Air management and physiological responses during simulated firefighting tasks in a high-rise structure

Air consumption, oxygen uptake (VO₂), carbon dioxide output (VCO₂) and respiratory exchange ratio (RER = VCO₂/VO₂) were measured directly from the self-contained breathing apparatus (SCBA) as 36 professional firefighters (three women) completed scenarios of high-rise stair climbing and fifth floor search and rescue. During stair climbing VO₂ was 75 ± 8% VO_2max (mean ± SD), RER = 1.10 ± 0.10, and heart rate = 91 ± 3% maximum (based on maximum treadmill data). Firefighters stopped climbing on consuming 55% of the air cylinder then descended. In the fifth floor search and rescue VO₂ was slightly lower than stair climbing but RER remained elevated (1.13 ± 0.12) reflecting high anaerobic metabolism. The first low air alarm sounded, indicating 25% of the air remaining in a “30-min cylinder”, during the stair climb at 8 min with 19 of 36 sounding before 12 min. Aggressive air management strategies are required for safety in high-rise firefighting.     

A Review of: “Influencing Organisational Change—The Role of the Personnel Specialist”. By CHARLES E. MARGHRISON. (London: Institute of Personnel Management, 1978.) [Pp. 219.] £5.25.

This study attempted to determine circadian rhythms in metabolic responses to submaximal and maximal workloads by concentrating on repeated observations of a male subject over 16 weeks. Altogether 36 experimental tests were undertaken on a cycle ergometer, six at each of the times, 0200, 0600, 1000, 1400, 1800 and 2200 hours. The work test comprised two consecutive 5-min periods at 82 and 147 W, followed immediately by an incremental workload to exhaustion. Significant circadian rhythms were found at rest pre-exercise for pulse rate (f_h), VO₂, V_E and rectal temperature (T_r) (p<0·001), with f_H leading the others in phase and T_t lagging significantly behind V_E (p<0·05). The circadian cycle in V_E persisted at both submaximal steady rates, with the VO₂ significant at the higher rate only when uncorrected for body weight. There was no evidence of a circadian variation in ‘muscular efficiency’. No significant rhythms were found in metabolic measures at maximal exercise or during recovery, indicating no time of day effect in the physiological capacity for exercise. The circadian variation in T_r persisted in phase and amplitude under maximal conditions and during recovery, indicating that the thermal load induced by a set exercise regime is independent of time of day.     

Physiological responses of firefighters and performance predictors during a simulated rescue of hospital patients

There is incomplete information about how physically demanding rescue work may be. The aim therefore of this paper was to examine the physiological responses of firefighters during a simulated rescue of hospital patients and to relate the firefighters' performance to their endurance, strength and working technique. Fourteen part-time male firefighters with a maximal oxygen uptake (VO_2max) of 4.4 ± 0.3 l/min (mean ± SD) served as subjects in this study. First, each firefighter ascended six floors (a 20.5 m vertical ascent) carrying tools, wearing protective clothing and a breathing apparatus, an extra mass of 37 kg. He thereafter ‘rescued’ six persons by dragging each person on a fire-sheet on a flat floor. The technique used was recorded and the O₂ uptake and the heart rate were measured continuously during the whole operation. The blood lactate concentration and the subjective rating of perceived exertion were measured during and just after the rescue. The VO_2max and the muscle strength were measured in the laboratory. The whole operation was carried out in the course of 5–9 min. The operation was a virtual all-out effort and the peak blood lactate concentration was 13 ± 3 mmol/l. The peak oxygen uptake was 3.7 ± 0.5 l/min (84% of the VO_2max) during the operation. Large and heavy firefighters carried out the task faster than smaller ones. The VO_2max in absolute terms and the dragging technique used were both related to the rescue performance. Rescuing patients at a hospital was physically very demanding and the time needed to complete the task depended on the VO_2max in absolute values and the working technique used. A minimum VO_2max of 4 l/min for firefighters was recommended.     

A note on finding all homogeneous set sandwiches

A module is a set of vertices H of a graph G=(V,E) such that each vertex of V?H is either adjacent to all vertices of H or to none of them. A homogeneous set is a nontrivial module. A graph G_s=(V,E_s) is a sandwich for a pair of graphs G_t=(V,E_t) and G=(V,E) if E_t⊆E_s⊆E. In a recent paper, Tang et al. [Inform. Process. Lett. 77 (2001) 17-22] described an O(Δn²) algorithm for testing the existence of a homogeneous set in sandwich graphs of G_t=(V,E_t) and G=(V,E) and then extended it to an enumerative algorithm computing all these possible homogeneous sets. In this paper, we invalidate this latter algorithm by proving there are possibly exponentially many such sets, even if we restrict our attention to strong modules. We then give a correct characterization of a homogeneous set of a sandwich graph.     

