bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of highly crystalline C60 thin films and their field‐effect mobility
Authors: Birendra Singh Th. , Yang H. , Plochberger B. , Yang L. , Sitter H. , Neugebauer H. , Sariciftci N. S.
Published: November 2007

Transistors fabricated from C60 films grown by hot wall epitaxy at elevated substrate temperature of 250 °C, show charge carrier mobility of ∼6 cm2/Vs. When grown at substrate temperature of 25 °C, mobilities of only 0.6–1 cm2/Vs are obtained. The C60 films were characterized using grazing‐incidence X‐ray diffraction and show increased crystalline properties when grown at elevated substrate temperature. The improvement in the charge carrier mobility is attributed to the higher crystalline nature of the thin films. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computer modeling of electronic structure of single‐wall carbon nanotubes affected by pressure
Authors: Osadchy A. V. , Obraztsova E. D.
Published: November 2007

In this paper, a principal calculation of the electronic structure of single‐wall carbon nanotubes at different pressure values has been performed. The simulations have been done for nanotubes aggregated in ropes. The pressure has been modeled by changing the distances between neighbor nanotubes in the rope. The results of the calculations show that the pressure increase leads to a decrease of energy of allowed optical transitions in nanotubes. This result corresponds to the experimental data published. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High pressure Raman study of the second‐order vibrational modes of single‐ and double‐walled carbon nanotubes
Authors: Papagelis K. , Andrikopoulos K. S. , Arvanitidis J. , Christofilos D. , Galiotis C. , Takenobu T. , Iwasa Y. , Kataura H. , Ves S. , Kourouklis G. A.
Published: November 2007

The pressure response of the second‐order Raman G′ band of bundled double‐ (DWCNTs) and single‐wall carbon nanotubes (SWCNTs) has been investigated by means of Raman spectroscopy using the 632.8 nm excitation. The different pressure responses of the G′ peak in SWCNTs and its corresponding components associated with the inner and the outer tubes in DWCNTs can be attributed to the different diameters of the resonantly probed tubes and the strength of the inner‐outer tube interaction. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ferrocene encapsulated in single‐wall carbon nanotubes: a precursor to secondary tubes
Authors: Shiozawa Hidetsugu , Pichler Thomas , Pfeiffer Rudolf , Kuzmany Hans , Kataura Hiromichi
Published: November 2007

We demonstrate filling of single‐wall carbon nanotubes with ferrocene. Encapsulated ferrocenes are utilized as a precursor to secondary inner tubes and iron dopant. The reaction pathway is traced by Raman and photoemission spectroscopy. From a comparison to the inner‐tube growth from C60 fillers we propose different mechanisms for the inner‐tube growth from fullerene and non‐fullerene precursors. This work pioneers a new chemistry using carbon nanotubes as a nano reaction furnace. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Extreme thermal stability of carbon nanotubes
Authors: Begtrup G. E. , Ray K. G. , Kessler B. M. , Yuzvinsky T. D. , Garcia H. , Zettl A.
Published: November 2007

The versatility of carbon–carbon bonding creates a wealth of extraordinary physical properties. Of the two common allotropes of carbon, diamond (sp‐3 bonded) exhibits record thermal conductivity but is meta‐stable and transits to graphite at elevated temperatures. Graphite (sp‐2) is electrically conducting but sublimes at temperatures as low as 2400 K. Carbon nanotubes (also sp‐2) capitalize on the extraordinary strength of the sp‐2 hybridized carbon–carbon bond and exhibit high electrical and thermal conductivities as well as tremendous mechanical strength. Here we report a new technique to measure the thermal properties of nanosystems. We apply this technique to determine the ultimate high temperature breakdown of multiwalled carbon nanotubes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carbon nanofoam as a potential hydrogen storage material
Authors: Blinc R. , Arčon D. , Umek P. , Apih T. , Milia F. , Rode A. V.
Published: November 2007

Hydrogen based fuel cells are considered to be an important future alternative to fossile based energy sources such as oil, natural gas and coal. For many applications such a hydrogen driven cars, the limiting factor is the weight of the hydrogen fuel storage device which seems to be excessive for hydrogen stored in metals. This is the reason for the search for ultralight hydrogen storage materials such as carbon nanotubes or graphite layers. Here we report on the investigation of the basic mechanism of H‐carbonaceous interactions leading to hydrogen storage. The system has an ultra‐low density of 2–10 mg/cm3 and a large surface area 300–400 m2/g. Electron diffraction showed the presence of hyperbolic “schwarzite” layers making the system suitable for hydrogen storage. Preliminary proton NMR experiments showed that hydrogen can indeed be reversibly stored in carbon nanofoam at room temperature and that the corresponding proton spin lattice relaxation time T1 of the stored hydrogen is 400 ms. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Single‐walled carbon nanotubes as nanotest tubes
Authors: Borowiak‐Palen E.
Published: November 2007

