Relationships Between the Performance of Time/Frequency Standards and Navigation/Communication Systems

The relationship between system performance and clock or oscillator performance is discussed. Tradeoffs discussed include: short term stability versus bandwidth requirements; frequency accuracy versus signal acquisition time; flicker of frequency and drift versus resynchronization time; frequency precision versus communications traffic volume; spectral purity versus bit error rate, and frequency standard stability versus frequency selection and adjustability. The benefits and tradeoffs of using precise frequency and time signals are various levels of precision and accuracy are emphasized

Small scale analysis of population structure in the woody cornelian cherry Cornus mas L. (Cornaceae) by AFLP accentuates the need for a population based conservation strategy

We investigated population differentiation among and within three populations (two natural, one artificial) of the cornelian cherry (Cornus mas L., Cornaceae) to examine the extent of gene flow from planted cornelian cherries commonly used in planting vegetations of public parks or streets into natural stands. Additionall we assessed if natural populations show any intrapopulational and/or interpopulational differentiation pointing towards restricted gene flow with possible necessity for a population based conservation strategy rather than a taxon based strategy. Results clearly indicated within and between population structure a radius of isolation by distance for pollen and seed dispersal of about 5.0 km. Interestingly genetic distance did not support coherence of the two natural populations but mirrored the historical origin of the innertown population from diverse natural sources reflecting the traditional use and selection of edible varieties from nature. The Nem value of 1.25 implicates the prevention of population differentation. However the low level of genetic diversity and distance at all might mislead the interpretation and the degree of distance reflects more ancient similarities than actual geneflow. Given this observable isolation by distance, conservation biology of Cornus mas requires a population based strategy rather than a broad taxon based strategy

Comment on "Quantum mechanics of smeared particles"

In a recent article, Sastry has proposed a quantum mechanics of smeared particles. We show that the effects induced by the modification of the Heisenberg algebra, proposed to take into account the delocalization of a particle defined via its Compton wavelength, are important enough to be excluded experimentally.Comment: 2 page

2s Hyperfine Structure in Hydrogen Atom and Helium-3 Ion

The usefulness of study of hyperfine splitting in the hydrogen atom is limited on a level of 10 ppm by our knowledge of the proton structure. One way to go beyond 10 ppm is to study a specific difference of the hyperfine structure intervals 8 Delta nu_2 - Delta nu_1. Nuclear effects for are not important this difference and it is of use to study higher-order QED corrections.Comment: 10 pages, presented at Hydrogen Atom II meeting (2000

Using Muonic Hydrogen in Optical Spectroscopy Experiment to Detect Extra Dimensions

Considering that gravitational force might deviate from Newton's inverse-square law (ISL) and become much stronger in small scale, we propose a kind of optical spectroscopy experiment to detect this possible deviation and take electronic, muonic and tauonic hydrogen atoms as examples. This experiment might be used to indirectly detect the deviation of ISL down to nanometer scale and to explore the possibility of three extra dimensions in ADD's model, while current direct gravity tests cannot break through micron scale and go beyond two extra dimensions scenario.Comment: 9 pages, 2 figures. To appear in IJT

Heart Rate Variability and Recurrent Stroke and Myocardial Infarction in Patients With Acute Mild to Moderate Stroke

Objectives: In patients with acute ischemic stroke, reduced heart rate variability (HRV) may indicate poor outcome. We tested whether HRV in the acute phase of stroke is associated with higher rates of mortality, recurrent stroke, myocardial infarction (MI) or functional outcome. Materials and Methods: Patients with acute mild to moderate ischemic stroke without known atrial fibrillation were prospectively enrolled to the investigator-initiated Heart and Brain interfaces in Acute Ischemic Stroke (HEBRAS) study (NCT 02142413). HRV parameters were assessed during the in-hospital stay using a 10-min section of each patient's ECG recording at day- and nighttime, calculating time and frequency domain HRV parameters. Frequency of a combined endpoint of recurrent stroke, MI or death of any cause and the respective individual events were assessed 12 months after the index stroke. Patients' functional outcome was measured by the modified Rankin Scale (mRS) at 12 months. Results: We included 308 patients (37% female, median NIHSS = 2 on admission, median age 69 years). Complete follow-up was achieved in 286/308 (93%) patients. At 12 months, 32 (9.5%), 5 (1.7%) and 13 (3.7%) patients had suffered a recurrent stroke, MI or death, respectively. After adjustment for age, sex, stroke severity and vascular risk factors, there was no significant association between HRV and recurrent stroke, MI, death or the combined endpoint. We did not find a significant impact of HRV on a mRS ≥ 2 12 months after the index stroke. Conclusion: HRV did not predict recurrent vascular events in patients with acute mild to moderate ischemic stroke

