bluuebunny/crossref_metadata_2025 huggingface dataset:
Resection of At‐Risk Mesenteric Lymph Nodes Is Associated with Improved Survival in Patients with Small Bowel Neuroendocrine Tumors
Authors: Landry Christine S. , Lin Heather Y. , Phan Alexandria , Charnsangavej Chusilp , Abdalla Eddie K. , Aloia Thomas , Nicolas Vauthey J. , Katz Matthew H. G. , Yao James C. , Fleming Jason B.
Published: May 2013

Background

Neuroendocrine tumors of the small intestine commonly metastasize to regional lymph nodes (LNs). Single‐institution reports suggest that removal of LNs improves outcome, but comprehensive data are lacking. We hypothesized that the extent of lymphadenectomy reported in a large administrative database would be associated with overall survival for jejunal and ileal neuroendocrine tumors.

Methods

A search of the Surveillance Epidemiology and End Results database was performed for patients with jejunal and ileal neuroendocrine tumors from 1977 to 2004. Descriptive patient characteristics were collected to include age at diagnosis, sex, race, grade, primary tumor size, LN status, number of LNs resected, presence of distant metastasis, and the type of operation. Statistical analyses were limited to patients with only one primary tumor to exclude patients with other malignancies. Univariate and multivariate analyses were performed to analyze the number of LNs resected and the LN ratio (number of positive LNs/total number of LNs removed) to determine the effect on cancer‐specific survival.

Results

Altogether, 1,364 patients were included in this analysis. Removal of any LNs was associated with improved cancer‐specific survival when compared to patients with no LN removal reported (p = 0.0027) on univariate analysis. Among those who had any LNs removed, a median of eight LNs were identified in resection specimens with a median LN ratio of 0.29 (range 0–1). On multivariate analysis (adjusting for age and tumor size), patients with >7 LNs removed experienced better cancer‐specific survival than those with ≤7 LNs removed (median survival not reached vs. 140 months): hazard ratio and 95 % confidence interval were 0.573 (0.402, 0.817) (p = 0.002).

Conclusions

This review of a large number of surgical patients demonstrates that regional mesenteric lymphadenectomy in conjunction with resection of the primary tumor is associated with improved survival of patients with small bowel neuroendocrine tumors.
Usefulness of an Inflammation‐Based Prognostic Score (mGPS) for Predicting Survival in Patients with Unresectable Malignant Biliary Obstruction
Authors: Iwasaki Yoshimi , Ishizuka Mitsuru , Kato Masato , Kita Junji , Shimoda Mitsugi , Kubota Keiichi
Published: May 2013

Background

An inflammation‐based prognostic score, the modified Glasgow Prognostic Score (mGPS), has been established as a useful tool for predicting postoperative outcome in patients with cancer. However, no studies have investigated the usefulness of the mGPS for prognostication in patients undergoing palliative surgery for unresectable malignant biliary obstruction (UMBO). The present study was conducted to investigate whether the mGPS is useful for predicting the postoperative survival of patients undergoing intraoperative placement of an expandable metal stent for UMBO, or not.

Methods

The mGPS was calculated as follows: patients with both an elevated level of C‐reactive protein (CRP) (>1.0 mg/dL) and hypoalbuminemia (<3.5 g/dL) were allocated a score of 2. Patients with only an elevated CRP level were allocated a score of 1, and patients without an elevated CRP level (≤1.0 mg/dL) were allocated a score of 0. Postoperative survival was evaluated by Kaplan–Meier analysis and log rank test. The significance of risk factors for postoperative survival was evaluated with the Cox proportional hazards model.

Results

Kaplan–Meier analysis revealed that patients with mGPS 0 (n = 36) and 1 (n = 7) had better postoperative survival (p = 0.017) than patients with mGPS 2 (n = 17). The 6‐month and 1‐year survival rates of patients with mGPS 0 and 1 were 58.1 and 27.3 %, and those for patients with mGPS 2 were 25.0 and 6.2 %, respectively. Multivariate analysis revealed that mGPS (0, 1/2) was a significant risk factor for postoperative survival (hazard ratio 3.271; 95 % CI 1.109–9.649; p = 0.032).

Conclusion

The mGPS is not only one of the most significant predictors of postoperative survival for UMBO patients receiving intraoperative biliary stenting but also a useful indicator capable of dividing such patients into two independent groups before surgery.
A freshwater ecoregion delineation approach based on freshwater macroinvertebrate community features and spatial environmental data in Taizi River Basin, northeastern China
Authors: Kong Weijing , Meng Wei , Zhang Yuan , Gippel Christopher , Qu Xiaodong
Published: May 2013

