bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison between endoscope‐assisted partial parotidectomy and conventional partial parotidectomy
Authors: Huang Xiaoming , Zheng Yiqing , Liu Xiang , Sun Wei , Zeng Liang , Cai Xiang , Liu Wei , Xu Yaodong , Zhang Zhigang , Huang Hongzhang
Published: January 2009

OBJECTIVE

To report the feasibility of endoscope‐assisted parotidectomy with an ultrasonic scalpel.

STUDY DESIGN

Randomized clinical trial.

SUBJECTS AND METHODS

A total of 38 patients were randomly assigned to conventional (20 patients) or endoscope‐assisted (18 patients) partial parotidectomy. Via retrograde approach, endoscopic and surgical instruments were inserted through two 20‐ to 25‐mm incisions (retromandibular and postauricular).

RESULTS

The endoscopic surgery lasted for 108.61 ± 11.86 minutes and the bleeding volume was significantly lower than in the conventional group. All 18 patients were satisfied with their cosmetic results; 14 patients (65%) were satisfied with the great auricular nerve preservation; only one patient had temporary facial paresis and salivary fistula. There was no tumor recurrence in both groups during the follow‐up after 26 to 40 months) the endoscope‐assisted parotidectomy group (median 30 months, range 26–40 months) and conventional group (median 32 months, range 26–40 months).

CONCLUSION

Endoscope‐assisted parotidectomy is a feasible technique. This procedure may serve as an alternative approach that allows a smaller incision.
A minimally invasive registration method using Surface Template‐Assisted Marker Positioning (STAMP) for image‐guided otologic surgery
Authors: Matsumoto Nozomu , Hong Jaesung , Hashizume Makoto , Komune Shizuo
Published: January 2009

OBJECTIVE

A new, minimally invasive registration method was developed for image‐guided otologic surgery. We utilized laser‐sintered template of the patient's bone surface to transfer the virtual markers to the patient's bone intraoperatively and eliminated the necessity for preoperative marker positioning or additional CT scan.

STUDY DESIGN

Simulation surgeries and clinical application.

SUBJECTS AND METHODS

We measured registration errors in 10 trials using replicas and six ear surgeries (two cochlear implant insertions, four translabyrinthine acoustic tumor removals).

RESULTS

The target registration errors varied among the surgical targets. Errors were less than 1 mm near the cochlear implant insertion target both in phantom study and in actual surgeries.

CONCLUSION

Our newly developed method reduced the preoperative procedures for patients but did not reduce the accuracy in cochlear implant surgery. Our method would be a useful image‐guided surgery method in the field of otology, where both accuracy and noninvasiveness are required.
Old and new aspects of middle turbinate histopathology
Authors: Berger Gilead , Finkelstein Yehuda , Ophir Dov , Landsberg Roee
Published: January 2009

OBJECTIVE

To study the histology of the normal and pathologic middle turbinate (MT).

STUDY DESIGN

Nonrandomized, controlled study.

SUBJECTS AND METHODS

Qualitative and quantitative assessment of soft tissue and bony elements of 14 normal and 10 chronic rhinosinusitis (CRS) MT samples (patients' mean CT score, 6.5 ± 6.7). A comparison with 14 normal inferior turbinate (IT) samples was accomplished. Quantitative assessment was limited to the lateral mucosal layer (LML).

RESULTS

The thickness of the LML was significantly greater in pathologic MT than in normal MT (P = 0.002). Except for veins that underwent significant increase (P = 0.036), other soft tissue constituents of the pathologic MT did not change significantly. Glands were more abundant in normal MT and veins in normal IT (P < 0.001, P = 0.001, respectively). Qualitative assessment showed larger veins in the normal IT compared with the normal MT. Inflammatory cell infiltrate, edema, and fibrosis were found in CRS. None of our MT bones exhibited osteomyelitic changes.

CONCLUSIONS

The different proportion of glands suggests varied functional roles for both the MT and IT. The significant involvement of the MT in the inflammatory process of CRS and the relatively small size and paucity of veins with relatively little effect on nasal airflow justify partial excision of the MT.
The Medicine and GERD of Immanuel Kant (1724–1804)
Authors: Filho Gilberto Vilela Figueiredo
Published: January 2009

We can place Kant as one of the pillars of contemporary medicine. Firstly, as an Illuminist, his work subordinates the collection of empirical data, which in medical science is constitutional to reason. This was the basis of a rational medical science. Secondly, he is the father of medical regulation, having set the philosophical control ground stone for physicians by the State. His work “Critique of Practical Reason” drafts all the future codes of ethics and bioethics. We will hereby study his relationship with medicine based on the text “The Conflict with the Faculty of Medicine” and other auxiliary texts. We can find in Kant's works the description of a series of symptoms that were related to a nonspecific dyspeptic syndrome that nowadays would be diagnosed as a strong indication that he suffered from gastroesophageal reflux disease (GERD).
Laryngeal and vocal evaluation in untreated growth hormone deficient adults
Authors: Barreto Valéria M. P. , D'Ávila Jeferson S. , Sales Neuza J. , Gonçalves Maria Iněs R. , Seabra Juliane Dantas , Salvatori Roberto , Aguiar‐Oliveira Manuel H.
Published: January 2009

OBJECTIVE

To evaluate the consequences of lifetime, severe and untreated isolated growth hormone deficiency (IGHD) on vocal and laryngeal function.

