bluuebunny/crossref_metadata_2025 huggingface dataset:
Three‐dimensional gravity inversion using simulated annealing: Constraints on the diapiric roots of allochthonous salt structures
Authors: Nagihara Seiichi , Hall Stuart A.
Published: October 2002

In the northern continental slope of the Gulf of Mexico, large oil and gas reservoirs are often found beneath sheetlike, allochthonous salt structures that are laterally extensive. Some of these salt structures retain their diapiric feeders or roots beneath them. These hidden roots are difficult to image seismically. In this study, we develop a method to locate and constrain the geometry of such roots through 3‐D inverse modeling of the gravity anomalies observed over the salt structures. This inversion method utilizes a priori information such as the upper surface topography of the salt, which can be delineated by a limited coverage of 2‐D seismic data; the sediment compaction curve in the region; and the continuity of the salt body. The inversion computation is based on the simulated annealing (SA) global optimization algorithm. The SA‐based gravity inversion has some advantages over the approach based on damped least‐squares inversion. It is computationally efficient, can solve underdetermined inverse problems, can more easily implement complex a priori information, and does not introduce smoothing effects in the final density structure model. We test this inversion method using synthetic gravity data for a type of salt geometry that is common among the allochthonous salt structures in the Gulf of Mexico and show that it is highly effective in constraining the diapiric root. We also show that carrying out multiple inversion runs helps reduce the uncertainty in the final density model.
Scalar reverse‐time depth migration of prestack elastic seismic data
Authors: Sun Robert , McMechan George A.
Published: October 2002

Reflected P‐to‐P and P‐to‐S converted seismic waves in a two‐component elastic common‐source gather generated with a P‐wave source in a two‐dimensional model can be imaged by two independent scalar reverse‐time depth migrations. The inputs to migration are pure P‐ and S‐waves that are extracted by divergence and curl calculations during (shallow) extrapolation of the elastic data recorded at the earth’s surface. For both P‐to‐P and P‐to‐S converted reflected waves, the imaging time at each point is the P‐wave traveltime from the source to that point. The extracted P‐wave is reverse‐time extrapolated and imaged with a P‐velocity model, using a finite difference solution of the scalar wave equation. The extracted S‐wave is reverse‐time extrapolated and imaged similarly, but with an S‐velocity model. Converted S‐wave data requires a polarity correction prior to migration to ensure constructive interference between data from adjacent sources. Synthetic examples show that the algorithm gives satisfactory results for laterally inhomogeneous models.
Numerical modeling and interpretation of drillstring waves
Authors: Poletto Flavio , Malusa Massimo , Miranda Francesco
Published: October 2002

Drill‐bit seismic and pilot seismograms contain drillstring periodicities from signal and environmental noise sources. These coherent components are similar in seismic‐while‐drilling correlations, and their joint contribution may cause distortions in signal processing. Numeric modeling of the drillstring transmission line is used to correctly interpret the axial and torsional events with similar propagating modes of signal and noise. The reflection coefficients are computed for drillstrings of arbitrary materials, and their average mechanical features are related to the axial and torsional group velocities obtained by the dispersion equations. Fitting of the periodical components in the real seismograms is used to automatically correct the drill‐bit pilot delays and to estimate the surface and downhole boundary conditions.
Resolving refractor ambiguities with amplitudes
Authors: Palmer Derecke
Published: October 2002

Amplitudes are used to constrain refraction models. This study demonstrates that the refraction time section generated through the convolution of forward and reverse refraction traces together with a static shift facilitates the convenient recognition of amplitude variations related to changes in refractor wavespeed. For large contrasts in wavespeeds between the upper layer and the refractor, the head coefficient is approximately proportional to the ratio of the specific acoustic impedances. Since the convolution operation effectively multiplies the amplitudes of the forward and reverse arrivals, the convolved amplitudes are proportional to the square of this ratio. In general, the higher the contrast in the refractor wavespeed and/or density, the lower the amplitude. The regions recognized in the wavespeed analysis function correlate with those determined with amplitudes, thereby providing an additional constraint on inversion with model‐based approaches.
Ore detection and grade estimation in the Sudbury mines using thermal infrared reflectance spectroscopy
Authors: Rivard Benoit , Feng Jilu , Gallie E. Ann , Francis Helen
Published: October 2002

This pilot study investigated the usefulness of thermal infrared reflectance (TIR) spectroscopy to estimate ore grade in an underground environment and to separate ore‐bearing samples from their host rocks. Work was carried out under laboratory conditions to test the initial concept; all samples had naturally broken faces to mimic the situation in a freshly blasted underground opening. A total of 26 samples, including massive and disseminated ores, were collected from eight mines around the Sudbury basin in Ontario. Rock surfaces were measured wet and dry to address environmental conditions encountered underground. To separate barren rocks from ores and for ore‐grade estimation, an important finding of this research is that, in the region of [Formula: see text], most known silicate minerals converge to a common reflectance minima (<1.5%), but massive and disseminated sulfides have distinctly higher reflectance. Individual sulfide minerals (chalcopyrite, pyrrhotite, pentlandite), however, do not reveal diagnostic features in this spectral region. When sulfides are disseminated in the host rock, the average reflectance of the rock increases but the correlation with abundance is not systematic. However, sulfide concentration as a function of continuum‐removed reflectance (CRR) is systematic. The empirical correlation between CRR at [Formula: see text] versus the total sulfide concentration, estimated via thin‐section point counts, gives a coefficient of determination value [Formula: see text] of 0.93 for measurement of dry and wet surfaces when averaged. Similar results are observed when dry and wet locations are analyzed separately. The relationship demonstrates the feasibility to estimate total sulfide concentration from TIR reflectance data even when samples are wet.
Denoising of aeromagnetic data via the wavelet transform
Authors: Leblanc George E. , Morris William A.
Published: October 2002