In this study a wet‐chemistry procedure to perform a metathesis reaction in the interior of single‐walled carbon nanotube (SWCNT) is shown. Initially, AgNO3 was placed into the tube interior. The AgNO3 filling was then transformed into AgCl through a metathesis reaction involving a treatment step with HCl. The reaction highlights the potential application of SWCNT as nanotest tubes. This was further demonstrated by the successful development of a facile and efficient wet‐chemistry route to purge the AgCl filling from the interior of the SWCNT. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Filling of carbon nanotubes for bio‐applications
Authors: Costa S. , Borowiak‐Palen E. , Bachmatiuk A. , Rümmeli M. H. , Gemming T. , Kaleńczuk R. J.
Published: November 2007

Carbon nanotubes (CNT) provide a smart carrier system on the nanometer scale. The system can be used as a template for ferromagnetic fillers. Such a molecular hybrid is a promising potential candidate for the controlled heating of tumour tissue at the cellular level. This is a key reason why it is important to optimize the synthesis route of metal filled carbon nanotubes with regards bulk scale synthesis and purity. In the current study we present multiwalled carbon nanotubes filled with α‐iron phase (Fe‐MWCNT). The influence of acid treatment on the stability of the filling and the sample purity is also presented. High resolution transmission microscopy, its Energy dispersive X‐Ray spectroscopy (EDX) and electron energy‐loss spectroscopy (EELS) modes have been applied for the analysis of the morphology and chemical composition of the samples. The phase of iron nanowires encapsulated into the carbon nanotubes was determined with selected area electron diffraction (SAED) on a local scale. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Method for continuous production of catalysts for synthesis of carbon nanotubes
Authors: Lima Márcio D. , Dettlaff Ursula , de Andrade Mônica J. , Skakalová Viera , Locatelli Andrei , Bergmann Carlos P. , Roth Siegmar
Published: November 2007

A new method for continuous production of carbon nanotube (CNT) catalysts is proposed in this study. The method is a modification of the solution combustion synthesis and was called continuous solution combustion synthesis (CSCS). The method consists of the atomization of the modified combustion synthesis precursor solution in a pilot flame. A combustible, like ethanol, is added to the precursor solution to improve the evaporation of the solvent and the atomization. The ignition of the precursor solution is self‐sufficient. A fine and porous powder is produced. The powder, collected through an electrostatic precipitator, has superior performance as a carbon nanotube catalyst. When comparing the production of Fe–Mo/MgO catalyst synthesized by the continuous method with the conventional route, it was observed that the amount of carbon nanotubes increased by 52 wt%, and the G/D ratio was also higher. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural properties and electrochemical behavior of CNT‐TiO2 nanocrystal heterostructures
Authors: Frank Otakar , Kalbac Martin , Kavan Ladislav , Zukalova Marketa , Prochazka Jan , Klementova Mariana , Dunsch Lothar
Published: November 2007

Different methods of preparation of CNT‐TiO2 (anatase) heterostructures have been tested in order to obtain information on the relationship between the preparation method, resulting structure of the material and its electrochemical behavior during Li+ insertion. The most complete TiO2 coverage of individual non‐functionalized MWCNT was achieved in block co‐polymer (Pluronic P123) templated TiO2 thin films. This heterostructure has the highest specific capacity of Li+ insertion into TiO2 lattice to form Lix TiO2 (688 C/g, x = 0.57), however, this was accompanied by the worst reversibility (76%). On the contrary, electrodeposited TiO2 on SWCNT covered only bundles of nanotubes and its Li+ insertion capacity was 507 C/g (x = 0.42). However, the reversibility for all electrodeposited samples was almost complete and varied around 98%. Furthermore, Li+ insertion behavior studied by the cyclic voltammetry technique showed unambiguously the presence of minute amounts of monoclinic TiO2(B) in addition to anatase in samples from both synthesis methods. Thirdly, non‐functionalized MWCNT have been mixed by phase pure anatase nanocrystals of average size 30 nm made by hydrolysis of Ti‐butoxide in ethanol dispersion of CNT. Electrochemical Li+ insertion showed x = 0.54 (charge capacity of 652 C/g) with 85% reversibility. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Combination of atomic force microscopy and photoluminescence microscopy for the investigation of individual carbon nanotubes on sapphire surfaces
Authors: Jester Stefan‐Sven , Kiowski Oliver , Lebedkin Sergei , Hennrich Frank , Fischer Regina , Stürzl Ninette , Hawecker Jacques , Kappes Manfred M.
Published: November 2007

Atomic force microscopy (AFM) and photoluminescence (PL) spectroscopy were applied to characterize single walled carbon nanotubes (SWNTs) deposited on sapphire. The electronic properties and structure of luminescent semiconducting SWNTs can be probed by PL spectroscopy. The diameter, length, spatial position, and angular orientation of deposited SWNTs can be accurately determined by intermittent contact AFM. We describe an approach to combine and compare the spectroscopic (PL) and topographical (AFM) information for the same individual nanotubes as well as nanotube aggregates. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theoretical Raman intensity of the radial breathing mode of single‐walled carbon nanotubes
Authors: Popov V. N. , Lambin P.
Published: November 2007