The ecoregion is currently widely used as the basic geospatial unit in freshwater biodiversity conservation. The popularly used delineation is usually based on the assumption that attributes of aquatic ecosystems are influenced by landscape‐scale environmental variables. However, few ecoregion delineations attempt to establish the local validity of this assumption prior to delineation, and few studies check the correspondence of the derived ecoregion boundaries with the distributions of attributes of aquatic biota. In this study, we established an approach to overcome these shortcomings. The notable features of the approach are: (1) the delineation variables were filtered through a series of analytical steps to select those that best represented the aquatic community traits, and which avoided redundancy in the data; (2) the method was quantitative and repeatable; and (3) the derived ecoregion boundaries were checked for consistency with the spatial attributes of aquatic biota. The approach was applied in the Taizi River Basin, northeast China. The procedure proposed here filtered out altitude and annual precipitation as the best variables to include in the freshwater ecoregion delineation. Then, using the quantitative ISODATA classification method, the basin was classified into three ecoregions. A test of accuracy indicated that freshwater ecoregions matched well with the spatial distribution pattern of macroinvertebrate community attributes. Statistical analysis showed that natural geographical attributes and river attributes were different in the three ecoregions, and indices representing macroinvertebrate community attributes are significantly different as a whole among the three ecoregions. The case study proved this approach effective on ecoregion delineation.
Holocene peatland development along the eastern margin of the Tibetan Plateau
Authors: Xu Hai , Liu Bin , Lan Jianghu , Sheng Enguo , Che Shuai , Xu Sheng
Published: May 2013

Knowledge of peatland initiation, accumulation, and decline or cessation is critical in understanding peatland development and the related carbon source/sink effect. In this study, we investigated the development of three peat profiles along the eastern margin of the Tibetan Plateau (ETP) and compared the results with those of our previous work along this transect. Our work showed that the initiation over the northern ETP is later and the slowdown/cessation earlier than in the middle to southern ETP. The timing of optimum peatland formation over the northern ETP lags the Holocene climatic optimum. These spatio-temporal differences are likely to be related to the intensity of Asian summer monsoon. Our work suggests that some peatlands along the ETP transect have returned or are now returning their previously captured carbon to the atmosphere and thus act as carbon sources. Some peatlands still have net accumulation at present, but the rates have been reduced concomitant with the decreasing summer monsoon intensity. We speculate that more of the previously stored carbon in the ETPpeatlands will be re-emitted to the atmosphere if the aridity continues, as might occur under a continuous global-warming scenario.
A new species ofFellhanera(lichenized Ascomycota:Pilocarpaceae) from central North America
Authors: MORSE Caleb A. , LADD Douglas
Published: May 2013

Fellhanera crucitignorum, a blastidiate crustose lichen with anthraquinones and submuriform ascospores, is described as new to science. The species is associated with exposures of non-calcareous sandstones in Kansas and Oklahoma, in the southern portion of North America's Great Plains. The authraquinones are typically concentrated in the blastidia, creating a distinctive grey thallus with localized orange granules.
The attitudes of Hong Kong students towards Hong Kong English and Mandarin-accented English
Authors: Zhang Qi
Published: May 2013

The development of Hong Kong English (henceforth HKE) has triggered a number of concerns amongst the local population with respect to its status (Joseph, 1996; Luk, 1998; Bolton & Lim, 2000; Pang, 2003; Stibbard, 2004). However, despite the prominence of research into attitudes towards language variation within sociolinguistics, very few studies focus on Hong Kong English (Bolton & Kwok, 1990; Candler, 2001; S. Poon, 2007) or Mandarin-accented English (He & Li, 2009; Hu, 2004; F. Poon, 2006). The aim of this study is to uncover language attitudes towards HKE and Mandarin-accented English (henceforth ME) in the Hong Kong region through the application of the verbal-guise technique.
Why can recognize be pronounced without /ɡ/? On silent letters and French origin in English – and what other explanations there can be
Authors: Huber Daniel
Published: May 2013

Investigating the phonological patterns, especially the stress patterns, of verbs ending in -ize such as finalize, constitutionalize, etc, the word recognize has attracted my attention. One would not generally attach too much attention to this word for its phonology: it seems to be a run-of-the-mill case of stressing the third-last (antepenultimate) syllable of a non-transparent derivation by -ize. For instance, Nádasdy (2006: 222) treats -ize as a basically neutral (strong) suffix, that is one that is not supposed to interfere with stress-patterns and otherwise of the stem to which it is attached. Following established analyses, he divides -ize words into two categories, though: those that are derived from a free stem ('character > 'characterize, 'final > 'finalize), where stress (indicated by the ' mark) does not shift in the derived verb, and those whose stem is non-transparent ('recognize, 'categorize), and where stress tends to be furthest away from the suffix itself. The fact that recognize has a non-transparent derivation means that there is no free English word *recogn. Ginésy (2004: 126) analyzes recognize as morphologically having a double prefix, re- and co-, which reduces the stem to Latinate -gn-, which is always bound in English. Whether his etymological analysis is warranted for the contemporary morphology of recognize is at least disputable today, but he correctly claims that 'recognize, with stress on the initial syllable, behaves like a non-transparent derivation so it receives antepenultimate stressing. In other words, the most wide-spread pronunciation of recognize, with initial stress, is generally unproblematic in the literature: it is a case of non-transparent derivation by -ize with antepenultimate stressing.
A role for lexical bundles in the implementation of Content and Language Integrated Learning programmes in Colombian universities
Authors: Torres Martínez Sergio
Published: May 2013

The production of content-appropriate discourse in academic English has proved a difficult task for learners in different disciplines in Colombian universities. There is plenty of blame to go around: among other problems, educators frequently point to the belief that language courses (isolated from university subjects) automatically promote linguistic skills transferable to a specific subject-language, the informal approach to subjects demanding high-skill communicative proficiency, the abuse of L1 informal register in both L1 and L2 academic writing and speaking; the idiosyncratic academic culture dominated by a blinkered return-of-investment thinking, and the lack of academic rigour leading to distinct increments in existing knowledge. In such a scenario, it becomes apparent that a practical, unambiguous approach is to be taken in order to facilitate the implementation of a more seamless integration of language and content in Colombian EAP classrooms.
Mainland Chinese students' English use in Macao
Authors: Zhang Kun
Published: May 2013