Noise has traditionally been suppressed or eliminated in aeromagnetic data sets by the use of Fourier analysis filters and, to a lesser degree, nonlinear statistical filters. Although these methods are quite useful under specific conditions, they produce undesirable effects when denoising features of moderate to large amplitude and spatial extent. In this study, a new wavelet analysis procedure is presented that substantially reduces the contribution from high‐frequency random noise and noise that is user defined. Applications to both synthetic data and aeromagnetic data from southern Alberta, Canada, show that the wavelet method eliminates the noise portion of the signal more efficiently and retains a greater amount of geologic data than other methods.
Optimizing operations in 3‐D land seismic surveys
Authors: Morrice Douglas J. , Kenyon Astrid S. , Beckett Christian J.
Published: October 2002

We formulate and solve a mathematical programming optimization model to find a minimum cost solution for an orthogonal split‐spread design in a 3‐D land seismic survey. The model contains decision variables on source and receiver location spacings, the amount of receiver equipment, and the production rate of the seismic crews. The model includes operational constraints for source and receiver movements. It also includes geophysical constraints for fold coverage, offset, and azimuth. To demonstrate the efficacy of the model, we include an example and solve it using the nonlinear optimization solver in Microsoft Excel. The model results demonstrate the classic trade‐off between source and receiver points to satisfy the geophysical requirements. In addition, we conduct sensitivity analysis on an important production parameter: the maximum number of source points that can be shot per day. We show that although changes to this parameter do not impact the decision variables, such changes do have a significant effect on the total cost of the survey.
Examination of AVO responses in the eastern deepwater Gulf of Mexico
Authors: Smith Tad M. , Sondergeld Carl H.
Published: October 2002

Exploration programs in deepwater Tertiary basins (e.g., the Gulf of Mexico) typically rely on bright‐spot and amplitude variation with offset (AVO) technology to help identify oil‐ and gas‐charged sands. The reliance on these attributes, along with the high cost of exploration programs in deepwater environments, has driven the need to examine the limitations of these technologies and to build robust models for the conditions under which AVO is useful as a fluid and/or lithology indicator. We build subregional AVO background trends for both brine‐ and gas‐saturated sands from several wells from the eastern deepwater Gulf of Mexico. These trends are built from the depth dependencies of velocities and densities for both shale and sands (brine saturated). Simple models of AVO gradient and intercept are constructed as a function of depth below the mud line. Sand and shale properties show little velocity contrast, justifying the interpretation of these data in the context of linearized AVO models. In addition to the in‐situ brine response, the response to gas is also calculated. These trend models indicate that the AVO response is suppressed (although still positive) below a depth of approximately 10 000 ft below the mud line. Even optimistic porosity modeling (sand porosity >30°) does not substantially change this conclusion. An important corollary is that the absence of a strong AVO anomaly at these deeper depths cannot be used with confidence when ruling out hydrocarbon presence. This observation also highlights the need to crossplot attributes to best predict hydrocarbon presence. Velocity data collected as part of this study are also used to generate a local shear velocity estimator for sands and shale. These shear estimators are similar in form to other published estimators, but minor differences in coefficients may become important in AVO modeling.
Geopressure prediction from automatically‐derived seismic velocities
Authors: Kan T. K. , Swan Herbert W.
Published: October 2002

The phenomenon of geopressure is essentially stratigraphic in nature. In most cases, its occurrence correlates strikingly well with some mappable geologic characteristics, such as lithology changes, sediment deformation, and faulting. High‐precision velocity estimates can be made from the apparent amplitude variations with offset (AVO) that result from moveout errors, even if the seismic data itself lacks any intrinsic AVO. These velocity estimates provide us with an opportunity to estimate cross‐sections and 3‐D volumes of the gradient of pore pressure with depth from surface seismic data. These cross‐sections and volumes may be obtained through the estimation of seismic interval velocities as a function of depth, subtraction of the shale compaction trend, and the calibration of trend deviations in terms of pore‐pressure gradients. When viewed in combination with stacked seismic sections, the pore‐pressure gradient sections provide the interpreter added information about the hydrogeology of the sediment. In this paper, we show examples of pressure gradients caused by a lithology change, sealing faults, and fluid migration flows. Pressure gradient cross‐sections are also extremely useful for the design of mud densities and casing prior to spudding a well.
Preventive Care in the Emergency Department: Screening and Brief Intervention for Alcohol Problems in the Emergency Department: A Systematic Review
Authors: D'Onofrio Gail , Degutis Linda C.
Published: October 2002