The atomistic calculations of the physical properties of perfect single‐walled carbon nanotubes can be performed successfully by use of the helical symmetry of the nanotubes. The efficiency of this approach is illustrated by calculations of the electronic band structure, lattice dynamics, and the resonant Raman intensity of the radial‐breathing mode for all nanotubes in the diameter range from 0.6 nm to 2.4 nm within a symmetry‐adapted nonorthogonal tight‐binding model. It is shown that the derived electron–phonon coupling and the Raman intensity are in fair agreement with recent Raman data on individual nanotubes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chemical vapor deposition of functionalized single‐walled carbon nanotubes with defined nitrogen doping
Authors: Ayala Paola , Freire Fernando L. , Rümmeli Mark H. , Grüneis Alexander , Pichler Thomas
Published: November 2007

Defined n‐doping of carbon nanotubes can find potential application in nanoelectronics and sensors. An efficient doping can be achieved by substituting Carbon by heteroatoms such as Nitrogen. We explored the formation process of N doped single‐walled nanotubes within hot wall chemical vapor deposition employing different (C/N) feedstocks and catalysts. The process was optimized regarding the formation of substitutionally doped SWCNT and double wall CNTs. Analysis of N content and bonding environment is presented. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A nanoscaled contactless thermometer for biological systems
Authors: Vyalikh A. , Klingeler R. , Hampel S. , Haase D. , Ritschel M. , Leonhardt A. , Borowiak‐Palen E. , Rümmeli M. , Bachmatiuk A. , Kalenczuk R. J. , Grafe H.‐J. , Büchner B.
Published: November 2007

We report on a systematic approach to exploit the potential of filled carbon nanotubes (CNT) to act as sensors that might provide non‐invasive temperature control in biological systems on a cellular level. In this case the temperature is detected by measuring NMR parameters on the filling materials. The beneficial feature of a carbon nanotube is to provide protection of both (i) a human body against toxic adverse effects from the filling material and (ii) a filling material against chemical and biochemical exposure. The feasibility of this concept has been demonstrated on the example of the temperature‐dependent NMR frequency and relaxation time measured on the CNT filled with the appropriate sensor materials. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Manipulation of quantum information in N@C60 using electron and nuclear magnetic resonance
Authors: Ardavan Arzhang , Morton John J. L. , Benjamin Simon C. , Porfyrakis Kyriakos , Briggs G. Andrew D. , Tyryshkin Alexei M. , Lyon S. A.
Published: November 2007

We review recent progress towards implementing quantum information processing protocols using electron and nuclear magnetic resonance in the molecule 14N@C60. Using conventional spectrometers, we measure the errors inherent in quantum manipulations of spins. By applying composite pulses, we correct the dominant error to a high degree. Identifying a two qubit computational basis out of the electron and nuclear spin levels of 14N@C60, we implement an ultrafast phase gate on the nuclear qubit by exciting an electron spin transition. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
N@C60 quantum bit engineering
Authors: Harneit W. , Huebener K. , Naydenov B. , Schaefer S. , Scheloske M.
Published: November 2007

We report on some engineering aspects in the context of utilizing N@C60 molecules as quantum bits. Multi‐step recycling HPLC leads to 100% pure material. Symmetry breaking environments provide full addressing of the high‐dimensional Hilbert space. AFM‐tip induced local anodic oxidation of silicon can be used for arrangements of fullerenes on surfaces. Finally, electrically detected magnetic resonance is capable of coherent manipulation and read‐out of spin evolution of fullerenes at room temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carbon nanotubes for ultrafast photonics
Authors: Scardaci V. , Rozhin A. G. , Tan P. H. , Wang F. , White I. H. , Milne W. I. , Ferrari A. C.
Published: November 2007

We report characterization by absorption and photoluminescence excitation (PLE) spectroscopy of carbon nanotube solutions, which are then used for nanotube‐based composite preparation. PLE shows the presence of bundles in the solution. The composite show a saturation intensity of 5 MW/cm2 and is used in a fibre laser to generate pulses as short as 866 fs at about 1530 nm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Silicon to nickel‐silicide axial nanowire heterostructures for high performance electronics
Authors: Weber Walter M. , Geelhaar Lutz , Unger Eugen , Chèze Caroline , Kreupl Franz , Riechert Henning , Lugli Paolo
Published: November 2007

Silicon to nickel disilicide axial nanowire (NW) heterostructures have been fabricated and investigated extensively. To this end, intrinsic Si‐NWs were grown by chemical vapor deposition using Au as the catalyst. The Si‐NWs were contacted with Ni reservoirs so that upon annealing Ni diffused axially into the NWs. Single‐crystalline NiSi2NW segments were formed at the diffusion path of Ni as proven by high‐resolution transmission electron microscopy images. Further, the axial NiSi2to Si interfaces showed a sharpness of a couple of nanometers. Fully silicided NiSi2‐NWs had maximal resistivities of 98 μΩ cm and conducted current densities of up to 205 MA/cm2before breakdown. Controlled silicidation from both NW ends gave NiSi2/Si/NiSi2axial NW heterostructures, which were implemented to fabricate Schottky contact field effect transistors (FET). The n++‐substrate was used as a common back gate and the Si to NiSi2interfaces formed the Schottky source‐ and drain‐(S/D) contacts to the active region. These Si‐NW SB‐FETs exhibited p‐type behavior, and current densities in the on state of up to 0.8 MA/cm2for 1 V bias, the drain current could be modulated over a range of 107. Moreover, the use of thin gate dielectrics enabled inverse subthreshold slopes as low as 110 mV/dec. These data show an efficient gate control over the devices by only using a back gate, due to an enhanced gate field coupling to the tip‐like S/D‐Schottky contacts. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Absorption of BN nanotubes under the influence of a perpendicular electric field
Authors: Attaccalite Claudio , Wirtz Ludger , Marini Andrea , Rubio Angel
Published: November 2007

