bluuebunny/crossref_metadata_2025 huggingface dataset:
Post‐initiation control by the initiation factor sigma
Authors: Artsimovitch Irina
Published: February 2008

Bacterial core RNA polymerase can initiate transcription at promoters only if guided by a σ subunit that directs the core enzyme to a subset of σ‐specific promoters. Specific and stable interactions between the promoter DNA elements and σ are required for efficient promoter recognition. At the same time, persistent σ‐DNA contacts can hinder RNA polymerase escape from a promoter or halt the enzyme downstream from the transcription start site, thereby reducing transcription of the affected genes. This microcommentary reviews recent data arguing that σ‐dependent stalled transcription complexes form frequently in vivo, where they likely play important and diverse regulatory roles.
Structural and mutational analysis of the cell division protein FtsQ
Authors: Van Den Ent Fusinita , Vinkenvleugel Thessa M. F. , Ind Alice , West Philip , Veprintsev Dmitry , Nanninga Nanne , Den Blaauwen Tanneke , Löwe Jan
Published: February 2008

Bacterial cytokinesis requires the divisome, a complex of proteins that co‐ordinates the invagination of the cytoplasmic membrane, inward growth of the peptidoglycan layer and the outer membrane. Assembly of the cell division proteins is tightly regulated and the order of appearance at the future division site is well organized. FtsQ is a highly conserved component of the divisome among bacteria that have a cell wall, where it plays a central role in the assembly of early and late cell division proteins. Here, we describe the crystal structure of the major, periplasmic domain of FtsQ from Escherichia coli and Yersinia enterocolitica. The crystal structure reveals two domains; the α‐domain has a striking similarity to polypeptide transport‐associated (POTRA) domains and the C‐terminal β‐domain forms an extended β‐sheet overlaid by two, slightly curved α‐helices. Mutagenesis experiments demonstrate that two functions of FtsQ, localization and recruitment, occur in two separate domains. Proteins that localize FtsQ need the second β‐strand of the POTRA domain and those that are recruited by FtsQ, like FtsL/FtsB, require the surface formed by the tip of the last α‐helix and the two C‐terminal β‐strands. Both domains act together to accomplish the role of FtsQ in linking upstream and downstream cell division proteins within the divisome.
Esterification of cholesterol by a type III secretion effector during intracellular Salmonella infection
Authors: Nawabi Parwez , Catron Drew M. , Haldar Kasturi
Published: February 2008

Survival of Salmonella typhimurium within a vacuole in host cells depends on secreted virulence factors encoded by the Salmonella pathogenicity island 2 (SPI‐2). High levels of cholesterol are detected at the Salmonella‐containing vacuole (SCV). Here we show that the SPI‐2 effector SseJ esterifies cholesterol in vitro, in cells and during infection. Intracellular infections with wild‐type as compared with ΔsseJ bacteria led to higher levels of cholesterol ester production in HeLa cells and RAW macrophages and were shown to increase levels of lipid droplets (structures enriched in cholesterol esters). Ectopic expression of SseJ reduced cholesterol levels in cellular membranes and antagonized a major membrane activity of a second bacterial effector known to be important to the stability of the SCV. Previous studies in mouse models of infection have established a virulence defect in ΔsseJ bacteria and have suggested a role for SseJ in regulating SCV dynamics. Our data indicating the molecular activity of SseJ suggest that cholesterol and its esterification at the SCV are functionally important for intracellular bacterial survival.
The ATP‐binding cassette transporter–encoding gene CgSNQ2 is contributing to the CgPDR1‐dependent azole resistance of Candida glabrata
Authors: Torelli Riccardo , Posteraro Brunella , Ferrari Sélène , La Sorda Marilena , Fadda Giovanni , Sanglard Dominique , Sanguinetti Maurizio
Published: February 2008

Our previous investigation on Candida glabrata azole‐resistant isolates identified two isolates with unaltered expression of CgCDR1/CgCDR2, but with upregulation of another ATP‐binding cassette transporter, CgSNQ2, which is a gene highly similar to ScSNQ2 from Saccharomyces cerevisiae. One of the two isolates (BPY55) was used here to elucidate this phenomenon. Disruption of CgSNQ2 in BPY55 decreased azole resistance, whereas reintroduction of the gene in a CgSNQ2 deletion mutant fully reversed this effect. Expression of CgSNQ2 in a S. cerevisiae strain lacking PDR5 mediated not only resistance to azoles but also to 4‐nitroquinoline N‐oxide, which is a ScSNQ2‐specific substrate. A putative gain‐of‐function mutation, P822L, was identified in CgPDR1 from BPY55. Disruption of CgPDR1 in BPY55 conferred enhanced azole susceptibility and eliminated CgSNQ2 expression, whereas introduction of the mutated allele in a susceptible strain where CgPDR1 had been disrupted conferred azole resistance and CgSNQ2 upregulation, indicating that CgSNQ2 was controlled by CgPDR1. Finally, CgSNQ2 was shown to be involved in the in vivo response to fluconazole. Together, our data first demonstrate that CgSNQ2 contributes to the development of CgPDR1‐dependent azole resistance in C. glabrata. The overlapping in function and regulation between CgSNQ2 and ScSNQ2 further highlight the relationship between S. cerevisiae and C. glabrata.
The tryptophan aminotransferase Tam1 catalyses the single biosynthetic step for tryptophan‐dependent pigment synthesis in Ustilago maydis
Authors: Zuther Katja , Mayser Peter , Hettwer Ursula , Wu Wenying , Spiteller Peter , Kindler Bernhard L. J. , Karlovsky Petr , Basse Christoph W. , Schirawski Jan
Published: February 2008

