bluuebunny/crossref_metadata_2025 huggingface dataset:
A NOTE ON POLYCYLIC RESIDUALLY FINITE-p GROUPS
Authors: CUTOLO GIOVANNI , SMITH HOWARD
Published: December 2009

A subgroup H of a residually finite-p group G is almost p-closed in G if H has finite p′-index in H, its closure with respect to the pro-p topology on G. We characterise polycyclic residually finite-p groups in which all subgroups are almost p-closed and discuss a few conditions that are sufficient for particular subgroups H to be almost p-closed. We also present, for each prime p, an example of a polycyclic residually-p group G for which |H: H| takes on all possible values, including infinity, as H varies.
FINITE GROUPS WITH SOME ℨ-PERMUTABLE SUBGROUPS
Authors: LI YANGMING , WANG LIFANG , WANG YANMING
Published: December 2009

Let ℨ be a complete set of Sylow subgroups of a finite group G; that is to say for each prime p dividing the order of G, ℨ contains one and only one Sylow p-subgroup of G. A subgroup H of G is said to be ℨ-permutable in G if H permutes with every member of ℨ. In this paper we characterise the structure of finite groups G with the assumption that (1) all the subgroups of Gp ∈ ℨ are ℨ-permutable in G, for all prime p ∈ π(G), or (2) all the subgroups of Gp ∩ F*(G) are ℨ-permutable in G, for all Gp ∈ ℨ and p ∈ π(G), where F*(G) is the generalised Fitting subgroup of G.
EXTENSIONS OF McCOY'S THEOREM
Authors: HONG CHAN YONG , KIM NAM KYUN , LEE YANG
Published: December 2009

McCoy proved that for a right ideal A of S = R[x1, . . ., xk] over a ring R, if rS(A) ≠ 0 then rR(A) ≠ 0. We extend the result to the Ore extensions, the skew monoid rings and the skew power series rings over non-commutative rings and so on.
NORMAL AUTOMORPHISMS OF A FREE METABELIAN NILPOTENT GROUP
Authors: ENDIMIONI GÉRARD
Published: December 2009

An automorphism φ of a group G is said to be normal if φ(H) = H for each normal subgroup H of G. These automorphisms form a group containing the group of inner automorphisms. When G is a non-abelian free (or free soluble) group, it is known that these groups of automorphisms coincide, but this is not always true when G is a free metabelian nilpotent group. The aim of this paper is to determine the group of normal automorphisms in this last case.
ON THE INVERSE MULTIFRACTAL FORMALISM
Authors: OLSEN L.
Published: December 2009

Two of the main objects of study in multifractal analysis of measures are the coarse multifractal spectra and the Rényi dimensions. In the 1980s it was conjectured in the physics literature that for ‘good’ measures the following result, relating the coarse multifractal spectra to the Legendre transform of the Rényi dimensions, holds, namely

This result is known as the multifractal formalism and has now been verified for many classes of measures exhibiting some degree of self-similarity. However, it is also well known that there is an abundance of measures not satisfying the multifractal formalism and that, in general, the Legendre transforms of the Rényi dimensions provide only upper bounds for the coarse multifractal spectra. The purpose of this paper is to prove that even though the multifractal formalism fails in general, it is nevertheless true that all measures (satisfying a mild regularity condition) satisfy the inverse of the multifractal formalism, namely
TRANSFORMATION AND REDUCTION FORMULAE FOR DOUBLE q-SERIES OF TYPE Φ2:1;λ2:0;μ
Authors: JIA CANGZHI , ZHANG XIANGDE
Published: December 2009

By applying the Sears non-terminating transformations, we establish four general transformation theorems for double basic hypergeometric series of type Φ2:1;λ2:0;μ. Moreover, several transformation, reduction and summation formulae on the double basic hypergeometric series Φ2:1;22:0;1, Φ2:1;32:0;2 and Φ2:1;42:0;3 are also derived through parameter specialisation.
PURE STATES ON FREE GROUP C*-ALGEBRAS
Authors: AKEMANN CHARLES , WASSERMANN SIMON , WEAVER NIK
Published: December 2009

We prove that all the pure states of the reduced C*-algebra of a free group on an uncountable set of generators are *-automorphism equivalent and extract some consequences of this fact.
Unsteady near-shore natural convection induced by surface cooling
Authors: MAO YADAN , LEI CHENGWANG , PATTERSON JOHN C.
Published: December 2009

Natural convection in calm near-shore waters induced by daytime heating or nighttime cooling plays a significant role in cross-shore exchanges with significant biological and environmental implications. Having previously reported an improved scaling analysis on the daytime radiation-induced natural convection, the authors present in this paper a detailed scaling analysis quantifying the flow properties at varying offshore distances induced by nighttime surface cooling. Two critical functions of offshore distance have been derived to identify the distinctness and the stability of the thermal boundary layer. Two flow scenarios are possible depending on the bottom slope. For the relatively large slope scenario, three flow regimes are possible, which are discussed in detail. For each flow regime, all the possible distinctive subregions are identified. Two different sets of scaling incorporating the offshore-distance dependency have been derived for the conduction-dominated region and stable-convection-dominated region respectively. It is found that the scaling for flow in the stable-convection-dominated region also applies to the time-averaged mean flow in the unstable region. The present scaling results are verified by numerical simulations.
Evolution and decay of a rotating flow over random topography
Authors: SANSÓN L. ZAVALA , GONZÁLEZ-VILLANUEVA A. , FLORES L. M.
Published: December 2009