We calculate the optical absorption spectra of prototype (6,6) and (9,9) BN nanotubes in the presence of a perpendicular electric field. This model mimics a gated BN nanotube device. Even though the band‐gap of the tubes decreases strongly as a function of the electric field strength, the absorption spectrum of the pure tubes remains remarkably constant up to high field‐strength. We show that, in contrast, the levels which are responsible for defect‐mediated photo‐luminescence are shifted by the electric field. We address the use of BN nanotubes for optoelectronic applications. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Excitons in carbon nanotubes: Diameter and chirality trends
Authors: Capaz Rodrigo B. , Spataru Catalin D. , Ismail‐Beigi Sohrab , Louie Steven G.
Published: November 2007

We provide a closer look into the diameter and chirality dependences of exciton properties in carbon nanotubes, using a variational methodology based on the effective mass and envelope function approximations, supported by ab initio parameters. Experimental measurements of the binding energy are reproduced within 0.02 eV for a large variety of tubes. We also report on the singlet‐triplet energy splittings, which show a 1/d2 diameter dependence. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of the shift of Raman modes of graphene flakes
Authors: Haluška M. , Obergfell D. , Meyer J. C. , Scalia G. , Ulbricht G. , Krauss B. , Chae D. H. , Lohmann T. , Lebert M. , Kaempgen M. , Hulman M. , Smet J. , Roth S. , Klitzing K. von
Published: November 2007

In the present work, we use Raman spectroscopy as sensitive tool for the characterization of graphene samples. We observed diverse shifts in the position of the Raman mode close to 2650 cm–1 in various as‐prepared graphene flakes. In order to elucidate the reason for this variation, we checked different substrates (Si/SiO2 and Si/Al2O3) and the effect of the annealing of graphene in argon. We find that most of as‐prepared graphene flakes were non‐intentional doped by holes, i.e. by physisorbed water and/or oxygen. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In situ time‐resolved measurements of carbon nanotube and nanohorn growth
Authors: Geohegan D. B. , Puretzky A. A. , Styers‐Barnett D. , Hu H. , Zhao B. , Cui H. , Rouleau C. M. , Eres G. , Jackson J. J. , Wood R. F. , Pannala S. , Wells J. C.
Published: November 2007

Growth mechanisms of carbon nanotubes are investigated and compared for both high‐ and low‐temperature synthesis methods through experiments utilizing time‐resolved, in situ imaging and spectroscopy. High‐speed videography and pyrometry measured the timeframes for growth for single‐wall carbon nanotubes (SWNTs) and nanohorns (SWNHs) by laser vaporization (LV) at 1150 °C, revealing that C can self‐assemble at high temperatures preferentially into SWNH structures without catalyst assistance at rates comparable to catalyst‐assisted SWNT growth by either laser vaporization or chemical vapor deposition (CVD). Laser interferometry and videography reveal the coordinated growth of vertically‐aligned nanotube arrays (VANTAs) by CVD at 550–900 °C. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chirality‐specific transport phenomena of isolated single‐walled carbon nanotube
Authors: Jeong Seung Yol , Perello David , Kim Sung Jin , Jang Jin Ho , Kang Bo Ram , Yu Woo Jong , Bae Dong Jae , Yun Minhee , Lee Young Hee
Published: November 2007

Single‐walled carbon nanotube‐field effect transistors (SWCNT‐FETs) have been fabricated using in‐situ thermal chemical vapor deposition. For isolated devices, the resonant Raman spectra confirmed that the full width at half maximum (FWHM) of the radial breathing mode (RBM) peaks was about 4 cm–1, consistent with atomic force microscopy (AFM) images that clearly revealed the individually isolated SWCNTs on the patterned substrate with a diameter of 1.3 nm. Subsequent I –V measurements of the SWCNT‐FET revealed a clear gating effect for samples with semiconducting SWCNTs. The transport phenomena of a device with mixed metallic and semiconducting SWCNTs network were governed by the metallic nanotube with severely suppressed gate modulation. Identification of the chirality of SWCNTs by resonant Raman spectroscopy prior to the I –V characteristics guarantees the validity of working FET devices. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Charge transport across single‐molecule junctions: charge reconfiguration and structural dynamics
Authors: Secker Daniel , Weber Heiko B.
Published: November 2007

The charge transport across single‐molecule junctions is often considered as a pure electronic phenomenon. Analysing experiments performed with the mechanically controlled break junction technique, we show that, additionally, both polarization and dynamic motion of the geometric structure of the molecule give important contributions to the charge transport across single‐molecule junctions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic properties of graphene
Authors: Novoselov K. S. , Morozov S. V. , Mohinddin T. M. G. , Ponomarenko L. A. , Elias D. C. , Yang R. , Barbolina I. I. , Blake P. , Booth T. J. , Jiang D. , Giesbers J. , Hill E. W. , Geim A. K.
Published: November 2007

