bluuebunny/crossref_metadata_2025 huggingface dataset:
New 3-DOFs Hybrid Mechanism for Ankle and Wrist of Humanoid Robot: Modeling, Simulation, and Experiments
Authors: Alfayad Samer , Ouezdou Fethi B. , Namoun Faycal
Published: January 2011

This paper deals with the design of a new class of hybrid mechanism dedicated to humanoid robotics application. Since the designing and control of humanoid robots are still open questions, we propose the use of a new class of mechanisms in order to face several challenges that are mainly the compactness and the high power to mass ratio. Human ankle and wrist joints can be considered more compact with the highest power capacity and the lowest weight. The very important role played by these joints during locomotion or manipulation tasks makes their design and control essential to achieve a robust full size humanoid robot. The analysis of all existing humanoid robots shows that classical solutions (serial or parallel) leading to bulky and heavy structures are usually used. To face these drawbacks and get a slender humanoid robot, a novel three degrees of freedom hybrid mechanism achieved with serial and parallel substructures with a minimal number of moving parts is proposed. This hybrid mechanism that is able to achieve pitch, yaw, and roll movements can be actuated either hydraulically or electrically. For the parallel submechanism, the power transmission is achieved, thanks to cables, which allow the alignment of actuators along the shin or the forearm main axes. Hence, the proposed solution fulfills the requirements induced by both geometrical, power transmission, and biomechanics (range of motion) constraints. All stages including kinematic modeling, mechanical design, and experimentation using the HYDROïD humanoid robot’s ankle mechanism are given in order to demonstrate the novelty and the efficiency of the proposed solution.
Traps and trapping phenomena and their implications on electrical behavior of high-k capacitor stacks
Authors: Paskaleva A. , Lemberger M. , Atanassova E. , Bauer A. J.
Published: January 2011

The traps and trapping phenomena and their implications on leakage currents, conduction mechanisms, and stress-induced leakage current in high-k dielectrics have been investigated. Various dielectrics (mostly multicomponent materials) have been studied to demonstrate the large diversity of phenomena that govern the electrical behavior of the structures depending on dielectric material, trap and stack parameters, and measurement conditions. The effects common for the most of high-k dielectrics and those typical for each individual structure have been discussed. The singly positively charged oxygen vacancy has been elucidated as the main electron transport site in the high-k materials. The role of the pre-existing traps for the electrical degradation of high-k stacks has been evidenced.
Temperature dependence of the emission and capture times of SiON individual traps after positive bias temperature stress
Authors: Toledano-Luque M. , Kaczer B. , Roussel Ph. , Cho M. J. , Grasser T. , Groeseneken G.
Published: January 2011

The authors study the statistical properties of individual defects in n-type metal-oxide-semiconductor field-effect transistors (nMOSFETs) using time dependent defect spectroscopy. This technique is based on the analysis of quantized threshold voltage transients observed on nanoscaled p-type metal-oxide-semiconductor field-effect transistors (pMOSFETs) after negative stress and provides the characteristic emission and capture times of individual traps. To complement to previous studies, the authors apply the methodology to SiON nMOSFETs and positive bias temperature stress. The authors demonstrate that the relaxation transients are due to the collective behavior of individual traps. Furthermore, a strong temperature dependence is observed for both emission and capture times. This is incompatible with elastic tunneling theory which is used in trap characterization techniques such as charge pumping, and also in simulations of erase and program transients of nonvolatile memories. The calculated thermal activation energies for both times are in the order of 0.6 eV and are close to the values obtained for SiON pMOSFETs when negatively stressed.
High-performance field-emission electron gun using a reticulated vitreous carbon cathode
Authors: Smith Brady C. , Hunt Charles E. , Brodie Ivor , Carpenter Arthur C.
Published: January 2011

Proof-of-concept experimental results stemming from beam simulations for a microfocus electron gun are presented. The simulations demonstrate the potential to produce 4 mA of current through a 40-μm-diameter spot, at an energy of 30 keV, emitted from a 1-mm-diameter cathode with low energy spread and high brightness. The experimental realization, scaled down for practicality, but consistent with and confirming the higher-energy simulation, produced 2 μA of current with an approximately 28 μm spot size at an energy of 9.3 keV. The electrons originated from an Ar+-ion-treated reticulated vitreous carbon (RVC) field-emission cathode shaped as an approximately 1-mm-diameter disk. The primary application for this work is a highly monochromatic microfocus x-ray source for use in phase-contrast imaging, although other beam applications exist. The use of an Ar+-ion-irradiated RVC cathode allows high, stable current at low electric field, superior to what is achievable using field-emitter arrays or carbon-nanotube cathodes. This method, scaled up to its maximum potential, also enables a high-current-density microfocus beam, which, to date, has not been demonstrated using thermionic cathodes. Such a beam applied to an x-ray source for phase-contrast imaging represents a significant benefit in medical diagnostics.
Faceted magnetron concept using field emission cathodes
Authors: Browning Jim , Watrous Jack
Published: January 2011

A magnetron concept using field emission cathodes has been modeled with the Air Force Research Laboratory particle-in-cell code ICEPIC and the two-dimensional particle trajectory simulation Lorentz2E. In this approach, field emitters are used to provide a distributed cathode in place of a traditional thermionic cathode. The emitters are placed below the interaction space in a shielded structure. The cathode is comprised of facet plates with slits to protect the emitters. Simulation of an L-band rising sun magnetron shows that the faceted magnetron will oscillate using both five and ten facet cathodes. The startup times are very similar to that of a cylindrical cathode magnetron. The electron trajectories of the shielded slit structure have been modeled, and the results indicate that electrons can be injected through the slits and into the interaction space using lateral edge emitters and a pusher electrode design.
Working model of an atomic force microscope
Authors: Bonson Kirsten , Headrick Randall L. , Hammond David , Hamblin Michael
Published: January 2011