The evolution and decay of a homogeneous flow over random topography in a rotating system is studied by means of numerical simulations and theoretical considerations. The analysis is based on a quasi-two-dimensional shallow-water approximation, in which the horizontal divergence is explicitly different from zero, and topographic variations are not restricted to be much smaller than the mean depth, as in quasi-geostrophic dynamics. The results are examined by comparing the evolution of a turbulent flow over different random bottom topographies characterized by a specific horizontal scale, or equivalently, a given mean slope. As in two-dimensional turbulence, the energy of the flow is transferred towards larger scales of motion; after some rotation periods, however, the process is halted as the flow pattern becomes aligned along the topographic contours with shallow water to the right. The quasi-steady state reached by the flow is characterized by a nearly linear relationship between potential vorticity and transport function in most parts of the domain, which is justified in terms of minimum-enstrophy arguments. It is found that global energy decays faster for topographies with shorter horizontal length scales due to more effective viscous dissipation. In addition, some comparisons between simulations based on the shallow-water and quasi-geostrophic formulations are carried out. The role of solid boundaries is also examined: it is shown that vorticity production at no-slip walls contributes for a slight disorganization of the flow.
Pre-operative parathyroid localisation: surgical review of sesta-methoxyisobutylisonitrile images is important
Authors: Awobem A A , England R J A
Published: December 2009

Objective:

To highlight the importance of pre-operative review of sesta-methoxyisobutylisonitrile imaging before parathyroid surgery.

Case report:

Technetium-99 m sesta-methoxyisobutylisonitrile scanning is a well established imaging modality undertaken to locate the parathyroid glands prior to parathyroidectomy. Because of the relative lack of detail in the images obtained, the radiological report is normally the most important piece of information used by the surgeon for surgical planning. We report a case that illustrates the importance of surgical image review prior to revision parathyroid surgery. We also present a review of literature highlighting the need for surgical review of such imaging.

Conclusion:

We propose that surgeons routinely review sesta-methoxyisobutylisonitrile images pre-operatively.
Unilateral combined laryngocoele with recurrent respiratory papillomatosis: case report
Authors: Bayan S , Mortensen M
Published: December 2009

Objective:

We report a case of unilateral combined laryngocoele occurring in conjunction with recurrent respiratory papillomatosis.

Methods:

Case report and review of the literature concerning the physiology underlying laryngocoele formation.

Results:

A laryngocoele is an abnormal, air-filled dilation of the laryngeal saccule which communicates with the laryngeal lumen. We report a case of a 53-year-old man with a unilateral combined laryngocoele occurring in conjunction with recurrent respiratory papillomatosis. Microlaryngoscopy demonstrated a papilloma obstructing the laryngeal saccule. Removal of papillomata via laser excision and marsupialisation of the left laryngocoele improved the patient's vocal symptoms. There was no recurrence of papillomata or the laryngocoele.

Conclusion:

While many laryngocoeles can be explained by altered laryngeal physiology, the papilloma described in this case acted as an anatomical obstruction that trapped air within the saccule, creating an environment conducive to laryngocoele formation.
Aggressive angiomyxoma of larynx: case report and literature review
Authors: Sylvester D C , Kortequee S , Moor J W , Woodhead C J , Maclennan K A
Published: December 2009

Objective:

We report the second known case of aggressive angiomyxoma of the larynx.

Method:

Case report and a review of the world literature concerning angiomyxoma of the larynx and recent advances in the immunohistochemical, cytogenic and clinical study of its female pelvic counterpart.

Results:

Aggressive angiomyxoma is a rare mesenchymal tumour originally thought only to occur in the female pelvis and peritoneum, or rarely in the male genital tract. A 47-year-old man presented with a one-month history of dysphonia. He was found to have a supraglottic mass on endoscopic examination, and underwent a laryngofissure approach excision biopsy and covering tracheostomy. Histological analysis showed a characteristic proliferation of spindle cells widely separated by loose, myxoid stroma with a prominent vascular component. Aggressive angiomyxoma was diagnosed.

Conclusion:

To our knowledge, this is the second report in the world literature of aggressive angiomyxoma of the larynx. Comparison with the female pelvic counterpart facilitates diagnosis, aided by recent advances, and suggests that complete surgical excision with a wide margin is the treatment of choice.
Notes on the sea caves of sub-Antarctic Macquarie Island, Southern Ocean
Authors: Harris Stephen , Copson Geof , d'Arville Louisa
Published: December 2009

Caves of marine origin occur in tectonically uplifted stacks on the coastal terrace and in plateau edge cliffs at a number of locations around Macquarie Island. Some of the caves have been located and their distributions mapped. Four of the best known caves are mapped in detail. Aspects of their geology, structure and biology, including speleothem development, clastic deposits, faunal remains and subfossil deposits are explored. Many of these caves contain deposits, which may have the potential to be investigated, as beach and peat deposits have been, for dating key time periods in the island's evolution. The palaeoenvironmental research potential of the sea caves on Macquarie Island has yet to be exploited. Further knowledge about these caves will assist in the understanding of the processes that have acted on Macquarie Island and other polar and sub-polar islands.
Retracing the route of Hans K. E. Krüger's 1930 German Arctic expedition
Authors: Stenton Douglas R. , Park Robert W. , Grant Tara
Published: December 2009