Tryptophan is a precursor for many biologically active secondary metabolites. We have investigated the origin of indole pigments first described in the pityriasis versicolor‐associated fungus Malassezia furfur. Some of the identified indole pigments have properties potentially explaining characteristics of the disease. As M. furfur is not amenable to genetic manipulation, we used Ustilago maydis to investigate the pathway leading to pigment production from tryptophan. We show by high‐performance liquid chromatography, mass spectrometry and nuclear magnetic resonance analysis that the compounds produced by U. maydis include those putatively involved in the etiology of pityriasis versicolor. Using a reverse genetics approach, we demonstrate that the tryptophan aminotransferase Tam1 catalyses pigment biosynthesis by conversion of tryptophan into indolepyruvate. A forward genetics approach led to the identification of mutants incapable of producing the pigments. These mutants were affected in the sir1 gene, presumably encoding a sulphite reductase. In vitro experiments with purified Tam1 showed that 2‐oxo 4‐methylthio butanoate serves as a substrate linking tryptophan deamination to sulphur metabolism. We provide the first direct evidence that these indole pigments form spontaneously from indolepyruvate and tryptophan without any enzymatic activity. This suggests that compounds with a proposed function in M. furfur‐associated disease consist of indolepyruvate‐derived spontaneously generated metabolic by‐products.
Delineation of the recombination sites necessary for integration of pathogenicity islands II and III into the Escherichia coli 536 chromosome
Authors: Wilde Caroline , Mazel Didier , Hochhut Bianca , Middendorf Barbara , Le Roux Frédérique , Carniel Elisabeth , Dobrindt Ulrich , Hacker Jörg
Published: February 2008

In uropathogenic Escherichia coli strain 536, six pathogenicity islands (PAIs) encode key virulence factors. All PAIs except PAI IV536 are flanked by direct repeats and four of them encode integrases responsible for their chromosomal excision. To study recombination sites used for the integration by PAI II536 and III536 integrases, we measured site‐specific recombination between the chromosomal integration site attB, and the PAI‐specific attachment site attP. We show that PAI III536 IntB, but not IntA, mediates PAI III536 integration. Studies of integrative recombination sites of both PAIs show that, when using a large cognate attP site (839 bp for PAI II536 and 268 bp for PAI III536), PAI II536 and III536 attB sites could be reduced to 16 bp and 20 bp, respectively, without affecting recombination. Further reduction to 14 bp for PAI II536 and 13 bp for PAI III536 diminished recombination efficiency. Surprisingly, attP sites could also be reduced to 14 bp (PAI II536) and 20 bp (PAI III536). The integration host factor (IHF) and the DNA‐bending HU protein do not influence PAI II536 recombination, but IHF enhances PAI‐III536 excision and negatively affects its integration. These data suggest that PAI intasomes differ from those of lambda and P4 integrase paradigms.
Patterns of chromosomal fragmentation due to uracil‐DNA incorporation reveal a novel mechanism of replication‐dependent double‐stranded breaks
Authors: Kouzminova Elena A. , Kuzminov Andrei
Published: February 2008

There is growing evidence that spontaneous chromosomal fragmentation, one of the main contributors to genetic instability, is intimately linked to DNA replication. In particular, we proposed before that uracil incorporation in DNA triggers chromosomal fragmentation due to replication fork collapse at uracil‐excision intermediates. We tested predictions of this model at the chromosomal level in the dut mutants of Escherichia coli, by determining the relationship between DNA replication and patterns of fragmentation in defined chromosomal segments. Here we show that the uracil‐DNA‐triggered chromosomal fragmentation: (i) has a gradient that parallels the replication gradient, (ii) shows polarity within defined segments pointing towards replication origins and (iii) reorganizes to match induced replication gradients, confirming its dynamic pattern. Unexpectedly, these fragmentation patterns not only support the replication fork collapse model, but also reveal another mechanism of the replication‐dependent chromosomal fragmentation triggered by uracil excision.
Abnormal IFN‐γ‐dependent immunoproteasome modulation by Trypanosoma cruzi‐infected macrophages
Authors: BERGERON M. , BLANCHETTE J. , ROULEAU P. , OLIVIER M.
Published: February 2008

Proteasomes are the main producers of Ag loaded onto MHC class I molecules. Following IFN‐γ stimulation however, the constitutive subunits of the proteasome are replaced by the immunosubunits low molecular weight protein 2 (LMP2), multicatalytic endopeptidase complex‐like 1 and low molecular weight protein 7 (LMP7), which generally heighten the immunogenecity of proteasome generated epitopes. Given that Trypanosoma cruzi, the aetiological agent of Chagas’ disease, elicits a Thelper1 response from its host if the infection is to be contained, the aim of this study was to verify whether this parasite modulates J774 and B10R mouse macrophage (ΜΦ) immunoproteasome subunit and MHC class I expressions and, if so, identify the mechanism(s) responsible for that modulation. Results show that T. cruzi infection of mouse ΜΦ reduces IFN‐γ‐mediated immunoproteasome synthesis, along with MHC class I mRNA synthesis and cell surface expression. The infection by T. cruzi induces the release of reactive oxygen species (ROS) from ΜΦ, and those ROS significantly inhibit protein tyrosine phosphatase activity, thereby leading to the activation of the SAPK/JNK signalling pathway, which is responsible for the observed IFN‐γ‐mediated immunoproteasome synthesis and MHC class I down‐regulation. To our knowledge, this is the first report that specifically identifies a mechanism by which a pathogen achieves immunoproteasome down‐modulation.
Multilevel genomic analysis of the response of transcripts, enzyme activities and metabolites inArabidopsisrosettes to a progressive decrease of temperature in the non‐freezing range
Authors: USADEL BJÖRN , BLÄSING OLIVER E. , GIBON YVES , POREE FABIEN , HÖHNE MELANIE , GÜNTER MANUELA , TRETHEWEY RICHARD , KAMLAGE BEATE , POORTER HENDRIK , STITT MARK
Published: February 2008

