A topological approach to the problem of searching on a contour map

Topological approach to obtain ground track of aircraft using height over terrain and contour ma

Larvae of the three common North American species of Phylocentropus (Trichoptera: Dipseudopsidae)

The caddisfly genus Phylocentropus includes 7 extant species globally, of which 5 occur in eastern North America and 2 in eastern Asia. Larvae of the 3 most common North American species [Phylocentropus carolinus Carpenter, P. lucidus (Hagen), and P. placidus (Banks)] were associated with identifiable adults and diagnostic characters are described. Larvae ofthese 3 species may be distinguished by overall length of mature larvae, head color pattern, and number of spines on the hind tibiae. Larvae of other species of this genus are unknown

Factors in the emergence of infectious diseases.

"Emerging" infectious diseases can be defined as infections that have newly appeared in a population or have existed but are rapidly increasing in incidence or geographic range. Among recent examples are HIV/AIDS, hantavirus pulmonary syndrome, Lyme disease, and hemolytic uremic syndrome (a foodborne infection caused by certain strains of Escherichia coli). Specific factors precipitating disease emergence can be identified in virtually all cases. These include ecological, environmental, or demographic factors that place people at increased contact with a previously unfamiliar microbe or its natural host or promote dissemination. These factors are increasing in prevalence; this increase, together with the ongoing evolution of viral and microbial variants and selection for drug resistance, suggests that infections will continue to emerge and probably increase and emphasizes the urgent need for effective surveillance and control. Dr. David Satcher's article and this overview inaugurate Perspectives, a regular section in this journal intended to present and develop unifying concepts and strategies for considering emerging infections and their underlying factors. The editors welcome, as contributions to the Perspectives section, overviews, syntheses, and case studies that shed light on how and why infections emerge, and how they may be anticipated and prevented

Materials and construction techniques for cryogenic wind tunnel facilities for instruction/research use

The results of the cryogenic wind tunnel program conducted at NASA Langley Research Center are presented to provide a starting point for the design of an instructional/research wind tunnel facility. The advantages of the cryogenic concept are discussed, and operating envelopes for a representative facility are presented to indicate the range and mode of operation. Special attention is given to the design, construction and materials problems peculiar to cryogenic wind tunnels. The control system for operation of a cryogenic tunnel is considered, and a portion of a linearized mathematical model is developed for determining the tunnel dynamic characteristics

An approach to comparing external and internal methods for analysing group dynamic

Beginning with the question, can a multi-methodology explore the nature of group work from both the inside out (group participant self-analysis) and the outside in (facilitator observed analysis), this paper presents the results of a statistical analysis comparing two different approaches to assessing group function: SYMLOG (A SYstem for the Multiple Level Observation of Groups) and BECM (Being, Engaging, Contextualising and Managing). SYMLOG is a quantitative internal assessment of group function made by members of the group, while BECM is qualitative external assessment made by an outsider observing the groups. Together, it is argued, they provide a unique, triangulated assessment of the group dynamic. By employing a ‘best subsets’ linear regression technique it was found that some of the 26 characteristics of SYMLOG are related to BECM scoring (adjusted R2 = 0.82). The paper discusses the reasons for this and the repercussions for such blending of approaches to understanding group dynamic. The paper ends by discussing the relative advantages and disadvantages of the two approaches and potential for further hybridising of them in blended group dynamic approaches