Graphene is the first example of truly two‐dimensional crystals – it's just one layer of carbon atoms. It turns out that graphene is a gapless semiconductor with unique electronic properties resulting from the fact that charge carriers in graphene obey linear dispersion relation, thus mimicking massless relativistic particles. This results in the observation of a number of very peculiar electronic properties – from an anomalous quantum Hall effect to the absence of localization. It also provides a bridge between condensed matter physics and quantum electrodynamics and opens new perspectives for carbon‐based electronics. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Special issue: Electronic Properties of Novel Nanostructures
Authors: Kuzmany Hans , Dinse Peter , Roth Siegmar , Thomsen Christian
Published: November 2007

This special issue of physica status solidi (b) contains contributions presented at the International Winterschool/Euroconference on Electronic Properties of Novel Materials (IWEPNM 2007). The meeting was held in March 2007 in Kirchberg, Austria.

The articles in this issue provide essential information on a wide spectrum of topics, including quantum information, Raman spectroscopy and optics of nanotubes, synthesis of carbon nanotubes, carbon nanotubes and DNA, graphite and graphene, electron and heat transport in carbon nanostructures, composites with carbon nanotubes, as well as on theory and applications of these materials.

As in previous years, the meeting was attended by many outstanding researchers from around the world and from a wide spectrum of scientific disciplines. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First principle study of the cation vacancy in anatase TiO2
Authors: Bai Yu , Chen Qiang
Published: November 2007

Based on first principle FP‐LAPW calculations, we have studied the electronic and magnetic properties of anatase TiO2 with Ti cation vacancy. We find that the Ti cation vacancy defect can induce a magnetic moment of about 4μB/supercell. The magnetic moment mainly comes from p‐orbitals of O atoms which surround the Ti vacancy. We also find that the two Ti vacancies in anatase always coupled ferromagnetically. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Matrix‐covariant representation of high‐order configuration interaction and coupled cluster theories
Authors: Luzanov Anatoliy V.
Published: November 2007

We present the closed form of the reduced density matrices (RDMs) of arbitrary order for configuration interaction (CI) wave functions at any excitation level, up to the full CI. A special operator technique due to Bogoliubov is applied and extended. It focuses on constructions of matrix‐covariant expressions independent of the basis set used. The corresponding variational CI equations are given in an explicit form containing the matrices related to conventional excitation operators. A subsequent transformation of the latter to an irreducible form makes it possible to generate the matrix‐covariant representation for coupled cluster (CC) models. Here this transformation is performed for a simplified high‐order CC scheme somewhat reminiscent of the quadratic CI model. A generalized spin‐flip approximation closely related to high‐order CI and CC models is presented, stressing on a possible inclusion of nondynamical and dynamical correlation effects for multiple bond breaking. A derivation of the full CI and simple CC models for systems involving effective three‐electron interactions is also given, thereby demonstrating the capability of the proposed method to deal with complicated many‐body problem. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Determination of long‐acting release octreotide, an octapeptide analogue of somatostation, in human plasma by liquid chromatography/tandem mass spectrometry
Authors: Jiang Yao , Wang Jiang , Wang Yingwu , Du Xiaolin , Zhang Yunhui , Fawcett J. Paul , Gu Jingkai
Published: November 2007

A sensitive and selective method for the determination of long‐acting released octreotide in human plasma has been developed based on liquid chromatography/tandem mass spectrometry (LC/MS/MS). Octreotide and the internal standard, triptorelin, were precipitated from the matrix, washed with dichloromethane and subsequently separated by reversed‐phase high‐performance liquid chromatography (HPLC) employing a 1% formic acid/methanol gradient system. Detection was by electrospray ionization mass spectrometry in the positive ion mode using multiple‐reaction monitoring. The assay was linear in the concentration range 0.0500–50.0 ng/mL with intra‐ and inter‐day precision (as relative standard deviation) of <2.95% and <8.37%, respectively. The limit of detection was 0.0200 ng/mL. The method was applied to a pharmacokinetic study of long‐acting released octreotide in healthy volunteers given an intramuscular injection containing 20 mg octreotide. Copyright © 2007 John Wiley & Sons, Ltd.
Shared environment representation for a human‐robot team performing information fusion
Authors: Kaupp Tobias , Douillard Bertrand , Ramos Fabio , Makarenko Alexei , Upcroft Ben
Published: November 2007

This paper addresses the problem of building a shared environment representation by a human‐robot team. Rich environment models are required in real applications for both autonomous operation of robots and to support human decision‐making. Two probabilistic models are used to describe outdoor environment features such as trees: geometric (position in the world) and visual. The visual representation is used to improve data association and to classify features. Both models are able to incorporate observations from robotic platforms and human operators. Physically, humans and robots form a heterogeneous sensor network. In our experiments, the human‐robot team consists of an unmanned air vehicle, a ground vehicle, and two human operators. They are deployed for an information gathering task and perform information fusion cooperatively. All aspects of the system including the fusion algorithms are fully decentralized. Experimental results are presented in form of the acquired multi‐attribute feature map, information exchange patterns demonstrating human‐robot information fusion, and quantitative model evaluation. Learned lessons from deploying the system in the field are also presented. © 2007 Wiley Periodicals, Inc.
Towards heterogeneous robot teams for disaster mitigation: Results and performance metrics from RoboCup rescue
Authors: Balakirsky Stephen , Carpin Stefano , Kleiner Alexander , Lewis Michael , Visser Arnoud , Wang Jijun , Ziparo Vittorio Amos
Published: November 2007