Prior to the discovery in 1999 of an archaeological site near Cape Southwest, on southern Axel Heiberg Island, little was known about the movements of the ill fated 1930 German Arctic Expedition, led by Hans K.E. Krüger. What was known was based on the content of three cairn documents that spanned a period of just thirteen days. This paper presents new information that expands our knowledge of the expedition's route using catalogue labels found with geological specimens collected by Krüger and recovered from the site. The movements of the expedition over a period of 43 days are reconstructed, ten additions are made to the known itinerary, and an approximate date of the group's arrival at Cape Southwest is presented. The data show that despite concerns about the health of both Krüger and his Danish assistant, and about the weight of equipment being transported, the expedition had made good progress prior to reaching Cape Southwest.
Monitoring the transformation of historic features in Antarctica and Svalbard: local processes and regional contexts
Authors: Roura Ricardo
Published: December 2009

Historical sites in Antarctica and Svalbard contain the material remains of past activities of exploration and exploitation of these regions. These sites have been subject to transformation by cultural and non-cultural (natural) processes since their abandonment to the present. For research and management purposes it is important to monitor and explain these changes. This article focuses on the transformation of historic features in Antarctica and Svalbard as assessed through repeat photography. Seven historical features were selected representing a range of site types and past and present site functions. Data collection was based on the opportunistic reproduction of photographs of historic features taken up to 20+ years previously. Data analysis was performed using the concepts of site formation processes developed by M.B. Schiffer (1983, 1987). Time-serial changes were observed in the seven photo-couples examined in the present instance. No feature degraded significantly during the monitoring period; rather, several features were restored in different ways. Changes were interpreted to result from a range of cultural processes (including conservation, research, and tourism) and natural processes (mainly wind action). Local changes take place in the context of broader regional developments in Antarctica and Svalbard. Despite the ‘time capsule’ narratives about some sites, historical sites in the polar regions are dynamic entities that not only reflect the past as it once was but are also a window onto the present.
Social Policy Digest Online
Authors: Bennett Fran , Jones Ken
Published: December 2009

The Social Policy Digest went online in 2002, and since then has developed into a major web-based resource on UK social policy issues. By the end of 2008 it contained over 22,000 entries, covering policy developments and research findings across the whole range of social policy fields.
Spatial resolution, contrast sensitivity, and sensitivity to defocus of chicken retinal ganglion cells in vitro
Authors: DIEDRICH ERICH , SCHAEFFEL FRANK
Published: December 2009

The chicken has been extensively studied as an animal model for myopia because its eye growth is tightly controlled by visual experience. It has been found that the retina controls the axial eye growth rates depending on the amount and the sign of defocus imposed in the projected image. Glucagonergic amacrine cells were discovered that appear to encode for the sign of imposed defocus. It is not clear whether the downstream neurons, the retinal ganglion cells, still have access to this information—and whether it ultimately reaches the brain. We have analyzed the spike rates of chicken retinal ganglion cells in vitro using a microelectrode array. For this purpose, we initially defined spatial resolution and contrast sensitivity in vitro. Two classes of chicken retinal ganglions were found, depending on the linearity of their responses with increasing contrast. Responses generally declined with increasing defocus of the visual stimulus. These responses were well predicted by the modulation transfer function for a diffraction-limited defocused optical system, the first Bessel function. Thus, the studied retinal ganglion cells did not distinguish between a loss of contrast at a given spatial frequency due to reduced contrast of the stimulus pattern or because the pattern was presented out of focus. Furthermore, there was no indication that the retinal ganglion cells responded differently to defocus of either sign, at least for the cells that were recorded in this study.
Process discovery and Petri nets
Authors: BUSI NADIA , PINNA G. MICHELE
Published: December 2009

The aim of the research domain known as process mining is to use process discovery to construct a process model as an abstract representation of event logs. The goal is to build a model (in terms of a Petri net) that can reproduce the logs under consideration, and does not allow different behaviours compared with those shown in the logs. In particular, process mining aims to verify the accuracy of the model design (represented as a Petri net), basically checking whether the same net can be rediscovered. However, the main mining methods proposed in the literature have some drawbacks: the classical α-algorithm is unable to rediscover various nets, while the region-based approach, which can mine them correctly, is too complex.

In this paper, we compare different approaches and propose some ideas to counter the weaknesses of the region-based approach.
Efficient computation in rational-valued P systems
Authors: BUSI NADIA , GUTIÉRREZ-NARANJO MIGUEL A. , PÉREZ-JIMÉNEZ MARIO J.
Published: December 2009

In this paper, we describe a new representation for deterministic rational-valued P systems that allows us to form a bridge between membrane computing and linear algebra. On the one hand, we prove that an efficient computation for these P systems can be described using linear algebra techniques. In particular, we show that the computation for getting a configuration in such P systems can be carried out by multiplying appropriate matrices. On the other hand, we also show that membrane computing techniques can be used to get the nth power of a given matrix.
On the expressive power of recursion, replication and iteration in process calculi
Authors: BUSI NADIA , GABBRIELLI MAURIZIO , ZAVATTARO GIANLUIGI
Published: December 2009

In this paper we investigate the expressive power of three alternative approaches to the definition of infinite behaviours in process calculi, namely, recursive definitions, replication and iteration. We prove several results discriminating between the calculi obtained from a core CCS by adding the three mechanisms mentioned above. These results are derived by considering the decidability of four basic properties: termination (that is, all computations are finite); convergence (that is, the existence of a finite computation); barb (that is, the ability to perform an action on a given channel) and weak bisimulation.