STUDY DESIGN

Cross‐sectional.

SUBJECTS AND METHODS

A total of 23 IGHD adult subjects and 22 controls were administered a questionnaire about vocal complaints and harmful voice habits, and underwent videolaryngostroboscopic examination, voice evaluation by perceptual‐auditory analysis with GRBAS scale including grade of dysphonia, roughness, breathiness, asthenia and strain items, objective voice evaluation by maximum phonation time (MPT), and acoustic analysis.

RESULTS

There was no difference in vocal complaints between IGHD subjects and controls. Vocal abuse and smoking were more frequent in IGHD subjects. IGHD subjects presented higher values for roughness, breathiness, and strain. Laryngopharyngeal reflux (LPR) signs and laryngeal constriction were more frequent in IGHD individuals. MPT was similar in the two groups. Fundamental frequency was higher in IGHD females and males. Harmonic to noise ratio was higher in IGHD in both genders and shimmer was lower in IGHD females.

CONCLUSIONS

IGHD subjects have higher prevalence of signs of LPR and laryngeal constriction, with high pitch in both genders, which suggests a prominent role of IGHD on these parameters.
Homotopy classification and the generalized Swan homomorphism
Authors: Johnson F.E.A.
Published: January 2009

In his fundamental paper on group cohomology [20] R.G. Swan defined a homomorphism for any finite group G which, in this restricted context, has since been used extensively both in the classification of projective modules and the algebraic homotopy theory of finite complexes ([3], [18], [21]). We extend the definition so that, for suitable modules J over reasonably general rings Λ, it takes the form here is the quotient of the category of Λ-homomorphisms obtained by setting ‘projective = 0’. We then employ it to give an exact classification of homotopy classes of extensions 0 → J → Fn → … → F0 → F0 → M → 0 where each Fr is finitely generated free.
k-invariants for K-theory of curves over global fields
Authors: Arlettaz Dominique , Banaszak Grzegorz
Published: January 2009

We investigate the k-invariants for the K-theory and étale K-theory spaces of schemes. We give numerical estimates of the orders of k-invariants for the K-theory and étale K-theory spaces of regular and proper models over of smooth, proper and geometrically irreducible curves defined over global fields F.
Thai Buddhism, Thai Buddhists and the southern conflict
Authors: McCargo Duncan
Published: January 2009

Thailand's ‘southern border provinces’ of Pattani, Yala and Narathiwat – along with four districts of neighbouring Songkhla – are the site of fiery political violence characterised by daily killings. The area was historically a Malay sultanate, and was only loosely under Thai suzerainty until the early twentieth century. During the twentieth century there was periodic resistance to Bangkok's attempts to suppress local identity and to incorporate this largely Malay-speaking, Muslim-majority area into a predominantly Buddhist nation-state. This resistance proved most intense during the 1960s and 1970s, when various armed groups (notably PULO [Patani United Liberation Organization] and BRN [Barisan Revolusi Nasional]) waged war on the Thai state, primarily targeting government officials and the security forces. In the early 1980s, the Prem Tinsulanond government brokered a deal with these armed groups and proceeded to co-opt the Malay-Muslim elite. By crafting mutually beneficial governance, security and financial arrangements, the Thai state was able largely to placate local political demands.
Landscapes of fear, horizons of trust: Villagers dealing with danger in Thailand's insurgent south
Authors: Askew Marc
Published: January 2009

Thai Buddhist and Malay Muslim neighbours in Thailand's Muslim-majority deep south face the challenge of managing everyday life in the midst of an enigmatic insurgency where both ethno-religious groups are victims of violence, but where the assailants are difficult to identify. This ethnographically-focused paper examines horizons of trust and suspicion as villagers confront threats to their safety, negotiate state authorities and encounter broader narratives about identity, allegiance and enemies. Although fear and suspicion sparked by the current violence have generated Buddhist–Muslim tensions in localities, neighbourhoods and village leaders also actively resist the multiple threats to their relationships and to inter-ethnic coexistence.
CrATP as a new inhibitor of ecto-ATPases of trypanosomatids
Authors: MOREIRA O. C. , RIOS P. F. , ESTEVES F. F. , MEYER-FERNANDES J. R. , BARRABIN H.
Published: January 2009

Trypanosomatid protozoa include heteroxenic species some of them pathogenic for men, animals and plants. Parasite membrane contains ecto-enzymes whose active sites face the external medium rather than the cytoplasm.Herpetomonassp. displayed a Mg2+-dependent ecto-ATPase activity, a Mg-independent ecto-ADPase and an ecto-phosphatase activity. Both, the ecto-ADPase and phosphatase activities were insensitive to CrATP (chromium(III) adenosine 5′-triphosphate complex). Ecto-ATPase activity was reversibly inhibited. At 2 mmATP the apparent Ki was 4·7±1·0 μmbut a fraction of about 40–50% was insensitive to CrATP. Remarkably, at low substrate concentration (0·2 mm) more than 90% of the ecto-ATPase was inhibited with Ki=0·33±0·10 μm. These parameter dependences are interpreted as the presence of 2 ecto-ATPases activities, one of them with high ATP apparent affinity and sensitivity to CrATP. DIDS (4,4 diisothiocyanatostilbene 2,2′ disulfonic acid), suramin and ADP were also effective as inhibitors. Only ADP presented no additive inhibition with CrATP. The pattern of partial inhibition by CrATP was also observed for the ecto-ATPase activities ofLeishmania amazonensis,Trypanosoma cruziandTrypanosoma rangeli. CrATP emerges as a new inhibitor of ecto-ATPases and as a tool for a better understanding of properties and role of ecto-ATPases in the biology of parasites.
Flow cytometry analysis of the circulating haemocytes from Biomphalaria glabrata and Biomphalaria tenagophila following Schistosoma mansoni infection
Authors: MARTINS-SOUZA R. L. , PEREIRA C. A. J. , COELHO P. M. Z. , MARTINS-FILHO O. A. , NEGRÃO-CORRÊA D.
Published: January 2009