To explain the principles of an atomic force microscope (AFM) at the level of introductory physics, we have created an inexpensive model of an AFM using a modified phonograph stylus in place of the AFM cantilever and tip. The sample is positioned under the stylus using a micrometer stage. A 10 mW laser diode is used to produce a beam, which reflects off a very small mirror glued to the end of the stylus. No electronic detection is used, and students measure the deflection of the tip directly from the movement of the laser beam on graph paper. The laser beam is deflected roughly 1 cm for each 10 μm of stylus deflection, making it easy to collect data.
Charge sniffer for electrostatics demonstrations
Authors: Dinca Mihai P.
Published: January 2011

An electronic electroscope with a special design for demonstrations and experiments on static electricity is described. It operates as an electric charge sniffer by detecting slightly charged objects when they are brought to the front of its sensing electrode. The sniffer has the advantage of combining high directional sensitivity with a logarithmic bar display. It allows for the identification of electric charge polarity during charge separation by friction, peeling, electrostatic induction, batteries, or secondary coils of power transformers. Other experiments in electrostatics, such as observing the electric field of an oscillating dipole and the distance dependence of the electric field generated by simple charge configurations, are also described.
Damped fall of magnets inside a conducting pipe
Authors: Donoso Guillermo , Ladera Celso L. , Martín Pablo
Published: January 2011

We consider the uniform motion of a short strong cylindrical magnet falling inside a conducting pipe and study the dependence of the magnetic braking force on the distance of the falling magnet from the pipe wall. We also consider two magnets falling together with parallel or opposite magnetic moments. We develop models for these three cases of magnetic braking and describe the experiments that validate our models. The experimental setups are inexpensive and can be readily assembled in a teaching laboratory.
Integrating electrostatics with demonstrations and interactive teaching
Authors: Chang Wheijen
Published: January 2011

Teaching electrostatics is challenging due to its complexity and high degree of abstraction. To facilitate students’ understanding of the meanings and relations of the key terms, this paper describes a series of demonstrations and conceptual questions based on an interactive teaching approach. The context was an introductory university physics course for engineering and science students in Taiwan. Features of the teaching intervention include the utilization of a series of demonstrations for repeated practice applying the important concepts, the incorporation of derivations of equations and verbal elaboration of concepts, and the engagement of students in thinking and discussing. Data show that the teaching intervention benefited the students’ academic performance and their satisfaction with the learning achievement.
Genome-Wide RNAi Screen Reveals Disease-Associated Genes That Are Common to Hedgehog and Wnt Signaling
Authors: Jacob Leni S. , Wu Xiaofeng , Dodge Michael E. , Fan Chih-Wei , Kulak Ozlem , Chen Baozhi , Tang Wei , Wang Baolin , Amatruda James F. , Lum Lawrence
Published: January 2011

Loss of the kinase and tumor suppressor Stk11 (Lkb1) has opposite effects on Hh and Wnt signaling.
Rho and Rho-Kinase Activity in Adipocytes Contributes to a Vicious Cycle in Obesity That May Involve Mechanical Stretch
Authors: Hara Yoshikazu , Wakino Shu , Tanabe Yoshiyuki , Saito Maki , Tokuyama Hirobumi , Washida Naoki , Tatematsu Satoru , Yoshioka Kyoko , Homma Koichiro , Hasegawa Kazuhiro , Minakuchi Hitoshi , Fujimura Keiko , Hosoya Koji , Hayashi Koichi , Nakayama Koichi , Itoh Hiroshi
Published: January 2011

Mechanical stretch activates Rho-kinase in adipocytes, promoting obesity and obesity-related complications.
The Role of L(u)ck in T Cell Triggering
Authors: Berry Richard
Published: January 2011

The Src family kinase Lck is activated prior to T cell receptor engagement and poised for action upon antigen binding.
Pharmacodynamics of Razupenem (PZ601) Studied in an
In Vitro
Pharmacokinetic Model of Infection
Authors: MacGowan Alasdair P. , Noel Alan , Tomaselli Sharon , Elliott Heather , Bowker Karen
Published: January 2011

