bluuebunny/crossref_metadata_2025 huggingface dataset:
Lectotypification of the names Arenaria graminifolia Ard., Arenaria rosani Ten. and Arenaria alpicola Ten. (Caryophyllaceae)
Authors: Conti Fabio , Santangelo Annalisa
Published: April 2006

Conti, F. & Santangelo, A.: Lectotypification of the names Arenaria graminifolia Ard., Arenaria rosani Ten. and Arenaria alpicola Ten. (Caryophyllaceae). – Taxon 50: 193–199. 2001. – ISSN 0040‐0262.

Three names based on Italian specimens relating to the Minuartia graminifolia complex are lectotypified. Arenaria graminifolia, the basionym of Minuartia graminifolia (Ard.) Jáv. subsp. graminifolia is lectotypified by an Arduino specimen at LINN, and Arenaria rosani, the basionym of M. graminifolia subsp. rosani (Ten.) Mattf. by a Tenore collection at NAP; both lectotypifications maintain current usage of these names. In addition, Arenaria alpicola Ten., now considered a synonym of Minuartia graminifolia subsp. clandestina (Portenschl.) Mattf., is also lectotypified by a Tenore collection at NAP referable to that subspecies.
Data model and comparison and query methods for interacting classifications in a taxonomic database
Authors: Zhong Yang , Jung Sungwon , Pramanik Sakti , Beaman John H.
Published: April 2006

Zhong, Y., Jung, S., Pramanik, S. & Beaman, J. H.: Data model and comparison and query methods for interacting classifications in a taxonomic database. – Taxon 45: 223‐241. 1996. –ISSN 0040‐0262.

An information‐theoretic view has been applied to biological classification to capture taxonomic concepts as taxonomic data entities and to develop a system for managing these concepts and the lineage relationships among them. In order to develop the data model, it has been necessary to apply explicit definitions to several taxonomic terms that generally have not been precisely defined and to coin and define several new terms and concepts. Methods are outlined for comparing interacting classifications and querying hierarchical taxonomic databases. A program/database system called HICLAS, which provides an X‐Window interface to query classification data, is available on the Internet.
A quick and easy method of drying plant specimens, including succulents, for the herbarium
Authors: Eggli Urs , Leuenberger Beat Ernst
Published: April 2006

Eggli, U. & Leuenberger, B. E.: A quick and easy method of drying plant specimens, including succulents, for the herbarium. – Taxon 45: 259‐261. 1996. – ISSN 0040‐0262.

The preparation of conventional pressed and dried herbarium specimens by using a commercial hair‐drier and a bag of tightly woven, fire‐resistant tissue is described. It has proved particularly useful for preparing specimens of succulent plants.
The suprema of the actual and virtual waiting times during a busy cycle of the Km/Kn/1 queueing system
Authors: Cohen J. W.
Published: April 2006

For the single server queueing system, whose distributions of service and inter-arrival times have rational Laplace-Stieltjes transforms, limit theorems are derived for the supremum of the virtual waiting time during k successive busy cycles for k→∞. Similarly, for the supremum of the actual waiting times of all customers arriving in k successive busy cycles. Only the cases with the load of the system less than one and equal to one are considered. The limit distributions are extreme value distributions. The results are obtained by first deriving a number of asymptotic expressions for the quantities which govern the analytic description of the system Km/Kn/1. Using these asymptotic relations limit theorems for entrance times can also be obtained, a few examples are given.
On generating a random sequence
Authors: Hwang F. K. , Lin S.
Published: April 2006

Suppose there are k kinds of balls identical except for their colours. The number of balls of the ith colour is ri (i = 1, 2, ···, k) and Put down the R balls in a sequence (a line), then an acceptable sequence is one which does not have two adjacent balls of the same colour. The problem is to generate a random sample of the set of acceptable sequences S(r1, r2, ···, rk).
On an extension of Gani's model for attachment of phages to bacteria
Authors: Bhat B. R.
Published: April 2006

In recent papers Yassky (1962) and Gani (1965) have considered respectively deterministic and stochastic models for the attachment of phages to bacteria. Following Brenner's (1965) conjecture they assumed that there is a maximum, S (say), to the number of phages that can be attached to a bacterium. In this note, Gani's (1965) results will be obtained starting from a different set of assumptions. This modification enables us to consider the case when S is a random variable, which probably is a more realistic assumption. Some remarks on the problem of estimation for the latter model are given in Section 3.
A stochastic model for two interacting populations
Authors: Becker Niels G.
Published: April 2006

To explain the growth of interacting populations, non-linear models need to be proposed and it is this non-linearity which proves to be most awkward in attempts at solving the resulting differential equations. A model with a particular non-linear component, initially proposed by Weiss (1965) for the spread of a carrier-borne epidemic, was solved completely by different methods by Dietz (1966) and Downton (1967). Immigration parameters were added to the model of Weiss and the resulting model was made the subject of a paper by Dietz and Downton (1968). It is the aim here to further generalize the model by introducing birth and death parameters so that the result is a linear birth and death process with immigration for each population plus the non-linear interaction component.
The limiting distribution of the maximum term in a sequence of random variables defined on a markov chain
Authors: Fabens Augustus J. , Neuts Marcel F.
Published: April 2006