This paper characterizes the transcriptional and metabolic response of a chilling‐tolerant species to an increasingly large decrease of the temperature.ArabidopsisCol‐0 was grown at 20 °C and transferred to 17, 14, 12, 10 or 8 °C for 6 and 78 h, before harvesting the rosette and profiling >22 000 transcripts, >20 enzyme activities and >80 metabolites. Most parameters showed a qualitatively similar response across the entire temperature range, with the amplitude increasing as the temperature decreased. Transcripts typically showed large changes after 6 h, which were often damped by 78 h. Genes were induced for sucrose, proline, raffinose, tocopherol and polyamine synthesis, phenylpropanoid and flavonoid metabolism, fermentation, non‐phosphorylating mitochondrial electron transport, RNA processing, and protein synthesis, targeting and folding. Genes were repressed for carbonic anhydrases, vacuolar invertase, and ethylene and jasmonic acid signalling. While some enzyme activities and metabolites changed rapidly, most changed slowly. After 6 h, there was an accumulation of phosphorylated intermediates, a shift of partitioning towards sucrose, and a perturbation of glycine decarboxylation and nitrogen metabolism. By 78 h, there was an increase of the overall protein content and many enzyme activities, a general increase of carbohydrates, organic and amino acids, and an increase of many stress‐responsive metabolites including raffinose, proline, tocopherol and polyamines. When the responses of transcripts and metabolism were compared, there was little agreement after 6 h, but considerable agreement after 78 h. Comparison with the published studies indicated that much, but not all, of the response was orchestrated by the CBF programme. Overall, our results showed that transcription and metabolism responded in a continuous manner across a wide range of temperatures. The general increase of enzyme activities and metabolites emphasized the positive and compensatory nature of this response.
An Association Analysis Between a Silent C558T Polymorphism at the Pig Vascular Cell Adhesion Molecule 1 Locus and Sow Reproduction and Piglet Survivability Traits
Authors: Ramirez O , Tomàs A , Casellas J , Blanch M , Noguera JL , Amills M
Published: February 2008

Contents

The vascular cell adhesion molecule 1 (VCAM1) has a strong influence on embryonic development and on the formation of the umbilical cord and placenta. These developmental processes are crucial to ensure the success of pregnancy. In this work, we have identified two T306A and C558T single nucleotide polymorphisms (SNP) at exons 2 and 3 of the pig VCAM1 locus, respectively. The T306A substitution involves a non conservative Asn to Lys replacement at amino acid position 102, whereas the C558T polymorphism is synonymous. An in silico prediction of the consequences of the Asn102→Lys102 mutation with the PolyPhen software revealed that it is not deleterious. The T306A SNP segregated in the Iberian, Piétrain, Duroc, Large White and Landrace breeds as well as in European wild boars. The C558T SNP also segregated and most of commercial standard breeds. The genotyping of the C558T SNP in an Iberian × Meishan intercross allowed to find a suggestive association (Bonferroni threshold, p < 0.004) between C558T genotype and time the newborn piglet needs to reach the udder (p = 0.013) as well as a significant one with time to make the first ingestion of colostrum (p = 0.003). The biological basis of these associations remains unclear and they should be interpreted with caution.
Optimal treatment of hypertension in the elderly: A Korean perspective
Authors: Kim Kwang‐Il , Cho Young‐Seok , Choi Dong‐Ju , Kim Cheol‐Ho
Published: February 2008

With the progression of the aging population, common diseases of the elderly have become the center of attention in most developed countries. Hypertension is one of the most common morbid conditions in the elderly and has a great impact on their health status because it is the main risk factor of cardiovascular and cerebrovascular diseases. However, a considerable amount of uncertainty remains regarding hypertension in the elderly, such as the benefits of hypertension control in oldest‐old populations, the optimal level of blood pressure control, and the efficacy of antihypertensive drugs for the prevention of cognitive dysfunction. While there are many controversial issues concerning the optimal management of hypertension in the elderly, the number of elderly hypertensive patients that require treatment is expected to increase due to the aging population. As a result, knowledge regarding the mechanisms of hypertension in the elderly and specific consideration in managing hypertensive elderly patients are needed to improve the clinical outcome. Furthermore, new therapeutic interventions that are aimed at attenuating age‐related vascular changes should be investigated, because hypertension in the elderly, especially isolated systolic hypertension has specific characteristics of increased arterial stiffness in most cases.
Factors associated with carotid atherosclerosis in community‐dwelling oldest elderly aged over 80 years
Authors: Fujisawa Michiko , Okumiya Kiyohito , Matsubayashi Kozo , Hamada Tomio , Endo Hidetoshi , Doi Yoshinori
Published: February 2008

Background:  Hypertension, hyperlipidemia, impaired glucose tolerance and smoking have been known to be risk factors for atherosclerosis. Recently, it was shown that hyperhomocysteinemia is also a risk factor for cerebral vascular disease and atherosclerosis. However, it is unknown if these are also risk factors in the oldest elderly population aged 80 years or older. We carried out a cross‐sectional analysis to determine the associated factors with carotid atherosclerosis in the oldest elderly living in the community.