Our results, which are summarised in Table 1, show that the three calculi form a strict expressiveness hierarchy in that: all the properties mentioned are undecidable in CCS with recursion; only termination and barb are decidable in CCS with replication; all the properties are decidable in CCS with iteration.

As a corollary, we also obtain a strict expressiveness hierarchy with respect to weak bisimulation, since there exist weak bisimulation preserving encodings of iteration in replication and of replication in recursion, whereas there are no weak bisimulation preserving encodings in the other directions.
Deciding reachability problems in Turing-complete fragments of Mobile Ambients
Authors: BUSI NADIA , ZAVATTARO GIANLUIGI
Published: December 2009

The calculus of Mobile Ambients was proposed by Cardelli and Gordon as a foundational calculus for mobile computing. Since its introduction, the computational strength and the decidability of properties have been investigated for several fragments and variants of the standard calculus. We consider the problem of reachability and characterise a public (that is, restriction-free) fragment for which it is decidable. This fragment is obtained by removing the open capability and restricting the application of the replication operator to guarded processes only. This decidability result may appear surprising in combination with the fact that the same fragment was shown to be Turing complete by Maffeis and Phillips. Finally, we extend our decidability result in two ways: we first prove the decidability of a more general property called target reachability (according to which the target of interest for the reachability analysis consists of a possibly infinite set of processes) and then show that our decidability results also hold for a more general calculus, which includes the sophisticated communication mechanisms of Boxed Ambients, which is the most relevant variant of Mobile Ambients without the open capability.
Mobile Petri nets
Authors: ASPERTI A. , BUSI N.
Published: December 2009

We add mobility to Place-Transition Petri nets: tokens are names for places, and an input token of a transition can be used in its postset to specify a destination. Mobile Petri nets are then further extended to dynamic nets by adding the possibility of creating new nets during the firing of a transition. In this way, starting from Petri nets, we define a simple hierarchy of nets with increasing degrees of dynamicity. For each class in this hierarchy, we provide its encoding in the former class.

Our work was largely inspired by the join-calculus of Fournet and Gonthier, which turns out to be a (well-motivated) particular case of dynamic Petri nets. The main difference is that, in the preset of a transition, we allow both non-linear patterns (name unification) and (locally) free names for input places (that is, we remove the locality constraint, and preserve reflexion).
An exploration of cognitive subgroups in Alzheimer’s disease
Authors: DAVIDSON JULIE E. , IRIZARRY MICHAEL C. , BRAY BETHANY C. , WETTEN SALLY , GALWEY NICHOLAS , GIBSON RACHEL , BORRIE MICHAEL , DELISLE RICHARD , FELDMAN HOWARD H. , HSIUNG GING-YUEK , FORNAZZARI LUIS , GAUTHIER SERGE , GUZMAN DANILO , LOY-ENGLISH INGE , KEREN RON , KERTESZ ANDREW , GEORGE-HYSLOP PETER ST. , WHERRETT JOHN , MONSCH ANDREAS U.
Published: December 2009

Heterogeneity is observed in the patterns of cognition in Alzheimer’s disease (AD). Such heterogeneity might suggest the involvement of different etiological pathways or different host responses to pathology. A total of 627 subjects with mild/moderate AD underwent cognitive assessment with the Mini-Mental State Examination (MMSE) and the Dementia Rating Scale-2 (DRS-2). Latent class analysis (LCA) was performed on cognition subscale data to identify and characterize cognitive subgroups. Clinical, demographic, and genetic factors were explored for association with class membership. LCA suggested the existence of four subgroups; one group with mild and another with severe global impairment across the cognitive domains, one group with primary impairments in attention and construction, and another group with primary deficits in memory and orientation. Education, disease duration, age, Apolipoprotein E-ε4 (APOE ε4) status, gender, presence of grasp reflex, white matter changes, and early or prominent visuospatial impairment were all associated with class membership. Our results support the existence of heterogeneity in patterns of cognitive impairment in AD. Our observation of classes characterized by predominant deficits in attention/construction and memory respectively deserves further exploration as does the association between membership in the attention/construction class and APOE ε4 negative status. (JINS, 2010, 16, 233–243.)
ERROR ESTIMATES FOR DOMINICI’S HERMITE FUNCTION ASYMPTOTIC FORMULA AND SOME APPLICATIONS
Authors: KERMAN R. , HUANG M. L. , BRANNAN M.
Published: December 2009

The aim of this paper is to find a concrete bound for the error involved when approximating the nth Hermite function (in the oscillating range) by an asymptotic formula due to D. Dominici. This bound is then used to study the accuracy of certain approximations to Hermite expansions and to Fourier transforms. A way of estimating an unknown probability density is proposed.
A VALUATION FORMULA FOR MULTI-ASSET, MULTI-PERIOD BINARIES IN A BLACK–SCHOLES ECONOMY
Authors: SKIPPER MAX , BUCHEN PETER
Published: December 2009

