bluuebunny/crossref_metadata_2025 huggingface dataset:
Intermittency of passive-scalar decay: Strange eigenmodes in random shear flows
Authors: Vanneste J.
Published: September 2006

The decay of the concentration of a passive scalar released in a spatially periodic shear flow with random time dependence is examined. Periodic boundary conditions are assumed, placing the problem in the strange-eigenmode regime where the concentration decay is exponential in the long-time limit. The focus is on the limit of small diffusivity κ⪡1 (large Péclet number), which is studied using a combination of asymptotic methods and numerical simulations. Two specific flows are considered: both have a sinusoidal velocity profile, but the random function of time is either (i) the amplitude of the sinusoid or (ii) its phase. The behavior of the passive scalar in each flow is very different. The decay rate (or Lyapunov exponent) λ, in particular, which characterizes the long-time decay in almost all flow realizations, scales as κ2∕3 in (i) and κ3∕8 in (ii). The temporal intermittency of the scalar decay, associated with fluctuations in the speed of decay, is examined in detail. It is quantified by comparing the decay rate λ with the decay rates γp of the ensemble-averaged pth moment of the concentration. The two flows exhibit some intermittency, with γp≠pλ. It is, however, much weaker for flow (i), where the γp and λ satisfy κ2∕3 power laws, than for flow (ii), where the γp are proportional to κ1∕2 and are therefore asymptotically smaller than λ. The results for flow (ii) highlight the possible difficulty in relating the behavior of the passive scalar in single flow realizations to predictions made for ensemble-averaged quantities such as concentration moments.
Characteristics of liquid sheets formed by two impinging jets
Authors: Li Ri , Ashgriz Nasser
Published: September 2006

An experimental investigation of liquid sheets formed by the impingement of two capillary liquid jets is conducted. The breakup mechanism of the sheet is categorized into two main regimes and five subregimes based on the experimental observations. Two types of Reynolds numbers (jet Reynolds number and sheet Reynolds number) are introduced to correlate with and map the reported breakup regimes. Breakup length and width are introduced, and their analytical models are derived. Both the analytical and experimental results show that the breakup length and width are linearly proportional to the Weber number of individual jets in the case of closed-rim sheets. The slopes of the two linear relations are dependent on the impinging angle. The distribution of fluid velocity in the sheet is examined and found to be in disagreement with the assumption of early models, which claims uniform velocity across the sheet. The nonuniform distribution of fluid velocity in the sheet causes a discrepancy between analytically predicted sheet thickness and the experimental results reported in early works.
Intersecting hypersurfaces in anti-de Sitter and Lovelock gravity
Authors: Gravanis Elias , Willison Steven
Published: September 2006

Colliding and intersecting hypersurfaces filled with matter (membranes) are studied in the Lovelock higher order curvature theory of gravity. Lovelock terms couple hypersurfaces of different dimensionalities, extending the range of possible intersection configurations. We restrict the study to constant curvature membranes in constant curvature anti-de Sitter (AdS) and dS background and consider their general intersections. This illustrates some key features which make the theory different from the Einstein gravity. Higher co-dimension membranes may lie at the intersection of co-dimension one hypersurfaces in Lovelock gravity; the hypersurfaces are located at the discontinuities of the first derivative of the metric, and they need not carry matter. The example of colliding membranes shows that general solutions can only be supported by (spacelike) matter at the collision surface, thus naturally conflicting with the dominant energy condition (DEC). The imposition of the DEC gives selection rules on the types of collision allowed. When the hypersurfaces do not carry matter, one gets a solitonlike configuration. Then, at the intersection one has a co-dimension two or higher membrane standing alone in AdS-vacuum space–time without conical singularities. Another result is that if the number of intersecting hypersurfaces goes to infinity the limiting space–time is free of curvature singularities if the intersection is put at the boundary of each AdS bulk.
Growth of epitaxial p-type ZnO thin films by codoping of Ga and N
Authors: Kumar Manoj , Kim Tae-Hwan , Kim Sang-Sub , Lee Byung-Teak
Published: September 2006

Codoping of Ga and N was utilized to realize p-type conduction in ZnO films using rf magnetron sputtering. The films obtained at 550°C on sapphire showed resistivity and hole concentrations of 38Ωcm and 3.9×1017cm−3, respectively. ZnO films also showed a p-type behavior on p-Si with better electrical properties. ZnO homojunctions synthesized by in situ deposition of Ga–N codoped p-ZnO layer on Ga doped n-ZnO layer showed clear p-n diode characteristics. Low temperature photoluminescence spectra of codoped films also revealed a dominant peak at 3.12eV. The codoped films showed a dense columnar structure with a c-axis preferred orientation.
Single crystal Fe films grown on Ge (001) substrates by magnetron sputtering
Authors: Lou J. , Daigle A. , Chen L. , Wu Y. Q. , Harris V. G. , Vittoria C. , Sun N. X.
Published: September 2006

Single crystal Fe films were grown on Ge (001) substrates by using dc magnetron sputtering. It was found that the microstructures and magnetic properties of Fe films on Ge substrates were strongly dependent upon the substrate temperature during the deposition process. There existed a narrow substrate temperature window of 125±25°C for achieving single crystal Fe film on Ge. Lower substrate temperature led to polycrystalline Fe films due to limited mobility of Fe atoms, while higher substrate temperatures resulted in amorphous Fe–Ge alloy due to severe interdiffusion.
Equilibrium structures in partially ionized rotating plasmas within Hall magnetohydrodynamics
Authors: Krishan V. , Yoshida Z.
Published: September 2006