Simulations of administration of razupenem at 1 g every 12 h by 1-h intravenous (i.v.) infusion were performed in an
in vitro
pharmacokinetic model of infection. The antibacterial effect of this razupenem dosing regimen against six strains of
Staphylococcus aureus
(one methicillin-sensitive
S. aureus
[MSSA] strain [MIC, 0.015 μg/ml] and five methicillin-resistant
S. aureus
[MRSA] strains [MIC range, 0.09 to 3 μg/ml]) and five strains of
Enterobacteriaceae
(three
Escherichia coli
strains [two containing extended-spectrum β-lactamases {ESBLs}] and two
Enterobacter
sp. strains [one with an AmpC enzyme and the other with a raised razupenem MIC; MIC range, 0.09 to 6 μg/ml]) was assessed. Against the MSSA and MRSA strains, razupenem produced a >3.5-log-unit reduction in viable count after 24 h. There were no changes in population profiles. In a second series of experiments, over 5 days there was rapid initial clearance of MRSA from the model followed by regrowth after 48 h. MRSA colonies appeared on 2× MIC recovery medium after 72 h with strain 33820 (MIC, 3.0 μg/ml) and at 120 h with strain 27706 (MIC, 1.5 μg/ml). Against
E. coli
and
Enterobacter
spp., razupenem produced a >3.5-log-unit reduction in bacterial counts for all strains except that with an MIC of 6 μg/ml, where razupenem had a notably poorer antibacterial effect. Population profiles were unchanged after 48 h of exposure to razupenem except for
Enterobacter
strain 34425 (MIC, 6.0 μg/ml), where colonies were recovered from media containing 2×, 4×, and 8× MIC. In dose-ranging studies with MRSA strains, the percentage of the dosing interval that the free drug concentration remained higher than the pathogen MIC (
fT
>MIC) for a 24-h bacteriostatic effect was 5.0% ± 1.4%, and that for a 1-log-unit reduction in count was 12.5% ± 5.8%. Population profiles indicated growth on 2× MIC recovery medium at
fT
>MIC values of 1 to 35% but not at a value of >35%. In a similar set of experiments with
Enterobacteriaceae
, the
fT
>MIC for a 24-h bacteriostatic effect was 34.2% ± 7.6% and that for a 1-log-unit reduction in count was 42.5% ± 7.8%. Population analysis profiles indicated growth on recovery media with 2×, 4×, and 8× MIC at
fT
>MICs in the range of 1 to 69% but rarely at values of ≥70%. In conclusion, razupenem at simulated human doses of 1 g i.v. every 12 h has a marked antibacterial effect on MSSA and MRSA strains with MICs of ≤3.0 μg/ml and
Enterobacteriaceae
with MICs of ≤0.4 μg/ml.
fT
>MIC targets of ≥35% for MRSA and ≥70% for
Enterobacteriaceae
should provide significant antibacterial effects combined with low risks of changing pathogen antibiotic population profiles.
Comparison of the Antibacterial Properties of Phage Endolysins SAL-1 and LysK
Authors: Jun Soo Youn , Jung Gi Mo , Son Jee-Soo , Yoon Seong Jun , Choi Yun-Jaie , Kang Sang Hyeon
Published: January 2011

In spite of the high degree of amino acid sequence similarity between the newly discovered phage endolysin SAL-1 and the phage endolysin LysK, SAL-1 has an approximately 2-fold-lower MIC against several
Staphylococcus aureus
strains and higher bacterial cell-wall-hydrolyzing activity than LysK. The amino acid residue change contributing the most to this enhanced enzymatic activity is a change from glutamic acid to glutamine at the 114th residue.
Penetration of Topically Administered 0.5-Percent Caspofungin Eye Drops into Human Aqueous Humor
Authors: Neoh Chin Fen , Leung Lok , Misra Anant , Vajpayee Rasik B. , Davies Geoffrey E. , Fullinfaw Robert O. , Stewart Kay , Kong David C. M.
Published: January 2011

Ten participants attending elective anterior segment eye surgery received 0.5% caspofungin eye drops either 1 drop hourly for 4 h or 1 drop an hour before surgery. The eye drops were generally well tolerated. In the absence of inflammation or corneal abrasion, topical caspofungin does not achieve clinically relevant concentrations.
Emergence of Linezolid-Resistant
Staphylococcus aureus
after Prolonged Treatment of Cystic Fibrosis Patients in Cleveland, Ohio
Authors: Endimiani Andrea , Blackford Martha , Dasenbrook Elliot C. , Reed Michael D. , Bajaksouszian Saralee , Hujer Andrea M. , Rudin Susan D. , Hujer Kristine M. , Perreten Vincent , Rice Louis B. , Jacobs Michael R. , Konstan Michael W. , Bonomo Robert A.
Published: January 2011

Linezolid (LZD)-resistant
Staphylococcus aureus
(LRSA) isolates were monitored from 2000 to 2009 in Cleveland, OH. LRSA first emerged in 2004 only in cystic fibrosis (CF) patients, with 11 LRSA-infected CF patients being identified by 2009. LRSA was isolated from 8 of 77 CF patients with
S. aureus
respiratory tract infection treated with LZD from 2000 to 2006. Analysis of clinical data showed that the 8 CF patients with LRSA received more LZD courses (18.8 versus 5.9;
P
= 0.001) for a longer duration (546.5 versus 211.9 days;
P
< 0.001) and had extended periods of exposure to LZD (83.1 versus 30.1 days/year;
P
< 0.001) than the 69 with LZD-susceptible isolates. Five LRSA isolates included in the clinical analysis (2000 to 2006) and three collected in 2009 were available for molecular studies. Genotyping by repetitive extrapalindromic PCR and pulsed-field gel electrophoresis revealed that seven of these eight LRSA strains from unique patients were genetically similar. By multilocus sequence typing, all LRSA isolates were included in clonal complex 5 (seven of sequence type 5 [ST5] and one of ST1788, a new single-locus variant of ST5). However, seven different variants were identified by
spa
typing. According to the
Escherichia coli
numbering system, seven LRSA isolates contained a G2576T mutation (G2603T,
S. aureus
numbering) in one to four of the five copies of domain V of the 23S rRNA genes. One strain also contained a mutation (C2461T,
E. coli
numbering) not previously reported. Two strains, including one without domain V mutations, possessed single amino acid substitutions (Gly152Asp or Gly139Arg) in the ribosomal protein L3 of the peptidyltransferase center, substitutions not previously reported in clinical isolates. Emergence of LRSA is a serious concern for CF patients who undergo prolonged courses of LZD therapy.
Mutational Analysis of the Thienamycin Biosynthetic Gene Cluster from
Streptomyces cattleya
Authors: Rodríguez Miriam , Núñez Luz Elena , Braña Alfredo F. , Méndez Carmen , Salas José A. , Blanco Gloria
Published: January 2011