Macao, a former colony of Portugal, is located in the western side of the Pearl River estuary, adjoining the Zhuhai Special Economic Zone and facing the South China Sea. It is much smaller than its ‘big brother’ Hong Kong, having a total land area of 29.5 sq km and a population of around 540,000, of which 94.3% are ethnic Chinese (DSEC, 2011).
Impossible, in a possible sort of way
Authors: Bulley Michael
Published: May 2013

The combination of possibly with can't and couldn't seems to me on the increase. Or perhaps I just notice it more since I've been living in France. For in French there is no direct equivalent of possibly. You have probablement (= probably), but there is no French word *possiblement. What, then, is going on when you find in English, to take a recent example, ‘For all the malfunctions of the past few years, it's assumed the structure of British society can't possibly be refashioned’ (standfirst to an article by Marina Hyde, The Guardian, 7 July 2012)?
Modeling of Brain Metabolism and Pyruvate Compartmentation Using 13C NMR in Vivo: Caution Required
Authors: Jeffrey F Mark , Marin-Valencia Isaac , Good Levi B , Shestov Alexander A , Henry Pierre-Gilles , Pascual Juan M , Malloy Craig R
Published: May 2013

Two variants of a widely used two-compartment model were prepared for fitting the time course of [1,6-13C2]glucose metabolism in rat brain. Features common to most models were included, but in one model the enrichment of the substrates entering the glia and neuronal citric acid cycles was allowed to differ. Furthermore, the models included the capacity to analyze multiplets arising from 13C spin-spin coupling, known to improve parameter estimates in heart. Data analyzed were from a literature report providing time courses of [1,6-13C2]glucose metabolism. Four analyses were used, two comparing the effect of different pyruvate enrichment in glia and neurons, and two for determining the effect of multiplets present in the data. When fit independently, the enrichment in glial pyruvate was less than in neurons. In the absence of multiplets, fit quality and parameter values were typical of those in the literature, whereas the multiplet curves were not modeled well. This prompted the use of robust statistical analysis (the Kolmogorov-Smirnov test of goodness of fit) to determine whether individual curves were modeled appropriately. At least 50% of the curves in each experiment were considered poorly fit. It was concluded that the model does not include all metabolic features required to analyze the data.
The APOE ε4/ε4 Genotype Potentiates Vascular Fibrin(Ogen) Deposition in Amyloid-Laden Vessels in the Brains of Alzheimer's Disease Patients
Authors: Hultman Karin , Strickland Sidney , Norris Erin H
Published: May 2013

Evidence indicates a critical role for cerebrovascular dysfunction in Alzheimer's disease (AD) pathophysiology. We have shown that fibrin(ogen), the principal blood-clotting protein, is deposited in the AD neurovasculature and interacts with beta-amyloid (Ab), resulting in increased formation of blood clots. As apolipoprotein E (ApoE), a lipid-transporting protein with three human isoforms (E2, E3, and E4), also binds to Aβ, we hypothesized that ApoE and fibrin(ogen) may have a combined effect on the vascular pathophysiology in AD. We assessed whether APOE genotype differentially influences vascular fibrin(ogen) deposition in postmortem brain tissue using immunohistochemistry. An increased deposition of fibrin(ogen) was observed in AD cases compared with non-demented controls, and there was a strong correlation between cerebral amyloid angiopathy (CAA) severity and fibrin(ogen) deposition. Moreover, brains from AD cases homozygous for APOE ε4 showed increased deposition of fibrin(ogen), specifically in CAA- and oligomeric Aβ-positive vessels compared with AD APOE ε2 and ε3 allele carriers, an effect that was not directly linked to CAA severity and cerebrovascular atherosclerosis. These data further support a role for fibrin(ogen) in AD pathophysiology and link the APOE ε4/ε4 genotype with increased thrombosis and/or impaired fibrinolysis in the human AD brain.
Thickness dependence of structure and piezoelectric properties at nanoscale of polycrystalline lead zirconate titanate thin films
Authors: Araújo E. B. , Lima E. C. , Bdikin I. K. , Kholkin A. L.
Published: May 2013

Lead zirconate titanate Pb(Zr0.50Ti0.50)O3 (PZT) thin films were deposited by a polymeric chemical method on Pt(111)/Ti/SiO2/Si substrates to understand the mechanisms of phase transformations and the effect of film thickness on the structure, dielectric, and piezoelectric properties in these films. PZT films pyrolyzed at temperatures higher than 350 °C present a coexistence of pyrochlore and perovskite phases, while only perovskite phase grows in films pyrolyzed at temperatures lower than 300 °C. For pyrochlore-free PZT thin films, a small (100)-orientation tendency near the film-substrate interface was observed. Finally, we demonstrate the existence of a self-polarization effect in the studied PZT thin films. The increase of self-polarization with the film thickness increasing from 200 nm to 710 nm suggests that Schottky barriers and/or mechanical coupling near the film-substrate interface are not primarily responsible for the observed self-polarization effect in our films.
Macroscopic and local piezoelectric properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals exhibiting giant piezoelectric response
Authors: Shvartsman V. V. , Kholkin A. L. , Raevski I. P. , Raevskaya S. I. , Savenko F. I. , Emelyanov A. S.
Published: May 2013