Application of thermoregulatory modeling to predict core and skin temperatures in firefighters

The purpose of the study was to compare body temperature responses from subjects who exercised while wearing firefighter clothing to predictive data from a real-time thermoregulatory model that had been initially developed and validated for use in the military. Data from two firefighter studies, firefighter study 1 (FFS1: 7 males and 3 females, continuous treadmill exercise at 50% VO_2max, 25 °C, 50% RH) and firefighter study 2 (FFS2: 6 males, intermittent treadmill exercise at 75% VO_2max, 35 °C, 50% RH), were utilized for the thermoregulatory modeling and comparison. The results showed that prediction error (RMSD) of the model for core and skin temperatures was 0.33 and 0.65 °C in FFS1 and 0.39 and 0.86 °C in FFS2, respectively. While the real-time thermoregulatory model tested in the present study showed the potential for providing a means for reasonably accurate prediction of body temperature responses in firefighters, further development on the model's metabolism algorithms to include adjustments for protective clothing, options to facilitate external work, inclusions of cooling effects are suggested.Relevance to industryFirefighters exposed to thermal extremes experience physiological strain, but direct monitoring of physiological variables is not always practical. Thermoregulatory models can simulate the thermal responses reasonably accurately by applying known thermo-physiological mechanisms together with heat loss mechanisms related to clothing and environment in an effort to improve firefighter safety.     

An efficient parallel strategy for the two-fixed-endpoint Hamiltonian path problem on distance-hereditary graphs

In this paper, we solve the two-fixed-endpoint Hamiltonian path problem on distance-hereditary graphs efficiently in parallel. Let T_d(|V|,|E|) and P_d(|V|,|E|) denote the parallel time and processor complexities, respectively, required to construct a decomposition tree of a distance-hereditary graph G=(V,E) on a PRAM model M_d. We show that this problem can be solved in O(T_d(|V|,|E|)+log|V|) time using O(P_d(|V|,|E|)+(|V|+|E|)/log|V|) processors on M_d. Moreover, if G is represented by its decomposition tree form, the problem can be solved optimally in O(log|V|) time using O((|V|+|E|)/log|V|) processors on an EREW PRAM. We also obtain a linear-time algorithm which is faster than the previous known O(|V|³) sequential algorithm.     

Note on the Homogeneous Set Sandwich Problem

A homogeneous set is a non-trivial module of a graph, i.e., a non-unitary, proper subset H of a graph's vertices such that all vertices in H have the same neighbors outside H. Given two graphs G₁(V,E₁), G₂(V,E₂), the Homogeneous Set Sandwich Problem asks whether there exists a sandwich graph GS(V,ES), E₁⊆ES⊆E₂, which has a homogeneous set. Recently, Tang et al. [Inform. Process. Lett. 77 (2001) 17-22] proposed an interesting O(_?1⋅n²) algorithm for this problem, which has been considered its most efficient algorithm since. We show the incorrectness of their algorithm by presenting three counterexamples.     

Counting edge crossings in a 2-layered drawing

Given a bipartite graph G=(V,W,E) with a bipartition {V,W} of a vertex set and an edge set E, a 2-layered drawing of G in the plane means that the vertices of V and W are respectively drawn as distinct points on two parallel lines and the edges as straight line segments. We consider the problem of counting the number of edge crossings. In this paper, we design two algorithms to this problem based on the dynamic programming and divide-and-conquer approaches. These algorithms run in O(n₁n₂) time and O(m) space and in O(min{n₁n₂,|E|log(min{|V|,|W|})}) time and O(m) space, respectively. Our algorithms outperform the previously fastest Θ(|E|log(min{|V|,|W|})) time algorithm for dense graphs.     

Iterative process with errors for fixed points of multivalued Φ-hemicontractive operators in uniformly smooth Banach spaces

Let E be a uniformly smooth Banach space and T : E → 2^E be a (not necessarily continuous) multivalued ø-hemicontractive mapping. This paper proves that, under suitable conditions, the multivalued Ishikawa iterative sequence with errors strongly converges to the unique fixed point of T. The related result deals with the strong convergence of the Ishikawa iterative sequence with errors to the unique solution of the equation f ∈ Tx when T : E → 2^E is multivalued ø-strongly accretive. These results generalize the results of the author [1], Ding [2,3], Osilike [4,5], Zhou [6,7], and Chidume [8,9] into more general multivalued ø-hemicontractive operators without the continuous assumption on operators T.     