The formation of equilibrium structures in partially ionized rotating plasmas, consisting of electrons, ions, and neutral molecules, including the Hall effect, is studied in order to diagnose the possible velocity and the magnetic field configurations in a self-consistent manner. A few simple examples show that the linear and the nonlinear force-free magnetic configurations along with essentially nonlinear Beltrami flow field seem to be the general features of plasmas in the special case of the Keplerian rotation relevant for astrophysical plasmas. Thus rotation along with axial bipolar flows emerges as a natural pattern in gravitationally controlled magnetohydrodynamic systems. However, the equilibrium conditions permit more general flow and the magnetic field profiles that can perhaps be fully explored numerically. A special class of equilibria with unit magnetic Prandtl number and equal values of the fractional ion mass density α=ρi∕ρn and the Hall parameter ϵ=λi∕L exists where ρ’s are the uniform mass densities, λi is the ion inertial scale, and L is the scale of the equilibrium structure. An approximate scaling law between the ionization fraction and the scale of the structure is found. Further by expressing the not so well known ionization fraction in terms of the temperature of the system, assuming thermal equilibrium, relationships among the extensive parameters such as the scale, the neutral particle density, the flow velocity, the temperature, and the magnetic field of the equilibrium structure can be determined. There seems to be a good overlap between the Hall and the thermal equilibria. The validity of the neglect of the ion dynamics is discussed.
LANL2DZ basis sets recontracted in the framework of density functional theory
Authors: Chiodo S. , Russo N. , Sicilia E.
Published: September 2006

In this paper we report recontracted LANL2DZ basis sets for first-row transition metals. The valence-electron shell basis functions were recontracted using the PWP86 generalized gradient approximation functional and the hybrid B3LYP one. Starting from the original LANL2DZ basis sets a cyclic method was used in order to optimize variationally the contraction coefficients, while the contraction scheme was held fixed at the original one of the LANL2DZ basis functions. The performance of the recontracted basis sets was analyzed by direct comparison between calculated and experimental excitation and ionization energies. Results reported here compared with those obtained using the original basis sets show clearly an improvement in the reproduction of the corresponding experimental gaps.
Fast three-dimensional nanostructure fabrication by laser-assisted nanotransfer printing
Authors: Le Drogoff B. , Cui B. , Veres T.
Published: September 2006

The authors present a laser-assisted nanotransfer printing technique for transferring metal nanopatterns onto prepatterned substrates. A fused quartz mold covered with an array of chromium nanodots is pressed against the surface of a photolithographically patterned substrate, while a single laser pulse from a quadrupled-frequency solid state Nd:YAG laser is used to melt the thin metal structures. By controlling the laser fluence, selective metal pattern transfer can be realized only on the protruded area of the substrate upon separation of the quartz support. The transferred chromium nanodots are then used as an etch mask to pattern three-dimensional structures.
Effects of germanium and carbon coimplants on phosphorus diffusion in silicon
Authors: Ku K. C. , Nieh C. F. , Gong J. , Huang L. P. , Sheu Y. M. , Wang C. C. , Chen C. H. , Chang H. , Wang L. T. , Lee T. L. , Chen S. C. , Liang M. S.
Published: September 2006

The authors have studied the interactions between implant defects and phosphorus diffusion in crystalline silicon. Defect engineering enables ultrashallow n+∕p junction formation using phosphorus, carbon, and germanium coimplants, and spike anneal. Their experimental data suggest that the positioning of a preamorphized layer using germanium implants plays an important role in phosphorus diffusion. They find that extending the overlap of germanium preamorphization and carbon profiles results in greater reduction of phosphorus transient-enhanced diffusion by trapping more excess interstitials. This conclusion is consistent with the end-of-range defects calculated by Monte Carlo simulation and annealed carbon profiles.
Kinetic theory of electromagnetic ion waves in relativistic plasmas
Authors: Marklund Mattias , Shukla Padma K.
Published: September 2006

A kinetic theory for electromagnetic ion waves in a cold relativistic plasma is derived. The kinetic equation for the broadband electromagnetic ion waves is coupled to the slow density response via an acoustic equation driven by a ponderomotive force-like term linear in the electromagnetic field amplitude. The modulational instability growth rate is derived for an arbitrary spectrum of waves. The monochromatic and random phase cases are studied.
Comparative study of single and multiemissive layers in inverted white organic light-emitting devices
Authors: Chu Ta-Ya , Chen Jenn-Fang , Chen Szu-Yi , Chen Chin H.
Published: September 2006

The authors have fabricated and compared highly efficient inverted white organic light-emitting devices (WOLEDs) with a single emission layer (SEL) and with a multiemission layer (MEL). The efficiency levels of the WOLEDs with a SEL and a MEL achieved 13.0cd∕A, 10.6lm∕W and 11.3cd∕A, 7.3lm∕W, respectively. The projected half lifetime of a SEL device under an initial luminance of 400cd∕m2 is expected to be over 34000h, which is five times better than that of a MEL device of 6350h. The Commission International de l’Eclairage coordinates of a SEL device are not affected by aging.
Organic-inorganic telechelic molecules: Solution properties from simulations
Authors: Striolo Alberto , McCabe Clare , Cummings Peter T.
Published: September 2006