Aiming to further characterize the haemocyte subsets in Biomphalaria snails, we have performed a detailed flow cytometric analysis of whole haemolymph cellular components using a multiparametric dual colour labelling procedure. Ethidium bromide/acridine orange fluorescence features were used to first select viable haemocytes followed by flow cytometric morphometric analysis based on the laser scatter properties (forward scatter-FSC and side scatter-SSC). Our findings demonstrated that B. glabrata (BG-BH, highly susceptible to S. mansoni) and 2 strains of B. tenagophila (BT-CF, moderately susceptible and BT-Taim, resistant to S. mansoni) have 3 major circulating haemocyte subsets, referred to as small, medium and large haemocytes. The frequency of small haemocytes was higher in BG-BH, while medium haemocytes were the most abundant cell-type in both B. tenagophila strains. Schistosoma mansoni infection resulted in early reduction of large and medium circulating haemocytes followed by an increase of small haemocytes. Although parasite infection induced haemocyte alterations in all Biomphalaria strains, the response was particularly intense in BT-Taim, the parasite-resistant snail. Interestingly, the trematode infection induces changes in haemocytes with less granular rather than in those with more granular profile. The results indicated that, in B. tenagophila of Taim strain, circulating haemocytes, especially the medium and high subset with less granular profile, are very reactive cells upon S. mansoni infection, suggesting that this cell subset would participate in the early parasite destruction observed in this snail strain.
Cysteine peptidases inHerpetomonas samuelpessoaiare modulated by temperature and dimethylsulfoxide-triggered differentiation
Authors: Pereira F. M. , Elias C. G. R. , d'Avila-Levy C. M. , Branquinha M. H. , Santos A. L. S.
Published: January 2009

Cysteine peptidases of protozoa have been implicated in a variety of biological events, and the expression of these enzymes is modulated in response to distinct stimuli, including environmental changes and differentiation. In the present work, we have examined the expression of cysteine peptidases fromHerpetomonas samuelpessoaigrown at distinct temperatures and during dimethylsulfoxide (DMSO)-elicited differentiation. We demonstrated that a 45 kDa cysteine peptidase had its activity reduced during the parasite growth at 37°C in comparison to 26°C, and when cultured up to 72 h in the presence of DMSO. The modulation in the 45 kDa cysteine peptidase expression is connected to the differentiation process, since both temperature and DMSO are able to trigger the promastigote to paramastigote transformation inH. samuelpessoai. The possible immunological similarity ofH. samuelpessoaiproteins with well-known cysteine peptidases produced by trypanosomatid pathogens, including cruzipain (Trypanosoma cruzi) and cysteine peptidase b (cpb) fromLeishmania mexicana, was also investigated, as well as with calpain molecules. The protein cellular lysate ofH. samuelpessoaireacted with antibodies raised against cpb ofL. mexicanaand calpain ofDrosophila melanogaster; however, no reaction was observed against cruzipain. The 35 kDa cpb-like protein had its expression diminished in DMSO-treated parasites, while the 80 kDa calpain-like molecule was enhanced and an additional 30 kDa calpain-related polypeptide was exclusively observed in these cells. Fluorescence microscopy and flow cytometry analyses corroborated these data. The results described above addH. samuelpessoaito the list of parasites whose differentiation seems to be correlated with cysteine peptidase expression.
Conditionals, Inference, and Possibility in Ancient Mesopotamian Science
Authors: Rochberg Francesca
Published: January 2009

Argument

This paper argues that ancient Babylonian signs (omens) reflect a mode of inferential reasoning as a function of their syntactic and logical structure as conditionals. Taking into account the institutional context that produced a systematic written body of omens, the paper is principally interested in the cognitive disposition of such texts. Investigating what constitutes system in these works, formal aspects of the material are examined in terms of the nature of conditionals and the logic of conditional statements. It is argued that conditional statements about ominous phenomena speak as much to a notion of conceivability and possibility as to empirical physical actuality. It is claimed that the epistemological character of the Babylonian compendia of signs cannot be understood without due attention to epistemic possibility and further, that the cuneiform omen texts comprise a different kind of scientific knowledge from that limited to a knowledge of physical phenomena and their laws.
Astronomical and Optical Principles in the Architecture of Hagia Sophia in Constantinople
Authors: Schibille Nadine
Published: January 2009