Gnedenko's classical work [1] on the limit of the distribution of the maximum of a sequence of independent random variables is extended to the distribution of the maximum of a sequence of random variables defined on a finite Markov chain.
Random size trees on the one and two dimensional integer lattice
Authors: Verhagen A.M.V.
Published: April 2006

A stochastic process in which any tree in a forest planted on an integer lattice eliminates its four neighbours when it exceeds their heights, is studied for the case when all heights are independent samples from a continuous distribution. The proportion of the trees of the forest eliminated in this manner is determined for both the one and the two dimensional integer lattices.
Dams in series with continuous release
Authors: Moran P.A.P.
Published: April 2006

In a previous paper (Moran (1956)) the theory of a dam with a continuous release was developed for a situation in which the input was defined by an additive homogeneous random process of gamma distribution type, and the release was defined to occur continuously at a fixed rate when the content of the dam was non-zero. In the present paper we modify these conditions by assuming first that the input is defined by a general additive homogeneous process with non-negative increments with finite second moment, and secondly that the rate of release is proportional to the content of the dam. This modification to the release rule ensures that the content of the dam is never zero and the theory is then so simplified that the distributional properties of the contents of a sequence of dams in series can be easily found.
A modification of a result due to Moran
Authors: Arnold Barry C.
Published: April 2006

Let {X(n): n = 0, 1, 2, …} be a Markov chain with state space {0, 1, 2, …, N} and transition probability matrix P = (pij).
Exponential ergodicity in Markov renewal processes
Authors: Teugels Jozef L.
Published: April 2006

In [3], Kendall proved a solidarity theorem for irreducible denumerable discrete time Markov chains. Vere-Jones refined Kendall's theorem by obtaining uniform estimates [14], while Kingman proved analogous results for an irreducible continuous time Markov chain [4], [5].

We derive similar solidarity theorems for an irreducible Markov renewal process. The transient case is discussed in Section 3, and Section 4 deals with the positive recurrent case. Recently Cheong also proved solidarity theorems for Semi-Markov processes [1]. His theorems use the Markovian structure, while our emphasis is on the renewal aspects of Markov renewal processes.

An application to the M/G/1 queue is included in the last section.
Truncation approximation of the limit probabilities for denumerable semi-Markov processes
Authors: Tweedie Richard L.
Published: April 2006

It is shown that methods used by the author to approximate limit probabilities for Markov processes from their Q-matrices extend to semi-Markov processes. The limit probabilities for semi-Markov processes can be approximated using only truncations of the embedded Markov chain transition matrix and the vector of mean holding times.
On optimal policies and martingales in dynamic programming
Authors: Rieder Ulrich
Published: April 2006

A martingale approach to a dynamic program with general state and action spaces is taken. Several necessary and sufficient conditions are given for a policy to be optimal. The results comprehend and modify different criteria of optimality given for dynamic programming problems. Finally, two applications are stated.
The recurrent epidemic
Authors: Billard L.
Published: April 2006

The recurrent epidemic model has hitherto proved mathematically intractable. It is shown here that by imposing the mild condition that the source of new susceptibles is initially of a constant size M for M sufficiently large that there is zero probability of more than M new susceptibles being added to the population in the course of the epidemic, then state probabilities for the stochastic recurrent epidemic model can be found.
Evaluations of barrier-crossing probabilities of Wiener paths
Authors: Park C. , Schuurmann F. J.
Published: April 2006

Let {W(t), 0 ≦ t < ∞} be the standard Wiener process. The main purpose of this paper is to present ways of obtaining probabilities of Wiener paths crossing certain curves on various intervals. The results are extended to other kinds of Gaussian processes.
A simple condition for regularity in negative programming
Authors: Whittle P.
Published: April 2006

A simple condition (the ‘bridging condition') is given for a Markov decision problem with non-negative costs to enjoy the regularity properties enunciated in Theorem 1. The bridging condition is sufficient for regularity, and is not far from being necessary, in a sense explained in Section 2. In Section 8 we consider the different classes of terminal loss functions (domains of attraction) associated with different solutions of (14). Some conjectures concerning these domains of attraction are either proved, or disproved by counter-example.
On best fractional linear generating function bounds
Authors: Hwang Tea-Yuan , Wang Nae-Sheng
Published: April 2006

Under weak conditions, this paper provides a best lower and a best upper bounding fractional linear generating function for any probability generating function when they have the same mean. These bounds can be used to obtain bounds for the expectation and the percentiles of the extinction-time distribution of a Galton-Watson branching process and other parameters of interest. For the special case of the four points probability generating function, the best bounds obtained are better than the bounds derived by Agresti (1974).
A limit theorem for the maximum term in a particular EARMA(1, 1) sequence
Authors: Chernick Michael R.
Published: April 2006