Objective: To systematically review the medical literature in order to determine the strength of the recommendation for screening and brief intervention (SBI) for alcohol‐related problems in the emergency department (ED) setting. Methods: The review followed the methodology of systematic reviews and was facilitated through the use of a structured template, a companion explanatory piece, and a grading and methodological scoring system based on published criteria for critical appraisal. The primary outcome measure was the prevention of mortality and morbidity secondary to alcohol‐related illnesses/injuries. The secondary outcome measures included: decreased consumption; fewer ED/outpatient visits and hospitalizations; a decrease in social consequences; and increased referrals for follow‐up and/or treatment. Three Medline searches as well as a search of the Cochrane Library were performed. Two team members reviewed the abstracts and selected pertinent articles. References were screened for additional pertinent articles. Results: Twenty‐seven articles were identified and reviewed, in addition to the 14 primary articles included in the 1996 U.S. Preventive Services Task Force Report. The study populations were diverse, including inpatient, outpatient, and college settings, with ages ranging from 12 to 70 years. Four studies were ED‐based and two included EDs as one of multiple sites. Thirty‐nine studies on SBI, 30 randomized controlled and nine cohort, were used to formulate the current recommendation. A positive effect of the intervention was demonstrated in 32 of these studies. Conclusions: The authors recommend that SBI for alcohol‐related problems in the ED be incorporated into clinical practice.
Selective Use of Ultrasonography for the Detection of Pneumoperitoneum
Authors: Chen Shyr‐Chyr , Wang Hsiu‐Po , Chen Wen‐Jone , Lin Fang‐Yue , Hsu Chieu‐Yao , Chang King‐Jen , Chen Wei‐Jao
Published: October 2002

Objective: Whether ultrasonography is superior to plain radiography for the detection of pneumoperitoneum is unknown. The goal of this study was to determine the value of ultrasonography for the detection of pneumoperitoneum. Methods: One hundred thirty‐two patients with suspected hollow‐organ perforation were prospectively selected for study. All 132 patients received ultrasonography, upright chest radiography, and left lateral decubitus abdominal radiography examinations. The diagnostic accuracies of chest and abdominal radiographs for the detection of pneumoperitoneum were compared with corresponding values from ultrasonography. Results: Of the 125 patients who underwent laparotomy, 121 patients had hollow‐organ perforation, three patients had perforated appendicitis, and one patient had acute cholecystitis. For the diagnosis of pneumoperitoneum, ultrasonography demonstrated a sensitivity of 93%, a specificity of 64%, a positive predictive value of 97%, a negative predictive value of 44%, and an accuracy of 90%. Plain radiography revealed a sensitivity of 79%, a specificity of 64%, a positive predictive value of 96%, a negative predictive value of 21%, and an accuracy of 77%. Conclusions: Ultrasonography is a more sensitive diagnosing modality than plain radiography for the diagnosis of pneumoperitoneum. The authors suggest that ultrasonography was a useful diagnostic modality when plain radiographs failed to reveal pneumoperitoneum among patients with suspected hollow‐organ perforation.
Treatment of Unfavorable Childhood Hodgkin’s Disease With VEPA and Low-Dose, Involved-Field Radiation
Authors: Friedmann Alison M. , Hudson Melissa M. , Weinstein Howard J. , Donaldson Sarah S. , Kun Larry , Tarbell Nancy J. , Link Michael P.
Published: October 2002

PURPOSE: Between January 1990 and April 1993, 56 pediatric patients with Hodgkin’s disease were treated on a single-arm trial at three institutions with a regimen designed to maintain high cure rates while minimizing the potential late effects of treatment, such as infertility, second malignant neoplasms, and cardiopulmonary injury.

PATIENTS AND METHODS: The regimen used combined-modality therapy with six cycles of vinblastine, etoposide, prednisone, and doxorubicin (VEPA) chemotherapy and low-dose, involved-field radiation. Unfavorable features comprised bulky presentations of localized (stage I or II) disease or advanced (stage III or IV) Hodgkin’s disease.

RESULTS: Of 56 patients enrolled, 26 (46%) had unfavorable presentations of stage I/II disease and 30 (54%) had advanced (stage III/IV) disease. Seventy-nine percent of the patients are alive without disease at a median follow-up time of 8.9 years from diagnosis. Nineteen patients had events at a median of 1.5 years (range, 0.4 to 7.9 years) from diagnosis; 17 patients relapsed, one died of cardiomyopathy, and one died of accidental injuries. Survival and event-free survival (EFS) estimates at 5 years for the entire cohort were 81.9% (SE, 5.2%) and 67.8% (SE, 6.3%), respectively. Five-year EFS by stage was 100% for stage I, 79.2% (SE, 8.3%) for stage II, 70% (SE, 14.5%) for stage III, and 49.5% (SE, 11.3%) for stage IV patients.

CONCLUSION: Combined-modality therapy with VEPA chemotherapy and low-dose, involved-field radiation is adequate for disease control of early-stage patients with unfavorable features, but it is inferior to other standard regimens for advanced-stage patients.
Anxiety Disorders in Cancer Patients: Their Nature, Associations, and Relation to Quality of Life
Authors: Stark D. , Kiely M. , Smith A. , Velikova G. , House A. , Selby P.
Published: October 2002

PURPOSE: We aimed to estimate the prevalence and types of anxiety disorders diagnosed according to standardized criteria in cancer patients, to compare screening tools in detecting them, and to examine their demographic, oncologic, and psychosocial associations.