Argument

Textual and material evidence suggests that early Byzantine architects, known asmechanikoi, were comprehensively educated in the mathematical sciences according to contemporary standards. This paper explores the significance of the astronomical and optical sciences for the working methods of the twomechanikoiof Hagia Sophia in Constantinople, Anthemios of Tralles and Isidoros of Miletus. It argues that one major concern in the sixth-century architectural design of the Great Church was the visual effect of its sacred interior, particularly the luminosity within. Anthemios and Isidoros seem to have been thoroughly conversant with the ancient corpus of astronomical and optical writings and, as will be shown, implemented their theoretical knowledge in the design of Hagia Sophia. Specifically, the paper demonstrates that the orientation of the building's longitudinal axis coincides with the sunrise on the winter solstice according to ancient computations, implying that the orientation was intentionally calculated in order to secure an advantageous natural illumination of the interior. Light and visual effects served to reinforce the symbolic significance of the sacred space that furthermore provides evidence for optical considerations with respect to late antique concepts of light and vision.
Egg-Forms and Measure-Bodies: Different Mathematical Practices in the Early History of the Modern Theory of Convexity
Authors: Kjeldsen Tinne Hoff
Published: January 2009

Argument

Two simultaneous episodes in late nineteenth-century mathematical research, one by Karl Hermann Brunn (1862–1939) and another by Hermann Minkowski (1864–1909), have been described as the origin of the theory of convex bodies. This article aims to understand and explain (1) how and why the concept of such bodies emerged in these two trajectories of mathematical research; and (2) why Minkowski's – and not Brunn's – strand of thought led to the development of a theory of convexity. Concrete pieces of Brunn's and Minkowski's mathematical work in the two episodes will, from the perspective of the above questions, be presented and analyzed with the use of the methodological framework of epistemic objects, techniques, and configurations as adapted from Hans-Jörg Rheinberger's work on empirical sciences to the historiography of mathematics by Moritz Epple. Based on detailed descriptions and a comparison of the objects and techniques that Brunn and Minkowski studied and used in these pieces it will be concluded that Brunn and Minkowski worked in different epistemic configurations, and it will be argued that this had a significant influence on the mathematics they developed for those bodies, which can provide answers to the two research questions listed above.
MONETARY PERSISTENCE, IMPERFECT COMPETITION, AND STAGGERING COMPLEMENTARITIES
Authors: Merkl Christian , Snower Dennis
Published: January 2009

This paper explores the influence of wage and price staggering on monetary persistence. We show that, for plausible parameter values, wage and price staggering are complementary in generating monetary persistence. We do so by proposing the new measure of “quantitative inertia,” after discussing weaknesses of the “contract multiplier,” a standard measure of monetary persistence. The existence of complementarities means that beyond understanding how wage and price staggering work in isolation, it is important to investigate their interactions. Furthermore, our analysis indicates that the degree of monetary persistence generated by wage vis-à-vis price staggering depends on the relative competitiveness of the labor and product markets. We show that the conventional finding that wage staggering generates more persistence than price staggering holds under homogeneous capital accumulation. Under firm-specific capital, wage staggering generates more persistence only when the labor market is sufficiently competitive relative to the product market.
SATISFICING SOLUTIONS TO A MONETARY POLICY PROBLEM
Authors: Krawczyk Jacek , Kim Kunhong
Published: January 2009

Herbert A. Simon, 1978 Economics Nobel Prize laureate, talked about satisficing (his neologism) rather than optimizing as being what economists really need. Indeed, optimization might be an unsuitable solution procedure (in that it suggests a unique “optimal” solution) for problems where many solutions could be satisfactory. We think that looking for an applicable monetary policy is a problem of this kind because there is no unique way in which a central bank can achieve a desired inflation (unemployment, etc.) path. We think that it is viability theory, which is a relatively young area of mathematics, that rigorously captures the essence of satisficing. We aim to use viability analysis to analyze a simple macro policy model and show how some robust adjustment rules can be endogenously obtained.
Laser-induced resonant excitation of ethylene molecules in C2H4/C2H2/O2 reactions to enhance diamond deposition
Authors: Ling H. , Sun J. , Han Y. X. , Gebre T. , Xie Z. Q. , Zhao M. , Lu Y. F.
Published: January 2009

Vibrational resonant excitation of ethylene (C2H4) molecules using a carbon dioxide laser was employed to promote reactions in precursors of ethylene, acetylene (C2H2), and oxygen to enhance diamond deposition. One of the vibrational modes (CH2 wag mode, v7) of the C2H4 molecules was selected to achieve the resonant excitation in the reactions. Optical emission spectroscopy was used to study the effects of laser resonant excitation on the reactions for diamond deposition. The optical emissions of CH and C2 species were enhanced with the laser excitation, indicating that there are more active species generated in the reactions. Thicknesses and grain sizes of the deposited films were increased correspondingly. Temperature calculations from the line set in the R-branch of CH emission spectra indicated that a nonthermal process is involved in the enhanced diamond deposition.
Verification and application of numerically generated magnetic coordinate systems in gyrokinetics
Authors: Xanthopoulos P. , Mikkelsen D. , Jenko F. , Dorland W. , Kalentev O.
Published: January 2009

In the context of linear gyrokinetic simulations, an analysis of the application of field-aligned coordinate systems generated numerically from magnetohydrodynamic equilibria is presented. This family of systems allows some flexibility in the choice of the coordinates, and gyrokinetic solvers often differ in this respect. Certain transformations are therefore required in order to compare physics results. Accordingly, benchmarks of a linear microinstability are carried out between two similar gyrokinetic codes. Effort is also put on the verification of the special properties of the generated systems through certain diagnostics.
A method for fast monitoring of flow rates in microfluidic channels
Authors: Plecis Adrien , Malaquin Laurent , Chen Yong
Published: January 2009