The Pair Completion algorithm for the Homogeneous Set Sandwich Problem

A homogeneous set is a non-trivial module of a graph, i.e., a non-empty, non-unitary, proper vertex subset such that all its elements present the same outer neighborhood. Given two graphs G₁(V,E₁) and G₂(V,E₂), the Homogeneous Set Sandwich Problem (HSSP) asks whether there exists a graph GS(V,ES), E₁⊆ES⊆E₂, which has a homogeneous set. This paper presents an algorithm that uses the concept of bias graph [S. Tang, F. Yeh, Y. Wang, An efficient algorithm for solving the homogeneous set sandwich problem, Inform. Process. Lett. 77 (2001) 17-22] to solve the problem in time, thus outperforming the other known HSSP deterministic algorithms for inputs where .     

A 1.5-approximation algorithm for augmenting edge-connectivity of a graph from 1 to 2

We consider the following NP-hard problem: given a connected graph G=(V,E) and a link set E on V disjoint to E, find a minimum size subset of edges F⊆E such that (V,E∪F) is 2-edge-connected. In G. Even et al. (2005) [2] we presented a 1.8-approximation for the problem. In this paper we improve the ratio to 1.5.     

A comparison of two physical ability tests for firefighters

Smoke diving is physically demanding, and firefighters must therefore meet certain minimum physical requirements. The aim of this study was to compare the physiological demands of two fire fitness tests: a test of 8-min treadmill walking approved by the Norwegian Labour Inspection Authority (NLIA) (a laboratory test) and a Canadian test consisting of 10 firefighting specific tasks carried out in sequence (an applied field test). If the Canadian field test is as physically demanding as the NLIA-approved laboratory test, it may be suitable for testing Norwegian firefighters. Twenty-two male professional firefighters were tested on separate days. In both tests, the subjects wore a complete firefighting outfit including a breathing apparatus. The test durations were 8 min (NLIA test) versus approximately 6 min (Canadian test). Neither the peak O₂ uptake (VO₂) of approximately 45 ml kg ^? 1 min ^? 1 nor the blood lactate concentration (BLC) at test termination ( ≈ 9 mmol L ^? 1) differed between the two tests. Rating of perceived exertion (RPE_CR-10) was lower for the Canadian test than for the Norwegian test (5.2 ± 1.5 vs. 7.0 ± 2.0, respectively), and the exercise time at a high VO₂ was also shorter. In conclusion, the Canadian test appeared to be almost as physically demanding as the NLIA-approved test, having equal peak VO₂ and BLC, but shorter time at a high VO₂ and shorter duration. It might thus be a suitable alternative to the NLIA test with some modifications. The advantage of the Canadian field test is the inclusion of specific firefighting-like tasks that are not part of the NLIA test.     

Max- and Min-Neighborhood Monopolies

Given a graph G=(V,E) and a set of vertices M ? V, a vertex v ∈ V is said to be controlled by M if the majority of v’s neighbors (including itself) belong to M. M is called a monopoly in G if every vertex v∈ V is controlled by M. For a specified M and a given range for edge set E (E ₁ ? E ? E ₂), we try to determine an E such that M is a monopoly in G=(V,E). We first present a polynomial algorithm for testing if such an E exists, by formulating it as a network flow problem. Assuming that a solution for E does exist, we then show that solutions with the maximum and minimum |E| , respectively, can be found in polynomial time, by solving weighted matching problems. In case there is no solution for E, we want to maximize the number of vertices controlled by the given M. Unfortunately, this problem turns out to be NP-hard. We, therefore, design a simple approximation algorithm which guarantees an approximation ratio of 2.     

Bipanconnectivity and edge-fault-tolerant bipancyclicity of hypercubes

A bipartite graph is bipancyclic if it contains a cycle of every even length from 4 to |V(G)| inclusive. It has been shown that Q_n is bipancyclic if and only if n?2. In this paper, we improve this result by showing that every edge of Q_n−E′ lies on a cycle of every even length from 4 to |V(G)| inclusive where E′ is a subset of E(Q_n) with |E′|?n−2. The result is proved to be optimal. To get this result, we also prove that there exists a path of length l joining any two different vertices x and y of Q_n when h(x,y)?l?|V(G)|−1 and l−h(x,y) is even where h(x,y) is the Hamming distance between x and y.     