The temperature and bias field dependences of macroscopic, measured by pulsating load method, and local, measured by piezoresponse force microscopy, longitudinal piezoelectric responses have been studied in (001)-oriented flux-grown (1 − x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (0.0 ≤ x ≤ 0.29) single crystals. Both types of responses exhibit a dramatic enhancement with increasing bias fields. At the same time, their temperature maxima shift from the Vogel-Fulcher temperature to the vicinity of the dielectric permittivity maximum, where the critical point in the E-T phase diagram is located. Both datasets confirm a quasicritical nature of the giant field-induced piezoelectric response in relaxor single crystals.
Nanoscale piezoelectric and ferroelectric behaviors of seashell by piezoresponse force microscopy
Authors: Li Tao , Zeng Kaiyang
Published: May 2013

Seashells, the armor of one of the most ancient species, have demonstrated outstanding mechanical properties such as simultaneous strengthening and toughening. The seashells have also been proven to exhibit piezoelectric and ferroelectric properties, which may contribute to their mechanical behaviors and various functionalities. This work has elaborated in more details of the piezoelectric and ferroelectric behaviors of the nacre by using the DART (Dual-AC Resonance Tracking) and vector-PFM (Piezoresponse Force Microscope), as well as the SS-PFM (Switching Spectroscopy PFM) techniques. By using the vector-PFM technique, the local polarization directions of intracrystalline biopolymers are found to be very close to the direction perpendicular to the platelet surface, and it, therefore, shows strong piezoresponse along this direction. On the other hand, the interlamellar biopolymer shows strong piezoresponse in the direction parallel to the platelet surface. This intrinsic piezoelectric property of the biopolymer may be the basis for sensing and actuating during biomineralization process. Besides the piezoresponse, the locations of various biopolymers are also revealed in-situ by using the PFM technique. The ferroelectric behaviors of nacre have been observed by SS-PFM method. Based on the shapes of the ferroelectric hysteresis loops, it is found that the biopolymers in nacre exhibit the similar behaviors to that of the polyvinylidene fluoride (PVDF) based co- or ter-polymers for energy storage applications.
Effective piezoelectric response of twin walls in ferroelectrics
Authors: Morozovska Anna N. , Eliseev Eugene A. , Varenyk Oleksandr V. , Kalinin Sergei V.
Published: May 2013

The effective piezoelectric coefficients of twin walls in tetragonal ferroelectric are calculated in the framework of decoupling approximation and Landau-Ginzburg-Devonshire theory allowing for polarization gradient terms, electrostriction and flexoelectric coupling. Using an example of piezoelectric response of a1-a2 twins to a homogeneous electric field, we show that the response is almost independent on the flexoelectric coupling, but is very sensitive to the values of polarization gradient coefficients. This behavior originates from the strong coupling between local dielectric susceptibility and the gradient coefficients. The enhancement of piezoelectric response from 10% up to a factor of 103 times is predicted. The local electromechanical response of the domain walls can thus provide information on the gradient terms in Ginzburg-Landau-Devonshire expansion and pinning mechanisms of the ferroelectric domain walls. The observability of these effects by the piezoresponse force microscopy of electroded structures and impact on the functional properties of the systems with dense domain structures are analyzed.
Resolution of the ferroelectric domains structure in (K,Na)NbO3-based lead-free ceramics by confocal Raman microscopy
Authors: Rubio-Marcos F. , Del Campo A. , Fernández J. F.
Published: May 2013

We highlight some practical aspects in the study of ferroelectric domains in lead-free modified (K,Na)NbO3 piezoceramics through Confocal Raman Microscopy (CRM). In addition, CRM allows the determination of the nature of domain walls and correlation between the structure and piezoelectric properties. The typical configuration of the ferroelectric domain is analyzed in polycrystalline grains of small sizes not exceeding 6 μm, where tetragonal and orthorhombic domains are coexisting. The accumulated stress produced by the phase coexistence softens the octahedron force constant and reduces the polarization. So, the polarization decrease is associated to the apparition of the orthorhombic phase (O). Finally, we believe that the general strategy and design principles described in this study will open new avenues in developing novel strategies of domains characterization that allow improving the piezoresponse.
Indentation of a punch with chemical or heat distribution at its base into transversely isotropic half-space: Application to local thermal and electrochemical probes
Authors: Karapetian Edgar , Kalinin Sergei V.
Published: May 2013

The exact solution to the coupled problem of indentation of the punch, subjected to either heat or chemical substance distribution at its base, into three-dimensional semi-infinite transversely isotropic material is presented. The entire set of field components are derived in terms of integrals of elementary functions using methods of the potential theory and recently obtained, by the authors, results for the general solution of the field equations in terms of four harmonic potential functions. The exact solution for the stiffness relations that relate applied force, total chemical diffusion/heat flux in the domain of the contact, with indenter displacement, temperature, or chemical substance distribution of diffusing species at the base, and materials' chemo/thermo-elastic properties are obtained in closed form and in terms of elementary functions. These results can be used to understand the image formation mechanisms in techniques such as thermal scanning probe microscopy and electrochemical strain microscopy.
Structures of protonated methanol clusters and temperature effects
Authors: Fifen Jean Jules , Nsangou Mama , Dhaouadi Zoubeida , Motapon Ousmanou , Jaidane Nejm-Eddine
Published: May 2013