We report molecular dynamics simulations for telechelic molecules composed of two polyhedral oligomeric silsesquioxane (POSS) cages connected by one hydrocarbon backbone dissolved in liquid normal hexane. Silsesquioxanes are novel hybrid organic-inorganic molecules that are useful as building blocks for the synthesis of nanostructured materials. By including POSS molecules within a polymeric material it is possible to modify mechanical properties such as resistance to heat and glass transition temperatures. Unfortunately, the molecular mechanisms responsible for these enhancements are at present not completely understood. In an effort to elucidate the molecular phenomena responsible for these effects, we have studied the conformation of telechelic POSS molecules in solution, as well as their self-diffusion coefficients, as a function of the length of the hydrocarbon backbone. We focus on molecules in which the radius of gyration of the alkane backbone is comparable to the size of the silsesquioxane cages. Our results indicate that the backbone has a significant influence on both the equilibrium and the transport properties of dissolved telechelic hybrid molecules. These observations are useful for developing strategies to direct the self-assembly of nanostructured materials.
Effect of impurities on the fixed charge of nanoscale HfO2 films grown by atomic layer deposition
Authors: Sreenivasan Raghavasimhan , McIntyre Paul C. , Kim Hyoungsub , Saraswat Krishna C.
Published: September 2006

Hf O 2 films were grown by atomic layer deposition using two different precursor chemistries—HfCl4 and tetrakis(diethylamido)hafnium (TDEAH) with H2O as the oxidant. Electrical measurements on capacitor structures fabricated using the films showed a 0.4V positive shift in the flatband voltage for the chloride-HfO2 with respect to the amide-derived HfO2, indicating a considerable negative fixed charge in the dielectric. Secondary ion mass spectrometry depth profiles of the gate stack showed that Cl segregated preferentially at the HfO2∕SiO2 interface for chloride-derived HfO2. In situ vacuum anneals of the HfCl4-derived films at 500°C did not affect the profile, indicating that Cl is stably bonded at that interface. A similar analysis of the TDEAH-derived HfO2 showed very low concentrations of C, N, and H impurities. A positive fixed charge of +4.5×1011∕cm2 was extracted for the amide-HfO2 whereas a negative fixed charge of −1.86×1012∕cm2 was estimated for the chloride-HfO2. Thus, Cl incorporation can significantly alter both the magnitude and sign of the fixed charge in the HfO2∕SiO2∕Si gate stacks.
Predication of an ultrahigh filling fraction for K in CoSb3
Authors: Zhang W. , Shi X. , Mei Z. G. , Xu Y. , Chen L. D. , Yang J. , Meisner G. P.
Published: September 2006

The filling fraction limit (FFL) for potassium in skutterudite CoSb3 has been investigated by first-principles methods. The FFL is derived by minimizing the formation energy of a reaction that includes the formation of both the filled skutterudite KyCo4Sb12 and the potential secondary phases KSb and CoSb2 when doping K into CoSb3. Our calculations show that K has an ultrahigh filling fraction up to more than 60% in CoSb3, as compared with those of previously reported fillers such as Sr, Ba, Ca, La, Ce, Eu, and Yb [X. Shi et al., Phys. Rev. Lett. 95, 185503 (2005)]. The extent to which this affects the thermoelectric properties of K-filled skutterudites is discussed.
Enhanced kinetics of Al0.97Ga0.03As wet oxidation through the use of hydrogenation
Authors: Le Dû M. , Sagnes I. , Beaudoin G. , Travers L. , Esnault J.-C. , Harmand J.-C.
Published: September 2006

This letter reports on a different kinetic behavior of the wet thermal oxidation process resulting in AlxOy material depending on the AlAs material growth method, molecular beam epitaxy (MBE) or metal organic vapor phase epitaxy (MOVPE). A higher oxidation rate for MOVPE-grown materia is systemically found. Considering the major role of hydrogen in the wet oxidation reaction, it is believed this observation could be linked with the higher hydrogen residual concentration in MOVPE layers. Using a hydrogen plasma, MBE-grown Al0.97Ga0.03As layers were hydrogened prior to oxidation. This hydrogenated sample showed a ten times enhanced oxidation rate as compared to the nonhydrogenated Al0.97Ga0.03As sample. This behavior is mainly attributed to a hydrogen induced modification of the diffusion limited regime, enhancing the diffusion length of oxidizing species and reaction products in the oxidized layers.
Photoinduced charge dynamics on BaTiO3 (001) surface characterized by scanning probe microscopy
Authors: Shao Rui , Nikiforov Maxim P. , Bonnell Dawn A.
Published: September 2006

The surface potential of a multidomain BaTiO3 (001) surface was imaged in the presence and absence of ultraviolet (UV) illumination. The UV radiation induces a decrease in the surface potential contrast between c+ and c− domains with a time constant of a few seconds due to redistribution of photocarriers and screening. A slower process of recovery was observed after illumination. In addition, scanning a conducting atomic force microscopy tip in contact under UV illumination destabilizes some ferroelectric domains.
Cutting of carbon nanotubes assisted with oxygen gas inside a scanning electron microscope
Authors: Liu Pou , Arai Fumihito , Fukuda Toshio
Published: September 2006

The authors report a cutting technique for carbon nanotubes (CNTs) assisted by the presence of oxygen gas. The cutting procedure is conducted in less than 1min using a low-energy electron beam inside a scanning electron microscope. The oxygen gas was regulated by a mass flow controller and was injected at 1SCCM. It was found that although the total pressure inside the specimen chamber reached 10−2Pa, high-speed cutting occurred only in an area close to the oxygen gas nozzle. They assume that the CNTs are cut only under a low acceleration voltage since the CNT molecules are easily excited and ionized by the low-energy electron beam.
Universal scaling features of spectroscopic constants for diatomic systems
Authors: Xie Rui-Hua , Heaven Michael C.
Published: September 2006