METHODS: In this cross-sectional observational study of 178 subjects with lymphoma, renal cell carcinoma, malignant melanoma, or plasma cell dyscrasia, we related responses to questionnaires (administered by computer touch-screen) measuring psychological symptoms, quality of life (QOL), and social support to standardized psychiatric interviews and cancer management.

RESULTS: Forty-eight percent of subjects reported sufficient anxiety for anxiety disorder to be considered. At subsequent diagnostic interview, 18% fulfilled International Classification of Disorders, 10th Revision criteria for anxiety disorder, including 6% of patients who reported low levels of anxiety by questionnaire. When subjects reported anxiety by questionnaire, if disruptive somatic anxiety was present, this increased the probability of diagnosable anxiety disorder from .31 to .7. The most accurate screening questionnaires were the trait scale of the State-Trait Anxiety Inventory and the Hospital Anxiety and Depression scale. Female sex and negative aspects of social support were associated with anxiety disorder in multivariate analyses. Anxiety disorder was independently associated with a deficit in QOL, particularly insomnia.

CONCLUSION: Anxiety symptoms are common in cancer patients. Screening by questionnaire seems to assess anxiety symptoms adequately but discriminates abnormal anxiety inadequately. To improve this, we may need to use criteria such as disruption from anxiety, as illustrated by the impact of anxiety disorders on QOL. There seem to be few oncologic variables that could target screening for anxiety disorders.
Impact of Race on Prostate-Specific Antigen Outcome After Radical Prostatectomy for Clinically Localized Adenocarcinoma of the Prostate
Authors: Cross Chaundre K. , Shultz Delray , Malkowicz S. Bruce , Huang William C. , Whittington Richard , Tomaszewski John E. , Renshaw Andrew A. , Richie Jerome P. , D’Amico Anthony V.
Published: October 2002

PURPOSE: To compare prostate-specific antigen (PSA) outcome after radical prostatectomy (RP) for prostate cancer in African-American and white men using previously established risk groups.

PATIENTS AND METHODS: Between 1989 and 2000, 2,036 men (n = 162 African-American men, n = 1,874 white men) underwent RP for clinically localized prostate cancer. Using pretreatment PSA, Gleason score, clinical T stage, and percentage of positive biopsy specimens, patients were stratified into low- and high-risk groups. For each risk group, PSA outcome was estimated using the actuarial method of Kaplan and Meier. Comparisons of PSA outcome between African-American and white men were made using the log-rank test.

RESULTS: The median age and PSA level for African-American and white men were 60 and 62 years old and 8.8 and 7.0 ng/mL, respectively. African-Americans had a statistically significant increase in PSA (P = .002), Gleason score (P = .003), clinical T stage (P = .004), and percentage of positive biopsy specimens (P = .04) at presentation. However, there was no statistical difference in the distribution of PSA, clinical T stage, or Gleason score between racial groups in the low- and high-risk groups. The 5-year estimate of PSA outcome was 87% in the low-risk group for all patients (P = .70) and 28% versus 32% in African-American and white patients in the high-risk group (P = .28), respectively. Longer follow-up is required to confirm if these results are maintained at 10 years.

CONCLUSION: Even though African-American men presented at a younger age and with more advanced disease compared with white men with prostate cancer, PSA outcome after RP when controlled for known clinical predictive factors was not statistically different. This study supports earlier screening in African-American men.
On the existence of the stable birth-type distribution in a general branching process cell cycle model with unequal cell division
Authors: Alexandersson Marina
Published: October 2002

We use multi-type branching process theory to construct a cell population model, general enough to include a large class of such models, and we use an abstract version of the Perron-Frobenius theorem to prove the existence of the stable birth-type distribution. The generality of the model implies that a stable birth-size distribution exists in most size-structured cell cycle models. By adding the assumption of a critical size that each cell has to pass before division, called the nonoverlapping case, we get an explicit analytical expression for the stable birth-type distribution.
Convergence of the number of failed components in a Markov system with nonidentical components
Authors: Bon Jean-Louis , Păltănea Eugen
Published: October 2002

For most repairable systems, the number N(t) of failed components at time t appears to be a good quality parameter, so it is critical to study this random function. Here the components are assumed to be independent and both their lifetime and their repair time are exponentially distributed. Moreover, the system is considered new at time 0. Our aim is to compare the random variable N(t) with N(∞), especially in terms of total variation distance. This analysis is used to prove a cut-off phenomenon in the same way as Ycart (1999) but without the assumption of identical components.
Optimal stopping on trajectories and the ballot problem
Authors: Tamaki Mitsushi
Published: October 2002

An urn contains m minus balls and p plus balls, and we draw balls from this urn one at a time randomly without replacement until we wish to stop. Let Pn and Mn denote the respective numbers of plus balls and minus balls drawn by time n and define Z0 = 0, Zn = Pn - Mn, 1 ≤ n ≤ m + p. The main problem of this paper is to stop with maximum probability on the maximum of the trajectory formed by . This problem is closely related to the celebrated ballot problem, so that we obtain some identities concerning the ballot problem and then derive the optimal stopping rule explicitly. Some related modifications are also studied.
Recursive estimation of distributional fix-points
Authors: Embrechts Paul , Walk Harro
Published: October 2002