The generation of non-thienamycin-producing mutants with mutations in the
thnL
,
thnN
,
thnO
, and
thnI
genes within the
thn
gene cluster from
Streptomyces cattleya
and their involvement in thienamycin biosynthesis and regulation were previously reported. Four additional mutations were independently generated in the
thnP
,
thnG
,
thnR
, and
thnT
genes by insertional inactivation. Only the first two genes were found to play a role in thienamycin biosynthesis, since these mutations negatively or positively affect antibiotic production. A mutation of
thnP
results in the absence of thienamycin production, whereas a 2- to 3-fold increase in thienamycin production was observed for the
thnG
mutant. On the other hand, mutations in
thnR
and
thnT
showed that although these genes were previously reported to participate in this pathway, they seem to be nonessential for thienamycin biosynthesis, as thienamycin production was not affected in these mutants. High-performance liquid chromatography (HPLC)-mass spectrometry (MS) analysis of all available mutants revealed some putative intermediates in the thienamycin biosynthetic pathway. A compound with a mass corresponding to carbapenam-3-carboxylic acid was detected in some of the mutants, suggesting that the assembly of the bicyclic nucleus of thienamycin might proceed in a way analogous to that of the simplest natural carbapenem, 1-carbapen-2-em-3-carboxylic acid biosynthesis. The accumulation of a compound with a mass corresponding to 2,3-dihydrothienamycin in the
thnG
mutant suggests that it might be the last intermediate in the biosynthetic pathway. These data, together with the establishment of cross-feeding relationships by the cosynthesis analysis of the non-thienamycin-producing mutants, lead to a proposal for some enzymatic steps during thienamycin assembly.
Combination Therapy of Murine Mucormycosis or Aspergillosis with Iron Chelation, Polyenes, and Echinocandins
Authors: Ibrahim Ashraf S. , Gebremariam Teclegiorgis , Luo Guanpingsheng , Fu Yue , French Samuel W. , Edwards John E. , Spellberg Brad
Published: January 2011

Liposomal amphotericin B (LAmB) combined wither either micafungin or deferasirox was synergistic in previous murine studies with mucormycosis or aspergillosis. We hypothesized that triple therapy using LAmB, micafungin, and deferasirox could further improve outcomes of mucormycosis or aspergillosis. Triple therapy improved survival and reduced tissue fungal burden of mice with mucormycosis and to a lesser extent with aspergillosis. Continued investigation into the use of triple therapy against mucormycosis and aspergillosis is warranted.
Effect of Half-Life on the Pharmacodynamic Index of Zanamivir against Influenza Virus Delineated by a Mathematical Model
Authors: Brown Ashley N. , Bulitta Jürgen B. , McSharry James J. , Weng Qingmei , Adams Jonathan R. , Kulawy Robert , Drusano George L.
Published: January 2011

Intravenous zanamivir is recommended for the treatment of hospitalized patients with complicated oseltamivir-resistant influenza virus infections. In a companion paper, we show that the time above the 50% effective concentration (time>EC
50
) is the pharmacodynamic (PD) index predicting the inhibition of viral replication by intravenous zanamivir. However, for other neuraminidase inhibitors, the ratio of the area under the concentration-time curve to the EC
50
(AUC/EC
50
) is the most predictive index. Our objectives are (i) to explain the dynamically linked variable of intravenous zanamivir by using different half-lives and (ii) to develop a new, mechanism-based population pharmacokinetic (PK)/PD model for the time course of viral load. We conducted dose fractionation studies in the hollow-fiber infection model (HFIM) system with zanamivir against an oseltamivir-resistant influenza virus. A clinical 2.5-h half-life and an artificially prolonged 8-h half-life were simulated for zanamivir. The values for the AUC from 0 to 24 h (AUC
0-24
) of zanamivir were equivalent for the two half-lives. Viral loads and zanamivir pharmacokinetics were comodeled using data from the present study and a previous dose range experiment via population PK/PD modeling in S-ADAPT. Dosing every 8 h (Q8h) suppressed the viral load better than dosing Q12h or Q24h at the 2.5-h half-life, whereas all regimens suppressed viral growth similarly at the 8-h half-life. The model provided unbiased and precise individual (Bayesian) (
r
2
, >0.96) and population (pre-Bayesian) (
r
2
, >0.87) fits for log
10
viral load. Zanamivir inhibited viral release (50% inhibitory concentration [IC
50
], 0.0168 mg/liter; maximum extent of inhibition, 0.990). We identified AUC/EC
50
as the pharmacodynamic index for zanamivir at the 8-h half-life, whereas time>EC
50
best predicted viral suppression at the 2.5-h half-life, since the trough concentrations approached the IC
50
for the 2.5-h but not for the 8-h half-life. The model explained data at both half-lives and holds promise for optimizing clinical zanamivir dosage regimens.
Dissemination of Persistent Intestinal Bacteria via the Mesenteric Lymph Nodes Causes Typhoid Relapse
Authors: Griffin Amanda J. , Li Lin-Xi , Voedisch Sabrina , Pabst Oliver , McSorley Stephen J.
Published: January 2011

