Optical guiding in meter-scale plasma waveguides

We demonstrate a new highly tunable technique for generating meter-scale low density plasma waveguides. Such guides can enable electron acceleration to tens of GeV in a single stage. Plasma waveguides are imprinted in hydrogen gas by optical field ionization induced by two time-separated Bessel beam pulses: The first pulse, a J_0 beam, generates the core of the waveguide, while the delayed second pulse, here a J_8 or J_16 beam, generates the waveguide cladding. We demonstrate guiding of intense laser pulses over hundreds of Rayleigh lengths with on axis plasma densities as low as N_e0=5x10^16 cm^-3

Changing Fitness Consequences of Hsp70 Copy Number in Transgenic Drosophila Larvae Undergoing Natural Thermal Stress

1. Transgenic Manipulation of the Gene Copy Number of Hsp70, Which Encodes the Major Inducible Heat-Shock Protein of Drosophila Melanogaster (Hsp70), Affects Both Hsp70 Levels and Inducible Thermotolerance in the Laboratory; Here Parallel Effects in Transgenic Drosophila Larvae Undergoing Natural or Simulated Natural Thermal Stress Are Demonstrated. 2. Necrotic Fruit Was Infested with Larvae of Either of Two Transgenic Strains, One Transformed with 12 Extra Copies of the Hsp70 Gene (Extra-Copy Strain) and a Sister Strain Possessing Only the Wild-Type Number (10) of Hsp70 Genes (Excision Strain), and Then Allowed to Heat to Variable Extents. 3. as the Intensity of Thermal Stress Increased, the Consequences of Extra Hsp70 Copies Reversed. after No or Moderate Thermal Stress, Excision Larvae Survived Better Than Did Extra Copy Larvae. by Contrast, Extra Copy Larvae Tolerated Intense Hyperthermia Better Than Did Excision Larvae. 4. These Results Establish that the Hsp70-Mediated Enhancement of Stress Tolerance, Previously Demonstrated Only for Artificial Stress Regimes in the Laboratory, Extends to Natural Stress Regimes. 5. Mortality Due to overexpression of Hsp70, However, Also Increases under Mild Natural Stress Regimes, Buttressing the Ecological Relevance of a Hypothesized Evolutionary Trade-Off of the Benefits and Adverse Consequences of Hsp70 Expression

New universality class for the three-dimensional XY model with correlated impurities: Application to 4^4He in aerogels

Encouraged by experiments on $^4$He in aerogels, we confine planar spins in the pores of simulated aerogels (diffusion limited cluster-cluster aggregation) in order to study the effect of quenched disorder on the critical behavior of the three-dimensional XY model. Monte Carlo simulations and finite-size scaling are used to determine critical couplings $K_c$ and exponents. In agreement with experiments, clear evidence of change in the thermal critical exponents $\nu$ and $\alpha$ is found at nonzero volume fractions of impurities. These changes are explained in terms of {\it hidden} long-range correlations within disorder distributions.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let

Extended microsatellite analysis in microsatellite stable, MSH2 and MLH1 mutation-negative HNPCC patients: Genetic reclassification and correlation with clinical features

Background: Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant disorder predisposing to predominantly colorectal cancer (CRC) and endometrial cancer frequently due to germline mutations in DNA mismatch repair (MMR) genes, mainly MLH1, MSH2 and also MSH6 in families seen to demonstrate an excess of endometrial cancer. As a consequence, tumors in HNPCC reveal alterations in the length of simple repetitive genomic sequences like poly-A, poly-T, CA or GT repeats (microsatellites) in at least 90% of the cases. Aim of the Study: The study cohort consisted of 25 HNPCC index patients ( 19 Amsterdam positive, 6 Bethesda positive) who revealed a microsatellite stable (MSS) - or low instable (MSI-L) - tumor phenotype with negative mutation analysis for the MMR genes MLH1 and MSH2. An extended marker panel (BAT40, D10S197, D13S153, D18S58, MYCL1) was analyzed for the tumors of these patients with regard to three aspects. First, to reconfirm the MSI-L phenotype found by the standard panel; second, to find minor MSIs which might point towards an MSH6 mutation, and third, to reconfirm the MSS status of hereditary tumors. The reconfirmation of the MSS status of tumors not caused by mutations in the MMR genes should allow one to define another entity of hereditary CRC. Their clinical features were compared with those of 150 patients with sporadic CRCs. Results: In this way, 17 MSS and 8 MSI-L tumors were reclassified as 5 MSS, 18 MSI-L and even 2 MSI-H ( high instability) tumors, the last being seen to demonstrate at least 4 instable markers out of 10. Among all family members, 87 malignancies were documented. The mean age of onset for CRCs was the lowest in the MSI-H-phenotyped patients with 40.5 +/- 4.9 years (vs. 47.0 +/- 14.6 and 49.8 +/- 11.9 years in MSI-L- and MSS-phenotyped patients, respectively). The percentage of CRC was the highest in families with MSS-phenotyped tumors (88%), followed by MSI-L-phenotyped ( 78%) and then by MSI-H-phenotyped (67%) tumors. MSS tumors were preferentially localized in the distal colon supposing a similar biologic behavior like sporadic CRC. MSH6 mutation analysis for the MSI-L and MSI-H patients revealed one truncating mutation for a patient initially with an MSS tumor, which was reclassified as MSI-L by analyzing the extended marker panel. Conclusion: Extended microsatellite analysis serves to evaluate the sensitivity of the reference panel for HNPCC detection and permits phenotype confirmation or upgrading. Additionally, it confirms the MSS status of hereditary CRCs not caused by the common mutations in the MMR genes and provides hints to another entity of hereditary CRC. Copyright (C) 2004 S. Karger AG, Basel