The EARMA(1, 1) process was described by Jacobs and Lewis (1977). Chernick (1978) showed that the limit for the maximum term is the same as for a sequence of independent, identically distributed exponential random variables when the parameter ρ is less than 1. When ρ = 1, a different limit theorem is obtained. The resulting limit distribution is not an extreme-value type. It is, however, of the general form given by Galambos (1978). The sequence is exchangeable.
Characterization of the optimal class of output policies in a control model of a finite dam
Authors: Zuckerman Dror
Published: April 2006

In this paper we characterize the optimal class of output policies in a control model of a dam having a finite capacity. The input of water into the dam is determined by a Wiener process with positive drift. Water may be released at either of two possible rates 0 or M. At any time the output rate can be increased from 0 to M with a cost of K, (K ≧ 0) or decreased from M to 0 with zero cost, any such changes taking effect instantaneously. There is a reward of A monetary units for each unit of output, (A ≧ 0). The problem is to formulate an optimal output policy which maximizes the long-run average net reward per unit time.
The interchangeability of ·/M/1 queues in series
Authors: Weber Richard R.
Published: April 2006

A series of queues consists of a number of · /M/1 queues arranged in a series order. Each queue has an infinite waiting room and a single exponential server. The rates of the servers may differ. Initially the system is empty. Customers enter the first queue according to an arbitrary stochastic input process and then pass through the queues in order: a customer leaving the first queue immediately enters the second queue, and so on. We are concerned with the stochastic output process of customer departures from the final queue. We show that the queues are interchangeable, in the sense that the output process has the same distribution for all series arrangements of the queues. The ‘output theorem' for the M/M/1 queue is a corollary of this result.
Uniform limit theorems for non-singular renewal and Markov renewal processes
Authors: Arjas Elja , Nummelin Esa , Tweedie Richard L.
Published: April 2006

We show that if the increment distribution of a renewal process has some convolution non-singular with respect to Lebesgue measure, then the skeletons of the forward recurrence time process are φ-irreducible positive recurrent Markov chains. Known convergence properties of such chains give simple proofs of uniform versions of some old and new key renewal theorems; these show in particular that non-singularity assumptions on the increment and initial distributions enable the assumption of direct Riemann integrability to be dropped from the standard key renewal theorem. An application to Markov renewal processes is given.
Distributed lag regression by an almost periodic design matrix
Authors: Katzoff M. J. , Shumway R. H.
Published: April 2006

Frequency domain estimation and tests of hypotheses are considered for a general multivariate distributed lag regression model. The usual vector of regression functions is replaced by a matrix of almost periodic functions, a case for which the terms appearing in the frequency domain estimators have well-defined limits. Asymptotic distributions and consistency are established for the regression coefficients and error spectra. A test statistic is proposed for the no regression hypothesis which is asymptotically central under the null hypothesis and converges to infinity under the alternative. In the multivariate case, a product of beta-distributed variables is obtained.
Strongly consistent estimation in a controlled Markov renewal model
Authors: Kolonko Michael
Published: April 2006

The optimal control of dynamic models which are not completely known to the controller often requires some kind of estimation of the unknown parameters. We present conditions under which a minimum contrast estimator will be strongly consistent independently of the control used. This kind of estimator is appropriate for the adaptive or ‘estimation and control' approach in dynamic programming under uncertainty. We consider a countable-state Markov renewal model and we impose bounding and recurrence conditions of the so-called Liapunov type.
Lumpability for non-irreducible finite markov chains
Authors: Abdel-Moneim Atef M. , Leysieffer Frederick W.
Published: April 2006

Conditions under which a function of a finite, discrete-time Markov chain, X(t), is again Markov are given, when X(t) is not irreducible. These conditions are given in terms of an interrelationship between two partitions of the state space of X(t), the partition induced by the minimal essential classes of X(t) and the partition with respect to which lumping is to be considered.
Population processes allowing emigration of families
Authors: Tessera Abebe
Published: April 2006

In the familiar immigration–birth–death process the events of immigration, birth and death relate to the individual. There are processes in which the whole family and not just an individual migrates. Such population growth models are studied in some detail.
Some limit theorems for a subcritical branching process by immigration
Authors: Chow Y. S. , Yu K. F.
Published: April 2006

The strong law of large numbers of the Marcinkiewicz–Zygmund type is established for the total population in a subcritical branching process with immigration. The moment convergence of the total population is obtained under appropriate moment conditions on the offspring distribution and the immigration distribution.
Partial barrier-absorption probabilities for the Wiener process
Authors: Park C. , Schuurmann F. J.
Published: April 2006

Let {W(t), 0 ≦ t < ∞} be the standard Wiener process. The techniques of computing probabilities of the type are well known. The main purpose of this paper is to present ways of finding barrier-absorption probabilities when the barrier function is defined only on sub-intervals of [0, T].
A note on survival models under a Markov process
Authors: Griffith William S. , Srinivasan C.
Published: April 2006

A number of extensions of the class preservation results in the Esary, Marshall and Proschan shock model have been investigated by various authors in recent years, most recently by Ghosh and Ebrahimi. In this note, generalizations are obtained using different methods for the IFR and NBUE cases when the shocking process is a regular continuous-time Markov process with stationary transition probabilites.
Conditions for the non-ergodicity of Markov chains with application to a communication system
Authors: Sennott Linn I.
Published: April 2006