The accurate evaluation of pKa’s, or solvation energies of the proton in methanol at a given temperature is subject to the determination of the most favored structures of various isomers of protonated (H+(MeOH)n) and neutral ((MeOH)n) methanol clusters in the gas phase and in methanol at that temperature. Solvation energies of the proton in a given medium, at a given temperature may help in the determination of proton affinities and proton dissociation energies related to the deprotonation process in that medium and at that temperature. pKa’s are related to numerous properties of drugs. In this work, we were interested in the determination of the most favored structures of various isomers of protonated methanol clusters in the gas phase and in methanol, at a given temperature. For this aim, the M062X/6-31++G(d,p) and B3LYP/6-31++G(d,p) levels of theory were used to perform geometries optimizations and frequency calculations on various isomers of (H+(MeOH)n) in both phases. Thermal effects were retrieved using our homemade FORTRAN code. Thus, we accessed the relative populations of various isomers of protonated methanol clusters, in both phases for temperatures ranging from 0 to 400 K. As results, in the gas phase, linear structures are entropically more favorable at high temperatures, while more compact ones are energetically more favorable at lower temperatures. The trend is somewhat different when bulk effects are taken into account. At high temperatures, the linear structure only dominates the population for n ⩽ 6, while it is dominated by the cyclic structure for larger cluster sizes. At lower temperatures, compact structures still dominate the population, but with an order different from the one established in the gas phase. Hence, temperature effects dominate solvent effects in small cluster sizes (n ⩽ 6), while the reverse trend is noted for larger cluster sizes.
Influence of electrical current variance and thermal resistances on optimum working conditions and geometry for thermoelectric energy harvesting
Authors: Gomez Miguel , Reid Rachel , Ohara Brandon , Lee Hohyun
Published: May 2013

Recent reports on enhanced thermoelectric figure of merits based on nanoscale effects have revived interest in potential applications of thermoelectric modules for waste heat recovery and distributed power generation. However, studies of optimized working conditions have not been thoroughly investigated. The majority of the previous studies on optimum load resistance for maximum power output or maximum efficiency assume temperatures at the ends of thermoelectric materials are known and constant. In reality, temperature should be determined by the energy conservation equations, which are functions of the load resistance, as well as the thermal resistances of the heat source, heat sink, and contact pads. This work exploits a numerical method to determine the actual temperature of thermoelectric materials, and optimum working conditions for thermoelectric energy harvesting are presented. The proposed model considers the effect of thermal resistances between a thermoelectric module and heat reservoirs, and the electrical current variation with respect to load resistance. The optimum condition for load resistance ratio was observed to occur at larger values than those obtained from traditional optimization work. Additionally, optimum geometry for a thermoelectric module is suggested for energy harvesting methods, where forced convection or oversized heat sinks cannot be used. Experimental results obtained from a commercial thermoelectric module are also presented to validate the proposed model. This work forms a basis to predict optimum working conditions in various thermoelectric energy harvesting applications.
Non-Markovianity during the quantum Zeno effect
Authors: Thilagam A.
Published: May 2013

We examine the Zeno and anti-Zeno effects in the context of non-Markovian dynamics in entangled spin-boson systems in contact with noninteracting reservoirs. We identify enhanced non-Markovian signatures in specific two-qubit partitions of a Bell-like initial state, with results showing that the intra-qubit Zeno effect or anti-Zeno effect occurs in conjunction with inter-qubit non-Markovian dynamics for a range of system parameters. The time domain of effective Zeno or anti-Zeno dynamics is about the same order of magnitude as the non-Markovian time scale of the reservoir correlation dynamics, and changes in decay rate due to the Zeno mechanism appears coordinated with information flow between specific two-qubit partitions. We extend our analysis to examine the Zeno mechanism-non-Markovianity link using the tripartite states arising from a donor-acceptor-sink model of photosynthetic biosystems.
Spherical vortex beams of high radial degree for enhanced single-beam tweezers
Authors: Baresch Diego , Thomas Jean-Louis , Marchiano Régis
Published: May 2013

We present, in our knowledge, the first theoretical demonstration of the possibility to trap and manipulate particles in three dimensions with the radiation pressure exerted by a single acoustical beam. Numerical examples demonstrate that single-beam acoustical tweezers operating in three dimensions are feasible with a large variety of materials and may widely extend the range of forces and operation regions that are currently available with optical tweezers. To do so, a method to model the focusing properties of acoustical beams with complex wavefronts using a spherical transducer is proposed. Then, the radiation forces exerted by various beams going from the classical vortex to the high radial degree spherical vortex beam that we introduce here are studied. While the first is shown to trap moderately small particles, the latter will stiffly trap large solid spheres in three dimensions. Even though this demonstration is carried out using a formalism suited to acoustics, it is easily applicable to trap non-transparent particles with optical tweezers that remain an issue.
On the origin and convergence of a post-quantization constrained propagator for path integral simulations of rigid bodies
Authors: Guillon Grégoire , Zeng Tao , Roy Pierre-Nicholas
Published: May 2013