Methods:  Subjects consisted of 136 oldest elderly aged 80 years or older living in the community. Blood pressure, orthostatic change of blood pressure, blood chemical parameters, height and bodyweight, lifestyle and medical history were examined. The thickness was measured of the total carotid artery intima‐media complex (IMT) by carotid artery ultrasonography and used the maximum thickness (max IMT) for analysis.

Results:  The factors that correlated with max IMT were age and low γ‐glutamyl transpeptidase in males, and serum homocysteine levels in females. The subjects were divided into two groups: those with a max IMT of less than 1.0 mm and those with that of 1.0 mm or more. Factors associated with max IMT were age and abstinence from alcohol in males, and orthostatic blood pressure change in females. Factors significantly associated with higher carotid artery IMT were aging in males and orthostatic blood pressure change in females.

Conclusion:  The factors associated with carotid artery IMT as an indicator of carotid atherosclerosis in community‐dwelling oldest elderly aged 80 years or older were sex, aging, orthostatic blood pressure change and no alcohol intake. There were differences in risk factors for carotid atherosclerosis between the male and female population.
Long‐term outcome after placement of a percutaneous endoscopic gastrostomy tube
Authors: Tokunaga Takanari , Kubo Tadahiko , Ryan Suhen , Tomizawa Muneo , Yoshida Shin‐ichi , Takagi Koutarou , Furui Kumiko , Gotoh Toshio
Published: February 2008

Aim:  To evaluate long‐term survival and prognostic factors in patients who have undergone placement of a percutaneous endoscopic gastrostomy tube.

Methods:  A retrospective analysis of all patients without malignancy who underwent percutaneous endoscopic gastrostomy at Hanyu General Hospital during the period January 2001–December 2005.

Results:  A total of 198 patients (100 men, 98 women) were assessed. Median age was 78 years (range, 25–97 years). The primary diagnosis was a cerebrovascular disorder in 149 (75.3%) of the patients. Prior to placement, 120 (60.6%) had suffered pneumonia. Survival was 87.4% at 1 month, 67.8% at 3 months, 52.6% at 6 months, 38.1% at 1 year, 27.8% at 2 years and 22.3% at 3 years. Pneumonia was the most common cause of death during the follow‐up period (91 of 140 patients, 65.0%). Cox's proportional hazards model showed independent predictors of mortality to be a low serum albumin concentration (≤2.9 g/dL) and history of pneumonia before the procedure.

Conclusions:  Mortality of patients who underwent percutaneous endoscopic gastrostomy appears to be high. In particular, the long‐term prognosis was poor for patients with hypoalbuminemia, and this procedure is probably not preferred for patients with recurrent aspiration pneumonia.
Comprehensive assessment of nutritional status and associated factors in the healthy, community‐dwelling elderly
Authors: Iizaka Shinji , Tadaka Etsuko , Sanada Hiromi
Published: February 2008

Background:  Malnutrition among the elderly has become a serious problem as their population increases in Japan. To approach the risk of malnutrition in the healthy, community‐dwelling elderly is important for early prevention of malnutrition. The nutritional status and mutable associated factors with poor nutritional status specific to the healthy elderly were examined comprehensively.

Methods:  One hundred and thirty healthy elderly people from a senior college in Tokyo, Japan were eligible for this study. Nutritional status was evaluated by Mini‐Nutritional Assessment (MNA). The demographic status and potential correlates with poor nutritional status, including the physical factors (mobility, cognitive impairment and oral status) and the psychosocial factors (depression, self‐efficacy, attitudes toward health, instrumental activities of daily living, public health service knowledge, and difficulty and dissatisfaction with meal preparation) were investigated. The multiple linear regression analysis using a stepwise procedure adjusted for demographic status was performed to detect independent associated factors.

Results:  There were 16 participants (12.6%) at risk of malnutrition. The independent associated factors with lower MNA scores were depression (β = −0.27, P = 0.005), lower self‐efficacy (β = 0.25, P = 0.009), lower attitudes toward health scores (β = 0.21, P = 0.02) and difficulty with meal preparation (β = −0.18, P = 0.03).

