgrade device, resulting in six NB sources with different tangency radii that will be available for heating and current drive. This work explores the properties of instabilities in the frequency range of the Toroidal Alfvén Eigenmode (TAE) for NSTX-U scenarios with various NB injection geometries, from more perpendicular to more tangential, and with increased toroidal magnetic field with respect to previous NSTX scenarios. Predictions are based on analysis through the ideal MHD code NOVA-K. For the scenarios considered in this work, modifications of the Alfvén continuum result in a frequency up-shift and a broadening of the radial mode structure. The latter effect may have consequences for fast ion transport and loss. Preliminary stability considerations indicate that TAEs are potentially unstable with ion Landau damping representing the dominant damping mechanism.
Unusually large spin polarization and magnetoresistance in a FeMg8–FeMg8 superatomic dimer
Authors: Zhu Lin , Qian Meichun , Khanna Shiv N.
Published: August 2013

Electronic transport across a FeMg8 magnetic superatom and its dimer has been investigated using a density functional theory combined with Keldysh nonequilibrium Green's-function formalism. For a single cluster, our studies for the cluster supported in various orientations on a Au(100) surface show that the transport is sensitive to the contact geometry. Investigations covering the cases where the axes of Mg square antiprism are 45°, perpendicular, and parallel to the transport direction, show that the equilibrium conductance, transferred charge, and current polarizations can all change significantly with orientation. Our studies on the transport across a magnetic superatom dimer FeMg8–FeMg8 focus on the effect of electrode contact distance and the support. The calculated I-V curves show negative differential resistance behavior at larger electrode-cluster contact distances. Further, the equilibrium conductance in ferromagnetic state shows an unusually high spin polarization that is about 81.48% for specific contact distance, and a large magnetoresistance ratio exceeding 500% is also found. The results show that the superatom assemblies can provide unusual transport characteristics, and that the spin polarization and magnetoresistance can be controlled via the contact geometry.
Numerical modelling of finite-size particle collisions in a viscous fluid
Authors: Brändle de Motta J. C. , Breugem W.-P. , Gazanion B. , Estivalezes J.-L. , Vincent S. , Climent E.
Published: August 2013

A general model is presented for short-range hydrodynamic interactions and head-on particle-particle/wall collisions. The model has been embedded in two distinct numerical methods for fully resolved simulation of finite-size particles in a viscous fluid. It accounts for the material properties of the particles and lubrication effects prior to collision that cannot be fully resolved on a fixed grid. We demonstrate that the model is able to reproduce experimental data for the coefficient of restitution of particle-wall collisions over a wide range of Stokes number based on the particle impact velocity. The set of model parameters we selected and more generally the modelling approach we propose can be efficiently used for fully resolved simulations of moderately dense solid-liquid suspensions.
Density functional theory for comprehensive orbital energy calculations
Authors: Nakata Ayako , Tsuneda Takao
Published: August 2013

This study reveals the reason core 1s orbital energies and the highest occupied molecular orbital (HOMO) energies of hydrogen and rare gas atoms are underestimated by long-range corrected (LC) density functional theory (DFT), which quantitatively reproduces the HOMO energies of other systems and the lowest unoccupied molecular orbital (LUMO) energies. Applying the pseudospectral regional (PR) self-interaction correction (SIC) drastically improved the underestimated orbital energies in LC-DFT calculations, while maintaining or improving the accuracies in the calculated valence HOMO and LUMO energies. This indicates that the self-interaction error in exchange functionals causes the underestimations of core 1s orbital energies and the HOMO energies of hydrogen and rare gas atoms in LC-DFT calculations. To clarify the reason for the improvement, the fractional occupation dependences of total electronic energies and orbital energies were examined. The calculated results clearly showed that the LC-PR functional gives almost linear dependences of total electronic energies for a slight decrease in the occupation number of core 1s orbitals, although this linear dependence disappears for significant decrease due to the shrinking of exchange self-interaction regions. It was also clarified that the PRSIC hardly affects the occupation number dependences of the total electronic energies and orbital energies for the fractional occupations of HOMOs and LUMOs. As a result, it was concluded that core orbital energies are obtained accurately by combining LC-DFT with PRSIC.
Energetics and electron states of Au/Ag incorporated into crystalline/amorphous silicon
Authors: Yang Moon Young , Kamiya Katsumasa , Yamauchi Takashi , Nakayama Takashi , Shiraishi Kenji
Published: August 2013

We report behaviors of gold (Au) and silver (Ag) incorporated into crystalline silicon (c-Si) and amorphous silicon (a-Si) based on first-principles calculations. Our results show that both Au and Ag exhibit different behaviors in between c-Si and a-Si. The Au/Ag atom locates at the tetrahedral interstitial site in c-Si and it takes a positively charged state as an energetically stable state for the wide range of band gap of c-Si. On the other hand, the Au/Ag atom tends to take a neutral charge state in a-Si. We reveal that both d- and s-orbitals of Au/Ag are deeply concerned in those different behaviors. This study indicates that Au/Ag changes the way to interact with Si depending on the geometric structure.
Theory and synthesis of bilayer graphene intercalated with ICl and IBr for low power device applications
Authors: Jadaun Priyamvada , Movva Hema C. P. , Register Leonard F. , Banerjee Sanjay K.
Published: August 2013