Enteric pathogens can cause relapsing infections in a proportion of treated patients, but greater understanding of this phenomenon is hindered by the lack of appropriate animal models. We report here a robust animal model of relapsing primary typhoid that initiates after apparently successful antibiotic treatment of susceptible mice. Four days of enrofloxacin treatment were sufficient to reduce bacterial loads below detectable levels in all major organs, and mice appeared otherwise healthy. However, any interruption of further antibiotic therapy allowed renewed fecal shedding and renewed bacterial growth in systemic tissues to occur, and mice eventually succumbed to relapsing infection.In vivoimaging of luminescentSalmonellaidentified the mesenteric lymph nodes (MLNs) as a major reservoir of relapsing infection. A magnetic-bead enrichment strategy isolated MLN-resident CD11b+Gr-1−monocytes associated with low numbers of persistentSalmonella. However, the removal of MLNs increased the severity of typhoid relapse, demonstrating that this organ serves as a protective filter to restrain the dissemination of bacteria during antibiotic therapy. Together, these data describe a robust animal model of typhoid relapse and identify an important intestinal phagocyte subset involved in protection against the systemic spread of enteric infection.
Listeria monocytogenes
Infection Induces Prosurvival Metabolic Signaling in Macrophages
Authors: Zou Tie , Garifulin Oleg , Berland Robert , Boyartchuk Victor L.
Published: January 2011

Host cells use metabolic signaling through the LXRα nuclear receptor to defend against
Listeria monocytogenes
infection. 25-Hydroxycholesterol is a natural ligand of LXRs that is produced by the enzyme cholesterol 25-hydroxylase (CH25H). We found that expression of
Ch25h
is upregulated following
L. monocytogenes
infection in a beta interferon (IFN-β)-dependent fashion. Moreover, increased
Ch25h
expression promotes survival of
L. monocytogenes
-infected cells and increases sensitivity of the host to infection. We determined that expression of
Cd5l
, a prosurvival gene, is controlled by CH25H. In addition, we found that CD5L inhibits activation of caspase-1, promoting survival of infected macrophages. Our results reveal a mechanism by which an intracellular pathogen can prolong survival of infected cells, thus providing itself with a protected environment in which to replicate.
HIV priorities and health distributions in a rural region in Tanzania: a qualitative study
Authors: Johansson Kjell Arne , Miljeteig Ingrid , Kigwangalla Hamisi , Norheim Ole Frithjof
Published: January 2011

Background

International and national agencies play a major role in setting HIV care-and-treatment priorities in low-income-countries. Little is known about priority setting at lower health-system levels. The objective of this article is to explore experiences of HIV priority decisions, at what levels these decisions are made and how they might influence the distribution of health benefits in a high-endemic region in Tanzania.

Methods

This is a qualitative study using observations, key documents and semistructured focus-group and individual interviews (43) with health workers, patients and administrators at one regional and one district hospital. The analysis was based on an editing analysis style.

Results

Health workers did not perceive themselves as bedside rationing agents and they reported following national recommendations and felt they have little impact on important priority decisions. Health benefit distributions were largely determined by priority decisions made at a national level. External factors, such as eligibility criteria, inadequate funding and barriers to access seemed to play a major role in the actual distribution of health services and benefits in the region. Patient groups who were actually given high priority were the sickest patients, those living near a facility and those who could afford long journeys and frequent visits. Low-priority groups were those experiencing other co-morbidities or treatment failure, children, asymptomatic patients and the poorest.

Conclusions/significance

The interaction of priority setting across health-system levels and their impact on distribution of health outcomes in the population has been underestimated. The distributional pattern of health outcomes calls for further normative assessment.
The hallucinations of Frédéric Chopin
Authors: Vázquez Caruncho Manuel , Brañas Fernández Franciso
Published: January 2011

Frédéric Chopin is the epitome of the romantic artist; he had a chronic pulmonary disease that ultimately caused his death at the age of 39. An overlooked neurological condition is discussed in this paper. We consider the possibility of a temporal lobe epilepsy, as throughout his life Chopin had hallucinatory episodes, which can accompany seizure disorders.
TRANSITION FROM EXPONENTIAL TO POWER LAW INCOME DISTRIBUTIONS IN A CHAOTIC MARKET
Authors: PELLICER-LOSTAO CARMEN , LOPEZ-RUIZ RICARDO
Published: January 2011

Economy is demanding new models, able to understand and predict the evolution of markets. To this respect, Econophysics offers models of markets as complex systems, that try to comprehend macro-, system-wide states of the economy from the interaction of many agents at micro-level. One of these models is the gas-like model for trading markets. This tries to predict money distributions in closed economies and quite simply, obtains the ones observed in real economies. However, it reveals technical hitches to explain the power law distribution, observed in individuals with high incomes. In this work, nonlinear dynamics is introduced in the gas-like model in an effort to overcomes these flaws. A particular chaotic dynamics is used to break the pairing symmetry of agents (i, j) ⇔ (j, i). The results demonstrate that a "chaotic gas-like model" can reproduce the Exponential and Power law distributions observed in real economies. Moreover, it controls the transition between them. This may give some insight of the micro-level causes that originate unfair distributions of money in a global society. Ultimately, the chaotic model makes obvious the inherent instability of asymmetric scenarios, where sinks of wealth appear and doom the market to extreme inequality.
FAMILY OF INVARIANT CANTOR SETS AS ORBITS OF DIFFERENTIAL EQUATIONS II: JULIA SETS
Authors: CHEN YI-CHIUAN , KAWAHIRA TOMOKI , LI HUA-LUN , YUAN JUAN-MING
Published: January 2011