Fast monitoring of flow rates in microchannels is needed for a variety of microfluidic investigations. We propose a simplified approach of conventional particle image velocimetry by using a full-frame correlation function based image algorithm. Experimentally, flow rates in microfluidic channels could be determined in a few seconds for a maximum flow velocity ranging from 10 μm s−1 to 1 mm s−1 with a standard deviation of less than 4%. The processing parameters have also been studied both experimentally and theoretically, in order to evaluate the validation range of the proposed method.
Microwave attenuation of hydrogen plasma in carbon nanotubes
Authors: Babaei S. , Solari M. Sh.
Published: January 2009

The attenuation (ATT) of hydrogen plasma in carbon nanotubes, grown by iron-catalyzed high-pressure carbon monoxide disproportionate process, is investigated. The effects of the incident wave, the electron density, the collision frequency, the thermal frequency, and the cyclotron frequency on the ATT of the microwave are discussed. Moreover, the impacts of thermal frequency and cyclotron frequency on the ATT are investigated separately. Numerical results indicate that position of the ATT peak and the ATT level depend on the incident frequency, the electron density, the collision frequency, the thermal frequency, and the cyclotron frequency. The results show that the cyclotron frequency highly influences the ATT level. In contrast, the shift frequency is more affected by the thermal frequency. The ATT is more sensitive at the middle band of incident frequency.
Stability in H1/2 of the sum of K solitons for the Benjamin–Ono equation
Authors: Gustafson Stephen , Takaoka Hideo , Tsai Tai-Peng
Published: January 2009

This note proves the orbital stability in the energy space H1/2 of the sum of widely spaced 1-solitons for the Benjamin–Ono equation, with speeds arranged so as to avoid collisions.
Gravitational collapse of homogeneous perfect fluids in higher order gravity theories
Authors: Giambò Roberto
Published: January 2009

This paper investigates the evolution of collapsing Friedmann–Robertson–Walker models with a scalar field having the potential which arises in the conformal frame of high order gravity theories, coupled to matter described by a perfect fluid with energy density ρ and pressure p, obeying a barotropic equation of state. The solutions are shown to evolve generically to a singular state in a finite time and they are used as sources for radiating objects undergoing complete gravitational collapse. Although these singularities may be naked in some special cases, it is shown that generically a black hole forms.
Velocity map imaging in time of flight mass spectrometry
Authors: Brouard M. , Campbell E. K. , Johnsen A. J. , Vallance C. , Yuen W. H. , Nomerotski A.
Published: January 2009

A new variation on time of flight mass spectrometry is presented, which uses a fast framing charge coupled device camera to velocity map image multiple product masses in a single acquisition. The technique is demonstrated on two photofragmentation processes, those of CS2 and CH3S2CH3 (dimethyldisulfide) at a photolysis wavelength of 193 nm. In both cases, several mass fragments are imaged simultaneously, and speed distributions and anisotropy parameters are extracted that are comparable to those obtained by imaging each fragment separately in conventional velocity map imaging studies.
Efficient wavelet ridge extraction method for asymptotic signal analysis
Authors: Dai Yu , Ma Qiang , Tang Wenyan
Published: January 2009

A wavelet ridge extraction method is proposed for efficient estimation of instantaneous frequency and amplitude of the asymptotic signal. Inequalities are derived to provide limitations on scale interval and sampling frequency. The evaluation of optimal scale interval and sampling frequency at any given accuracy can be done by solving these inequalities and minimizing the computational complexity of continuous wavelet transform. After the continuous wavelet transform of the signal is completed with these optimal parameters, a more reliable ridge can be formed using only the discontinuity points on the ridge extracted using the conventional method. The results of a system identification simulation test performed to verify the efficiency of the proposed method indicate that the computational load of the proposed method is about 1/6 of that of the conventional method. When the system identification method is used to measure samples with known moment of inertia, the relative error below 0.08% is achieved.
Self-assembly of rodlike receptors from bulk solution
Authors: Kurunczi Sándor , Horvath Robert , Yeh Yun-Peng , Muskotál Adél , Sebestyén Anett , Vonderviszt Ferenc , Ramsden Jeremy J.
Published: January 2009

Optical waveguide lightmode spectroscopy has been used to observe the deposition of bacterial flagellar filaments of mean length 350 nm from bulk solution onto a smooth planar substratum, chemically modified to covalently bind the flagellar filaments on contact. At the highest practicable bulk concentration, the filaments follow the theoretically predicted kinetics of random sequential addition of highly elongated rigid rods to the substratum, but addition terminates with the rods almost perpendicular to the substratum. Rod-rod correlations in the bulk anomalously accelerate the rate of arrival of the filaments at the surface of the substratum, relative to spheres. At lower concentrations, this effect is absent, and the rods have time to order themselves on the substratum, forming a two-dimensional array.
Antihydrogen formation from antiprotons in a pure positron plasma
Authors: Bass Eric M. , Dubin Daniel H. E.
Published: January 2009