Based on a new criterion that was proposed to search for the universality of spectroscopic constants for bound ground-state diatomics [R. H. Xie and P. S. Hsu, Phys. Rev. Lett. 96, 243201 (2006)], we have found universal scaling relations between spectroscopic constants of diatomic systems with s-, p-, and d-type valence-shell constituents. Our study suggests a useful empirical approach for the prediction of molecular spectroscopic constants.
Rovibrational photoionization dynamics of methyl and its isotopomers studied by high-resolution photoionization and photoelectron spectroscopy
Authors: Schulenburg A. M. , Alcaraz Ch. , Grassi G. , Merkt F.
Published: September 2006

High-resolution photoionization and pulsed-field-ionization zero-kinetic-energy photoelectron spectra of CH3, CH2D, CHD2, and CD3 have been recorded in the vicinity of the first adiabatic ionization threshold following single-photon excitation from the ground neutral state using a narrow-bandwidth vacuum-ultraviolet laser. The radicals were produced from the precursor molecules methyl-bromide, methyl-iodide, dimethyl-thioether, acetone, and nitromethane by 193nm excimer photolysis in a quartz capillary and were subsequently cooled to a rotational temperature Trot≈30K in a supersonic expansion. Nitromethane was identified as a particularly suitable photolytic precursor of methyl for studies by photoionization and threshold photoelectron spectroscopy. Thanks to the cold rotational temperature reached in the supersonic expansion, the rotational structure of the threshold ionization spectra could be resolved, and the photoionization dynamics investigated. Rydberg series converging on excited rotational levels of CH3+ could be observed in the range of principal quantum number n=30–50, and both rotational autoionization and predissociation were identified as decay processes in the threshold region. The observed photoionization transitions can be understood in the realm of an orbital model for direct ionization but the intensity distributions can only be fully accounted for if the rotational channel interactions mediated by the quadrupole of the cation are considered. Improved values of the adiabatic ionization thresholds were derived for all isotopomers [CH3: 79356.2(15)cm−1, CH2D: 79338.8(15)cm−1, CHD2: 79319.1(15)cm−1, and CD3: 79296.4(15)cm−1].
Formation and photoluminescent properties of embedded ZnO quantum dots in ZnO∕ZnMgO multiple-quantum-well-structured nanorods
Authors: Kim Chinkyo , Park Won Il , Yi Gyu-Chul , Kim Miyoung
Published: September 2006

Zn O ∕ Zn 0.8 Mg 0.2 O multiple-quantum-well (MQW) nanorods with a different number of periods and well widths were grown by catalyst-free metal-organic vapor phase epitaxy. Their optical and structural characteristics were investigated using photoluminescence, transmission electron microscopy, and field emission scanning electron microscopy. Unlike ZnO∕ZnMgO MQW thin films, it was observed that embedded quantum dots played a more important role in the optical characteristics of ZnO∕ZnMgO MQW nanorods than quantum confined Stark effect due to polarization field.
Three-dimensional stereoscopy of Yukawa (Coulomb) balls in dusty plasmas
Authors: Käding Sebastian , Melzer André
Published: September 2006

A stereoscopic approach with standard video cameras for positioning and tracking of micrometer sized polymer particles in a radio-frequency gas discharge is presented. The stereoscopy is applied to simultaneously determine the positions of all particles in a three-dimensional strongly coupled spherical dusty plasma (Yukawa ball). The accuracy of the stereoscopic method is discussed. The shell structure and the occupation number of various Yukawa balls are determined and compared to recent simulations and models.
Phoretic nest parasites use sexual deception to obtain transport to their host's nest
Authors: Saul-Gershenz Leslie S. , Millar Jocelyn G.
Published: September 2006

Cooperative behaviors are common among social insects such as bees, wasps, ants, and termites, but they have not been reported from insect species that use aggressive mimicry to manipulate and exploit prey or hosts. Here we show that larval aggregations of the blister beetle
Meloe franciscanus
, which parasitize nests of the solitary bee
Habropoda pallida
, cooperate to exploit the sexual communication system of their hosts by producing a chemical cue that mimics the sex pheromone of the female bee. Male bees are lured to larval aggregations, and upon contact (pseudocopulation) the beetle larvae attach to the male bees. The larvae transfer to female bees during mating and subsequently are transported to the nests of their hosts. To mimic the chemical and visual signals of female bees effectively, the parasite larvae must cooperate, emphasizing the adaptive value of cooperation between larvae. The aggressive chemical mimicry by the beetle larvae and their subsequent transport to their hosts' nests by the hosts themselves provide an efficient solution to the problem of locating a critical but scarce resource in a harsh environment.
PKA-activated ApAF–ApC/EBP heterodimer is a key downstream effector of ApCREB and is necessary and sufficient for the consolidation of long-term facilitation
Authors: Lee Jin-A , Lee Sue-Hyun , Lee Changhoon , Chang Deok-Jin , Lee Yong , Kim Hyoung , Cheang Ye-Hwang , Ko Hyoung-Gon , Lee Yong-Seok , Jun Heejung , Bartsch Dusan , Kandel Eric R. , Kaang Bong-Kiun
Published: September 2006