In various stochastic models the random equation of implicit renewal theory appears where the real random variable S and the stochastic process Ψ with index space and state space R are independent. By use of stochastic approximation the distribution function of S is recursively estimated on the basis of independent or ergodic copies of Ψ. Under integrability assumptions almost sure L1-convergence is proved. The choice of gains in the recursion is discussed. Applications are given to insurance mathematics (perpetuities) and queueing theory (stationary waiting and queueing times).
A general minimal repair model
Authors: Aven Terje , Jensen Uwe
Published: October 2002

Minimal repairs have been given considerable attention in the reliability literature. Instead of replacing a failed system by a new one, such a minimal repair restores the system to the state it had just before failure. But the state just before failure depends on the information which is available about the system. Different information levels are possible. This paper gives a general definition characterizing point processes which describe time points of minimal repairs with respect to a certain information level. Some examples demonstrate the wide range of applications.
Passage time moments for multidimensional diffusions
Authors: Balaji S. , Ramasubramanian S.
Published: October 2002

Let τr denote the hitting time of B(0:r) for a multidimensional diffusion process. We give verifiable criteria for finiteness/infiniteness of As an application we exhibit classes of diffusion processes which are recurrent but is infinite for all p > 0, |x| > r > 0; this includes the two-dimensional Brownian motion and the reflecting Brownian motion in a wedge with a certain parameter α = 0.
Ornstein-Uhlenbeck type processes and branching processes with immigration
Authors: Li Zeng-Hu
Published: October 2002

It is shown that an Ornstein-Uhlenbeck type process associated with a spectrally
positive Lévy process can be obtained as the fluctuation limits of both discrete state and continuous state branching processes with immigration.
Estimation of limiting availability for a stationary bivariate process
Authors: Abraham B. , Balakrishna N.
Published: October 2002

We estimate the limiting availability of a system when the operating and repair times form a stationary bivariate sequence. These estimators are shown to be consistent and asymptotically normal under certain conditions. In particular, we estimate the limiting availability for a bivariate exponential autoregressive process.
Taylor's formula and preservation of generalized convexity for positive linear operators
Authors: Adell José A. , Lekuona Alberto
Published: October 2002

In this paper, we consider positive linear operators L representable in terms of stochastic processes Z having right-continuous non-decreasing paths. We introduce the equivalent notions of derived operator and derived process of order n of L and Z, respectively. When acting on absolutely continuous functions of order n, we obtain a Taylor's formula of the same order for such operators, thus extending to a positive linear operator setting the classical Taylor's formula for differentiable functions. It is also shown that the operators satisfying Taylor's formula are those which preserve generalized convexity of order n. We illustrate the preceding results by considering discrete time processes, counting and renewal processes, centred subordinators and the Yule birth process.
Level phase independence for GI/M/1-type Markov chains
Authors: Latouche Guy , Taylor P. G.
Published: October 2002

GI/M/1-type Markov chains make up a class of two-dimensional Markov chains. One dimension is usually called the level, and the other is often called the phase. Transitions from states in level k are restricted to states in levels less than or equal to k+1. For given transition probabilities in the interior of the state space, we show that it is always possible to define the boundary transition probabilities in such a way that the level and phase are independent under the stationary distribution. We motivate our analysis by first considering the quasi-birth-and-death process special case in which transitions from any state are restricted to states in the same, or adjacent, levels.
Some risk management problems for firms with internal competition and debt
Authors: Guo Xin
Published: October 2002

Consider an optimization problem for a company with the following parameters: a constant liability payment rate (δ), an average return (μ) and a risk (σ) proportional to the size of the business unit, and an internal competition factor (α) between different units. The goal is to maximize the expected present value of the total dividend distributions, via controls (Ut, Zt), where Ut is the size of the business unit and Zt is the total dividend payoff up to time t. We formulate this as a stochastic control problem for a diffusion process Xt and derive an explicit solution by solving the corresponding Hamilton-Jacobi-Bellman equation. The resulting optimal control policy involves a mixture of a nonlinear control for Ut and a singular control for Zt. The optimal strategies are different for the cases δ < 0 and δ = 0. When δ > 0, it is optimal to play bold: the initial optimal investment size should be proportional to the debt rate δ. Under this optimal rule, however, the probability of bankruptcy in finite time is 1. When δ = 0, i.e. when the company is free of debt, the probability of going broke in finite time reduces to 0. Moreover, when δ = 0, the value function is singular at X0 = 0. Our analytical result shows considerable consistency with daily business practices. For instance, it shows that ‘too many people is counter-productive’. In fact, the maximal optimal size of the business unit should be inversely proportional to α. This eliminates the redundant and simplistic technical assumption of a known uniform upper bound on the size of the firm.
A class of interacting marked point processes: rate of convergence to equilibrium
Authors: Torrisi G. L.
Published: October 2002