Neuromyelitis optica and pregnancy during therapeutic B cell depletion: infant exposure to anti-AQP4 antibody and prevention of rebound relapses with low-dose rituximab postpartum

Neuromyelitis optica (NMO) predominantly affects women, some in childbearing age, and requires early therapeutic intervention to prevent disabling relapses. We report an anti-AQP4 antibody-seropositive patient who became pregnant seven months after low-dose (100 mg) rituximab application. Pregnancy showed no complications, and low-dose rituximab restarted two days after delivery resulted in neurological stability for 24 months. Remarkably, her otherwise healthy newborn presented with anti-AQP4 antibody and reduced B lymphocyte counts in umbilical cord blood, which normalized three months later. Confirming and extending previous reports, our case suggests that low-dose rituximab might be compatible with pregnancy and prevent rebound NMO disease activity postpartum

Morphological and molecular analysis of natural hybrids between the diploid Centaurea aspera L. and the tetraploid C. seridis L. (Compositae)

[EN] Polyploidy and hybridisation are the basis of the evolution of Centaurea (Compositae). At the El Saler dune field (eastern Spain), the diploid Centaurea aspera ssp. stenophylla and the tetraploid C. seridis ssp. maritima form a polyploid complex in which C. x subdecurrens individuals occur. This polyploid complex was analysed morphologically and genetically, using random amplified polymorphic DNA (RAPD) and tubulin-based polymorphism (TBP) markers. Flow cytometry showed that the hybrids are triploid, which is a rare finding in Centaurea. Morphologically, in contrast to leaf characters, flowering characters clearly discriminated the three taxa. The genetic analyses confirm that C. x subdecurrens is a result of the hybridisation between Centaurea aspera ssp. stenophylla and C. seridis ssp. maritima, and suggest that backcrossing events and gene flow are very rare or absent. Although the hybrids likely represent true F1 offspring, they displayed some genetic diversity that is probably due to the combination of alleles. Genetic diversity was higher in diploid than in tetraploid individuals. This fact, and the high degree of sterility of the triploid hybrids, may reflect a cytotype minority exclusion effect. This may cause spatial segregation, which effectively takes place in the study area. Dune disturbance may lead to an overlapping of the parents' distribution areas, facilitating hybridisation.This work is posthumously dedicated to Antonio Samo Lumbreras, to whom we are very grateful for all his help. This study was sponsored by the Valencian Government (Research Project GVPRE/2008/130) and the Universitat Politecnica de Valencia (Research Project Ref. 3241).Ferriol Molina, M.; Garmendia, A.; Ruiz, J.; Merle Farinós, HB.; Boira Tortajada, H. (2012). Morphological and molecular analysis of natural hybrids between the diploid Centaurea aspera L. and the tetraploid C. seridis L. (Compositae). Plant Biosystems. 146(1):86-100. https://doi.org/10.1080/11263504.2012.727878S86100146

Disorder effects in electronic structure of substituted transition metal compounds

Investigating LaNi(1-x)M(x)O3 (M = Mn and Fe), we identify a characteristic evolution of the spectral function with increasing disorder in presence of strong interaction effects across the metal-insulator transition. We discuss these results vis-a-vis existing theories of electronic structure in simultaneous presence of disorder and interaction.Comment: Revtex, 4 pages, 3 postscript figures (To appear in Phys. Rev. Lett