The Julia set of the quadratic map fμ(z) = μz(1 - z) for μ not belonging to the Mandelbrot set is hyperbolic, thus varies continuously. It follows that a continuous curve in the exterior of the Mandelbrot set induces a continuous family of Julia sets. The focus of this article is to show that this family can be obtained explicitly by solving the initial value problem of a system of infinitely coupled differential equations. A key point is that the required initial values can be obtained from the anti-integrable limit μ → ∞. The system of infinitely coupled differential equations reduces to a finitely coupled one if we are only concerned with some invariant finite subset of the Julia set. Therefore, it can be employed to find periodic orbits as well. We conduct numerical approximations to the Julia sets when parameter μ is located at the Misiurewicz points with external angle 1/2, 1/6, or 5/12. We approximate these Julia sets by their invariant finite subsets that are integrated along the reciprocal of corresponding external rays of the Mandelbrot set starting from the anti-integrable limit μ = ∞. When μ is at the Misiurewicz point of angle 1/128, a 98-period orbit of prescribed itinerary obtained by this method is presented, without having to find a root of a 298-degree polynomial. The Julia sets (or their subsets) obtained are independent of integral curves, but in order to make sure that the integral curves are contained in the exterior of the Mandelbrot set, we use the external rays of the Mandelbrot set as integral curves. Two ways of obtaining the external rays are discussed, one based on the series expansion (the Jungreis–Ewing–Schober algorithm), the other based on Newton's method (the OTIS algorithm). We establish tables comparing the values of some Misiurewicz points of small denominators obtained by these two algorithms with the theoretical values.
STRUCTURAL PRINCIPLES FOR COMPLEX DYNAMICS IN GLASS NETWORKS
Authors: LU LINGHONG , EDWARDS RODERICK
Published: January 2011

Gene-regulatory networks are potentially capable of more complex behavior than convergence to a stationary state, or even cycling through a simple sequence of expression patterns. The analysis of qualitative dynamics for these networks is facilitated by using piecewise-linear equations and its state transition diagram (an n-dimensional hypercube, in the case of n genes with a single effective threshold for the protein product of each). Our previous work has dealt with cycles of states in the state transition diagram that allow periodic solutions. Here, we study a particular kind of figure-8 pattern in the state transition diagram and determine conditions that allow complex behavior. Previous studies of complex behavior, such as chaos, in such networks have dealt only with specific examples. Our approach allows an appreciation of the design principles that give rise to complex dynamics, which may have application in assessing the dynamical possibilities of gene networks with poorly known parameters, or for synthesis or control of gene networks with complex behavior.
BIFURCATION STRUCTURES IN A MODEL OF A CO2 LASER WITH A FAST SATURABLE ABSORBER
Authors: DOEDEL EUSEBIUS J. , OLDEMAN BART E. , PANDO L. CARLOS L.
Published: January 2011

We consider a new mathematical model of a CO 2 laser with a fast saturable absorber. The system exhibits isolas of periodic solutions, along with their bifurcations, as the main parameter, the incoherent pump of the laser, is changed. The characteristic feature of these lasers is their spiking behavior; the spikes, passive Q-switching pulses, correspond to stable periodic solutions on the isolas. We also study the changes in the solution structure as a second parameter varies, namely, the one that is responsible for the extent of nonlinear losses. In particular, we determine what happens to the isolas and to the stability properties of the periodic solutions along them.
ASYMPTOTIC STOCHASTIC CHARACTERIZATION OF PHASE AND AMPLITUDE NOISE IN FREE-RUNNING OSCILLATORS
Authors: TRAVERSA FABIO L. , BONANI FABRIZIO
Published: January 2011

Starting from the definition of the stochastic differential equation for amplitude and phase fluctuations of an oscillator described by an ordinary differential equation, we study the associated Fokker–Planck equation by using tools from stochastic integral calculus, harmonic analysis and Floquet theory. We provide an asymptotic characterization of the relevant correlation functions, showing that within the assumption of a linear perturbative analysis for the amplitude fluctuations phase noise and orbital fluctuations at the same time are asymptotically statistically independent, and therefore the nonlinear perturbative analysis of phase noise recently derived still exactly holds even if orbital noise is taken into account.
THE ORTHOGONAL V-SYSTEM DETRENDED FLUCTUATION ANALYSIS
Authors: LIN AIJING , SHANG PENGJIAN , MA HUI
Published: January 2011

The Detrended Fluctuation Analysis (DFA) and its extensions (MF-DFA) have been proposed as robust techniques to determine possible long-range correlations in self-affine signals. However, many studies have reported the susceptibility of DFA to trends which give rise to spurious crossovers and prevent reliable estimations of the scaling exponents. Lately, several modifications of the DFA method have been reported with many different techniques for eliminating the monotonous and periodic trends. In this study, a smoothing algorithm based on the Orthogonal V-system (OVS) is proposed to minimize the effect of power-law trends, periodic trends, assembled trends and piecewise function trends. The effectiveness of the new method is demonstrated on monofractal data and multifractal data corrupted with different trends.
ON THE FORMATION OF TITANIUM/TITANIUM OXIDE NANOFIBROUS STRUCTURES AND NANOSPHERES USING FEMTOSECOND LASER IN AIR
Authors: ALUBAIDY M. , VENKATAKRISHNAN K. , TAN B.
Published: January 2011