This paper investigates the evolution in binding energy of antihydrogen atoms formed from stationary antiprotons located within a strongly magnetized positron plasma. Three-body recombination and a collisional cascade to deeper binding, limited by a kinetic bottleneck at a binding energy of 4T, dominate the initial antihydrogen formation process. A classical Monte-Carlo simulation is used to determine the collisional transition rate between atomic binding energies, using the drift approximation for initial conditions that allow it, and full dynamics for initial conditions resulting in chaotic motion. These transition rates are employed in determining mean energy-loss rates for an ensemble of atoms, as well as in a numerical solution of the master equation to find the rate at which atoms are formed over a range of binding energies. The highly excited atoms formed by this process separate into guiding-center drift atoms and chaotic atoms. The phase-space distributions of the atoms are investigated, along with their implications for magnetic confinement and radiative energy loss. Estimates of radiative energy loss indicate that radiation is unimportant for guiding-center atoms, but increases rapidly near the chaotic regime, taking over as the dominant energy-loss process for parameters typical of recent experiments. Furthermore, the fraction of low-magnetic field seekers is considerably larger than suggested by estimates of the magnetic moment based on guiding-center dynamics, due to effects associated with chaos.
Direct role of surface oxygen vacancies in visible light emission of tin dioxide nanowires
Authors: Lettieri S. , Causà M. , Setaro A. , Trani F. , Barone V. , Ninno D. , Maddalena P.
Published: January 2009

Tin dioxide (SnO2) nanowires exhibit a strong visible photoluminescence that is not observed in bulk crystalline SnO2. To explain such effect, oxygen vacancies are often invoked without clarifying if they represent the direct origin of luminescence or if their presence triggers other radiative processes. Here we report an investigation of the nature of the visible light emission in SnO2 nanowires, showing that both experimental and theoretical ab initio analyses support the first hypothesis. On the basis of photoluminescence quenching analysis and of first-principles calculations we show that surface bridging oxygen vacancies in SnO2 lead to formation of occupied and empty surface bands whose transition energies are in strong agreement with luminescence features and whose luminescence activity can be switched off by surface adsorption of oxidizing molecules. Finally, we discuss how such findings may explain the decoupling between “electrical-active” and “optical-active” states in SnO2 gas nanosensors [G. Faglia et al., Appl. Phys. Lett. 86, 011923 (2005)].
Gas-phase spectroscopy of the 2 Σ3−−X̃ Σ3− electronic transition of CCS
Authors: Nakajima Masakazu , Schmidt Timothy W. , Miyoshi Akira , Sumiyoshi Yoshihiro , Endo Yasuki
Published: January 2009

Gas-phase laser excitation spectra of the jet-cooled CCS radical were observed for the 2 Σ3−−X̃ Σ3− electronic transition in a discharge of a gas mixture containing acetylene and H2S in Ar. The observed excitation spectra show complicated rotational structures, consisting of a much larger number of rotational lines than those expected for this size of linear molecule. The excited vibronic levels emit fluorescence, the lifetime of which is much longer than that estimated theoretically, indicating that the upper levels are strongly mixed with many “dark” background levels. Dispersed fluorescence spectra from single vibrational levels of the 2 Σ3− state show long progressions of the C–S stretching mode, enabling observations of many vibrational levels in the ground electronic state.
Molecular dynamics simulation of imidazolium-based ionic liquids. II. Transport coefficients
Authors: Kowsari M. H. , Alavi Saman , Ashrafizaadeh Mahmud , Najafi Bijan
Published: January 2009

A systematic molecular dynamics study is performed to determine the dynamics and transport properties of 12 room-temperature ionic liquids family with 1-alkyl-3-methylimidazolium cation, [amim]+ (alkyl=methyl, ethyl, propyl, and butyl), with counterions, PF6−, NO3−, and Cl−. The goal of the work is to provide molecular level understanding of the transport coefficients of these liquids as guidance to experimentalists on choosing anion and cation pairs to match required properties of ionic liquid solvents. In the earlier paper (Part I), we characterized the dynamics of ionic liquids and provided a detailed comparison of the diffusion coefficients for each ion using the Einstein and Green–Kubo formulas. In this second part, other transport properties of imidazolium salts are calculated, in particular, the electrical conductivity is calculated from the Nernst–Einstein and Green–Kubo formulas. The viscosity is also determined from the Stokes–Einstein relation. The results of the calculated transport coefficients are consistent with the previous computational and experimental studies of imidazolium salts. Generally, the simulations give electrical conductivity lower than experiment while the viscosity estimate is higher than experiment. Within the same cation family, the ionic liquids with the NO3− counterion have the highest electrical conductivities: σ[NO3]−>σ[PF6]−>σ[Cl]−. The [dmim][X] series, due to their symmetric cationic structure and good packing and the [bmim][X] series due to higher inductive van der Waals interactions of [bmim]+, have the highest viscosities in these ionic liquid series. Our simulations show that the major factors determining the magnitude of the self-diffusion, electrical conductivity, and viscosity are the geometric shape, ion size, and the delocalization of the ionic charge in the anion.
Application of state-specific multireference Møller–Plesset perturbation theory to nonsinglet states
Authors: Mahapatra Uttam Sinha , Chattopadhyay Sudip , Chaudhuri Rajat K.
Published: January 2009