Conclusion:  The prevalence of the healthy elderly at the initial risk of malnutrition was relatively high and should not be overlooked. The comprehensive geriatric screening and intervention including mental health, health management and life‐situation will be important for the healthy, community‐dwelling elderly.
THE ROLE OF RESEARCH IN A FIRM'S DECISION TO ENTER A MARKET AND IN ITS SUBSEQUENT OPERATIONS*
Authors: Sharp D. P.
Published: February 2008

Market research can often help in deciding whether it is advisable to enter the market for a new product. In the case below, it was decided not to enter the market; but, for completeness, the further steps to be taken if the decision had been otherwise are given in some detail.
CONFIDENCE REGIONS FOR REGRESSION PARAMETERS
Authors: Maritz J. S.
Published: February 2008

Suggestions for combining confidence interval estimates and extensions of the procedures to the determination of confidence regions for regression curves have been put forward. The merit of these ideas is believed to lie in their simplicity and potential wide applicability to a variety of regression problems.
SAMPLES OF TWO UNITS DRAWN WITH UNEQUAL PROBABILITIES WITHOUT REPLACEMENT1
Authors: Brewer K. R. W. , Udny G. C.
Published: February 2008

The method of sampling without replacement suggested by Narain, with total probability of selection proportional to size, is considered in detail. The conditions under which it is of practical value are discussed. Narain's equations for the selection probability function are examined and it is shown that they do not yield the correct solution in every case. A revised set of equations is given which is proved to yield a unique correct solution for every possible case. From this investigation, a fast iterative method of solution is derived. Prooi is offered that there is always a decrease in variance compared with sampling with replacement. A formula derived by Sen (1953) in a slightly different context is used to obtain a positive unbiased estimator of variance. Finally, the case is considered where one unit covers more than half the stratum size.
A MODEL OF SYSTEMATIC SAMPLING WITH UNEQUAL PROBABILITIES
Authors: Brewer K. R. W.
Published: February 2008

A new method is described of drawing, without replacement, two sample units per stratum from any population. The method is developed from a consideration of the asymptotic properties of systematic sampling with unequal probabilities, as the sizes of the population units tend to zero. The essential properties of this method are very easily analysed. They also converge, over a large number of strata, to those of systematic sampling from the same strata with their population units arranged in random order. In proving this, the assumption is made that the underlying population is of the type to which it is appropriate to apply ratio estimation. The sampling method described is, however, simple enough to commend itself as an alternative to systematic sampling when the underlying population is not of this type. Consideration is given to the case where the sizes of some of the population units exceed the skip interval.
GROUPING CORRECTIONS FOR SEQUENTIAL TESTS
Authors: McNeil D. R.
Published: February 2008

When testing sequentially with grouped data, we may or may not adjust the test statistic to allow for the grouping. If the test statistic is not adjusted, the whole power curve will be altered by the grouping, while if the statistic is adjusted, the power curve is altered, but the probability levels or errors of the first and second kind, being distribution‐free, are unchanged. It is shown, even for very coarse grouping of the data, that the power curve is only slightly affected by using the unadjusted statistic for tests on the mean or the variance of a normal distribution. For certain other distributions, however, in particular the negative exponential distribution, this procedure breaks down completely if the group width exceeds a certain value.
INCOMPLETE SAMPLING FOR SELECTION OF A FIXED PROPORTION
Authors: James J. W.
Published: February 2008

Testing only a sample of a population from which a fixed proportion are to be chosen for further use is considered in relation to the balance between testing costs and extra value achieved by culling the poorest members of the population. It is shown that in some circumstances the greatest return is obtained by testing some, but not all, members of the population. Optimum sampling fractions are deducted for selection on a quantitative chaaracter having a normal distribution, and approximate results are given for selection on a qualitative character.
ON IMBEDDING DISCRETE CHAINS IN CONTINUOUS TIME1
Authors: Seneta E.
Published: February 2008

Introduction and Summary

Markov chains, deflned on a discrete state‐space and a t discrete time‐points, are often used as models of processes actually occurring i J i Continuous time, by a suitable selection of the time points.

In the present note we briefly consider the reverse problem, vix. how a discrete Markov chain may be imbedded into a continuous‐time process (specifically, a Markov process) on the same states. Using simple criteria for the imbedding, i t is shown that there may be several such processes corresponding to a discrete chain. Conversely, the criteria enable us to produce several discrete chains from a single %rkov process, in such a way that the usual imbedded chain (i.e. talien a t thc instant of change of state of the process) can be interpreted in a ilrttural way.

An example is taken from population genetics where two different processes arise from a single chain, as a result of differing descriptions lcsding t o the chain. The example is then used to discuss the correspondence between certain functions of the chain and the associated process.
THE EFFECT OF POSTPONABLE INTERRUPTIONS ON A M/G/1 SYSTEM WITH IMPATIENT CUSTOMERS
Authors: Rao S. Subba
Published: February 2008

This paper considers a waiting line system where units become impatient after having waited for certain time and leave the queue (renege) without being serviced. The servicing of the units is subject to interruption by the arrival of an “interruption ” possessing a priority for service over the ordinary units, head‐of‐the‐line priority discipline being prevalent. The busy period process is investigated first, making use of the supplementary variable method. Later, the general process is studied in terms of the busy period process and renewal distributions. Lastly, the ergodic properties of the general process are examined by appealing to some results of renewal theory.
THE SAMPLING VARIANCE OF THE RELATIVE EFFICIENCY OF INDIRECT TO DIRECT SELECTION WHEN USING VARIANCE‐COVARIANCE COMPONENTS
Authors: Scheinberg Eliyahu
Published: February 2008

A formula to compute the sampling variance of the relative efficiency of indirect to direct selection is developed for the case when the genetic and phenotypic components are estimated from the analyses of variance and covariance. This formula holds provided that the genetic and phenotypic variances and covariances are bounded away from zero. It is also assumed that the number of offspring per mating group, k, is constant. The effect of varying k values and the distribution of the ratio estimator of indirect to direct selection, û, are briefly discussed. An example from an expriment using Tribolium castaneum is also given.
A NOTE ON ESTIMATING THE LOCATION AND SCALE PARAMETERS OF THE EXPONENTIAL DISTRIBUTION FROM A CENSORED SAMPLE
Authors: Tiku M. L.
Published: February 2008