We obtain a sufficient condition for the transience of a Markov chain, and a sufficient condition for its null recurrence. These are applied to characterize the stability of a multiple-access communication system. Performance bounds for the system are also obtained.
Busy-period analysis of a correlated queue with exponential demand and service
Authors: Langaris Christos
Published: April 2006

In this paper we investigate the server's busy period in a single-server queueing situation in which the interarrival interval T preceding the arrival of a customer and his service time S are assumed correlated. A closed-form expression is obtained for the Laplace transform bn(z) of the joint probability and probability density function of the busy period duration and the number of customers served in it. Some numerical values are given showing the effect of correlation between T and S.
Quantile spectral analysis and long-memory time series
Authors: Parzen Emanuel
Published: April 2006

An approach to time series model identification is described which involves the simultaneous use of frequency, time and quantile domain algorithms; the approach is called quantile spectral analysis. It proposes a framework to integrate the analysis of long-memory (non-stationary) time series with the analysis of short-memory (stationary) time series.
An L2 convergence theorem for random affine mappings
Authors: Burton Robert M. , Rösler Uwe
Published: April 2006

We consider the composition of random i.i.d. affine maps of a Hilbert space to itself. We show convergence of the nth composition of these maps in the Wasserstein metric via a contraction argument. The contraction condition involves the operator norm of the expectation of a bilinear form. This is contrasted with the usual contraction condition of a negative Lyapunov exponent. Our condition is stronger and easier to check. In addition, our condition allows us to conclude convergence of second moments as well as convergence in distribution.
A linear birth-and-death predator–prey process
Authors: Coffey John
Published: April 2006

A new stochastic predator-prey model is introduced. The predator population X(t) is described by a linear birth-and-death process with birth rate λ1X and death rate μ1X. The prey population Y(t) is described by a linear birth-and-death process in which the birth rate is λ2Y and the death rate is . It is proven that and iff
General branching processes with immigration
Authors: Olofsson Peter
Published: April 2006

A general multi-type branching process where new individuals immigrate according to some point process is considered. An intrinsic submartingale is defined and a convergence result for processes counted with random characteristics is obtained. Some examples are given.
An inequality for pairs of martingales and its application to fractal image coding
Authors: Dekking F. M.
Published: April 2006

We prove a monotonicity property for a function of general square integrable pairs of martingales which is useful in fractal-based algorithms for compression of image data.
Functional limit theory for the spectral covariance estimator
Authors: Dehay Dominique , Leśkow Jacek
Published: April 2006

Processes that exhibit repeatability in their kth-order moments are frequently studied in signal analysis. Such repeatability can be conveniently expressed with the help of almost periodicity. In particular, almost periodically correlated (APC) processes play an important role in the analysis of repeatable signals. This paper presents a study of asymptotic distributions of the estimator of the spectral covariance function for APC processes. It is demonstrated that, for a large class of APC processes, the functional central limit theorem holds.
A comparison of convergence rates for three models in the theory of dams
Authors: Lund Robert , Smith Walter
Published: April 2006

This paper compares the convergence rate properties of three storage models (dams) driven by time-homogeneous jump process input: the infinitely high dam, the finite dam, and the infinitely deep dam. We show that the convergence rate of the infinitely high dam depends on the moment properties of the input process, the finite dam always approaches its limiting distribution exponentially fast, and the infinitely deep dam approaches its limiting distribution exponentially fast under very general conditions. Our methods make use of rate results for regenerative processes and several sample path orderings.
Birth and death on a Brownian flow: a Feller semigroup and its generator and a martingale problem
Authors: Phelan Michael J.
Published: April 2006

We consider a system of particles in birth and death on a stochastic flow. The system includes a particle process tracking the spatial configuration of live particles on the flow. The particle process is a Markov process on the space of bounded counting measures. We show that its transition semigroup is a Feller semigroup and exhibit its pregenerator. The pregenerator defines a martingale problem. We show that the particle process solves the problem uniquely.
The censored Markov chain and the best augmentation
Authors: Zhao Y. Quennel , Liu Danielle
Published: April 2006

Computationally, when we solve for the stationary probabilities for a countable-state Markov chain, the transition probability matrix of the Markov chain has to be truncated, in some way, into a finite matrix. Different augmentation methods might be valid such that the stationary probability distribution for the truncated Markov chain approaches that for the countable Markov chain as the truncation size gets large. In this paper, we prove that the censored (watched) Markov chain provides the best approximation in the sense that, for a given truncation size, the sum of errors is the minimum and show, by examples, that the method of augmenting the last column only is not always the best.
Duration of a secretary problem
Authors: Yeo Geoffrey F.
Published: April 2006

The distribution of the number of items drawn in a secretary problem, with an order s selection role and a success if any of the best s items is selected, is obtained by a probabilistic argument. Moments and asymptotics readily follow.
Looking after well siblings of adolescent girls with anorexia: an important parental role
Authors: Honey A. , Halse C.
Published: April 2006

Background  Research has suggested that well siblings of children with chronic and life‐threatening illnesses are at risk for negative outcomes and that parents’ responses to the illnesses can influence the adaptation of well siblings. Yet, parents’ efforts to look after well siblings in the context of illness are rarely considered in literature about sibling adaptation. The importance of attending to the needs of well siblings was a major theme to emerge from a qualitative analysis of the experiences of parents of adolescent girls with anorexia nervosa.

