Ultra-broadband wavelength-swept Tm-doped fiber laser using wavelength-combined gain stages

A wavelength-swept thulium-doped fiber laser system employing two parallel cavities with two different fiber gain stages is reported. The fiber gain stages were tailored to provide emission in complementary bands with external wavelength-dependent feedback cavities sharing a common rotating polygon mirror for wavelength scanning. The wavelength-swept laser outputs from the fiber gain elements were spectrally combined by means of a dichroic mirror and yielded over 500 mW of output with a scanning range from ~1740 nm to ~2070 nm for a scanning frequency of ~340 Hz

Recognizing Treelike k-Dissimilarities

A k-dissimilarity D on a finite set X, |X| >= k, is a map from the set of size k subsets of X to the real numbers. Such maps naturally arise from edge-weighted trees T with leaf-set X: Given a subset Y of X of size k, D(Y) is defined to be the total length of the smallest subtree of T with leaf-set Y . In case k = 2, it is well-known that 2-dissimilarities arising in this way can be characterized by the so-called "4-point condition". However, in case k > 2 Pachter and Speyer recently posed the following question: Given an arbitrary k-dissimilarity, how do we test whether this map comes from a tree? In this paper, we provide an answer to this question, showing that for k >= 3 a k-dissimilarity on a set X arises from a tree if and only if its restriction to every 2k-element subset of X arises from some tree, and that 2k is the least possible subset size to ensure that this is the case. As a corollary, we show that there exists a polynomial-time algorithm to determine when a k-dissimilarity arises from a tree. We also give a 6-point condition for determining when a 3-dissimilarity arises from a tree, that is similar to the aforementioned 4-point condition.Comment: 18 pages, 4 figure

The operational space for divertor power exhaust in DEMO with a super-X divertor

SOLPS-ITER simulations of the European DEMO reactor with a Super-X divertor, which has larger major radius at the outer target and increased connection length, show an increased operational space for divertor power exhaust compared to the conventional single-null configuration. Using a multi-fluid approach with fluid neutrals and charge-state bundling of impurities, we assessed the existence and boundaries of the operational space in the single-null and Super-X configurations by carrying out fuelling, seeding and power scans. Compared to the conventional single-null divertor, the Super-X divertor offers lower impurity concentration (factor ∼2 lower) at the same main plasma density, and consistent with this, it has lower main plasma density at the same impurity concentration level. This observed difference is in line with the simple analytical Lengyel model predictions resulting from the increased connection length in the super-X configuration. DEMO with a Super-X divertor demonstrates remarkable robustness against increases in input power, and in this study is able to exhaust the maximum expected steady-state separatrix-crossing power of 300 MW while maintaining acceptable impurity concentration along the separatrix This is something that was not possible in the single-null configuration in this study. This robustness of the Super-X divertor lies mostly in its capability to sufficiently dissipate power in its divertor via argon (Ar) radiation at acceptable Ar concentration, which is related to two factors: long (with respect to single-null) parallel connection length from the upstream to the outer target and higher but tolerable extrinsic impurity concentration at higher input powers. Finally, consistent with neon-seeded simulations of ITER, it is observed in all our simulations that the plasma density drops with increasing Ar concentration given fixed power input. We find that as the Ar content increases, the accompanying enhancement of Ar radiation reduces the power available for deuterium (D) to be ionized, thus limiting the D ionization particle source, and consequently reducing the plasma density

Serum Iron Level is Associated with Time to Antibiotics in Cystic Fibrosis

Background: Serum levels of hepcidin‐25, a peptide hormone that reduces blood iron content, are elevated when patients with cystic fibrosis (CF) develop pulmonary exacerbation (PEx). Because hepcidin‐25 is unavailable as a clinical laboratory test, we questioned whether a one‐time serum iron level was associated with the subsequent number of days until PEx, as defined by the need to receive systemic antibiotics (ABX) for health deterioration. Methods: Clinical, biochemical, and microbiological parameters were simultaneously checked in 54 adults with CF. Charts were reviewed to determine when they first experienced a PEx after these parameters were assessed. Time to ABX was compared in subgroups with and without specific attributes. Multivariate linear regression was used to identify parameters that significantly explained variation in time to ABX. Results: In univariate analyses, time to ABX was significantly shorter in subjects with Aspergillus‐positive sputum cultures and CF‐related diabetes. Multivariate linear regression models demonstrated that shorter time to ABX was associated with younger age, lower serum iron level, and Aspergillus sputum culture positivity. Conclusions: Serum iron, age, and Aspergillus sputum culture positivity are factors associated with shorter time to subsequent PEx in CF adults