In this paper, we report a unique growth of nanofibrous structures and nanospheres of titanium using femtosecond laser in air and without the need for any type of catalyst. The femtosecond laser was used to generate nanoparts on a titanium substrate. The irradiated substrate is assumed to be subjected to plane stress type of temperature variation and a new method combining finite difference and Runge–Kutta 4 transient thermal model has been developed to calculate the temperature distribution on the top surface of the substrate during laser ablation. A Matlab code has been developed and validated with the known results from the literature. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffractograms (XRD) and micro-Raman analysis were conducted to characterize the microstructure and revealed metallic and oxide phases in the nanostructure analyses. Results showed that nanofibers and nanospheres were grown in the order of few hundreds nanometers or more. The effect of the laser power on the energy/pulse and hence the temperature was studied. It was found that high temperature results in the formation of nanofibers while lower temperature results in formation of nanospheres. This first time observation could have potential application in biomedical, optoelectronics and photocatalysis.
ENHANCEMENT MECHANISM OF NANOSTRUCTURE FORSTERITE FORMATION RATE BY MECHANICAL ACTIVATION AND AMMONIUM CHLORIDE
Authors: TAVANGARIAN FARIBORZ , EMADI RAHMATOLLAH
Published: January 2011

The single-phase nanostructure forsterite powder was successfully synthesized by mechanical activation of talc and magnesium carbonate powder mixture followed by annealing in the presence and absence of ammonium chloride. Mechanical activation was used as an efficient method for the optimization of powder properties by means of combination and uttermost homogenization of the powder mass. Besides, the presence of chlorine ion affected the forsterite formation rate via producing smaller particle size during subsequent annealing which is very important in the case of diffusion-controlled reactions. The single-phase nanostructure forsterite powder with crystallite size of about 36 nm was successfully synthesized by 10 h mechanical activation with subsequent annealing at 1000°C for 1 h. While in the presence of chlorine ion, the single-phase nanostructure forsterite powder with crystallite size of about 20 nm could be obtained by 5 h of mechanical activation with subsequent annealing at 1000°C for 2 min.
RAPID SYNTHESIS OF PURE AND Pr-DOPED TiCeO4 NANOPIGMENTS BY SOLUTION COMBUSTION METHOD
Authors: SAM S. P. CHANDINI , PRASAD V. S. , KUMAR K. SUDARSANA
Published: January 2011

Combustion synthesis has emerged as a facile and economically viable technique for the preparation of advanced ceramics, catalysts and nanomaterials. This paper is the report of the investigations carried out on the synthesis of titania–rare-earth mixed oxide pigments: TiCe 1-x Pr x O 4-δ by the solution combustion method and their characterization by X-ray powder diffraction, transmission electron microscopy, reflectance spectral data, thermal analysis and surface area measurements. The synthesized nanopigments exhibit yellow to brick red color with the increase of praseodymium content. The dominant reflectance of these pigments lies above a wavelength of 600 nm. These pigments are found to be promising candidates as ecological pigments because of their high reflectance, lightness and intense coloration.
Mn SUBSTITUTION EFFECTS AND ASSOCIATED DEFECTS IN ZnO NANOPARTICLES STUDIED BY POSITRON ANNIHILATION
Authors: ROY B. , KARMAKAR B. , NAMBISSAN P. M. G. , PAL M.
Published: January 2011

Nanocrystalline ZnO particles substituted with different concentrations (0–30%) of Mn were synthesized by using a modified ceramic route and characterized by X-ray diffraction, transmission electron microscopy, selected area electron diffraction and energy dispersive X-ray analysis methods. Positron lifetime and coincidence Doppler broadening measurements were used as probes to identify the vacancy-type defects present in them and monitor the changes while doping. The predominant positron trapping center in the undoped ZnO is identified as the trivacancy-type cluster V Zn + O + Zn , which is negatively charged, and it transformed to the neutral divacancy V Zn + O on doping with Mn 2+ ions. The intensity of the defect-specific positron lifetime component got reduced initially indicating partial occupancy of the vacancies by the doped cations but then recovered on further doping due to the additional Zn vacancies created as a result of the increasing strain introduced by the Mn ions of larger radius. The creation of a new phase ZnMn 2 O 4 thereafter changed the course of variation of the annihilation parameters, as the positrons got increasingly trapped in the vacancies at the tetrahedral and octahedral sites of the spinel nanomanganite.
THE ADVANTAGE OF LOW GROWTH TEMPERATURE AND V/III RATIO FOR InxGa1-xAs NANOWIRES GROWTH
Authors: WIBOWO EDY , OTHAMAN ZULKAFLI , SAKRANI SAMSUDI , SUMPONO IMAM
Published: January 2011

Cylindrical In x Ga 1-x As nanowires (NWs) perpendicular to the substrate have been successfully grown using MOCVD. Morphology of In x Ga 1-x As NWs has been observed using Field Emission-Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM). Both FE-SEM and TEM results show that the NWs grown at low growth temperature and V/III ratio were via direct impinging mechanism. Energy Dispersive X-ray spectroscopy (EDX) results confirm that the cylindrical NWs grown via direct impinging mechanism and tends to have uniform chemical composition.
OPTIMIZATION OF THE MECHANICAL STRENGTH PROPERTIES OF POLY(L-LACTIDE)/MULTI-WALLED CARBON NANOTUBE SCAFFOLDS USING RESPONSE SURFACE METHODOLOGY
Authors: ADELI HASSAN , SHARIF ZEIN SHARIF HUSSEIN , TAN SOON HUAT , AHMAD ABDUL LATIF
Published: January 2011