Methods  In‐depth interviews were conducted with 24 parents of adolescent girls with anorexia and analysed using grounded theory method.

Results  The data indicated that parents viewed caring for well siblings in the context of anorexia as an important role and responsibility. Parents reported making conscious and active efforts to look after well siblings by: maintaining normality; compensating for changes to routines; protecting siblings; providing emotional support; and managing the consequences.

Conclusions  This paper provides a picture of the actions parents take to help well siblings adapt to anorexia in the family. Further research is needed to develop and expand this understanding to families experiencing a wide range of chronic and life‐threatening illnesses. The findings underline the importance of clinical attention and further research into the critical parental role of caring for well siblings.
Hyperthyroidism is characterized by both increased sympathetic and decreased vagal modulation of heart rate: evidence from spectral analysis of heart rate variability
Authors: Chen Jin‐Long , Chiu Hung‐Wen , Tseng Yin‐Jiun , Chu Woei‐Chyn
Published: April 2006

Objective  The clinical manifestations of hyperthyroidism resemble those of the hyperadrenergic state. This study was designed to evaluate the impact of hyperthyroidism on the autonomic nervous system (ANS) and to investigate the relationship between serum thyroid hormone concentrations and parameters of spectral heart rate variability (HRV) analysis in hyperthyroidism.

Design and patients  Thirty‐two hyperthyroid Graves’ disease patients (mean age 31 years) and 32 sex‐, age‐, and body mass index (BMI)‐matched normal control subjects were recruited to receive one‐channel electrocardiogram (ECG) recording.

Measurements  The cardiac autonomic nervous function was evaluated by the spectral analysis of HRV, which indicates the autonomic modulation of the sinus node. The correlation coefficients between serum thyroid hormone concentrations and parameters of the spectral HRV analysis were also computed.

Results  The hyperthyroid patients revealed significant differences (P < 0·001) compared with the controls in the following HRV parameters: a decrease in total power (TP), very low frequency power (VLF), low frequency power (LF), high frequency power (HF), and HF in normalized units (HF%); and an increase in LF in normalized units (LF%) and in the ratio of LF to HF (LF/HF). After correction of hyperthyroidism in 28 patients, all of the above parameters were restored to levels comparable to those of the controls. In addition, serum thyroid hormone concentrations showed significant correlations with spectral HRV parameters.

Conclusions  Hyperthyroidism is in a sympathovagal imbalanced state, characterized by both increased sympathetic and decreased vagal modulation of the heart rate. These autonomic dysfunctions can be detected simultaneously by spectral analysis of HRV, and the spectral HRV parameters could reflect the disease severity in hyperthyroid patients.
Lithium as adjuvant to radioiodine therapy in differentiated thyroid carcinoma: clinical and in vitro studies
Authors: Liu Y.Y. , Van Der Pluijm G. , Karperien M. , Stokkel M. P. M. , Pereira A. M. , Morreau J. , Kievit J. , Romijn J. A. , Smit J. W. A.
Published: April 2006

Objective  Lithium has been reported to increase radioactive iodine (RaI) doses in benign thyroid disease and in differentiated thyroid carcinoma (DTC). It is not known whether lithium influences the outcome of RaI therapy in DTC. We therefore studied the clinical effects of RaI without and with lithium carbonate in patients with proven metastatic DTC. Controversy also exists on the mechanism by which lithium increases RaI dose in DTC. We performed an in vitro study specifically aimed at examining the effects of lithium on the sodium iodide symporter (NIS).

Design  In a clinical study, 12 patients were selected with metastases of DTC who had received previous RaI therapy without lithium (control) that had not influenced tumour progression, despite RaI accumulation in metastases. The patients received 1200 mg lithium carbonate/day followed by 6000 MBq RaI. Outcome parameters were RaI uptake, serum thyroglobulin (Tg) levels and radiological dimensions of metastases compared between RaI with lithium and control. In an in vitro study, iodide uptake was studied in the benign rat thyroid cell line FRTL‐5, in the polarized non‐thyroid MDCK cell line, stably transfected with human sodium iodide symporter (hNIS) to study the effects of lithium on NIS in a non‐thyroid background, and the human follicular thyroid carcinoma cell line FTC133‐hNIS to study lithium effects in a background of DTC. Lithium chloride (LiCl) was added in concentrations up to 2 mm for 0–48 h. Both steady‐state iodide uptake (30 min) and initial rate (2 min) were studied using a specific activity of 100 mCi/mmol I, the latter experiment to determine lithium effects on substrate dependency. Iodide efflux studies were performed as well.