Graphene intercalation materials are potentially promising for the implementation of the ultra-low power, excitonic-condensate-based Bilayer pseudoSpin Field-Effect Transistor (BiSFETs) concept, as well as other novel device concepts requiring a graphene interlayer dielectric. Using density functional theory, we study the structural and electronic properties of bilayer graphene intercalated with iodine monochloride (ICl) and iodine monobromide (IBr). We determine the structural configuration of ICl and IBr graphene intercalation compounds (GICs). We also conduct an in-depth exploration of inter-layer electronic coupling, using ab initio calculations. The presence of intercalants dopes the graphene layer. It also reduces, but does not eliminate, the electronic coupling between graphene layers, which may enable BiSFET operation. In addition, we present experimental results for ICl-GIC synthesis and characterization.
Principle of operation and modeling of source-gated transistors
Authors: Valletta A. , Mariucci L. , Rapisarda M. , Fortunato G.
Published: August 2013

We have analyzed the characteristics of hydrogenated amorphous silicon source gated transistors (SGTs) by using numerical simulations and we found that the original SGT characteristics can be reproduced without introducing barrier lowering mechanisms at the Schottky contact. Output characteristics show reduced current increase when pinch-off of the source end of the channel is triggered by increasing Vds, while perfect saturation of the drain current is achieved when pinch-off at the drain occurs. According to our simulations, even in the saturation regime the current at metal-semiconductor interface does not reach the thermionic emission limit and remains diffusion limited. Gate bias dependence of the saturation current can be simply explained as a combination of increased saturation voltage and reduced output conductance, without invoking barrier lowering mechanisms. SGT contact effects were modeled by introducing a distributed diode equivalent circuit for the source contact, which reproduces very well the device characteristics and can be easily implemented in a circuit simulator.
Origin of the vanishing critical thickness for ferroelectricity in free-standing PbTiO3 ultrathin films from first principles
Authors: Yin Binglun , Qu Shaoxing
Published: August 2013

Theoretical investigations in earlier literatures have shown that there is no critical thickness for ferroelectricity existing in the free-standing PbTiO3 ultrathin films. In this work, we report the origin of the vanishing critical thickness by comparing the properties of PbTiO3 and BaTiO3 ultrathin films based on ab initio investigations. Attributing to the covalency of the Pb-O bond, spontaneous strain gradient appears in the PbTiO3 ultrathin films, which breaks the inversion symmetry and makes the ferroelectric polarizations be sustained.
Ion chemistry in H2-Ar low temperature plasmas
Authors: Sode M. , Schwarz-Selinger T. , Jacob W.
Published: August 2013

A rate equation model is devised to study the ion composition of inductively coupled H2-Ar plasmas with different H2-Ar mixing ratios. The model is applied to calculate the ion densities ni, the wall loss probability of atomic hydrogen βH, and the electron temperature Te. The calculated ni's of Ar+, H+, H2+, H3+, and ArH+ are compared with experimental results. Calculations were made for a total gas pressure of 1.0 Pa. The production and loss channels of all ions are presented and discussed in detail. With the production and loss rates, the density dependence of each ion on the plasma parameters is explained. It is shown that the primary ions H2+ and Ar+ which are produced by ionization of the background gas by electron collisions are effectively converted into H3+ and ArH+. The high density of ArH+ and Ar+ is attributed to the low loss to the walls compared to hydrogen ions. It is shown that the H+/H2+ density ratio is strongly correlated to the H/H2 density ratio. The dissociation degree is around 1.7%. From matching the calculated to the measured atomic hydrogen density nH, the wall loss probability of atomic hydrogen on stainless steel βH was determined to be βH=0.24. The model results were compared with recently published experimental results. The calculated and experimentally obtained data are in fair agreement.
Regenerative feedback resonant circuit to detect transient changes in electromagnetic properties of semi-insulating materials
Authors: Jones A. Mark , Kelly James F. , Severtsen Ronald H. , McCloy John S.
Published: August 2013

A prototype regenerative feedback resonant circuit has been developed for measuring the transient spectral response due to perturbations in properties of various electromagnetic materials. The circuit can accommodate a variety of cavity resonators, shown here in the 8 GHz range, with passive quality factors (Qstat) as high as 7000 depending upon material loading. The positive feedback enhanced dynamic quality factors (Qdyn) of resonator/material combinations in the regenerative circuit are on the order of 107-108. The theory, design, and implementation of the circuit is discussed along with real-time monitored example measurements of effects due to photon-induced charge carriers in high-resistivity silicon wafers and magnetic-field induced perturbations of yttrium-iron garnet.