Long-term memory requires transcriptional regulation by a combination of positive and negative transcription factors. Aplysia activating factor (ApAF) is known to be a positive transcription factor that forms heterodimers with ApC/EBP and ApCREB2. How these heterodimers are regulated and how they participate in the consolidation of long-term facilitation (LTF) has not, however, been characterized. We found that the functional activation of ApAF required phosphorylation of ApAF by PKA on Ser-266. In addition, ApAF lowered the threshold of LTF by forming a heterodimer with ApCREB2. Moreover, once activated by PKA, the ApAF–ApC/EBP heterodimer transactivates enhancer response element–containing genes and can induce LTF in the absence of CRE- and CREB-mediated gene expression. Collectively, these results suggest that PKA-activated ApAF–ApC/EBP heterodimer is a core downstream effector of ApCREB in the consolidation of LTF.
Direct measurement of the lamellipodial protrusive force in a migrating cell
Authors: Prass Marcus , Jacobson Ken , Mogilner Alex , Radmacher Manfred
Published: September 2006

There has been a great deal of interest in the mechanism of lamellipodial protrusion (Pollard, T., and G. Borisy. 2003. Cell. 112:453–465). However, one of this mechanism's endpoints, the force of protrusion, has never been directly measured. We place an atomic force microscopy cantilever in the path of a migrating keratocyte. The deflection of the cantilever, which occurs over a period of ∼10 s, provides a direct measure of the force exerted by the lamellipodial leading edge. Stall forces are consistent with ∼100 polymerizing actin filaments per micrometer of the leading edge, each working as an elastic Brownian ratchet and generating a force of several piconewtons. However, the force-velocity curves obtained from this measurement, in which velocity drops sharply under very small loads, is not sensitive to low loading forces, and finally stalls rapidly at large loads, are not consistent with current theoretical models for the actin polymerization force. Rather, the curves indicate that the protrusive force generation is a complex multiphase process involving actin and adhesion dynamics.
Ca2+ store depletion causes STIM1 to accumulate in ER regions closely associated with the plasma membrane
Authors: Wu Minnie M. , Buchanan JoAnn , Luik Riina M. , Lewis Richard S.
Published: September 2006

Stromal interacting molecule 1 (STIM1), reported to be an endoplasmic reticulum (ER) Ca2+ sensor controlling store-operated Ca2+ entry, redistributes from a diffuse ER localization into puncta at the cell periphery after store depletion. STIM1 redistribution is proposed to be necessary for Ca2+ release–activated Ca2+ (CRAC) channel activation, but it is unclear whether redistribution is rapid enough to play a causal role. Furthermore, the location of STIM1 puncta is uncertain, with recent reports supporting retention in the ER as well as insertion into the plasma membrane (PM). Using total internal reflection fluorescence (TIRF) microscopy and patch-clamp recording from single Jurkat cells, we show that STIM1 puncta form several seconds before CRAC channels open, supporting a causal role in channel activation. Fluorescence quenching and electron microscopy analysis reveal that puncta correspond to STIM1 accumulation in discrete subregions of junctional ER located 10–25 nm from the PM, without detectable insertion of STIM1 into the PM. Roughly one third of these ER–PM contacts form in response to store depletion. These studies identify an ER structure underlying store-operated Ca2+ entry, whose extreme proximity to the PM may enable STIM1 to interact with CRAC channels or associated proteins.
The elementary unit of store-operated Ca2+ entry: local activation of CRAC channels by STIM1 at ER–plasma membrane junctions
Authors: Luik Riina M. , Wu Minnie M. , Buchanan JoAnn , Lewis Richard S.
Published: September 2006

The activation of store-operated Ca2+ entry by Ca2+ store depletion has long been hypothesized to occur via local interactions of the endoplasmic reticulum (ER) and plasma membrane, but the structure involved has never been identified. Store depletion causes the ER Ca2+ sensor stromal interacting molecule 1 (STIM1) to form puncta by accumulating in junctional ER located 10–25 nm from the plasma membrane (see Wu et al. on p. 803 of this issue). We have combined total internal reflection fluorescence (TIRF) microscopy and patch-clamp recording to localize STIM1 and sites of Ca2+ influx through open Ca2+ release–activated Ca2+ (CRAC) channels in Jurkat T cells after store depletion. CRAC channels open only in the immediate vicinity of STIM1 puncta, restricting Ca2+ entry to discrete sites comprising a small fraction of the cell surface. Orai1, an essential component of the CRAC channel, colocalizes with STIM1 after store depletion, providing a physical basis for the local activation of Ca2+ influx. These studies reveal for the first time that STIM1 and Orai1 move in a coordinated fashion to form closely apposed clusters in the ER and plasma membranes, thereby creating the elementary unit of store-operated Ca2+ entry.
Mouse Emi2 is required to enter meiosis II by reestablishing cyclin B1 during interkinesis
Authors: Madgwick Suzanne , Hansen David V. , Levasseur Mark , Jackson Peter K. , Jones Keith T.
Published: September 2006

During interkinesis, a metaphase II (MetII) spindle is built immediately after the completion of meiosis I. Oocytes then remain MetII arrested until fertilization. In mouse, we find that early mitotic inhibitor 2 (Emi2), which is an anaphase-promoting complex inhibitor, is involved in both the establishment and the maintenance of MetII arrest. In MetII oocytes, Emi2 needs to be degraded for oocytes to exit meiosis, and such degradation, as visualized by fluorescent protein tagging, occurred tens of minutes ahead of cyclin B1.