Results  Despite an increased uptake of RaI in seven patients, no beneficial effect of RaI with lithium was observed on the clinical course as assessed by serum Tg measurements and radiographically. In the in vitro studies, no effects of LiCl on iodide uptake or efflux were observed.

Conclusions  The addition of lithium to RaI did not have any beneficial effects on the clinical course in 12 patients with metastatic DTC. No beneficial effects of lithium on iodide uptake were observed in vitro. Therefore, the clinical value of lithium in DTC remains subject to debate.
Effects of aggregation pheromone on individual behaviour and food web interactions: a field study onDrosophila
Authors: Wertheim Bregje , Allemand Roland , Vet Louise E. M. , Dicke Marcel
Published: April 2006

Abstract. 1. The effects of an aggregation pheromone on individual behaviour and food web interactions were investigated in two ecological communities, usingDrosophila melanogasterandD. simulansas focal species.

2. Fruit substrates with aggregation pheromone were significantly more attractive to adultD. melanogasterandD. simulansthan control fruit substrates, and the response was positively dose dependent. Competing species and natural enemies were also significantly attracted to substrates with the aggregation pheromone ofD. melanogasterandD. simulans.

3. Significantly more eggs were deposited on pheromone‐treated fruits than on control fruits, and the microdistribution of eggs within fruits was correlated to the microdistribution of the pheromone. The aggregation pheromone induced more females to share the breeding site.

4. The extremely high densities of fruit flies in the large aggregations appeared to reduce the oviposition rate of females. Physical interactions with conspecific and heterospecifics were frequently observed in the aggregations, and often led to patch leaving of the fruit flies.

5. Competition for food among larvae occurred at high densities and parasitism was density dependent. Aggregation pheromones can be directly responsible for these patterns through their effects on the con‐ and heterospecific behaviour.

6. The combined results show that aggregation pheromones affect a multitude of aspects in the ecology of interacting animals. The importance of incorporating the communication signals in ecological theory of aggregations is discussed.
Changes in secondary phenolic metabolites during storage as an aqueous suspension in comparison with the content in harvested Aloe arborescens leaves
Authors: Gutterman Yitzchak , Chauser‐Volfson Elena
Published: April 2006

Aloe arborescens is a very important plant used in the cosmetics and pharmaceutical industries. The main problem using this plant for medicinal and cosmetic purposes is the rapid destruction of the active compounds in aquatic solutions. By frequently pruning the leaves, the content of three secondary phenolic metabolites (SPhMs), barbaloin, aloeresin and aloenin, in the leaves can be increased dramatically. The changes in these SPhMs were studied in an aqueous suspension of leaf exudate powder and in harvested leaves after storage for 1–45 days at 4 °C in darkness. During storage in water there was rapid degradation of aloenin, but a gradual and slow degradation of barbaloin and aloeresin. In contrast, in stored leaves, the change in the relative amounts of the three SPhMs was similar, but the percentage of aloenin was higher even after 3.5 months. When these SPhMs are stored as dry powder they may last for some years.
Determinants of the biogeographical distribution of butterflies in boreal regions
Authors: Luoto M. , Heikkinen R. K. , Pöyry J. , Saarinen K.
Published: April 2006

Aim We explored the relative contributions of climatic and land‐cover factors in explaining the distribution patterns of butterflies in a boreal region.

Location Finland, northern Europe.

Methods Data from a national butterfly atlas survey carried out during 1991–2003, with a 10‐km grain grid system, were used in these analyses. We used generalized additive models (GAM) and hierarchical partitioning (HP) to explore the main environmental correlates (climate and land‐cover) of the realized niches of 98 butterfly species. The accuracy of the distribution models (GAMs) was validated by resubstitution and cross‐validation approaches, using the area under the curve (AUC) derived from the receiver operating characteristic (ROC) plots.

Results Predictive accuracies of the 98 individual environment–butterfly models varied from low to very high (cross‐validated AUC values 0.48–0.99), with a mean of 0.79. The results of both the GAM and HP analyses were broadly concordant. Most of the variation in butterfly distributions is associated with growing degree‐days, mean temperature of the coldest month and cover of built‐up area in all six phylogenetic groups (butterfly families). There were no statistically significant differences in predictive accuracy among the different butterfly families.

Main conclusions About three‐quarters of the distributions of butterfly species in Finland appear to be governed principally by climatic, predominantly temperature‐related, factors. This indicates that many butterfly species may respond rapidly to the projected climate change in boreal regions. By determining the ecological niches of multiple species, we can project their range shifts in response to changes in climate and land‐cover, and identify species that are particularly sensitive to forecasted global changes.
Nurses as providers of support for mothers of premature infants
Authors: Mok Esther , Leung Sui Foon
Published: April 2006

Aim.  The study aims to explore the supportive behaviour of nurses as experienced by mothers of premature infants in Hong Kong.

Background.  The sudden, unexpected delivery of a premature infant is an extreme shock to parents. Studies have confirmed the importance of nursing support to the relief of stress of parents.

Design.  A descriptive study design.