Replacing f (x)/F (x) by α+β(x‐ θ)/σ in the maximum likelihood equations ∂L/∂θ and ∂L/∂σ calculated from a censored sample, a pair of estimators θe and σe, is obtained. The variances and covariances of these estimators are calculated and compared with the corresponding values for the best linear unbiassed (BLU) estimators.
ON CERTAIN CONNECTIONS BETWEEN ALGEBRAIC GEOMETRY AND STATISTICS
Authors: Linnik Yu. V.
Published: February 2008

Abstracts

The Department of Mathematical Statistics of the University of Sydney invited Professor Yu. V. Linnik, of Leningrad University, to deliver a public address to be attended by, among others, members of the 36th Congress of the International Statistical Institute. A summary of this address, delivered at 8.30 p.m. on Thursday, August 30, 1967, at the University of Sydney, is given below. Professor Linnik referred to related work of other authors, including Professors C. R. Rao and P. Whittle, who were present. Professor Rao later gave a short account of his recent work. Professor A. T. James moved a vote of thanks, which was carried by acclamation by a large audience. Reprints of the paper are being sent to those members of the International Statistical Institute present at the meeting.—EDITOR.
ON THE OPTIMAL ASYMPTOTIC TESTS FOR THE EFFECTS OF CLOUD SEEDING ON RAINFALL (1) THE CASE OF FIXED EFFECTS
Authors: Kulkarni S. R.
Published: February 2008

In this paper we consider a sequence of experimental units {un} which are t o be treated according to some random scheme. A general randomized design is suggested for the purpose. Asymptotic tests, optimal in some sense, are derived for testing the absence of the effects of the treatment. These tests are applicable in various situations, for example, when the treatment effects are additive or when they are multiplicative. Based on the asymptotic power of the tests obtained, optimality of various designs is discussed. The randomized designs discussed here have a wide range of applicability, e.g. in weather modification experiments and bio‐assay.
ON DERIVATION OF INITIAL BLOCKS OF B.I.B. DESIGNS WITH MORE THAN ONE INITIAL BLOCK
Authors: Das M. N. , Kulshreshtha A. C.
Published: February 2008

Introduction and Summary

A good amount of work has been done on the construction of balanced incomplete block (B.I.B.) designs by Bose (1939, 1942), Sprott (1954, 1956), Rao (1961), Takeuchi (1962) and others. Sprott (1954, 1956) obtained several series of B.I.B. designs through difference sets.

The main purpose of the present investigation is to provide two methods of construction of B.I.B. designs obtainable through more than one initial block. The first method derives initial blocks of a series of designs from some specified blocks of a B.I.B. design obtainable by developing one or more initial blocks. The second method attempts to obtain one of the initial blocks (the basic initial block) through the different powers of an element of a finite field; then an appropriate method for generating the other initial blocks from it is discussed. A table showing the basic initial block for different designs has been presented.

By these methods several solutions of some B.I.B. designs could be obtained from different initial blocks. An examination was therefore made to see if these designs were all isomorphic.
A REGRESSION‐ TYPE ESTIMATOR IN SAMPLING WITH PPS AND WITH REPLACEMENT
Authors: Tripathi T. P.
Published: February 2008

A regression‐type estimator is proposed for the population total of a charactery, when sample‐units are selected with probability proportional to some measure of sizez (pps) and with replacement; and the information on yet another variatex is used. The proposed estimator is shown to be superior to the well‐known estimator (pps with replacement), and the ratio estimator (pps with replacement). It is also shown to be superior to the simple random estimator under some general conditions.
DOUBLY NON‐CENTRAL t DISTRIBUTION
Authors: Tiku M. L.
Published: February 2008

The probability integral of the doubly non‐central t distribution is expressed as a series expansion that is easy to programme for an electronic computer.
ON TWO‐STAGE SUCCESSIVE SAMPLING
Authors: Singh D. , Kathuria O. P.
Published: February 2008

In repeated sampling enquiries application of method of successive sampling with partial replacement of units is advantageous. In this paper use of successive sampling technique when the sampling design is multi‐stage has been studied. Estimates of population mean and its variance have been obtained (a) on the second occasion, and (b) on the h‐th occasion under two systems of replacement, namely (i) by retaining only a fraction p of psu's along with their sample of ssu's, and (ii) by retaining all the psu's on the second occasion, but from each psu only a fraction p of the ssu's within them is retained. A cost function suitable to the design has been illustrated, with the help of data collected from a sample survey conducted by the Indian Council of Agricultural Research.
A TWO‐PHASE SAMPLING ESTIMATOR IN SAMPLE SURVEYS
Authors: Srivastava Surendra K.
Published: February 2008

A two‐phase sampling estimator of the ratio‐type for estimating the mean Ȳ of a finite population, has been considered where the value of ρCy/Cx can be guessed or estimated in advance. Here Cy and Cx denote respectively the coefficients of variation of the characteristic under study, y, and the auxiliary characteristic x and ρ denotes the coefficient of correlation between y and x. When the value of ρCy/Cx is guessed or estimated exactly, the estimator has a smaller large‐sample variance compared with either an ordinary ratio estimator or an ordinary linear regression estimator in two‐phase sampling in the case where the first‐phase sample is drawn independently from the second‐phase sample. If the sample at the second phase is a subsample of the first‐phass̀e sample, the estimator has variance equal to that of the linear regression estimator. The largest value of the difference between the assumed value and the actual value of ρCy/Cx has been obtained so as not to result in the variance of the estimator being larger than the variances of either an ordinary ratio estimator or an ordinary linear regression estimator.
DISTRIBUTION OF THE NUMBER OF MARKOVIAN RENEWALS IN AN ARBITRARY INTERVAL
Authors: Kshirsagar A. M. , Gupta Y. P.
Published: February 2008