Single-qubit unitary gates by graph scattering

We consider the effects of plane-wave states scattering off finite graphs, as an approach to implementing single-qubit unitary operations within the continuous-time quantum walk framework of universal quantum computation. Four semi-infinite tails are attached at arbitrary points of a given graph, representing the input and output registers of a single qubit. For a range of momentum eigenstates, we enumerate all of the graphs with up to $n=9$ vertices for which the scattering implements a single-qubit gate. As $n$ increases, the number of new unitary operations increases exponentially, and for $n>6$ the majority correspond to rotations about axes distributed roughly uniformly across the Bloch sphere. Rotations by both rational and irrational multiples of $\pi$ are found.Comment: 8 pages, 7 figure

Stretched exponentials and power laws in granular avalanching

We introduce a model for granular avalanching which exhibits both stretched exponential and power law avalanching over its parameter range. Two modes of transport are incorporated, a rolling layer consisting of individual particles and the overdamped, sliding motion of particle clusters. The crossover in behaviour observed in experiments on piles of rice is attributed to a change in the dominant mode of transport. We predict that power law avalanching will be observed whenever surface flow is dominated by clustered motion. Comment: 8 pages, more concise and some points clarified

On retracts, absolute retracts, and folds in cographs

Let G and H be two cographs. We show that the problem to determine whether H is a retract of G is NP-complete. We show that this problem is fixed-parameter tractable when parameterized by the size of H. When restricted to the class of threshold graphs or to the class of trivially perfect graphs, the problem becomes tractable in polynomial time. The problem is also soluble when one cograph is given as an induced subgraph of the other. We characterize absolute retracts of cographs.Comment: 15 page

Shape deformations and angular momentum transfer in trapped Bose-Einstein condensates

Angular momentum can be transferred to a trapped Bose-Einstein condensate by distorting its shape with an external rotating field, provided the rotational frequency is larger than a critical frequency fixed by the energy and angular momentum of the excited states of the system. By using the Gross-Pitaevskii equation and sum rules, we explore the dependence of such a critical frequency on the multipolarity of the excitations and the asymmetry of the confining potential. We also discuss its possible relevance for vortex nucleation in rotating traps.Comment: 4 pages revtex, 2 figures include

Distinguishing cancerous from non-cancerous cells through analysis of electrical noise

Since 1984, electric cell-substrate impedance sensing (ECIS) has been used to monitor cell behavior in tissue culture and has proven sensitive to cell morphological changes and cell motility. We have taken ECIS measurements on several cultures of non-cancerous (HOSE) and cancerous (SKOV) human ovarian surface epithelial cells. By analyzing the noise in real and imaginary electrical impedance, we demonstrate that it is possible to distinguish the two cell types purely from signatures of their electrical noise. Our measures include power-spectral exponents, Hurst and detrended fluctuation analysis, and estimates of correlation time; principal-component analysis combines all the measures. The noise from both cancerous and non-cancerous cultures shows correlations on many time scales, but these correlations are stronger for the non-cancerous cells.Comment: 8 pages, 4 figures; submitted to PR

Changes in Thermotolerance and Hsp70 Expression with Domestication in Drosophila melanogaster

To examine how the duration of laboratory domestication may affect Drosophila stocks used in studies of thermotolerance, we measured expression of the inducible heat-shock protein Hsp70 and survival after heat shock in D. melanogaster strains recently collected from nature and maintained in laboratory culture for up to 50 or more generations. After an initial increase in both Hsp70 expression and thermotolerance immediately after transfer to laboratory medium, both traits remained fairly constant over time and variation among strains persisted through laboratory domestication. Furthermore, variation in heat tolerance and Hsp70 expression did not correlate with the length of time populations evolved in the laboratory. Therefore, while environmental variation likely contributed most to early shifts in strain tolerance and Hsp70 expression, other population parameters, for example genetic drift, inbreeding, and selection likely affected these traits little. As long as populations are maintained with large numbers of individuals, the culture of insects in the laboratory may have little effect on the tolerance of different strains to thermal stress