Alcohol and traffic safety: A sensitivity analysis of data from composite sources

Risk factors associated with single-vehicle driver fatalities are explored in a sensitivity analysis of data from composite sources. Information on fatalities was taken from the Federal Accident Reporting System data base for 1976-1981. Characteristics of the driving population were given by the 1973 National Roadside Breath Testing Survey (Wolfe 1974). Using Bayes theorem and logistic regression analysis, the effect of changing driver characteristics on the probability of a fatality was explored. The method used is proposed for a case-control study in which the controls may not accurately represent the population from which the cases were drawn. Risk factors identified are generally in agreement with previous reports.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28061/1/0000500.pd

Taenia solium Cysticercosis Hotspots Surrounding Tapeworm Carriers: Clustering on Human Seroprevalence but Not on Seizures

Cysticercosis is a parasitic disease caused by the tapeworm Taenia solium, common in areas with limited sanitation or with migration from these populations. The adult parasite is hosted in the human intestine and releases large numbers of eggs with the feces. Human beings sometimes ingest eggs due to poor hygiene, and then eggs sometimes lodge on the brain and after a few years can cause intense headaches and seizures. During a study in seven rural communities in Peru, individuals exposed to T. solium eggs were often tightly clustered at the homes or immediate surrounding of the carriers of the adult parasite. However, no aggregation of cases of seizures was found near carriers. It appears that seizures do not cluster around carriers because several years pass between exposure to T. solium eggs and the onset of seizures. During these years the adult parasite has probably died or people had moved within or even outside their communities. Therefore, only a partial understanding of the epidemiology of cysticercosis is gained by studying seizures cases

An ordinary differential equation model for full thickness wounds and the effects of diabetes

Wound healing is a complex process in which a sequence of interrelated phases contributes to a reduction in wound size. For diabetic patients, many of these processes are compromised, so that wound healing slows down. In this paper we present a simple ordinary differential equation model for wound healing in which attention focusses on the dominant processes that contribute to closure of a full thickness wound. Asymptotic analysis of the resulting model reveals that normal healing occurs in stages: the initial and rapid elastic recoil of the wound is followed by a longer proliferative phase during which growth in the dermis dominates healing. At longer times, fibroblasts exert contractile forces on the dermal tissue, the resulting tension stimulating further dermal tissue growth and enhancing wound closure. By fitting the model to experimental data we find that the major difference between normal and diabetic healing is a marked reduction in the rate of dermal tissue growth for diabetic patients. The model is used to estimate the breakdown of dermal healing into two processes: tissue growth and contraction, the proportions of which provide information about the quality of the healed wound. We show further that increasing dermal tissue growth in the diabetic wound produces closure times similar to those associated with normal healing and we discuss the clinical implications of this hypothesised treatment

Relative Equilibria in the Four-Vortex Problem with Two Pairs of Equal Vorticities

We examine in detail the relative equilibria in the four-vortex problem where two pairs of vortices have equal strength, that is, \Gamma_1 = \Gamma_2 = 1 and \Gamma_3 = \Gamma_4 = m where m is a nonzero real parameter. One main result is that for m > 0, the convex configurations all contain a line of symmetry, forming a rhombus or an isosceles trapezoid. The rhombus solutions exist for all m but the isosceles trapezoid case exists only when m is positive. In fact, there exist asymmetric convex configurations when m < 0. In contrast to the Newtonian four-body problem with two equal pairs of masses, where the symmetry of all convex central configurations is unproven, the equations in the vortex case are easier to handle, allowing for a complete classification of all solutions. Precise counts on the number and type of solutions (equivalence classes) for different values of m, as well as a description of some of the bifurcations that occur, are provided. Our techniques involve a combination of analysis and modern and computational algebraic geometry

Periodic orbits in the restricted three-body problem and Arnold's J+J^+-invariant

We apply Arnold's theory of generic smooth plane curves to Stark-Zeeman systems. This is a class of Hamiltonian dynamical systems that describes the dynamics of an electron in an external electric and magnetic field, and includes many systems from celestial mechanics. Based on Arnold's $J^+$-invariant, we introduce invariants of periodic orbits in planar Stark-Zeeman systems and study their behaviour.Comment: 36 Pages, 16 Figure