Urban Search and Rescue is a growing area of robotic research. The RoboCup Federation has recognized this, and has created the new Virtual Robots competition to complement its existing physical robot and agent competitions. In order to successfully compete in this competition, teams need to field multi‐robot solutions that cooperatively explore and map an environment while searching for victims. This paper presents the results of the first annual RoboCup Rescue Virtual competition. It provides details on the metrics used to judge the contestants as well as summaries of the algorithms used by the top four teams. This allows readers to compare and contrast these effective approaches. Furthermore, the simulation engine itself is examined and real‐world validation results on the engine and algorithms are offered. © 2007 Wiley Periodicals, Inc.
TRESSA: Teamed robots for exploration and science on steep areas
Authors: Huntsberger Terry , Stroupe Ashley , Aghazarian Hrand , Garrett Mike , Younse Paulo , Powell Mark
Published: November 2007

Long‐duration robotic missions on lunar and planetary surfaces (for example, the Mars Exploration Rovers have operated continuously on the Martian surface for close to 3 years) provide the opportunity to acquire scientifically interesting information from a diverse set of surface and subsurface sites and to explore multiple sites in greater detail. Exploring a wide range of terrain types, including plains, cliffs, sand dunes, and lava tubes, requires the development of robotic systems with mobility enhanced beyond that which is currently fielded. These systems include single as well as teams of robots. TRESSA (Teamed Robots for Exploration and Science on Steep Areas) is a closely coupled three‐robot team developed at the Jet Propulsion Laboratory (JPL) that previously demonstrated the ability to drive on soil‐covered slopes up to 70 deg. In this paper, we present results from field demonstrations of the TRESSA system in even more challenging terrain: rough rocky slopes of up to 85 deg. In addition, the integration of a robotic arm and instrument suite has allowed TRESSA to demonstrate semi‐autonomous science investigation of the cliffs and science sample collection. TRESSA successfully traversed cliffs and collected samples at three Mars analog sites in Svalbard, Norway as part of a recent geological and astrobiological field investigation called AMASE: Arctic Mars Analog Svalbard Expedition under the NASA ASTEP (Astrobiology Science and Technology for Exploring Planets) program. © 2007 Wiley Periodicals, Inc.
Adaptive teams of autonomous aerial and ground robots for situational awareness
Authors: Hsieh M. Ani , Cowley Anthony , Keller James F. , Chaimowicz Luiz , Grocholsky Ben , Kumar Vijay , Taylor Camillo J. , Endo Yoichiro , Arkin Ronald C. , Jung Boyoon , Wolf Denis F. , Sukhatme Gaurav S. , MacKenzie Douglas C.
Published: November 2007

In this paper, we report on the integration challenges of the various component technologies developed toward the establishment of a framework for deploying an adaptive system of heterogeneous robots for urban surveillance. In our integrated experiment and demonstration, aerial robots generate maps that are used to design navigation controllers and plan missions for the team. A team of ground robots constructs a radio‐signal strength map that is used as an aid for planning missions. Multiple robots establish a mobile ad hoc communication network that is aware of the radio‐signal strength between nodes, and can adapt to changing conditions to maintain connectivity. Finally, the team of aerial and ground robots is able to monitor a small village, and search for and localize human targets by the color of the uniform, while ensuring that the information from the team is available to a remotely located human operator. The key component technologies and contributions include: (a) Mission specification and planning software; (b) exploration and mapping of radio‐signal strengths in an urban environment; (c) programming abstractions and composition of controllers for multirobot deployment; (d) cooperative control strategies for search, identification, and localization of targets; and (e) three‐dimensional mapping in an urban setting. © 2007 Wiley Periodicals, Inc.
Human assisted robotic team campaigns for aquatic monitoring
Authors: Singh Amarjeet , Stealey Michael J. , Chen Victor , Kaiser William J. , Batalin Maxim , Lam Yeung , Zhang Bin , Dhariwal Amit , Oberg Carl , Pereira Arvind , Sukhatme Gaurav S. , Stauffer Beth , Moorthi Stefanie , Caron Dave , Hansen Mark
Published: November 2007