On vertex ranking of a starlike graph

A vertex coloring c:V→{1,2,…,t} of a graph G=(V,E) is a vertex t-ranking if for any two vertices of the same color every path between them contains a vertex of larger color. The vertex ranking number χ_r(G) is the smallest value of t such that G has a vertex t-ranking. A χ_r(G)-ranking of G is said to be an optimal vertex ranking. In this paper, we present an O(|V|+|E|) time algorithm for finding an optimal vertex ranking of a starlike graph G=(V,E). Our result implies that an optimal vertex ranking of a split graph can be computed in linear time.     

Computing Modular Invariants of p-groups

Let V be a finite dimensional representation of a p -group, G, over a field,k , of characteristic p. We show that there exists a choice of basis and monomial order for which the ring of invariants, k [ V ]^G, has a finite SAGBI basis. We describe two algorithms for constructing a generating set for k [ V ] G. We use these methods to analyse k [2V₃ ]^U₃where U₃is the p -Sylow subgroup ofGL₃ (F_p) and 2 V₃is the sum of two copies of the canonical representation. We give a generating set for k [2 V₃]^U₃forp =  3 and prove that the invariants fail to be Cohen–Macaulay forp >  2. We also give a minimal generating set for k [mV₂ ]^Z / pwere V₂is the two-dimensional indecomposable representation of the cyclic group Z / p.     

Correlated change in normalized difference vegetation index and the seasonal trajectory of photosynthetic capacity in a conifer stand

Seasonal changes in canopy photosynthetic activity play an important role in carbon assimilation. However, few simulation models for estimating carbon balances have included them due to scarcity in quality data. This paper investigates some important aspects of the relationship between the seasonal trajectory of photosynthetic capacity and the time series of a common vegetation index (normalized difference vegetation index, NDVI), which was derived from on site micrometeorological measurements or smoothed and downscaled from satellite‐borne NDVI sensors. A parameter indicating the seasonality of canopy physiological activity, P _E, was retrieved through fitting a half‐hour step process model, PROXEL_NEE, to gross primary production (GPP) estimates by inversion for carboxylation and light utilization efficiencies. The relative maximum rate of carboxylation (V _rm), a parameter that indicates the seasonality of CO₂ uptake potential under prevailing temperature, was then calculated from P _E and daily average air temperature. Statistical analysis revealed that there were obvious exponential relationships between NDVI and the seasonal courses for both canopy physiological activities P _E and V _rm. Among them, the on‐site broadband NDVI provided a robust and consistent relationship with canopy physiological activities (R ² = 0.84). The relationships between satellite‐borne NDVI time series with instantaneous canopy physiological activities at the time of satellite passing were also checked. The results indicate that daily step NDVI time series (data downscaled from composite temporal resolution NDVI) better represent the daily average activity of the canopy. These findings may enable us to retrieve the seasonal course of canopy physiological activity from widely available NDVI data series and, thus, to include it into carbon assimilation models. However, both smoothing methods for satellite‐borne NDVI time series may generate incorrect estimates and must be treated with care.     

Critical evaluation and thermodynamic optimization of the V–O system

The V–O system has been critically evaluated and thermodynamically assessed based on the available phase diagram and thermodynamic data using the CALPHAD method. The liquid phase over the whole composition range from metallic liquid to oxide melt is described by the modified quasichemical model with five species: V^II, V^III, V^IV, V^V and O, which takes short-range ordering in liquid solution into account. All solid solutions are modeled considering respective crystal structures. A set of self-consistent thermodynamic parameters of the V–O system is obtained and the available experimental data are reproduced well within experimental error limits. Especially for the VO_x solid solution, the site fractions of vacancies in both vanadium and oxygen sublattices are reproduced well using the present model and parameters.     

Memetic search for the max-bisection problem

Given an undirected graph G=(V,E)$G=(V,E)$ with weights on the edges, the max-bisection problem (MBP) is to find a partition of the vertex set V$V$ into two subsets V₁ and V₂ of equal cardinality such that the sum of the weights of the edges crossing V₁ and V₂ is maximized. Relaxing the equal cardinality, constraint leads to the max-cut problem (MCP). In this work, we present a memetic algorithm for MBP which integrates a grouping crossover operator and a tabu search optimization procedure. The proposed crossover operator preserves the largest common vertex groupings with respect to the parent solutions while controlling the distance between the offspring solution and its parents. Extensive experimental studies on 71 well-known G-set benchmark instances demonstrate that our memetic algorithm improves, in many cases, the current best known solutions for both MBP and MCP.