Emi2 antisense morpholino knockdown during oocyte maturation did not affect polar body (PB) extrusion. However, in interkinesis the central spindle microtubules from meiosis I persisted for a short time, and a MetII spindle failed to assemble. The chromatin in the oocyte quickly decondensed and a nucleus formed. All of these effects were caused by the essential role of Emi2 in stabilizing cyclin B1 after the first PB extrusion because in Emi2 knockdown oocytes a MetII spindle was recovered by Emi2 rescue or by expression of nondegradable cyclin B1 after meiosis I.
A hitchhiker's guide to survival finally makes CENs
Authors: Malik Harmit S.
Published: September 2006

Most strains of the yeast Saccharomyces cerevisiae contain many copies of a 2-μm plasmid, a selfish autonomously replicating DNA that relies on two different mechanisms to ensure its survival. One of these mechanisms involves the high fidelity segregation of the plasmids to daughter cells during cell division, a property that is starkly reminiscent of centromeres. A new study reported in this issue (see Hajra et al. on p. 779) demonstrates that this high fidelity is achieved by the 2-μm plasmid, effectively recruiting the centromeric histone Cse4 from its host yeast cell to forge its own centromere and finally revealing how the 2-μm plasmid has survived in budding yeasts over millions of years.
An observational study of practice during transfer of patients from anaesthetic room to operating theatre*
Authors: Broom M. A. , Slater J. , Ure D. S.
Published: September 2006

We observed practice during transfer of 80 patients from anaesthetic room to operating theatre, to determine the duration of apnoea and the time without monitoring during the transfer process. Median (IQR [range]) time from disconnection of the breathing system in the anaesthetic room to the first breath in theatre was 54 (44–65 [27–196]) s, and from disconnection of the pulse oximetry probe to the first reading in theatre was 90 (74–103 [44–182]) s. In four patients (5%) arterial oxygen saturation fell to 94%, with the greatest desaturation observed 11%. The transfer process may represent a window of opportunity for the occurrence of harm or the first step in a chain of events leading to harm, and is difficult to justify on patient safety grounds.
Peri‐operative trans‐oesophageal echocardiography and nitric oxide during general anaesthesia in a patient with Eisenmenger's syndrome
Authors: Bouch D. C. , Allsager C. M. , Moore N.
Published: September 2006

We describe the peri‐operative care of a patient with Eisenmenger's syndrome presenting for laparotomy. These patients require techniques to prevent the potential increase in intracardiac shunt caused by anaesthesia, by minimising increases in pulmonary artery pressure and reductions in systemic vascular resistance. The successful use of combined epidural and general anaesthesia with elective use of inhaled nitric oxide as a pulmonary vasodilator, and intra‐operative trans‐oesophageal echocardiography is described.
Hereditary neuropathy with liability to pressure palsies and anaesthesia: peri‐operative nerve injury
Authors: Wijayasiri L. , Batas D. , Quiney N.
Published: September 2006

A 43‐year‐old female with carcinoma of the left breast underwent wide local excision of the tumour and sentinel lymph node biopsy under general anaesthesia. Three lymph nodes were removed uneventfully during the operation. Postoperatively, the patient complained of weakness and decreased sensation of her left arm. A diagnosis of peri‐operative neuropraxia was made. This resolved completely over the following 4 weeks. Genetic testing confirmed a diagnosis of hereditary neuropathy with liability to pressure palsies.
Touch sensitivity with sterile standard surgical gloves and single‐use protective gloves
Authors: Tiefenthaler W. , Gimpl S. , Wechselberger G. , Benzer A.
Published: September 2006

The purpose of this study was to evaluate touch sensitivity and static two‐point discrimination of the dominant index and middle finger in 20 anaesthetists wearing no gloves, single‐use protective gloves or sterile standard surgical gloves. Semmes‐Weinstein filaments were used to measure cutaneous pressure thresholds, and a Two‐Point‐Discriminator to estimate static two‐point discrimination. Wearing gloves significantly reduced touch sensitivity (p < 0.01), but not two‐point discrimination. No difference in touch sensitivity or two‐point discrimination was found between different types of gloves. The results of our study suggest that the additional cost of sterile standard surgical gloves can not be justified in terms of touch sensitivity.
A national survey of intensive care follow‐up clinics
Authors: Griffiths J. A. , Barber V. S. , Cuthbertson B. H. , Young J. D.
Published: September 2006

Intensive care follow‐up clinics allow extended review of survivors of critical illness. However, the current provision of intensive care follow‐up clinics in the UK is unknown. We performed a survey of intensive care follow‐up clinic practice in the UK. A questionnaire was sent to 298 intensive care units in the UK to determine the number of follow‐up clinics and details of current follow‐up practice. Responses were received from 266 intensive care units, an 89% response rate. Eighty units (30%) ran a follow‐up clinic. Only 47 (59%) of these clinics were funded. Of those intensive care units without a follow‐up clinic, 158 (88%) cited ‘financial constraints’ as the reason. Over half of the follow‐up clinics (44 clinics, 55%) were nurse‐led, and the majority (56 clinics, 77%) only routinely review patients treated on the intensive care unit for 3 or 4 days or longer. Nearly half of the follow‐up clinics (39 clinics, 49%) have pre‐negotiated access to at least one other out‐patient service.
Target ranges and the apparent compliance with tight glycaemic control
Authors: Bone E. G. , Young D. , Chantler J.
Published: September 2006