In this paper we obtain the rate of convergence to equilibrium of a class of interacting marked point processes, introduced by Kerstan, in two different situations. Indeed, we prove the exponential and subexponential ergodicity of such a class of stochastic processes. Our results are an extension of the corresponding results of Brémaud, Nappo and Torrisi. The generality of the dynamics which we take into account allows the application to the so-called loss networks, and multivariate birth and death processes.
On higher-order properties of compound geometric distributions
Authors: Willmot Gordon E.
Published: October 2002

An explicit convolution representation for the equilibrium residual lifetime distribution of compound zero-modified geometric distributions is derived. Second-order reliability properties are seen to be essentially preserved under geometric compounding, and complement results of Brown (1990) and Cai and Kalashnikov (2000). The convolution representation is then extended to the nth-order equilibrium distribution. This higher-order convolution representation is used to evaluate the stop-loss premium and higher stop-loss moments of the compound zero-modified geometric distribution, as well as the Laplace transform of the kth moment of the time of ruin in the classical risk model.
Kousseff syndrome caused by deletion of chromosome 22q11‐13
Authors: Forrester Shawnia , Kovach Margaret J. , Smith Randell E. , Rimer Lisa , Wesson Melissa , Kimonis Virginia E.
Published: October 2002

Kousseff syndrome was originally described by Boris Kousseff in 1984: Pediatrics 74:395–398 in three siblings whose main features were conotruncal heart defects, neural tube defects, and dysmorphic features. The proband is a white male who has spina bifida, shunted hydrocephalus, cleft palate, short stature, cognitive impairment, and the typical craniofacial features of velo‐cardio‐facial syndrome (VCFS), including low‐set and dysplastic ears, broad base of the nose, narrow alae nasi, and retrognathia. The family history is significant for a brother who died at 2 weeks of age with myelomeningocele, hydrocephalus, transposition of the great vessels, and unilateral renal agenesis, and a sister who died at 11 days of age with myelomeningocele, truncus arteriosus, hypocalcemia, and autopsy findings of absent thymus and parathyroid glands, consistent with DiGeorge anomaly. Given the clinical findings, family history, and recent knowledge that open neural tube defects can occur in VCFS/DiGeorge anomaly, FISH analysis for 22q11‐13 deletion was performed on the proband. A deletion was detected in him and subsequently confirmed in his father. Molecular analysis on autopsy material confirmed the deletion in the proband's deceased brother. We suggest that individuals with neural tube defects associated with other anomalies such as congenital heart defects or cleft palate be evaluated for 22q deletions. © 2002 Wiley‐Liss, Inc.
Dermoscopic and histopathologic diagnosis of equivocal melanocytic skin lesions
Authors: Ferrara Gerardo , Argenziano Giuseppe , Soyer H. Peter , Corona Rosamaria , Sera Francesco , Brunetti Bruno , Cerroni Lorenzo , Chimenti Sergio , El Shabrawi‐Caelen Laila , Ferrari Angela , Hofmann‐Wellenhof Rainer , Kaddu Steven , Piccolo Domenico , Scalvenzi Massimiliano , Staibano Stefania , Wolf Ingrid H. , De Rosa Gaetano
Published: October 2002

BACKGROUND

Dermoscopy (dermatoscopy, epiluminescence microscopy) is increasingly employed for the preoperative detection of cutaneous melanoma; dermoscopic features of pigmented skin lesions have been previously defined using histopathology as the key to the code. In a preliminary study on 10 cases evaluated by nine dermoscopists and nine histopathologists, the authors experienced that when at least two dermoscopists disagree in evaluating a melanocytic lesion, even histopathologic consultations may give equivocal results.

METHODS

One hundred seven melanocytic skin lesions, consecutively excised because of equivocal clinical and/or dermoscopic features, were retrospectively examined by eight dermoscopists and eight histopathologists; the diagnostic interobserver agreement was calculated by means of the Schouten k statistics. After histopathologic consultations, all 107 lesions underwent unblinded dermoscopic re‐evaluation in order to find which dermoscopic features had given rise to histopathologic diagnostic difficulties.

RESULTS

The interobserver ageement was good for both dermoscopy (k = 0.53) and histopathology (k = 0.74). Out of 48 cases evaluated by the dermoscopists in complete accordance, only 8 (16.7%) received at least one conflicting histopathologic diagnosis. Instead, among the remaining 59 cases with at least one disagreeing dermoscopic diagnosis, 21 (35.6%) received at least one disagreeing histopathologic diagnosis. The unblinded dermoscopic re‐evaluation showed that five out of seven lesions with clear‐cut regression structures were histopathologically controversial.

CONCLUSIONS

At least for selected and reasonably difficult lesions, a diagnostic discrepancy among formally trained dermoscopists seems to be predictive for a diagnostic disagreement among histopathologists. Lesions showing clear‐cut regression structures are prone to give some histopathologic disagreement. Cancer 2002;95:1094–1100. © 2002 American Cancer Society.