A Markov Renewal Process (M.R.P.) is one which records at each time t, the number of times a system visits each of m states in time t, if the transitions from state to state are according to a Markov chain and if the time required for each successive move is a random variable whose distribution function (d.f.) depends on the two states between which the move is made. In this paper, the distribution of the number of times each state is visited in an arbitrary interval (t0, t0+t) is derived. Asymptotic expressions for the mean and variance of this distribution are also obtained.
MINIMUM RATE OF PROGRESS FORMULAE AT UNIVERSITIES1
Authors: Pollard A. H.
Published: February 2008

In an earlier paper by the present author (1970) a comparison was made of graduation rates and pass rates under a pass‐on‐the‐year system with those under a credit points system. In the present paper attention is focused on the effect, under these two systems, of regulations which exclude students who have not achieved the required minimum rate of progress. The paper traces the progress made by homogeneous groups of students when there is no exclusion formula, points out why such formulae are needed under both systems, and measures the efficiency of a university system in terms of the proportion of a given quality intake which it graduates and of the cost measured by the number of students required to be maintained on campus to produce one graduate.

Precise definitions of the terms used are not repeated here because they are in common usage; they are, however, given in the earlier
On Some Chemical Balance Weighing Designs
Authors: Dey A.
Published: February 2008

The present paper deals with certain chemical balance weighing designs. The incidence matrices of BIB designs and balanced ternary designs have been used to construct these designs. Conditions have been obtained to make some of these designs “optimum”.
Student's Distribution Under Non‐Normal Situations
Authors: Tiku M. L.
Published: February 2008

The distribution of Student's t statistic under non‐normal situations is obtained. The effect of non‐normality on type I error and the power of the two‐sided t‐test is studied in some detail.
On a Theorem of Quine and Seneta for the Galton‐Watson Process With Immigration
Authors: Pakes A. G.
Published: February 2008

Recently a limit theorem has been obtained for the limiting‐stationary distribution of a process in which individuals reproduce as in a subcritical Galton‐Watson process and are subject to an independent immigration component at each generation. This paper provides a different proof of this theorem, and under slightly weaker conditions. A similar approach is used to obtain a limit form of Taglom's theorem for the ordinary subcritical Galton‐Watson process.
A NOTE ON THE DISTRIBUTION OF THE DOUBLY NON‐CENTRAL F DISTRIBUTION1
Authors: Tiku M. L.
Published: February 2008

A three‐moment central‐F approximation is examined for its usefulness in giving accurate values of the probability integral of the doubly non‐central F distribution.
ROBUST ESTIMATION FOR A SIMPLE EXPONENTIAL MODEL1
Authors: Bao P.V.
Published: February 2008

A Hodges‐Lehmann type estimator (Hodges and Lehmann, 1963) is proposed for the parameter p in the simple exponential model (1) y=1‐exp.(‐ρx)+ε Some exact and asymptotic properties of the proposed estimator are also given.
LEAST SQUARES ANALYSIS OF FREIGHT‐RATE ANOMALIES1
Authors: KERR J. D.
Published: February 2008

Regression methods are applied to freight rate data providing a simple method of identifying anomalies, and calculating and adjusting charges. Application to problems of assessing economic consequences of changes are indicated.
AN ASYMPTOTIC EXPANSION FOR THE VARIANCE OF THE ERRORS OF MISCLASSIFICATION OF THE LINEAR DISCRIMINANT FUNCTION1
Authors: McLachlan G.J.
Published: February 2008

A technique for deriving asymptotic expansions for the variances of the errors of misclassification of the linear discriminant function (Anderson's classification statistic) is developed. These expansions are shown to be in reasonable agreement with the sample values of the variances of the errors obtained from some sampling experiments.
MOMENTS OF A LINEARLY TRUNCATED BIVARIATE NORMAL DISTRIBUTION1
Authors: Nath G. Baikunth
Published: February 2008

The moments are obtained for a bivariate normal distribution which is linearly truncated with respect to both variables; the variables may be correlated. From these moments the parameters of the distribution can be estimated.
ON THE DISTRIBUTIONS OF ORDER STATISTICS1
Authors: Tiku M. L. , Malik H. J.
Published: February 2008

Approximations to the distributions of order statistics based on x2t are obtained. These are easy to compute and provide reasonably accurate values for the percentage points and probability integrals of the distributions.
A NOTE ON SAMPLING OVER TWO OCCASIONS1
Authors: Singh Ravindra
Published: February 2008

Using simple random sampling without replacement (SRSWOR) on both occasions, a new scheme of selecting the unmatched part of the sample on second occasion is presented. The proposed estimate of the population mean has been shown to be more efficient than the estimate of Pathak and Rao (1967) for the same expected cost. Kulldorff's estimate as considered by Rao and Ghangurde (1969), however, remains superior to the proposed estimate.
ON SOME PRODUCT TYPE ESTIMATORS IN VARYING PROBABILITY1
Authors: Gupta P. C.
Published: February 2008