We present a new methodological procedure, based on Post-Quantization Constraints (PQC), to obtain approximate density matrices and energy estimators for use in path integral molecular dynamics and Monte Carlo simulations. The approach serves as a justification of the use of “RATTLE & SHAKE” type methods for path integrals. A thorough discussion of the underlying geometrical concepts is given. Two standard model systems, the particle on a ring and the three-dimensional linear rotor, are used to illustrate and benchmark the approach. In these two cases, matrix elements of the newly defined propagator are explicitly computed in both “angular coordinate” and “angular momentum” bases. A detailed analysis of the convergence properties of the density matrix, and energy estimator with respect to their “exact” counterparts, is presented along with numerical illustrations. We conclude that the use of a PQC-type propagator is justified and practical.
Thermodynamic anomaly of the sub-Tg relaxation in hyperquenched metallic glasses
Authors: Hu Lina , Zhou Chao , Zhang Chunzhi , Yue Yuanzheng
Published: May 2013

Recently, we observed an unusual non-monotonic glass relaxation phenomenon, i.e., the three-step sub-Tg relaxation in hyperquenched CuZrAl glass ribbons [L. N. Hu and Y. Z. Yue, Appl. Phys. Lett. 98, 081904 (2011)10.1063/1.3556659]. In the present work, we reveal the origin of this abnormal behavior by studying the cooling rate dependence of the sub-Tg enthalpy relaxation in two metallic glasses. For the Cu46Zr46Al8 glass ribbons the sub-Tg enthalpy relaxation pattern exhibits a three-step trend with the annealing temperature only when the ribbons are fabricated below a critical cooling rate. For the La55Al25Ni20 glass ribbons the activation energy for the onset of the sub-Tg enthalpy relaxation also varies non-monotonically with the cooling rate of fabrication. These abnormal relaxation phenomena are explained in terms of the competition between the low and the high temperature clusters during the fragile-to-strong transition. By comparisons of chemical heterogeneity between Cu46Zr46Al8 and La55Al25Ni20, we predict that the abnormal relaxation behavior could be a general feature for the HQ metallic glasses.
Mean field QM/MM method: Average position approximation
Authors: Cui Fengchao , Li Hui
Published: May 2013

The average position mean field combined quantum mechanical (QM) and molecular mechanical (MM) method, denoted as QM/⟨MM⟩, is described. This method can drastically reduce the QM/⟨MM⟩ molecular dynamics simulation time to a level similar to pure MM methods, enabling the sampling of millions of configurations. A rigorous analysis shows that there is a general and significant error (up to 7 kcal/mol) in mean field QM/⟨MM⟩ methods arising from the loss of instantaneous polarization of the QM electronic wavefunction. To reach high level of accuracy and efficiency, polarizable force field should be used to represent the QM region in mean field QM/⟨MM⟩ methods.
Rovibronically selected and resolved two-color laser photoionization and photoelectron study of titanium monoxide cation
Authors: Huang Huang , Luo Zhihong , Chang Yih Chung , Lau Kai-Chung , Ng C. Y.
Published: May 2013

Two-color visible-ultraviolet (VIS-UV) resonance-enhanced laser photoionization and pulsed field ionization-photoelectron (PFI-PE) study of gaseous titanium monoxide (TiO) in the total energy range of 55 000–57 320 cm−1 has been conducted. The TiO molecules were selectively excited to single J′ rotational levels of the intermediate TiO*(B3Π1, ν′ = 0) state by using a VIS dye laser and then ionized by using another UV laser. This two-color photoexcitation method has allowed the measurement of cleanly J+-resolved PFI-PE spectra for the TiO+(X 2Δ5/2,3/2; v+ = 0, 1, and 2) vibrational bands. By simulating the rotationally resolved PFI-PE spectra, J+ = 3/2 is determined to be the lowest rotational level of the ground electronic state, confirming that the symmetry of the TiO+ ground state is 2Δ3/2. Irregular intensity patterns for rotational PFI-PE peaks that deviated from the regular patterns that favor the rotational transitions with small change of the core rotational angular momentum, are observed. This observation is indicative of strong perturbations of the PFI-PE rotational transitions, possibly by a channel-coupling mechanism. The analysis of the PFI-PE spectra yields highly precise values for the adiabatic ionization energy of TiO [IE(TiO) = 55 005.4 ± 0.8 cm−1 (6.81980 ± 0.00010 eV)], and the vibrational frequency (ωe+ = 1056.1 ± 0.8 cm−1), the anharmonicity constant (ωe+χe+ = 4.4 ± 0.8 cm−1), the rotational constants (Be+ = 0.5613 ± 0.0009 cm−1 and αe+ = 0.0029 ± 0.0008 cm−1), and the equilibrium bond length (re+ = 1.583 Å) for the TiO+(X 2Δ3/2) ground state, the vibrational frequency (ωe+ = 1058.4 ± 0.8 cm−1), the anharmonicity constant (ωe+χe+ = 5.1 ± 0.8 cm−1), the rotational constants (Be+ = 0.5715 ± 0.0007 cm−1 and αe+ = 0.0030 ± 0.0004 cm−1) and the equilibrium bond length (re+ = 1.568 Å) for the excited spin orbit state TiO+(X 2Δ5/2), along with the spin-orbit coupling constant (A = 105.9 ± 0.2 cm−1) for TiO+(X 2Δ5/2,3/2).
Fiber-optic Fourier transform infrared spectroscopy for remote label-free sensing of medical device surface contamination
Authors: Hassan Moinuddin , Tan Xin , Welle Elissa , Ilev Ilko
Published: May 2013