We present molecular applications of a spin free size-extensive state-specific multireference perturbation theory (SS-MRPT), which is valid for model functions of arbitrary spin and generality. In addition to the singlet states, this method is equally capable to handle nonsinglet states. The formulation based on Rayleigh–Schrödinger approach works with a complete active space and treats each of the model space functions democratically. The method is capable of handling varying degrees of quasidegeneracy and of ensuring size consistency as a consequence of size extensivity. In this paper, we illustrate the effectiveness of the Møller–Plesset (MP) partitioning based spin free SS-MRPT [termed as SS-MRPT(MP)] in computations of energetics of the nonsinglet states of several chemically interesting and demanding molecular examples such as LiH, NH2, and CH3. The spectroscopic constants of Σ3− state of NH and OH+ molecular systems and the ground Σ1g+ as well as excited Σ3u+ states of N2 have been investigated and comparison with experimental and full configuration interaction values (wherever available) has also been provided. We have been able to demonstrate here that the SS-MRPT(MP) method is an intrinsically consistent and promising approach to compute reliable energies of nonsinglet states over different geometries.
The rotational spectrum of the CCP (XΠr2) radical and its C13 isotopologues at microwave, millimeter, and submillimeter wavelengths
Authors: Halfen D. T. , Sun M. , Clouthier D. J. , Ziurys L. M.
Published: January 2009

The pure rotational spectrum of CCP (XΠr2) has been measured at microwave, millimeter, and submillimeter wavelengths (17–545GHz), along with its C13 isotopologues (C13C13P, CC13P, and C13CP). The spectra of these species were recorded using a combination of millimeter/submillimeter direct absorption methods and Fourier transform microwave (FTMW) techniques. The phosphorus dicarbides were created in the gas phase from the reaction of red phosphorus and acetylene or methane in argon in an ac discharge for the direct absorption experiments, and using PCl3 as the phosphorus source in a pulsed dc nozzle discharge for the FTMW measurements. A total of 35 rotational transitions were recorded for the main isotopologue, and between 2 and 8 for the C13−substituted species. Both spin-orbit components were identified for CCP, while only the Ω=1∕2 ladder was observed for C13C13P, CC13P, and C13CP. Hyperfine splittings due to phosphorus were observed for each species, as well as carbon-13 hyperfine structure for each of the C13−substituted isotopologues. The data were fitted with a Hund’s case (a) Hamiltonian, and rotational, fine structure, and hyperfine parameters were determined for each species. The rm(1) bond lengths established for CCP, r(CC)=1.289(1)Å and r(CP)=1.621(1)Å, imply that there are double bonds between both the two carbon atoms and the carbon and phosphorus atoms. The hyperfine constants suggest that the unpaired electron in this radical is primarily located on the phosphorus nucleus, but with some electron density also on the terminal carbon atom. There appears to be a minor resonance structure where the unpaired electron is on the nucleus of the end carbon. The multiple double bond structure forces the molecule to be linear, as opposed to other main group dicarbides, such as SiC2, which have cyclic geometries.
Influence of molten status on nanoquasicrystalline-forming Zr-based metallic glasses
Authors: Fan Cang , Chen D. , Liaw P. K. , Choo H. , Benmore C. , Siewenie J. , Chen G. L. , Xie J. X. , Liu C. T.
Published: January 2009

Quasicrystals, formed during the primary crystallization stage of annealing Zr70−XCu25Pt5AlX metallic glasses, decrease in size from 100 to 5 nm as the Al content is increased from 8 to 10 at. %. The glass transition and crystallization processes during annealing at fixed heating rate were found to be influenced by the thermal history of the melt. Pair distribution function analyses of neutron scattering data revealed that the broad peak from the nearest atomic pairs separates into multiple peaks with lower melt quenching temperatures (TL). These results suggest that the short-range order is enhanced with decreased TL. Such ordered regions remain in the glass upon quenching and contribute to nanoquasicrystal formation upon heating.
Optical absorption from solvation-induced polarons on nanotubes
Authors: Ussery G. L. , Gartstein Yu. N.
Published: January 2009

When an excess charge carrier is added to a one-dimensional (1D) wide-band semiconductor immersed in a polar solvent, the carrier can undergo self-localization into a large-radius adiabatic polaron. We explore the local optical absorption from the ground state of 1D polarons using a simplified theoretical model for small-diameter tubular structures. It is found that about 90% of the absorption strength is contained in the transition to the second lowest-energy localized electronic level formed in the polarization potential well, with the equilibrium transition energy larger than the binding energy of the polaron. Thermal fluctuations, however, can cause a very substantial—an order of magnitude larger than the thermal energy—broadening of the transition. The resulting broad absorption feature may serve as a signature for the optical detection of solvated charge carriers.
Proton-proton homonuclear dipolar decoupling in solid-state NMR using rotor-synchronized z-rotation pulse sequences
Authors: Lafon Olivier , Wang Qiang , Hu Bingwen , Trébosc Julien , Deng Feng , Amoureux Jean-Paul
Published: January 2009

We present a theoretical analysis of rotor-synchronized homonuclear dipolar decoupling schemes that cause a z-rotation of the spins. These pulse sequences applicable at high spinning rates (νr≥30 kHz) yield high-resolution proton NMR spectra that are free of artifacts, such as zero lines and image peaks. We show that the scaled isotropic chemical-shift positions of proton lines can be calculated from the zero-order average Hamiltonian and that the scaling factor does not depend on offset. The effects of different adjustable parameters (rf field, spinning rate, pulse shape, offset) on the decoupling performance are analyzed by numerical simulations of proton spectra and by H1 solid-state NMR experiments on NaH2PO4 and glycine.
Raman spectroscopic studies of hydrogen clathrate hydrates
Authors: Strobel Timothy A. , Sloan E. Dendy , Koh Carolyn A.
Published: January 2009