We performed a retrospective audit of blood glucose control after introducing a new protocol for insulin infusion. The audit showed a sustained reduction in the median blood glucose, which decreased from 7.0 to 6.8 mmol.l−1, primarily because of a reduction in the proportion of values above 6 mmol.l−1. When we examined the proportion of readings with previously published ‘acceptable’ ranges we found that small, probably clinically insignificant, changes in the accepted range have a major effect on apparent compliance with glycaemic control. This is because a large number of results fall within a narrow range of values. As a result there is a nearly 2.5‐fold difference in compliance for a change in the upper limit of the target range of just 2.2 mmol.l−1. Different target ranges have been recommended for tight glycaemic control. When comparing compliance with tight glycaemic control between intensive care units, target ranges should be identical.
The MLL partial tandem duplication in acute myeloid leukaemia
Authors: Basecke Jorg , Whelan Jarrett T. , Griesinger Frank , Bertrand Fred E.
Published: September 2006

Mixed lineage leukaemia gene‐partial tandem duplications (MLL‐PTD) characterise acute myeloid leukaemia (AML) with trisomy 11 and AML with a normal karyotype. MLL‐PTD confer a worse prognosis with shortened overall and event free survival in childhood and adult AML. In spite of these clinical observations, the leukaemogenic mechanism has, so far, not been determined. This review summarises clinical studies on MLL‐PTD positive AML and recent experimental findings on the putative leukaemogenic role of MLL‐PTD.
Harsh summer conditions caused structural and specific functional changes of microbial communities in an arable soil
Authors: Levy W. , Radl V. , Ruth B. , Schmid M. , Munch J. C. , Schroll R.
Published: September 2006

The mineralization of the herbicide 3‐(4‐isopropylphenyl)‐1,1‐dimethylurea (isoproturon) was reduced after the dry and hot summer 2003 in a soil profile placed in a field lysimeter. A different isoproturon mineralization pattern remained in soil material taken at two different soil depths (0–5 cm and 15–20 cm), although soil material was re‐equilibrated at adequate climatic conditions. Special soil microcosms were designed to determine if the changes in this special soil function ‘isoproturon mineralization’ were related to the climatic scenario of summer 2003. These microcosms were filled with lysimeter soil from the 15–20 cm depth and the temperature and dryness of summer 2003 were simulated. Afterwards, soil samples were taken from the microcosms and re‐equilibrated under controlled conditions for 4 weeks. Subsequently, isoproturon mineralization was investigated. The soil microbial community reduced drastically its original capability of isoproturon mineralization in the course of the model experiments.

Analysis of 16S‐rRNA by denaturing gel gradient electrophoresis (DGGE) revealed substantial differences in the band patterns of the bacterial communities from both depths of the field lysimeter soil and from the soil incubated in microcosms. The different soil microbial biomass determined by microcalorimetry reinforced these results. In conclusion, the factors higher temperature and smaller soil moisture content generated important and enduring changes in the microbial community structure and therefore in specific soil functions of the community, as shown here by the function of isoproturon degradation. Results are discussed in connection with environmental conditions and conservation tillage.
Enriched stable isotopes for determining the isotopically exchangeable element content in soils
Authors: Gäbler H.‐E. , Bahr A. , Heidkamp A. , Utermann J.
Published: September 2006

The proportion of metals in soils in equilibrium with soil solution can be determined using isotopic dilution. For this purpose, an isotope dilution mass spectrometric (IDMS) technique has been applied for the elements Cd, Cr, Cu, Mo, Ni, Pb, Tl and Zn. Conventionally, sorbed amounts of heavy metals in soils are analysed by ethylenediamine tetra‐acetic acid (EDTA) extraction. The IDMS technique and EDTA extraction were both applied to 115 soil samples and compared. For Cd, Cu, Ni, Pb and Zn, the results of the IDMS technique correlated well with the results of EDTA extractions (rs(Cd) = 0.965, rs(Cu) = 0.916, rs(Ni) = 0.878, rs(Pb) = 0.922, rs(Zn) = 0.962; all at P < 0.001). For Cd and Zn, no significant differences between the results of both methods could be observed, which suggests that EDTA and IDMS determined the same pool. EDTA extracted more Cu, Ni and Pb than was determined by IDMS (7, 26 and 13%, respectively). The correlation between EDTA extraction and IDMS for Cr was significant but weak (rs(Cr) = 0.361). For Tl and Mo, EDTA extraction and IDMS did not correlate, and IDMS yielded larger concentrations than EDTA. This can be explained by the fact that Tl and Mo do not form stable EDTA complexes, which are essential for the EDTA technique. Recovery experiments demonstrated that added Cd, Cu, Mo, Ni, Pb, Tl and Zn could be recovered successfully by IDMS analysis (mean recovery = 103 ± 9%). Adsorption isotherms for soil samples were determined for Tl, thereby demonstrating that IDMS gave a better estimation of the native content of sorbed Tl in soils than EDTA extraction.
Autogenous transplantation of teeth with complete root formation: two case reports
Authors: Teixeira C. S. , Pasternak B. , Vansan L. P. , Sousa‐Neto M. D.
Published: September 2006

Aim  Autotransplantation is an alternative treatment for replacing lost teeth when suitable donor teeth are available. This paper presents two cases of successful autogenous tooth transplantation.

Summary  Two third molars with complete root development were autogenously transplanted from their original sockets into new recipient sites on the same side of the mouth, one in the maxilla and one in the mandible. In both cases, the third molars were transplanted immediately after the first molar extractions. To provide better adaptation of the donor teeth, the recipient alveolar sites were remodelled using surgical burs. Semi‐rigid splints were maintained for 45 and 15 days, respectively. Root canal treatment commenced one a week after transplantation and the canals were medicated with a calcium hydroxide paste before they were filled. Clinical and radiographic findings after 5 and 3 years of follow‐up, respectively, are discussed in relation to the literature.