As a potential major source of biochemical contamination, medical device surfaces are of critical safety concerns in the clinical practice and public health. The development of innovative sensing methods for accurate and real-time detection of medical device surface contamination is essential to protect patients from high risk infection. In this paper, we demonstrate an alternative fiber-optic Fourier Transform Infrared (FTIR) spectroscopy based sensing approach for remote, non-contact, and label-free detection of biochemical contaminants in the mid-infrared (mid-IR) region. The sensing probe is designed using mid-IR hollow fibers and FTIR measurements are carried out in reflection mode. Bovine Serum Albumin (BSA) and bacterial endotoxin of different concentrations under thoroughly dry condition are used to evaluate the detection sensitivity. The devised system can identify ≤0.0025% (≤4 × 1011 molecules) BSA and 0.5% (0.5 EU/ml) endotoxin concentration. The developed sensing approach may be applied to detect various pathogens that pose public health threats.
Resonant two-photon ionization spectroscopy of jet-cooled UN: Determination of the ground state
Authors: Matthew Daniel J. , Morse Michael D.
Published: May 2013

The optical transitions of supersonically cooled uranium nitride (UN) have been investigated in the range from 19 200 to 23 900 cm−1 using resonant two-photon ionization spectroscopy. A large number of bands have been observed, of which seven have been rotationally resolved and analyzed. All are found to arise from the same state, which is presumably the ground state of the molecule. From the analysis of the bands, the ground state has Ω = 3.5, with a bond length of 1.7650(12) Å. Comparisons to the known isovalent molecules are made, and the variations in ground state configuration are explained in terms of the configurational reordering that occurs with changes in the nuclear and ligand charges. It is concluded that the UN molecule is best considered as a U3+N3− species in which the closed shell nitride ligand interacts with a U3+ ion. The ground state of the molecule derives from a U3+ ion in its 7s15f 2 atomic configuration.
A seven-crystal Johann-type hard x-ray spectrometer at the Stanford Synchrotron Radiation Lightsource
Authors: Sokaras D. , Weng T.-C. , Nordlund D. , Alonso-Mori R. , Velikov P. , Wenger D. , Garachtchenko A. , George M. , Borzenets V. , Johnson B. , Rabedeau T. , Bergmann U.
Published: May 2013

We present a multicrystal Johann-type hard x-ray spectrometer (∼5–18 keV) recently developed, installed, and operated at the Stanford Synchrotron Radiation Lightsource. The instrument is set at the wiggler beamline 6-2 equipped with two liquid nitrogen cooled monochromators – Si(111) and Si(311) – as well as collimating and focusing optics. The spectrometer consists of seven spherically bent crystal analyzers placed on intersecting vertical Rowland circles of 1 m of diameter. The spectrometer is scanned vertically capturing an extended backscattering Bragg angular range (88°–74°) while maintaining all crystals on the Rowland circle trace. The instrument operates in atmospheric pressure by means of a helium bag and when all the seven crystals are used (100 mm of projected diameter each), has a solid angle of about 0.45% of 4π sr. The typical resolving power is in the order of \documentclass[12pt]{minimal}\begin{document}$\frac{E}{\Delta E} \sim 10\,000$\end{document}EΔE∼10000. The spectrometer's high detection efficiency combined with the beamline 6-2 characteristics permits routine studies of x-ray emission, high energy resolution fluorescence detected x-ray absorption and resonant inelastic x-ray scattering of very diluted samples as well as implementation of demanding in situ environments.
The impact of quasiparticle tunnel injection on the proximity effect in Pb/Sn sandwich
Authors: Rudenko E. M. , Dubyna D. S. , Krakovny A. A.
Published: May 2013

The proximity effect in Pb/Sn sandwich under the impact of quasiparticle tunnel injection has been studied. The estimation of the γ and γBN proximity effect parameters has been made; the dependence of the γ and γBN parameters on the Sn thickness has been built. It has been shown by studying the current-voltage characteristics of the double-barrier tunnel junction with a Pb/Sn intermediate proximity electrode that an increase of the γm parameter of the strength of the proximity effect occurs as a result of quasiparticle tunnel injection into the Pb/Sn proximity electrode.
Multiscale modelling on the shock-induced chemical reactions of multifunctional energetic structural materials
Authors: Qiao L. , Zhang X. F. , He Y. , Zhao X. N. , Guan Z. W.
Published: May 2013

Multifunctional energetic structural materials (MESMs) are usually granular mixtures, which release energy due to exothermic chemical reaction initiated under shock loading conditions. The mesostructure, in terms of the size, shape, and distribution of granular mixture, plays a significant role in chemical reaction and the energy release characteristics of MESMs. However, it is difficult to model such a complex process involving thermal-mechanical-chemical responses, especially the effects of the initial mesostructures. In this paper, a multiscale modelling approach is proposed to simulate the chemical reaction of MESMs under a shock compression. The thermal-mechanical response of MESMs is first obtained from mesoscale simulations. Then, the macroscale thermochemical model for a shock-induced chemical reaction is given, in which the extent of reaction is considered. Finally, the spatial profiles of temperature and pressure from the mesoscale heterogeneous simulation are homogenized into cells as an initial state for chemical reaction and further combined with the thermochemical model in macroscale. Hence this provides insight into thermal-mechanical-chemical responses based on the initial mesostructures. Aluminum/Tungsten/Polytetrafluoroethylene granular mixture is selected to demonstrate the method and the effects of volume fraction and impact velocity on the shock-induced chemical reaction. The multiscale approach developed, which combines the mesoscale simulation and macroscale thermochemical modelling, can be used to predict the shock-induced chemical reaction of MESMs with different mesoscale characteristics over a wide range of impact velocities.
Evaluation and interpretation of bubble size distributions in pulsed megasonic fields
Authors: Hauptmann M. , Struyf H. , De Gendt S. , Glorieux C. , Brems S.
Published: May 2013