We present a new valuation formula for a generic, multi-period binary option in a multi-asset Black–Scholes economy. The payoff of this so-called M-binary is the most general possible, subject to the condition that a simple analytic expression exists for the present value. Portfolios of M-binaries can be used to statically replicate many European exotics for which there exist closed-form Black–Scholes prices.
UNSTEADY BOUNDARY LAYERS: CONVECTIVE HEAT TRANSFER OVER A VERTICAL FLAT PLATE
Authors: VAN GORDER ROBERT A. , VAJRAVELU K.
Published: December 2009

In this paper, we extend the results in the literature for boundary layer flow over a horizontal plate, by considering the buoyancy force term in the momentum equation. Using a similarity transformation, we transform the partial differential equations of the problem into coupled nonlinear ordinary differential equations. We first analyse several special cases dealing with the properties of the exact and approximate solutions. Then, for the general problem, we construct series solutions for arbitrary values of the physical parameters. Furthermore, we obtain numerical solutions for several sets of values of the parameters. The numerical results thus obtained are presented through graphs and tables and the effects of the physical parameters on the flow and heat transfer characteristics are discussed. The results obtained reveal many interesting behaviours that warrant further study of the equations related to non-Newtonian fluid phenomena, especially the shear-thinning phenomena. Shear thinning reduces the wall shear stress.
High‐resolution onshore seismic imaging of complex volcanic structures: An example from Vulcano Island, Italy
Authors: Bruno Pier Paolo G. , Castiello Antonio
Published: December 2009

Detailed seismic images of subsurface structures of volcanic calderas are fundamental to improve the structural and volcanological knowledge of these high‐risk volcanoes. However, high‐quality seismic data are difficult to obtain in volcanic areas, especially on shore. We report the results of a high‐resolution seismic profiling of the western sector of La Fossa Caldera (Vulcano Island, Italy). Using a high‐resolution vibrating source and both alternative acquisition and processing techniques, we were able to overcome most of the inconvenience caused by volcanic lithotypes. This study provides the subsurface distribution of volcanic deposits as well as the recognition of some significant intracaldera structures. We located a parasitic vent or hyaloclastite mound buried under La Fossa Caldera, which is dissipating CO2 in an area where earthquakes have been recorded at about 1 km depth. Furthermore, the deformation pattern found at the southernmost part of the profile is consistent with a caldera collapse after a dome intrusion. The results suggest that the use of high‐resolution vibrating sources combined with alternative seismic acquisition techniques and nonconventional processing could help to recover detailed information on the shallow structures of volcanic areas.
How ice shelf morphology controls basal melting
Authors: Little Christopher M. , Gnanadesikan Anand , Oppenheimer Michael
Published: December 2009

The response of ice shelf basal melting to climate is a function of ocean temperature, circulation, and mixing in the open ocean and the coupling of this external forcing to the sub–ice shelf circulation. Because slope strongly influences the properties of buoyancy‐driven flow near the ice shelf base, ice shelf morphology plays a critical role in linking external, subsurface heat sources to the ice. In this paper, the slope‐driven dynamic control of local and area‐integrated melting rates is examined under a wide range of ocean temperatures and ice shelf shapes, with an emphasis on smaller, steeper ice shelves. A 3‐D numerical ocean model is used to simulate the circulation underneath five idealized ice shelves, forced with subsurface ocean temperatures ranging from −2.0°C to 1.5°C. In the sub–ice shelf mixed layer, three spatially distinct dynamic regimes are present. Entrainment of heat occurs predominately under deeper sections of the ice shelf; local and area‐integrated melting rates are most sensitive to changes in slope in this “initiation” region. Some entrained heat is advected upslope and used to melt ice in the “maintenance” region; however, flow convergence in the “outflow” region limits heat loss in flatter portions of the ice shelf. Heat flux to the ice exhibits (1) a spatially nonuniform, superlinear dependence on slope and (2) a shape‐ and temperature‐dependent, internally controlled efficiency. Because the efficiency of heat flux through the mixed layer decreases with increasing ocean temperature, numerical simulations diverge from a simple quadratic scaling law.
Tectonic control on southern Sierra Nevada topography, California
Authors: Mahéo Gweltaz , Saleeby Jason , Saleeby Zorka , Farley Kenneth A.
Published: December 2009

In this study we integrate the apatite (U‐Th)/He thermochronometric technique with geomorphic, structural, and stratigraphic studies to pursue the origin and evolution of topographic relief related to extensive late Cenozoic faulting in the southern Sierra Nevada. The geomorphology of this region reflects a transition from a vast region to the north characterized by nonequilibrium fluvial modification of a relict low‐relief landscape, little affected by internal deformation, to a more complex landscape affected by numerous faults. Regionally, the relict landscape surface is readily resolved by age‐elevation relationships of apatite He ages coupled to geomorphology. These relationships can be extended into the study area and used as a structural datum for the resolution of fault offsets and related tilting. On the basis of 63 new apatite He ages and stratigraphic data from proximal parts of the San Joaquin basin we resolve two sets of normal faults oriented approximately N–S and approximately NW. Quaternary west‐side‐up normal faulting along the N–S Breckenridge–Kern Canyon zone has resulted in a southwest step over from the Owens Valley system in the controlling structure on the regional west tilt of Sierran basement. This zone has also served as a transfer structure partitioning Neogene‐Quaternary extension resulting from normal displacements on the NW fault set. This fault system for the most part nucleated along Late Cretaceous structures with late Cenozoic remobilization representing passive extension by oblate flattening as the region rose and stretched in response to the passage of a slab window and the ensuing delamination of the mantle lithosphere from beneath the region.
Global terrestrial water storage capacity and flood potential using GRACE
Authors: Reager J. T. , Famiglietti J. S.
Published: December 2009