Large‐scale environmental sensing, e.g., understanding microbial processes in an aquatic ecosystem, requires coordination across a multidisciplinary team of experts working closely with a robotic sensing and sampling system. We describe a human‐robot team that conducted an aquatic sampling campaign in Lake Fulmor, San Jacinto Mountains Reserve, California during three consecutive site visits (May 9–11, June 19–22, and August 28–31, 2006). The goal of the campaign was to study the behavior of phytoplankton in the lake and their relationship to the underlying physical, chemical, and biological parameters. Phytoplankton form the largest source of oxygen and the foundation of the food web in most aquatic ecosystems. The reported campaign consisted of three system deployments spanning four months. The robotic system consisted of two subsystems—NAMOS (networked aquatic microbial observing systems) comprised of a robotic boat and static buoys, and NIMS‐RD (rapidly deployable networked infomechanical systems) comprised of an infrastructure‐supported tethered robotic system capable of high‐resolution sampling in a two‐dimensional cross section (vertical plane) of the lake. The multidisciplinary human team consisted of 25 investigators from robotics, computer science, engineering, biology, and statistics.We describe the lake profiling campaign requirements, the robotic systems assisted by a human team to perform high fidelity sampling, and the sensing devices used during the campaign to observe several environmental parameters. We discuss measures taken to ensure system robustness and quality of the collected data. Finally, we present an analysis of the data collected by iteratively adapting our experiment design to the observations in the sampled environment. We conclude with the plans for future deployments. © 2007 Wiley Periodicals, Inc.
Origin and development of ecological philosophy and environmental ethics and their impact on the idea of sustainable development
Authors: Tyburski Włodzimierz
Published: November 2007

A critical review of environmental philosophy and environmental ethics is discussed in relation to the idea of sustainable development. The article makes reference to 19th century influences that inspired thought orientated towards protecting the natural environment, and then presents the stages of the development of ecological philosophy, the main standpoints and their representatives. The main features of Polish eco‐philosophical thought are presented together with an outline of the most significant achievements of these disciplines on a global scale. The influence of environmental philosophy and ethics on social aspects of sustainable development is also presented. Copyright © 2007 John Wiley & Sons, Ltd and ERP Environment.
Technical uncertainty in the back‐calculation of occupational exposure to dioxins
Authors: Heinzl Harald , Mittlböck Martina , Edler Lutz
Published: November 2007

Members of a cohort of workers in chemical industry (the so‐called Boehringer cohort) exposed to 2, 3, 7, 8‐tetrachlorodibenzo‐para‐dioxin (TCDD) from 1950 to 1984 were subject in the years 1985–1986 and 1992–1994 to an extensive biomonitoring programme on the TCDD levels of the individual workers. For establishing a dose–response relationship between TCDD‐exposure and potentially carcinogenic response, the individual TCDD concentration–time courses had to be back‐calculated over a period of up to more than four decades. Two back‐calculations were attempted for this sophisticated modelling and estimation task, both based on the same toxicokinetic model but yielding different results.

We demonstrate here by means of a computer simulation study that these differences could be plausibly explained by the so‐called technical uncertainty caused by the employment of differently statistical estimation techniques. We show that the estimation techniques perform particularly differently in the presence of workplace misclassification and TCDD measurement error, two complications of exposure assessment that are with high probability affecting concurrently that cohort's data.

We conclude that technical uncertainty sensibly enlarges the pool of possible explanations for contradictory empirical results of complex modelling and estimation approaches and should be considered as an obligatory uncertainty analysis step after the primary risk analysis evaluation in epidemiological and environmental studies. Copyright © 2007 John Wiley & Sons, Ltd.
Non‐parametric estimation and model checking procedures for marginal gap time distributions for recurrent events
Authors: Kvist Kajsa , Gerster Mette , Andersen Per Kragh , Kessing Lars Vedel
Published: November 2007

For recurrent events there is evidence that misspecification of the frailty distribution can cause severe bias in estimated regression coefficients (Am. J. Epidemiol 1998; 149:404–411; Statist. Med. 2006; 25:1672–1684). In this paper we adapt a procedure originally suggested in (Biometrika 1999; 86:381–393) for parallel data for checking the gamma frailty to recurrent events. To apply the model checking procedure, a consistent non‐parametric estimator for the marginal gap time distributions is needed. This is in general not possible due to induced dependent censoring in the recurrent events setting, however, in (Biometrika 1999; 86:59–70) a non‐parametric estimator for the joint gap time distributions based on the principle of inverse probability of censoring weights is suggested. Here, we attempt to apply this estimator in the model checking procedure and the performance of the method is investigated with simulations and applied to Danish registry data. The method is further investigated using the usual Kaplan–Meier estimator and a marginalized estimator for the marginal gap time distributions. We conclude that the procedure only works when the recurrent event is common and when the intra‐individual association between gap times is weak. Copyright © 2007 John Wiley & Sons, Ltd.
First‐trimester biochemical markers of aneuploidy and the prediction of small‐for‐gestational age fetuses
Authors: Spencer K. , Cowans N. J. , Avgidou K. , Molina F. , Nicolaides K. H.
Published: November 2007

Objectives

To examine the clinical utility of the first‐trimester biochemical markers of aneuploidy in their ability to predict subsequent delivery of a small‐for‐gestational age (SGA) infant.

Methods

We examined singleton pregnancies with no chromosomal abnormality and with complete outcome data that had undergone screening for trisomy 21 by a combination of fetal nuchal translucency (NT) thickness and maternal serum free β‐human chorionic gonadotropin (β‐hCG) and pregnancy‐associated plasma protein‐A (PAPP‐A) at 11 + 0 and 13 + 6 weeks' gestation. The biochemical markers were converted to multiples of the expected normal median (MoM) for a pregnancy of the same gestation. The association between free β‐hCG and PAPP‐A and the incidence of SGA were assessed by comparing the relative incidence at MoM cut‐offs and birth‐weight centile cut‐offs. At various marker levels the likelihood ratios (LR) for SGA were also calculated after excluding other adverse pregnancy complications.