Methods.  A convenience sampling of 37 mothers in a neonatal Intensive Care Unit were recruited from a regional hospital to complete the ‘Nurses Parent Support Tool’ (NPST) which consists of four aspects: communication information support, emotional support, parental esteem support and quality care‐giving support. Six mothers were interviewed after the completion of the tool to give examples of supportive and non‐supportive behaviour.

Results.  The results showed that all of the mothers rated all nursing support items as important. However, there was a significant mean difference between perceived and received nursing support. These findings demonstrated that parents desired more nursing support than they received, particularly in the area of supportive communication and the giving of information. Comparatively, emotional support was rated less important as well as having been less often received than the other three domains of support. Interviews with six mothers further gave examples and described the types, attributes and the phases of support in the Chinese setting.

Conclusion.  The findings indicate that Chinese parents are desirous of more nursing support than they received.

Relevance to clinical practice.  Nurses should be aware of the importance of tailoring nursing support to meet the needs of parents of premature infants.
Communities of arbuscular mycorrhizal fungi in arable soils are not necessarily low in diversity
Authors: HIJRI ISABELLE , SÝKOROVÁ ZUZANA , OEHL FRITZ , INEICHEN KURT , MÄDER PAUL , WIEMKEN ANDRES , REDECKER DIRK
Published: April 2006

Communities of arbuscular mycorrhizal fungi (AMF) in five agricultural field sites of different management intensities were studied. Variable regions of the ribosomal RNA genes were used to detect and identify AMF directly within colonized roots. Roots from a continuous maize monoculture showed low AMF diversity, in agreement with previous reports on molecular diversity of AMF in agricultural soils. In contrast, a substantially higher diversity of AMF was found throughout the long term ‘DOK’ field experiment, where organic and conventional agricultural practices have been compared side by side since 1978. In this experiment, a 7‐year crop rotation is performed under lower levels of inorganic fertilizer input and chemical pest control. These results are in good agreement with analyses of the spore community previously conducted in these field sites. In a third site, an organically managed leek field with soil of very high phosphate content reflecting the highly intensive conventional field history and intensive tillage, we detected a low‐diversity community comparable to the maize monoculture. In addition to fungi from Glomus group A, which have previously been reported to dominate arable soils, we regularly found members of the genera Scutellospora, Paraglomus and Acaulospora. The genus Acaulospora was shown to occur more frequently early in the growing season, suggesting that the life history strategy of AMF may influence the active community at a given time. These data show that the diversity of AMF is not always low in arable soils. Furthermore, low‐input agriculture involving crop rotation may provide better conditions to preserve AMF diversity, by preventing the selection for the few AMF taxa tolerating high nutrient levels.
Flat-spectrum symmetric objects with ∼1 kpc sizes – I. The candidates
Authors: Augusto Pedro , Gonzalez-Serrano J. Ignacio , Perez-Fournon Ismael , Wilkinson Peter N.
Published: April 2006

In order to understand the origin and evolution of radio galaxies, searches for the youngest such sources have been conducted. Compact symmetric objects (CSOs)/medium symmetric objects (MSOs) are thought to be the earliest stages of radio sources, with possible ages of ≲103 yr for CSOs (<1 kpc in size) and 104–105 yr for MSOs (1–15 kpc). From a literature selection in heterogeneous surveys, we have established a sample of 37 confirmed CSOs. In addition, we only found three confirmed flat-spectrum MSOs in the literature. The typical CSO resides on a z≲ 0.5 galaxy, has a flat radio spectrum (αthin < 0.5; Sν∝ν−α), is <0.3 kpc in size, has an arm length ratio ≤ 2, and well-aligned (θ≤ 20°) opposite lobes with a flux density ratio ≤10. In order to populate the 0.3–1 kpc size range (large CSOs) and also in order to find more flat-spectrum MSOs, we have built a sample of 157 radio sources with α4.851.40 < 0.5 that were resolved with the Very Large Array A configuration (VLA-A) 8.4 GHz. As first results, we have ‘rediscovered’ nine of the known CSO/MSOs while identifying two new ∼14 kpc MSOs and two candidate CSO/MSOs (which only lack redshifts for final classification). We were able to reject 61 of the remaining 144 objects from literature information alone. In the series of papers that starts with this one we plan to classify the remaining 83 CSO/MSO candidates (thanks to radio and optical observations) as well as characterize the physical properties of the (likely) many 0.3–15 kpc flat-spectrum CSO/MSOs to be found.
Radial asymmetry of the upper oesophageal sphincter pressure profile: fact or artefact
Authors: Bardan E. , Kern M. , Torrico S. , Arndorfer R. C. , Massey B. T. , Shaker R.
Published: April 2006

Abstract  Radial asymmetry of the upper oesophageal sphincter high‐pressure zone (UESHPZ) is an accepted notion based on manometric studies.