Terrestrial water storage anomaly from the Gravity Recovery and Climate Experiment (GRACE) and precipitation observations from the Global Precipitation Climatology Project (GPCP) are applied at the regional scale to show the usefulness of a remotely sensed, storage‐based flood potential method. Over the GRACE record length, instances of repeated maxima in water storage anomaly that fall short of variable maxima in cumulative precipitation suggest an effective storage capacity for a given region, beyond which additional precipitation must be met by marked increases in runoff or evaporation. These saturation periods indicate the possible transition to a flood‐prone situation. To investigate spatially and temporally variable storage overflow, a monthly storage deficit variable is created and a global map of effective storage capacity is presented for possible use in land surface models. To highlight a flood‐potential application, we design a monthly global flood index and compare with Dartmouth Flood Observatory flood maps.
Dynamics and implications of slab detachment due to ridge‐trench collision
Authors: Burkett Erin R. , Billen Magali I.
Published: December 2009

The approach of a buoyant spreading ridge to a subduction zone may lead to detachment of a subducted slab. Previous work has called upon the detachment process as an explanation for observed ridge abandonment and slab window related magmatism (e.g., in Baja California), but such a scenario has not been tested using fully dynamic numerical models. We use dynamic two‐dimensional models including a non‐Newtonian rheology to study the approach of a trench‐parallel spreading ridge to a subduction zone. We find that before the ridge approaches within 100 km of the trench, detachment of the subducted slab occurs due to the combined effects of increased buoyancy and reduced strength of the lithosphere with ridge proximity. In models exploring effects of subducted slab length, distance of the ridge from the trench, shear zone strength, and lithospheric yield strength, we find the following: (1) a decrease in subduction velocity as the ridge approaches the trench, (2) a shrinking surface plate that maintains a uniform plate‐like subduction velocity, (3) ridge abandonment distances 100–275 km from the trench, and (4) slab gap distances 195–285 km from the trench. These results are consistent with observations in Baja California, where detachment of the Cocos slab may explain abandonment of observed segments of the East Pacific Rise 50–200 km outboard of the trench and the presence of nonarc related magmatism located 100–250 km inboard of the trench. Ridge subduction does not occur within any of these two‐dimensional cases of ridge‐trench collision, indicating that 3‐D geometric effects may be responsible for ridge subduction.
Probing polarization and dielectric function of molecules with higher order harmonics in scattering–near-field scanning optical microscopy
Authors: Nikiforov Maxim P. , Kehr Susanne C. , Park Tae-Hong , Milde Peter , Zerweck Ulrich , Loppacher Christian , Eng Lukas M. , Therien Michael J. , Engheta Nader , Bonnell Dawn
Published: December 2009

The idealized system of an atomically flat metallic surface [highly oriented pyrolytic graphite (HOPG)] and an organic monolayer (porphyrin) was used to determine whether the dielectric function and associated properties of thin films can be accessed with scanning–near-field scanning optical microscopy (s-NSOM). Here, we demonstrate the use of harmonics up to fourth order and the polarization dependence of incident light to probe dielectric properties on idealized samples of monolayers of organic molecules on atomically smooth substrates. An analytical treatment of light/sample interaction using the s-NSOM tip was developed in order to quantify the dielectric properties. The theoretical analysis and numerical modeling, as well as experimental data, demonstrate that higher order harmonic scattering can be used to extract the dielectric properties of materials with tens of nanometer spatial resolution. To date, the third harmonic provides the best lateral resolution(∼50 nm) and dielectric constant contrast for a porphyrin film on HOPG.
Mixed hierarchy of soliton equations
Authors: Zhou Ruguang
Published: December 2009

The mixed hierarchy of soliton equations in (1+1) dimensions is introduced. It contains nonholonomic deformations of soliton equations such the KdV6 equation and the Kupershmidt deformations of soliton equations as special members. Based on the commutator representation method, a recipe for constructing zero curvature representations of mixed hierarchy is proposed. As applications, we obtain the mixed hierarchies and their zero curvature representations for the Korteweg–de Vries hierarchy, the Ablowitz–Kaup–Newell–Segur hierarchy, the modified Korteweg–de Vries hierarchy, the Toda lattice hierarchy, and the Volterra lattice hierarchy.
Solid and liquid spectroscopic analysis (SALSA)–a soft x-ray spectroscopy endstation with a novel flow-through liquid cell
Authors: Blum M. , Weinhardt L. , Fuchs O. , Bär M. , Zhang Y. , Weigand M. , Krause S. , Pookpanratana S. , Hofmann T. , Yang W. , Denlinger J. D. , Umbach E. , Heske C.
Published: December 2009