Raman spectroscopic measurements of simple hydrogen and tetrahydrofuran+hydrogen sII clathrate hydrates have been performed. Both the roton and vibron bands illuminate interesting quantum dynamics of enclathrated H2 molecules. The complex vibron region of the Raman spectrum has been interpreted by observing the change in population of these bands with temperature, measuring the absolute H2 content as a function of pressure, and with D2 isotopic substitution. Quadruple occupancy of the large sII clathrate cavity shows the highest H2 vibrational frequency, followed by triple and double occupancies. Singly occupied small cavities display the lowest vibrational frequency. The vibrational frequencies of H2 within all cavity environments are redshifted from the free gas phase value. At 76 K, the progression from ortho- to para-H2 occurs over a relatively slow time period (days). The rotational degeneracy of H2 molecules within the clathrate cavities is lifted, observed directly in splitting of the para-H2 roton band. Raman spectra from H2 and D2 hydrates suggest that the occupancy patterns between the two hydrates are analogous, increasing confidence that D2 is a suitable substitute for H2. The measurements suggest that Raman is an effective and convenient method to determine the relative occupancy of hydrogen molecules in different clathrate cavities.
Explosive vapor sensor using poly (3-hexylthiophene) and CuII tetraphenylporphyrin composite based organic field effect transistors
Authors: Dudhe Ravishankar S. , Tiwari S. P. , Raval Harshil N. , Khaderbad Mrunal A. , Singh Rahul , Sinha Jasmine , Yedukondalu M. , Ravikanth M. , Kumar Anil , Rao V. Ramgopal
Published: January 2009

Organic field effect transistors based on poly(3-hexylthiophene) and CuII tetraphenylporphyrin composite were investigated as sensors for detection of vapors of nitrobased explosive compounds, viz., 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 2,4,6-trinitrotoluene (TNT), and dinitrobenzene, which are also strong oxidizing agents. Significant changes, suitable for sensor response, were observed in transistor “on” current (Ion) and conductance (S) after exposure. A similar device response was, however, not observed for oxidizing agents such as benzoquinone and benzophenone. The Fourier transform infrared spectrometry experiments supported the results, where exposure to RDX and TNT vapors resulted in a significant shift in IR peaks.
Anomalous dependence of response time on the electric field in an electroclinic liquid crystal with large induced tilt and polarization
Authors: Manna U. , Song Jang-Kun , Vij J. K. , Naciri J.
Published: January 2009

We investigate the response time of an electroclinic liquid crystal with large induced tilt and polarization (de Vries smectic A∗). The response time is found to increase with the increase in electric field up to a threshold value in contrast with the general case of a decrease with field. This behavior is unusual and contrasts with that observed for a conventional smectic-A∗ phase. The anomalous behavior is explained by the Langevin process of the director reorientation by assuming an increase in the effective dipole moment (μeff) with field. The response time decreases with the increase in temperature in the smectic-A∗ phase. We find the existence of a finite correlation length of a few tens of nm which in both temperature and field dependent.
Thermodynamics and phase behavior of a triangle-well model and density-dependent variety
Authors: Zhou Shiqi
Published: January 2009

A hard sphere+triangle-well potential is employed to test a recently proposed thermodynamic perturbation theory (TPT) based on a coupling parameter expansion. It is found that the second-order term of the coupling parameter expansion surpasses by far that of a high temperature series expansion under a macroscopic compressibility approximation and several varieties. It is also found that the fifth-order version displays best among all of the numerically accessible versions with dissimilar truncation orders. Particularly, the superiority of the fifth-order TPT from other available liquid state theories is exhibited the most incisively when the temperature of interest obviously falls. We investigate the modification of the phase behavior of the hard sphere+triangle-well fluid resulting from a density dependence imposed on the original potential function. It is shown that (1) the density dependence induces polymorphism of fluid phase, particularly liquid-liquid transition in metastable supercooled region, and (2) along with enhanced decaying of the potential function as a function of bulk density, both the liquid-liquid transition and vapor-liquid transition tend to be situated at the domain of lower temperature, somewhat similar to a previously disclosed thumb rule that the fluid phase transition tends to metastable with respect to the fluid-solid transition as the range of the attraction part of a density-independence potential is sufficiently short compared to the range of the repulsion part of the same density-independence potential.
Surface-induced morphologies of lamella-forming diblock copolymers confined in nanorod arrays
Authors: Li Shiben , Chen Peng , Wang Xianghong , Zhang Linxi , Liang Haojun
Published: January 2009

Using the real-space self-consistent field theory, we investigate the effects of geometry confinement and surface field on the morphologies of lamella-forming diblock copolymers confined in the periodic nanorod arrays. The array confinement provides a fractional confinement dimension where the diblock copolymers are incompletely confined at each spatial direction and the novel morphologies may be surface induced. In the arrays with neutral surfaces, we observe several confinement-induced morphologies, such as perpendicular lamellae and double-cylinder network structures, by varying the degree of confinement. For the arrays with preferential surfaces, a rich variety of morphologies including undulated lamellae, perforated lamellae, and cylindrical lamellae are investigated as a function of the strength of surface field. The predicted morphologies and the corresponding ordered transitions can be reasonably comprehended based on the commensurability between the array period and the bulk lamella period, as well as the cylindrical symmetry about the surface field.