In this study the response surface methodology (RSM) coupled with the central composite design (CCD) were used to optimize the mechanical strength properties of poly(L-lactide)/multi-walled carbon nanotube (MWCNT) scaffolds. The scaffolds were prepared by the freeze-extraction method. MWCNTs were incorporated into PLLA composite as a reinforcement agent in order to improve the strength properties of the scaffolds. The effect of process parameters such as ratio of PLLA/(PLLA + MWCNT) (93–100%), solvent amount (100–200 ml), freezing time (5–7 h) and immersing time (2–4 days) were studied using the design of experiment (DOE). Based on CCD, quadratic model was obtained and developed to correlate the process parameters to the strength of the scaffolds. An analysis of variance (ANOVA) was applied to determine the significant factors affecting the experimental design response (strength) of the scaffolds. The predicted values after optimization process were in good agreement with the experimental values. The model was able to accurately predict the response of strength with less than 5% error.
COMPACT BRAZED PLATE HEAT EXCHANGERS FOR CO2 HEAT PUMP WATER HEATERS
Authors: LEIGHTON DANIEL , HWANG YUNHO , RADERMACHER REINHARD
Published: January 2011

The plate-type heat exchanger is found to be well suited for the application of a transcritical CO2 heat pump water heater. A CO2 heat pump water heater test facility was used to evaluate the performance of a high-pressure plate-type heat exchanger. The performance characteristics of heat exchanger effectiveness, capacity, and pressure drop were evaluated over a range of CO2 gas cooler inlet pressures and temperatures. For the ambient temperature range of 10°C to 30°C, the maximum observed capacities ranged from 4.46 kW to 5.34 kW, with the capacity increasing approximately linearly with increasing ambient temperature. Over this maximum capacity range, the effectiveness of the gas cooler ranged from 98.7% to 99.4%, with the effectiveness increasing with decreasing ambient temperature. The largest gas cooler pressure drop was approximately 130 kPa at a volumetric flow rate of 128 cm3/s, which is the flow rate resulting from the optimum system operating conditions at an ambient temperature of 30°C.
FIELD EXPERIMENT OF TRAIN-INDUCED WIND PRESSURE ON PLATFORM SCREEN DOOR AT SUBWAY STATION
Authors: KIM JUNG-YUP
Published: January 2011

In a bid to evaluate the train wind pressure on platform screen door installed on the platform of the subway station, the field test was conducted in existing Seoul Metropolitan Subway Line 2 in operation now. Variations in wind pressure on platform screen door, which were caused by the running train were measured depending on four different train operation patterns. The highest pressure of 28.1 kgf/m2 was indicated on platform screen doors while two trains were passing the platform in different directions at a speed of 60 km/h.
EXPERIMENTAL ANALYSIS OF TWO-PHASE EJECTOR SYSTEM WITH VARYING MIXING CROSS-SECTIONAL AREA USING NATURAL REFRIGERANT CO2
Authors: NAKAGAWA MASAFUMI , MARASIGAN ARIEL R. , MATSUKAWA TAKANORI
Published: January 2011

The use of two-phase ejector in improving the performance of transcritical CO2 refrigeration system needs further experimental verification particularly the effects of its geometrical design. In this study, experimental data were gathered for ejectors with different mixing cross-sectional areas at different operating temperature and pressure. The results have shown that a smaller mixing area yields higher efficiency due to its higher pressure recovery and entrainment ratio, but its advantages are limited to lower ejector inlet pressure Pc. A larger mixing area is required for higher cooling capacity which can be achieved at higher ejector inlet pressure or lower ejector inlet temperature but excessive increase in this area considerably decreases the efficiency of the system. In this study, the ejector with the largest mixing area was the most inefficient and reduced the COP up to 10% compared to most efficient type. It demonstrates the significant effect of ejector's geometrical features, particularly the mixing cross-sectional area and its related geometrical ratio, in the performance of CO2 ejector system. The effect of motive nozzle inlet condition on pressure recovery profile has been more evident for ejector with smaller mixing area while the evaporator temperature has the least effect in the performance of the system. In the conditions used in this study, using ejector yielded a COP improvement of up to 35% compared to the conventional system.
AN EXPERIMENTAL STUDY ON THE DEFROSTING PERFORMANCE OF A PCM-BASED REVERSE-CYCLE DEFROSTING METHOD FOR AIR SOURCE HEAT PUMPS
Authors: QU MINGLU , DENG SHIMING , JIANG YIQIANG
Published: January 2011

When an ASHP unit operates in heating mode, frost can be accumulated on the surface of its outdoor coil. Currently the most widely used defrosting method for ASHPs is reverse cycle defrost. However, the fundamental problem for such a method is that there is insufficient heat available for ASHPs during defrosting. This paper reports on an experimental study of developing a novel reverse-defrosting method which was thermal energy storage (TES) based on using phase change material (PCM). Comparative experiments were carried out at two operating conditions: standard defrosting condition and the PCM-based defrosting condition. Results indicated that the use of this PCM-based reverse defrosting method could help shorten defrosting time, increase defrost COP d, enhance system reliability, reduce transition duration from defrost to normal space heating operation, and improve indoor thermal comfort for occupants during defrosting and heating resumption process while without degrading the quality of space heating provided by the ASHP during heat operation.