We present a novel synchrotron endstation with a flow-through liquid cell designed to study the electronic structure of liquids using soft x-ray spectroscopies. In this cell, the liquid under study is separated from the vacuum by a thin window membrane, such that the sample liquid can be investigated at ambient pressure. The temperature of the probing volume can be varied in a broad range and with a fast temperature response. The optimized design of the cell significantly reduces the amount of required sample liquid and allows the use of different window membrane types necessary to cover a broad energy range. The liquid cell is integrated into the solid and liquid spectroscopic analysis (SALSA) endstation that includes a high-resolution, high-transmission x-ray spectrometer and a state-of-the-art electron analyzer. The modular design of SALSA also allows the measurement of solid-state samples. The capabilities of the liquid cell and the x-ray spectrometer are demonstrated using a resonant inelastic x-ray scattering map of a 25 wt % NaOD solution.
One-photon and two-photon excited fluorescence microscopies based on polarization-control: Applications to tip-enhanced microscopy
Authors: Hayazawa Norihiko , Furusawa Kentaro , Taguchi Atsushi , Kawata Satoshi
Published: December 2009

One-photon and two-photon excited fluorescence microscopies using either radial or azimuthal polarization have been developed and applied to the imaging of quantum dots. In both cases (one-photon and two-photon excitations), the fluorescence image profile of each quantum dot is in good agreement with the electric field intensity distribution of a tightly focused spot using a high numerical aperture objective lens. While this polarization dependence of the absorption/emission of quantum dots (or other dye molecules) is useful for characterizing the orientation of the quantum dots, most of the biological applications that employ quantum dots or dye molecules as labels require the information describing not only the orientation but also the precise position of each dot. In order to improve the sensing accuracy of the dot’s position, we employ a modified near-field fluorescence microscopy system that utilizes a tip-enhancement technique and radially polarized two-photon excitations. For the tip enhancement, a commercially available silicon cantilever tip has been successfully utilized instead of metallic tips, as the latter tip can drastically quench the near-field fluorescence. Our tip-enhanced two-photon excited fluorescence microscopy technique enables visualization of the quantum dots distributed on a cover slip beyond the diffraction limit of light. We demonstrate that our approach is advantageous not only due to its high spatial resolution but also due to its high sensitivity by showing that the fluorescence signal is not detectable without the aid of the tip enhancement in some cases.
Effect of cubic phase evolution on field emission properties of boron nitride island films
Authors: Teii Kungen , Yamao Ryota , Matsumoto Seiichiro
Published: December 2009

Field emission performance of boron nitride (BN) island films is studied in terms of cubic phase evolution in plasma-enhanced chemical vapor deposition. Fine-grained island films with large surface roughness can be grown for initial sp2-bonded BN and subsequent cubic BN (cBN) phases by using low-energy (∼20 eV) ion bombardment. Ultraviolet photoelectron spectroscopy reveals that the electron affinity is as low as 0.3 eV for both sp2-bonded BN and cBN phases. The evolution of cBN islands reduces the turn-on field down to around 9 V/μm and increases the current density up to 10−4 A/cm2. The emission is facilitated by the larger field enhancement due to the larger roughness and the higher conduction of cBN islands. The potential barrier height is estimated to be about 3.4 eV for emission from the Fermi level, while it is only about 0.3 eV for “conduction band emission.”
Laminar dispersion at high Péclet numbers in finite-length channels: Effects of the near-wall velocity profile and connection with the generalized Leveque problem
Authors: Giona M. , Adrover A. , Cerbelli S. , Garofalo F.
Published: December 2009

This article develops the theory of laminar dispersion in finite-length channel flows at high Péclet numbers, completing the classical Taylor–Aris theory which applies for long-term, long-distance properties. It is shown, by means of scaling analysis and invariant reformulation of the moment equations, that solute dispersion in finite length channels is characterized by the occurrence of a new regime, referred to as the convection-dominated transport. In this regime, the properties of the dispersion boundary layer and the values of the scaling exponents controlling the dependence of the moment hierarchy on the Péclet number are determined by the local near-wall behavior of the axial velocity. Specifically, different scaling laws in the behavior of the moment hierarchy occur, depending whether the cross-sectional boundary is smooth or nonsmooth (e.g., presenting corner points or cusps). This phenomenon marks the difference between the dispersion boundary layer and the thermal boundary layer in the classical Leveque problem. Analytical and numerical results are presented for typical channel cross sections in the Stokes regime.
Dynamic critical curve of a synthetic antiferromagnet
Authors: Pham Huy , Cimpoesu Dorin , Plamadă Andrei-Valentin , Stancu Alexandru , Spinu Leonard
Published: December 2009

In this letter, a dynamic generalization of static critical curves (sCCs) for synthetic antiferromagnet (SAF) structures is presented, analyzing the magnetization switching of SAF elements subjected to pulsed magnetic fields. The dependence of dynamic critical curves (dCCs) on field pulse’s shape and length, on damping, and on magnetostatic coupling is investigated. Comparing sCCs, which are currently used for studying the switching in toggle magnetic random access memories, with dCCs, it is shown that a consistent switching can be achieved only under specific conditions that take into account the dynamics of the systems. The study relies on the Landau–Lifshitz–Gilbert equation.
Single-molecule photon emission statistics for systems with explicit time dependence: Generating function approach
Authors: Peng Yonggang , Xie Shijie , Zheng Yujun , Brown Frank L. H.
Published: December 2009