Results

There were 46 262 pregnancies resulting in live births with birth weight at or above the 10th centile, and 3539 below the 10th centile for gestation (SGA). There was a significant inverse association between the risk for SGA and maternal serum PAPP‐A MoM but not free β‐hCG MoM. At the 5th centile of the normal outcome group for PAPP‐A (0.415 MoM) the odds ratios for SGA below the 10th, 5th and 3rd centiles of normal were 2.70, 3.21 and 3.66 and the respective detection rates for SGA were 12.0%, 14.0% and 16.0%.

Conclusions

Low levels of maternal serum PAPP‐A are associated, in the absence of an abnormal karyotype, with an increased risk for subsequent delivery of an SGA infant. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.
A unification of probabilistic choice within a design-based model of reversible computation
Authors: Stoddart Bill , Zeyda Frank
Published: November 2007

We see reversible computing as a generalisation of sequential computation obtained by revoking the law of the excluded miracle. Our execution language includes naked guarded commands and non-deterministic choice. Choices which lead to miraculous continuations invoke reverse computation, and non-deterministic choice plays the rôle of provisional choice within a backtracking context. We require probabilistic choice for symmetry breaking and sampling large search spaces, but must formulate it differently from previous approaches to obtain the required interactions between probabilistic choice and non-deterministic choice and between probabilistic choice and feasibility. Our formulation allows us to derive the post-distributions which characterise a program, and we use these to construct a relational model. We consider refinement as containment of convex closures within distribution space, qualified with additional conditions to avoid over-refinement. We link the non-probabilistic and probabilistic versions of the model with a Galois connection and show that classical designs are a retract of our probabilistic designs. We consider the interaction between probabilistic and non-deterministic choice and find the same initially counter-intuitive results that have been noted by other investigators. We provide an alternative formulation, within the same model, of oblivious non-determinism, which allows all non-deterministic choices to be moved to the start of a computation. We consider the interaction between probabilistic choice and feasibility that is required to match an operational interpretation in which infeasible commands provoke reverse execution, and we present a small case study to show how the interaction between probabilistic choice and feasibility can be exploited in a practical program. All programming structures described here are supported by our implementation platform, the Reversible Virtual Machine, whose development has accompanied our theoretical investigations.
The role of exercise on the innate immunity of the elderly
Authors: Malaguarnera Lucia , Cristaldi Erika , Vinci Maria , Malaguarnera Mariano
Published: November 2007

The increased life span in human population has shown that some diseases, as infections, cancer and autoimmune phenomena, occur more frequently in the elderly than in the younger. We describe the ageing process involving the innate immune system and the improvement given by moderate physical activity. In addition, we discuss the altered neutrophil granulocytes function, the role of macrophages and natural killer cells, besides the influence of cytokines and secretory IgA. The acquired information help us to explain how these changes could favor the onset of diseases in the elderly and how they may boost their immune function.
Electron States and Light Absorption in Strongly Oblate and Strongly Prolate Ellipsoidal Quantum Dots in Presence of Electrical and Magnetic Fields
Authors: Dvoyan Karen G , Hayrapetyan David B , Kazaryan Eduard M , Tshantshapanyan Ani A
Published: November 2007

In framework of the adiabatic approximation the energy states of electron as well as direct light absorption are investigated in strongly oblate and strongly prolate ellipsoidal quantum dots (QDs) at presence of electric and magnetic fields. Analytical expressions for particle energy spectrum are obtained. The dependence of energy levels’ configuration on QD geometrical parameters and field intensities is analytically obtained. The energy levels of electrons are shown to be equidistant both for strongly oblate and prolate QDs. The effect of the external fields on direct light absorption of a QD was investigated. The dependence of the absorption edge on geometrical parameters of QDs and intensities of the electric and magnetic fields is obtained. Selection rules are obtained at presence as well as absence of external electric and magnetic fields. In particular, it is shown that the presence of the electric field cancels the quantum numbers selection rules at the field direction, whereas in radial direction the selection rules are preserved. Perspectives of practical applications for device manufacturing based on ellipsoidal quantum dots are outlined.
Wettability Switching Techniques on Superhydrophobic Surfaces
Authors: Verplanck Nicolas , Coffinier Yannick , Thomy Vincent , Boukherroub Rabah
Published: November 2007

The wetting properties of superhydrophobic surfaces have generated worldwide research interest. A water drop on these surfaces forms a nearly perfect spherical pearl. Superhydrophobic materials hold considerable promise for potential applications ranging from self cleaning surfaces, completely water impermeable textiles to low cost energy displacement of liquids in lab-on-chip devices. However, the dynamic modification of the liquid droplets behavior and in particular of their wetting properties on these surfaces is still a challenging issue. In this review, after a brief overview on superhydrophobic states definition, the techniques leading to the modification of wettability behavior on superhydrophobic surfaces under specific conditions: optical, magnetic, mechanical, chemical, thermal are discussed. Finally, a focus on electrowetting is made from historical phenomenon pointed out some decades ago on classical planar hydrophobic surfaces to recent breakthrough obtained on superhydrophobic surfaces.