DOI 10.1002/cncr.10768
Phase II study of paclitaxel plus carboplatin in patients with advanced carcinoma of the urothelium and renal dysfunction (E2896)
Authors: Vaughn David J. , Manola Judith , Dreicer Robert , See William , Levitt Ralph , Wilding George
Published: October 2002

BACKGROUND

Chemotherapy options for the patients with advanced urothelial carcinoma and renal dysfunction are limited. The authors performed a Phase II trial of paclitaxel plus carboplatin in patients with advanced carcinoma of the urothelium and renal dysfunction.

METHODS

Forty‐two patients were accrued; 37 eligible patients were treated. Patients received paclitaxel 225 mg/m2 over three hours followed by carboplatin targeted area under the concentration‐time curve = 6 mg/mL · minute every three weeks for up to six cycles.

RESULTS

The median number of cycles received was four (range, one to six). The objective response rate was 24.3% (95% confidence interval, 11.9–41.7%). The median progression free survival was 3 months and the median overall survival was 7.1 months. The number of poor prognostic risk factors (Eastern Cooperative Oncology Group performance status > 1 or lung, liver, or bone metastases) significantly predicted for survival. The most common ≥ 1 Grade 3 toxicities included granulocytopenia (60%) and neurotoxicity (35%).

CONCLUSIONS

Paclitaxel/carboplatin is a chemotherapy option for patients with advanced urothelial carcinoma and renal dysfunction. Future trials in chemotherapy development for this patient population are warranted. Cancer 2002;95:1022–7. © 2002 American Cancer Society.

DOI 10.1002/cncr.10782
Selection and description of cancer clinical trials participants—Science or happenstance?
Authors: Swanson G. Marie , Bailar John C.
Published: October 2002

BACKGROUND

The selection of clinical trials participants is a critical step in study design, because it affects the generalizability of recommendations made on the basis of trial results and public acceptance of medical research. The authors assessed the heterogeneity of subgroups in cancer treatment and prevention trials and the analysis of subgroups in the evaluation of trial outcomes.

METHODS

The authors reviewed published reports (1990–2000) of cancer prevention and treatment trials from 11 journals. They report here on all Phase III cancer treatment and prevention trials that had at least 100 participants and were conducted among adults in the United States. A structured abstract was developed and used to extract data from the 261 published reports. Descriptive summaries of the abstracted data provided the information included in this systematic review.

RESULTS

Age and gender of study participants were reported in more than 90% of these trials, whereas fewer than 30% of the trials reported race or ethnicity. Gender was reported as an explicit criterion for participant selection primarily in studies of gender specific malignancies. Race and ethnicity were reported as explicit selection criteria for participant selection for five of the prevention trials and for none of the cancer treatment trials. The 105 treatment trials that reported including both men and women had 42,355 participants, and 38.6% of those participants were women. The 26 prevention trials that reported including both men and women had 73,995 participants, and 34.7% of those participants were women. Fifty‐seven treatment trials reported participant ethnic diversity: There were 45,815 participants, with 10.5% African‐American participants and with less than 1% Hispanic, Asian, or Native American participants. Seventeen prevention trials reported participant ethnic diversity: There were 91,741 participants, with 5.5% African‐American participants, 1.7% Hispanic participants, and less than 1% Asian or Native American participants.

CONCLUSIONS

Cancer treatment and prevention trial reports provide scant information about participant race and ethnicity. Such studies use participant selection criteria that do not define diverse subgroups, and few subgroup analyses are conducted. Improvements in the selection, reporting, and analysis of clinical trials participants are needed. Cancer 2002;95:950–9. © 2002 American Cancer Society.

DOI 10.1002/cncr.10785
Immunohistochemical expression of erythropoietin and erythropoietin receptor in breast carcinoma
Authors: Acs Geza , Zhang Paul J. , Rebbeck Timothy R. , Acs Peter , Verma Ajay
Published: October 2002

BACKGROUND

Erythropoietin (Epo), induced by hypoxia, controls the survival, proliferation, and differentiation of Epo receptor (EpoR)‐bearing erythroid progenitors and plays a role in the protection of neurons from hypoxic damage. Hypoxia in malignant disease is associated with invasion, metastasis, resistance to therapy, and selection for cells with diminished apoptotic potential. The authors recently demonstrated the basal and hypoxia‐stimulated expression of Epo and EpoR in human breast carcinoma cell lines and in breast carcinomas, suggesting a role for autocrine Epo signaling in the hypoxic adaptations of mammary neoplasms.

METHODS

The authors characterized the expression of Epo and EpoR by immunohistochemistry in 184 invasive mammary carcinomas and 158 in situ mammary carcinomas and benign mammary epithelium. They analyzed the correlation of Epo and EpoR immunostaining with clinicopathologic tumor features and the patients' smoking history.

RESULTS

Benign mammary epithelial cells showed weak‐to‐moderate expression of Epo and EpoR. EpoR immunostaining was increased in carcinomas compared with benign epithelium both in nonsmokers and smokers, and Epo immunostaining was increased in carcinomas compared with benign epithelium in nonsmokers but not in smokers. Prominent Epo staining was seen in tumor cells adjacent to necrotic areas and at the infiltrating edge of tumors. EpoR staining, but not Epo staining, was significantly greater in tumors that showed high histologic grade, tumor necrosis, lymphovascular invasion, lymph node metastases, and loss of hormone receptor expression.