Generating function calculations are extended to allow for laser pulse envelopes of arbitrary shape in numerical applications. We investigate photon emission statistics for two-level and V- and Λ-type three-level systems under time-dependent excitation. Applications relevant to electromagnetically induced transparency and photon emission from single quantum dots are presented.
Analytical energy gradient for reference interaction site model self-consistent field explicitly including spatial electron density distribution
Authors: Yokogawa Daisuke , Sato Hirofumi , Sakaki Shigeyoshi
Published: December 2009

Analytical energy gradient formula was derived for reference interaction site model self-consistent field explicitly including spatial electron density distribution (RISM-SCF-SEDD). RISM-SCF-SEDD is a combination method of ab initio electronic structure theory and statistical mechanics for molecular liquids [D. Yokogawa et al., J. Chem. Phys. 126, 244504 (2007)]. As shown previously, RISM-SCF-SEDD is numerically stable and has expanded the applicability of the solvation theory. The energy gradient is an indispensable tool to compute molecular geometry and its implementation further extends the capability of RISM-SCF-SEDD. The present method was applied to chemical systems in aqueous solution; hydration structure and geometry of phosphate anion PO43− and tautomerization between 2-pyridone and 2-hydroxypyridine. Compared to available experimental data, the present method correctly reproduced the geometries and relative energies of solvated molecules with microscopic solvent distribution. It is clearly shown that highly sophisticated quantum chemical calculation such as coupled cluster with single and double and perturbative triple excitations coupled with solvation effect is a powerful tool to accurately evaluate molecular properties.
Surface influenced magnetostructural transition in FeRh films
Authors: Kim J. W. , Ryan P. J. , Ding Y. , Lewis L. H. , Ali M. , Kinane C. J. , Hickey B. J. , Marrows C. H. , Arena D. A.
Published: December 2009

Surface structural effects accompanying the antiferromagnetic-ferromagnetic magnetostructral transition of epitaxial FeRh thin films were investigated by grazing incidence x-ray scattering. Measurement of the film lattice parameters and variation of x-ray incident angles allow observation of the transition character on scales ranging from a few nm to the total through-thickness of the film. Out-of-plane lattice measurements confirm that the ferromagnetic phase nucleates from the surface during the heating process and is retained at the surface below the transition temperature during the cooling process. These results suggest that surface strain relief fosters nucleation of the ferromagnetic phase.
Evaluations of pressure-transmitting media for cryogenic experiments with diamond anvil cell
Authors: Tateiwa Naoyuki , Haga Yoshinori
Published: December 2009

The fourteen kinds of pressure-transmitting media were evaluated by the ruby fluorescence method at room temperature, 77 K using the diamond anvil cell (DAC) up to 10 GPa in order to find appropriate media for use in low temperature physics. The investigated media are a 1:1 mixture by volume of Fluorinert FC-70 and FC-77, Daphne 7373 and 7474, NaCl, silicon oil (polydimethylsiloxane), Vaseline, 2-propanol, glycerin, a 1:1 mixture by volume of n-pentane and isopentane, a 4:1 mixture by volume of methanol and ethanol, petroleum ether, nitrogen, argon, and helium. The nonhydrostaticity of the pressure is discussed from the viewpoint of the broadening effect of the ruby R1 fluorescence line. The R1 line basically broadens above the liquid-solid transition pressure at room temperature. However, the nonhydrostatic effects do constantly develop in all the media from the low-pressure region at low temperature. The relative strength of the nonhydrostatic effects in the media at the low temperature region is discussed. The broadening effect of the ruby R1 line in the nitrogen, argon, and helium media are significantly small at 77 K, suggesting that the media are more appropriate for cryogenic experiments under high pressure up to 10 GPa with the DAC. The availability of the three media was also confirmed at 4.2 K.
Focused ion beam generated antimony nanowires for microscale pH sensors
Authors: Avdić A. , Lugstein A. , Schöndorfer C. , Bertagnolli E.
Published: December 2009

We demonstrate the formation of a complementary metal-oxide semiconductor compatible micro scale pH sensor with an antimony (Sb) nanowire network as the solid state pH electrode. The sensor is formed combining well known semiconductor processing techniques with a focused ion beam based approach inducing the self assembled formation of Sb nanowires in room temperature ambient without using any additional material source. The microscale pH sensor shows a highly linear relation in standardized pH buffer solutions with a sensitivity of 55.9 mV/pH and a very short response time of less than 8 s.
Size effect of nanometer vacuum gap thermionic power conversion device with CsI coated graphite electrodes
Authors: Lee Jeong Ik , Jeong Yong Hoon , No Hee-Cheon , Hannebauer Rob , Yoo Sang-Keun
Published: December 2009

Cesium iodide (CsI) coated graphite is a good candidate for an electrode material of a thermionic power generation device due to its low work function. In this letter, a thermionic device with a nanometer-scale vacuum gap between a CsI coated graphite emitter and a collector will be investigated while considering various gap-size effects. It is shown that a nanometer scale gap-size not only affects electron transport but also photon transport, and that all of these effects must be taken into account when estimating the device’s performance.