It is shown that varying probability in product method estimation increases the efficiency of estimate under some usual conditions. Further, a necessary condition, for the product estimate from a sample drawn with pps and without replacement to be more efficient than the product estimate from a sample drawn with pps and replacement, has been obtained; incidentally, it is the same as obtained by Narain (1951) for varying probability without replacement to be more efficient than varying probability with replacement. The use of the R.H.C. sampling scheme has also been suggested, and its variance and bias has been shown to be always less than that of pps with replacement.
IN JUSTIFICATION OF WALD'S CRITERION OF EFFICIENCY OF EXPERIMENTAL DESIGNS IN RELATION TO THE WEIGHING PROBLEM1
Authors: Banerjee K. S.
Published: February 2008

Wald (1943), among others, examined the question of efficiency of experimental designs in general and suggested the criterion of maximization of the det. [X'X] for the purpose, where X denotes the design matrix. In the same context, Ehrenfeld (1955) recommended the maximization of the minimum eigenvalue of [X'X] as the desideratum. It has been shown in this note that for weighing designs in general maximization of det. [X'X] may be preferred to the latter criterion.
LIKELIHOODS WITH ROUNDED DATA
Authors: Lambert J. A.
Published: February 2008

Observed continuous random variates are effectively “discretized” by the limited accuracy with which they can be recorded. The effects of this on the likelihood function and on maximum likelihood estimation are often overlooked. Some published data for the exponential distribution are examined and the results compared with earlier studies. A note on estimation for the normal distribution is also given.
A NOTE ON TRANSITION PROBABILITY ESTIMATION
Authors: Dent Warren
Published: February 2008

The usual regression model for the estimation of Markovian transition probabilities is examined under the assumption that the disturbance terms are normally distributed. It is found that for a certain variance‐covariance structure, the regular quadratic programming estimates are the same as the maximum likelihood estimates when non‐negativity is imposed.
ESTIMATION OF SCALE AND LOCATION PARAMETERS, USING QUADRATIC COEFFICIENTS
Authors: Hirai Abdul Samad
Published: February 2008

A particular linear estimate with three terms approximation using ordered observations is discussed which seems to be simple to calculate. This estimate is applicable for any sample size for some special distributions without considerable loss in efficiency and is, therefore, of practical value.
ESTIMATION OF LLUCH'S EXTENDED LINEAR EXPENDITURE SYSTEM FROM CROSS‐SECTIONAL DATA1
Authors: Powell Alan
Published: February 2008

Complete sets of demand relations may be fitted using varying types of sample information and varying a priori specifications. In this paper the identification and estimation of Lluch's extended linear expenditure system (ELES) from cross‐sectional data alone is investigated. Under the most favourable conditions of data availability, all of the parameters of the ELES model are identified, and are estimable by the method of reduced form least squares. This is the case where observations on permanent income are available for the consuming units of the cross section and where, in addition, prices are recorded (even though they do not vary from one consuming unit to the next). Under the least favourable conditions only the marginal budget shares are identified. This corresponds to the case where no data on permanent income, or on savings, are available. The conventional ordinary least squares estimators of the marginal budget shares are, under these conditions, biased and inconsistent. Expressions are developed for the large‐sample biases.
WAITING TIME IN THE COUPON‐COLLECTOR'S PROBLEM1
Authors: Nath Harmindar B.
Published: February 2008

The coupon collector's problem is generalized by allowing unequal proportions of the various types of coupons. The upper tail probabilities are used to find the probability distribution of the waiting time. The probability generating function is expressed in terms of the hypergeometric functions and therefrom the mean and the variance are derived.
VARIABLE WEIGHT DISTRIBUTED LAGS: HOUSING COMPLETIONS IN AUSTRALIA1
Authors: Williams Ross A.
Published: February 2008

This paper presents a convenient way of allowing the weights of a (truncated) geometric lag distribution to vary in the short‐run around the average relationship. An alternative version which amounts to an inverted‐V lag distribution is developed. The models are applied to the relationship between work done on dwellings and dwelling commencements in Australia over the past decade.
ON TESTING THE EQUALITY OF LOCATION PARAMETERS IN k CENSORED EXPONENTIAL DISTRIBUTIONS
Authors: Khatri C. G.
Published: February 2008

Kumar and Patel (1971) have considered the problem of testing the equality of location parameters of two exponential distributions on the basis of samples censored from above, when the scale parameters are the same and unknown. The test proposed by them is shown to be biased for n1≠n2, while for n1=n2 the test possesses the property of monotonicity and is equivalent to the likelihood ratio test, which is considered by Epstein and Tsao (1953) and Dubey (1963a, 1963b). Epstein and Tsao state that the test is unbiased. We may note that when the scale parameters of k exponential distributions are unknown the problem of testing the equality of location parameters is reducible to that of testing the equality of parameters in k rectangular populations for which a test and its power function were given by Khatri (1960, 1965); Jaiswal (1969) considered similar problems in his thesis. Here we extend the problem of testing the equality of k exponential distributions on the basis of samples censored from above when the scale parameters are equal and unknown, and we establish the likelihood ratio test (LET) and the union‐intersection test (UIT) procedures. Using the results previously derived by Jaiswal (1969), we obtain the power function for the LET and for k= 2 show that the test possesses the property of monotonicity. The power function of the UIT is also given.