Our aim was to evaluate the effect of the catheter diameter and configuration on the resting pressure profile of the UES. We studied 14 young (30 ± 2 years) and 14 healthy elderly volunteers (77 ± 2 years) using the station pull‐through technique. We used a specially designed water perfused manometric assembly that incorporated a proximal round cross‐section (4.8 mm) and a distal flat cross‐section (4.8 × 1.2 mm). Anterior and posterior manometric sites on the round catheter measured significantly higher pressure values than did the sites oriented laterally at the same level (P < 0.001) in both young and elderly. In contrast, the flat‐shaped catheter measured statistically indistinguishable pressures from all four orientations in both age groups. In both young and elderly the anterio‐posterior, but not lateral pressures by the round catheter were significantly higher (P < 0.001) than those of the flat catheter. An exaggerated anteriorly and posteriorly oriented pressure may be recorded compared with lateral pressures depending on the diameter and non‐conforming shape of the recording catheter with respect to the UES producing the appearance of radial asymmetry in the UESHPZ.
Regulation of secondary metabolism by the carbon–nitrogen status in tobacco: nitrate inhibits large sectors of phenylpropanoid metabolism
Authors: Fritz Christina , Palacios‐Rojas Natalia , Feil Regina , Stitt Mark
Published: April 2006

Interactions between nitrogen and carbon metabolism modulate many aspects of the metabolism, physiology and development of plants. This paper investigates the contribution of nitrate and nitrogen metabolism to the regulation of phenylpropanoid and nicotine synthesis. Wild‐type tobacco was grown on 12 or 0.2 mmnitrate and compared with a nitrate reductase‐deficient mutant [Nia30(145)] growing on 12 mmnitrate. Nitrate‐deficient wild‐type plants accumulate high levels of a range of phenylpropanoids including chlorogenic acid, contain high levels of rutin, are highly lignified, but contain less nicotine than nitrogen‐replete wild‐type tobacco. Nia30(145) resembles nitrate‐deficient wild‐type plants with respect to the levels of amino acids, but accumulates large amounts of nitrate. The levels of phenylpropanoids, rutin and lignin resemble those in nitrogen‐replete wild‐type plants, whereas the level of nicotine resembles that in nitrate‐deficient wild‐type plants. Expression arrays and real time RT‐PCR revealed that a set of genes required for phenylpropanoid metabolism includingPAL,4CLandHQTare induced in nitrogen‐deficient wild‐type plants but not in Nia30(145). It is concluded that nitrogen deficiency leads to a marked shift from the nitrogen‐containing alkaloid nicotine to carbon‐rich phenylpropanoids. The stimulation of phenylpropanoid metabolism is triggered by changes of nitrate, rather than downstream nitrogen metabolites, and is mediated by induction of a set of enzymes in the early steps of the phenylpropanoid biosynthetic pathway.
Microsatellite variation among diverging populations ofDrosophila mojavensis
Authors: Ross C. L. , Markow T. A.
Published: April 2006

Divergence and speciation may occur by various means, depending on the particular history, selective environments, and genetic composition of populations. In Drosophila mojavensis, a good model of incipient speciation, understanding the population genetic structure within this group facilitates our ability to understand the context in which reproductive isolation among populations is developing. Here we report the genetic structure and relationships of D. mojavensis populations at nuclear loci. We surveyed 29 populations throughout the distribution of D. mojavensis for four microsatellite loci to differentiation among populations of this species. These loci reveal four distinct geographical regions of D. mojavensis populations in the south-western United States and north-western Mexico – (i) Baja California peninsula (Baja), (ii) Sonora, Mexico–southern Arizona, United States (Sonora), (iii) Mojave Desert and Grand Canyon (Mojave), and (iv) Santa Catalina Island (Catalina). While all regions show strong isolation, Mojave and Catalina are highly diverged from other regions. Within any region, populations are largely homogenous over broad geographical distances. Based on the population structure, we find clear geographical barriers to gene flow appear to have a strong effect in isolating populations across regions for this species.
Structure and activity of bacterial community inhabiting rice roots and the rhizosphere
Authors: Lu Yahai , Rosencrantz Dirk , Liesack Werner , Conrad Ralf
Published: April 2006

Root‐derived carbon provides a major source for microbial production and emission of CH4 from rice field soils. Therefore, we characterized the structure and activity of the bacterial community inhabiting rice roots and the rhizosphere. In the first experiment, DNA retrieved from rice roots was analysed for bacterial 16S rRNA genes using cloning, sequencing and in situ hybridization. In the second experiment, rice plants were pulse‐labelled with 13CO2 (99% of atom 13C) for 7 days, and the bacterial RNA was isolated from rhizosphere soil and subjected to density gradient centrifugation. RNA samples from density fractions were analysed by terminal restriction fragment length polymorphism fingerprinting, cloning and sequencing. The experiments showed that the dominant bacteria inhabiting rice roots and the rhizosphere particularly belonged to the Alphaproteobacteria, Betaproteobacteria and Firmicutes. The RNA stable isotope probing revealed that the bacteria actively assimilating C derived from the pulse‐labelled rice plants were Azospirillum spp. (Alphaproteobacteria) and members of Burkholderiaceae (Betaproteobacteria). Both anaerobic (e.g. Clostridia) and aerobic (e.g. Comamonas) degraders were present at high abundance, indicating that root environments and degradation processes were highly heterogeneous. The relative importance of iron and sulfate reducers suggested that cycling of iron and sulfur is active in the rhizosphere.