Key learning points

• Autogenous transplantation of teeth with complete root formation may be considered as a viable treatment option to conventional prosthetic and implant rehabilitation for both therapeutic and economic reasons.

• Careful surgical and endodontic procedure, together with careful case selection may lead to satisfactory aesthetic and functional outcomes.
Effect of bonded restorations on the fracture resistance of root filled teeth
Authors: Sagsen B. , Aslan B.
Published: September 2006

Aim  To evaluate the fracture resistance of root filled maxillary premolars restored with different techniques.

Methodology  One hundred and twenty single‐rooted maxillary premolar teeth were divided randomly into six groups of 20 teeth and subjected to the following procedures: group 1: intact teeth. Group 2: endodontic access cavities prepared. Group 3: MOD cavities were prepared, root canals were filled and no restoration was placed. Group 4: teeth were prepared as group 3 and restored conventionally with amalgam. Group 5: teeth were prepared as group 3 and restored with amalgam using a bonding material. Group 6: teeth were prepared as group 3 and restored with composite resin using the same bonding material. Teeth were embedded in acrylic resin and the loads for fracture strength were applied vertically with a constant speed of 1 mm min−1. Data were evaluated statistically with anova and Tukey's tests.

Results  The mean force of fracture values were 1191.41, 599.86, 233.03, 494.72, 962.81 and 856.48 N for groups 1, 2, 3, 4, 5 and 6, respectively. The fracture resistance of group 5 was similar to group 1 (P > 0.05). The mean force at fracture of group 5 and group 6 was not significantly different. The fracture resistance of groups 5 and 6 was significantly higher than group 4 (P < 0.001).

Conclusions  The group, restored with conventional amalgam, had the weakest resistance to fracture when compared with the bonded restorations. No statistically significant differences were found between the bonded amalgam and composite resin groups.
A probability‐based analysis of temporal and spatial co‐occurrence in grassland birds
Authors: Veech Joseph A.
Published: September 2006

Aim  To test for non‐random co‐occurrence in 36 species of grassland birds using a new metric and the C‐score. The analysis used presence–absence data of birds distributed among 305 sites (or landscapes) over a period of 35 years. This analysis departs from traditional analyses of species co‐occurrence in its use of temporal data and of individual species’ probabilities of occurrence to derive analytically the expected co‐occurrence between paired species.

Location  Great Plains region, USA.

Methods  Presence–absence data for the bird species were obtained from the North American Breeding Bird Survey. The analysis was restricted to species pairs whose geographic ranges overlapped. Each of 541 species pairs was classified as a positive, negative, or non‐significant association depending on the mean difference between the observed and expected frequencies of co‐occurrence over the 35‐year time‐span.

Results  Of the 541 species pairs that were examined, 202 to 293 (37–54%) were positively associated, depending on which of two null models was used. However, only a few species pairs (<5%) were negatively associated. An additional 89 species pairs did not have overlapping ranges and hence represented de facto negative associations. The results from analyses based on C‐scores generally agreed with the analyses based on the difference between observed and expected co‐occurrence, although the latter analyses were slightly more powerful.

Main conclusions  Grassland birds within the Great Plains region are primarily distributed among landscapes either independently or in conjunction with one another. Only a few species pairs exhibited repulsed or segregated distributions. This indicates that the shared preference for grassland habitat may be more important in producing coexistence than are negative species interactions in preventing it. The large number of non‐significant associations may represent random associations and thereby indicate that the presence/absence of other grassland bird species may have little effect on whether a given focal species is also found within the landscape. In a broader context, the probability‐based approach used in this study may be useful in future studies of species co‐occurrence.
Changes in distribution of an archaic moth, Micropterix calthella, in St Petersburg, Russia, between 1989 and 2005
Authors: Kozlov Mikhail V.
Published: September 2006

Aim  This work aimed to assess changes in the number of suitable habitats and habitat occupancy by Micropterix calthella (L.) moths (Lepidoptera, Micropterigidae) in the city of St Petersburg between 1989 and 2005.

Location  The city of St Petersburg, Russia.

Methods  The study compares results of the survey conducted on 9–12 June 2005 with data collected in 1989 and is based on the assessment of the quality and occupancy of 103 habitats that were found potentially suitable for M. calthella in 1989. If habitats contained wet microsites with undisturbed litter and dense field layer vegetation with a high abundance of flowering Ranunculus sp., they were considered potentially suitable for M. calthella; in these habitats, moths were searched for on flowers of Ranunculus– visually and/or by extensive sweep‐netting.

Results  Both the number of habitats suitable for M. calthella and the number of habitats occupied by this species decreased since 1986 from 103 to 72 and from 58 to 34, respectively. The disappearance of habitats was primarily due to the building of residential blocks within the city (16 sites) and railway renovation (10 sites), while changes in habitat management, primarily in parks and recreation zones (five sites), were less important. The average distance from the city centre to the nearest population of M. calthella increased from 8.7 ± 1.5 to 12.9 ± 3.0 km (mean ± SE).

Main conclusion  The data for 2005 fit the prediction that M. calthella moths, which are unable to re‐colonize potentially suitable habitats due to their low migratory ability, will disappear from the city. At the present rate of extinction, this process may take some 20–30 years to complete (or nearly complete).