Distance and intersection number in the curve graph of a surface

In this work, we study the cellular decomposition of $S$ induced by a filling pair of curves $v$ and $w$, $Dec_{v,w}(S) = S - (v \cup w)$, and its connection to the distance function $d(v,w)$ in the curve graph of a closed orientable surface $S$ of genus $g$. Efficient geodesics were introduced by the first author in joint work with Margalit and Menasco in 2016, giving an algorithm that begins with a pair of non-separating filling curves that determine vertices $(v,w)$ in the curve graph of a closed orientable surface $S$ and computing from them a finite set of {\it efficient} geodesics. We extend the tools of efficient geodesics to study the relationship between distance $d(v,w)$, intersection number $i(v,w)$, and $Dec_{v,w}(S)$. The main result is the development and analysis of particular configurations of rectangles in $Dec_{v,w}(S)$ called \textit{spirals}. We are able to show that, in some special cases, the efficient geodesic algorithm can be used to build an algorithm that reduces $i(v,w)$ while preserving $d(v,w)$. At the end of the paper, we note a connection of our work to the notion of extending geodesics.Comment: 20 pages, 17 figures. Changes: A key lemma (Lemma 5.6) was revised to be more precise, an irrelevant proposition (Proposition 2.1) and example were removed, unnecessary background material was taken out, some of the definitions and cited results were clarified (including added figures,) and Proposition 5.7 and Theorem 5.8 have been merged into a single theorem, Theorem 4.

Global Infectious Disease Surveillance And Health Intelligence

Current concerns about the spread of infectious diseases, especially unexpected (“emerging”) infections such as pandemic influenza or severe acute respiratory syndrome (SARS), have renewed focus on the critical importance of global early warning and rapid response. Although considerable progress has been made, many gaps remain. A number of the gaps can be addressed through increased political will, resources for reporting, improved coordination and sharing of information, raising clinicians’ awareness, and additional research to develop more rigorous triggers for action. The increasing availability of communications and information technologies worldwide offers new opportunities for reporting even in low-capacity settings

A Hybrid Observer for a Distributed Linear System with a Changing Neighbor Graph

A hybrid observer is described for estimating the state of an $m>0$ channel, $n$-dimensional, continuous-time, distributed linear system of the form $\dot{x} = Ax,\;y_i = C_ix,\;i\in\{1,2,\ldots, m\}$. The system's state $x$ is simultaneously estimated by $m$ agents assuming each agent $i$ senses $y_i$ and receives appropriately defined data from each of its current neighbors. Neighbor relations are characterized by a time-varying directed graph $\mathbb{N}(t)$ whose vertices correspond to agents and whose arcs depict neighbor relations. Agent $i$ updates its estimate $x_i$ of $x$ at "event times" $t_1,t_2,\ldots$ using a local observer and a local parameter estimator. The local observer is a continuous time linear system whose input is $y_i$ and whose output $w_i$ is an asymptotically correct estimate of $L_ix$ where $L_i$ a matrix with kernel equaling the unobservable space of $(C_i,A)$. The local parameter estimator is a recursive algorithm designed to estimate, prior to each event time $t_j$, a constant parameter $p_j$ which satisfies the linear equations $w_k(t_j-\tau) = L_kp_j+\mu_k(t_j-\tau),\;k\in\{1,2,\ldots,m\}$, where $\tau$ is a small positive constant and $\mu_k$ is the state estimation error of local observer $k$. Agent $i$ accomplishes this by iterating its parameter estimator state $z_i$, $q$ times within the interval $[t_j-\tau, t_j)$, and by making use of the state of each of its neighbors' parameter estimators at each iteration. The updated value of $x_i$ at event time $t_j$ is then $x_i(t_j) = e^{A\tau}z_i(q)$. Subject to the assumptions that (i) the neighbor graph $\mathbb{N}(t)$ is strongly connected for all time, (ii) the system whose state is to be estimated is jointly observable, (iii) $q$ is sufficiently large, it is shown that each estimate $x_i$ converges to $x$ exponentially fast as $t\rightarrow \infty$ at a rate which can be controlled.Comment: 7 pages, the 56th IEEE Conference on Decision and Contro

Global Preparedness for Public Health

There are many reasons to be interested in public health in China. China is the single most populous nation on earth and was the point of origin for SARS and probably for most pandemic influenza viruses, past and future. In this issue of the Journal, we get a valuable window into the organization of public health emergency preparedness in China in the form of the paper, "Preparing and responding to public health emergencies in China: Results of a focus group study". This paper summarizes the results of focus groups conducted with 47 local- and provincial-level public health officials, and includes some of the most complete information on Chinese public health emergency preparedness at the working level. That makes it an invaluable contribution to the growing literature on public health emergency preparedness