The occurrence of acoustic cavitation is incorporating a multitude of interdependent effects that strongly depend on the bubble size. Therefore, bubble size control would be beneficial for biological and industrial processes that rely on acoustic cavitation. A pulsed acoustic field can result in bubble size control and the repeated dissolution and reactivation (“recycling”) of potentially active bubbles. As a consequence, a pulsed field can strongly enhance cavitation activity. In this paper, we present a modified methodology for the evaluation of the active bubble size distribution by means of a combination of cavitation noise measurements and ultrasonic pulsing. The key component of this modified methodology is the definition of an upper size limit, below which bubbles—in between subsequent pulses—have to dissolve, in order to be sustainably recycled. This upper limit makes it possible to explain and link the enhancement of cavitation activity to a bubble size distribution. The experimentally determined bubble size distributions for different power densities are interpreted in the frame of numerical calculations of the oscillatory responses of the bubbles to the intermittent driving sound field. The distributions are found to be shaped by the size dependent interplay between bubble pulsations, rectified diffusion, coalescence, and the development of parametrically amplified shape instabilities. Also, a phenomenological reactivation-deactivation model is proposed to explain and quantify the observed enhancement of cavitation activity under pulsed, with respect to continuous sonication. In this model, the pulse-duration determines the magnitude of the reactivation of partially dissolved bubbles and the deactivation of activated bubbles by coalescence. It is shown that the subsequent recycling of previously active bubbles leads to an accumulation of cavitation activity, which saturates after a certain number of pulses. The model is fitted to the experimental data for the cavitation activity measured by means of ultraharmonic cavitation noise as a function of the pulse duration. Measurements of the development of the cavitation noise and sonochemiluminescence over a sequence of pulses for different pulse durations and separations confirm the general validity of the proposed model. Size distributions of the larger, inactive bubbles that were extracted from High-speed images of the cavitation field, relate the deactivation of activated bubbles by coalescence to the increase in volume concentrations of larger bubbles as observed by others.
Epitaxial strain effect in tetragonal SrRuO3 thin films
Authors: Kan Daisuke , Aso Ryotaro , Kurata Hiroki , Shimakawa Yuichi
Published: May 2013

We report on our characterization of the structural, electrical, and magnetic properties of tetragonal SrRuO3 (SRO) thin films stabilized under both compressive and tensile strain. These tetragonal films consisting of the deformed RuO6 octahedra without rotations were coherently grown on (110)ortho NdGaO3 and (110)ortho GdScO3 substrates, which provide compressive (−1.7%) and tensile (+1.0%) strains, respectively. The ferromagnetic transition temperature TC for the compressively strained film is found to be as high as 155 K, while TC of the film under tensile strain is only 100 K. The longitudinal resistivity ρxx of the compressively strained films is lower than that of the films under the tensile strain. This is attributed to the enhanced mobility for the compressive-strain case. The magnetic anisotropy also exhibits strong dependence on the substrate-induced epitaxial strain. The film under the compressive strain has the uniaxial magnetic easy axis along the out-of-plane direction, while the easy axis of the film under the tensile strain lies along the in-plane direction parallel to the [1-10]GSO one. The results demonstrate that the electrical and magnetic properties of the tetragonal SRO thin films are closely related to the RuO6 octahedral deformations due to the substrate-induced strain.
Fluctuating zonal flows in the I-mode regime in Alcator C-Mod
Authors: Cziegler I. , Diamond P. H. , Fedorczak N. , Manz P. , Tynan G. R. , Xu M. , Churchill R. M. , Hubbard A. E. , Lipschultz B. , Sierchio J. M. , Terry J. L. , Theiler C.
Published: May 2013

Velocity fields and density fluctuations of edge turbulence are studied in I-mode [F. Ryter et al., Plasma Phys. Controlled Fusion 40, 725 (1998)] plasmas of the Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] tokamak, which are characterized by a strong thermal transport barrier in the edge while providing little or no barrier to the transport of both bulk and impurity particles. Although previous work showed no clear geodesic-acoustic modes (GAM) on C-Mod, using a newly implemented, gas-puff-imaging based time-delay-estimate velocity inference algorithm, GAM are now shown to be ubiquitous in all I-mode discharges examined to date, with the time histories of the GAM and the I-mode specific [D. Whyte et al., Nucl. Fusion 50, 105005 (2010)] Weakly Coherent Mode (WCM, f = 100–300 kHz, Δf/f≈0.5, and kθ≈1.3 cm−1) closely following each other through the entire duration of the regime. Thus, the I-mode presents an example of a plasma state in which zero frequency zonal flows and GAM continuously coexist. Using two-field (density-velocity and radial-poloidal velocity) bispectral methods, the GAM are shown to be coupled to the WCM and to be responsible for its broad frequency structure. The effective nonlinear growth rate of the GAM is estimated, and its comparison to the collisional damping rate seems to suggest a new view on I-mode threshold physics.