CONCLUSIONS

The current findings suggest that increased EpoR expression may play an important role in breast carcinogenesis. The induction of autocrine or paracrine Epo signaling may represent a novel mechanism by which hypoxia can promote breast carcinoma. Cancer 2002;95:969–81. © 2002 American Cancer Society.

DOI 10.1002/cncr.10787
Characterization of integration patterns and flanking cellular sequences of hepatitis B virus in childhood hepatocellular carcinomas
Authors: Tsuei Daw‐Jen , Chang Mei‐Hwei , Chen Pei‐Jer , Hsu Tsuey‐Ying , Ni Yen‐Hsuan
Published: October 2002

Hepatitis B virus (HBV) DNA integration into host chromosomes is detected in more than 80% of HBV‐related hepatocellular carcinomas (HCC), yet its significance in tumor development remains obscure. In this study, we re‐examined the integration pattern of HBV in childhood HCC tissues, which has less environmental confounding factors than adult HCC. The HBV junctions and flanking cellular sequences were amplified from five childhood HCC patients by the inverse polymerase chain reaction (IPCR) method using primers located near HBV direct repeats (DR) 1 and 2. The viral junctions in nine of the ten obtained IPCR clones were demonstrated to be located near HBV DR1, and their patterns were classified to type I integrants. Southern blot analyses demonstrate that the cellular junctions derived from two of the five HCC tissues were male specific and contained sequences homologous to human long interspersed DNA elements (LINE‐1). HBV integrant of one HCC tissue (1217T) was integrated into a RNA binding motif Y chromosome (RBMY) gene. The expression of RBMY, which is normally found only in male germ cells, was detected in HCC tissue 1217T by RT‐PCR but not in the corresponding non‐tumor liver tissue. The prevalence of RBMY expression in liver tissues from the tumor and non‐tumor parts of ten other HCC children and seven biliary atresia (BA) children was studied by RT‐PCR. No RBMY transcripts were detected in the non‐tumor parts of HCC patients or the cirrhotic livers of BA children, whereas 30% (three of ten) of HCC tissues specifically expressed RBMY. The results indicate that HBV integration and activation of RBMY gene expression in liver cells may be associated with the development of childhood HCC. J. Med. Virol. 68:513–521, 2002. © 2002 Wiley‐Liss, Inc.
Mutation analysis of the BCL10 gene in childhood solid malignancies
Authors: Miao Jiangyong , Kusafuka Takeshi , Udatsu Yuko , Okada Akira
Published: October 2002

Background

BCL10, a gene involved in apoptosis signaling, has recently been identified at chromosome 1p22. This gene was found to be mutated in several types of lymphomas and other kinds of solid tumors. Especially in hepatocellular carcinoma, high mutation rates have been reported. These findings suggest that its inactivation may play an important pathogenetic role in tumorigenesis. Furthermore, abnormalities of chromosome 1 where the BCL10 gene is located are a common feature in pediatric solid tumors. Therefore, we analyzed 95 pediatric solid cancers for genomic BCL10 mutations.

Procedure

Three exons, which encode the whole coding region, were examined in 95 tumor tissues by PCR‐SSCP method. Samples revealing aberrant band patterns were subjected to direct sequencing analysis.

Results

A total of six nucleotide changes were detected. Two were in intron 1 (IVS1 + 11C > G, IVS1 + 58G > C) and four were in exons 1 or 3 (Ala5Ser, Leu8Leu, Thr162Met and Gly213Glu). Of four exonic changes, three at codons 5, 162, and 213 resulted in amino acid substitution. In non‐tumor tissues, however, similar mutation types were found, suggesting that all nucleotide changes detected were genetic polymorphisms.

Conclusions

This study represents the first genetic analysis of the BCL10 gene in pediatric solid malignant tumors. Our results suggest that BCL10 mutation as a mechanism involved in tumorigenesis is unlikely to be associated with most childhood malignancies. Med Pediatr Oncol 2002;39:543–546. © 2002 Wiley‐Liss, Inc.
Differential quadrature method for pricing American options
Authors: Xionghua Wu , Zhihong Ding
Published: October 2002

In this article, differential quadrature method (DQM), a highly accurate and efficient numerical method for solving nonlinear problems, is used to overcome the difficulty in determining the optimal exercise boundary of American option. The following three parts of the problem in pricing American options are solved. The first part is how to treat the uncertainty of the early exercise boundary, or free boundary in the language of the PDE treatment of the American option, because American options can be exercised before the date of expiration. The second part is how to solve the nonlinear problem, because the problem of pricing American options is nonlinear. And the third part is how to treat the initial value condition with the singularity and the boundary conditions in the DQM. Numerical results for the free boundary of American option obtained by both DQM and finite difference method (FDM) are given and from which it can be seen the computational efficiency is greatly improved by DQM. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 711–725, 2002; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/num.10028.
Learning on the job: The acquisition of scientific competence
Authors: Lottero‐Perdue Pamela S. , Brickhouse Nancy W.
Published: October 2002

This study attempts to help us better understand scientific competence and how it is acquired. We interviewed 10 associates at a company that produces unique technical products. Although none of the 10 had obtained degrees beyond high school, they all engaged in highly technical work that would be typical of a practicing engineer. These associates described to us their learning of science as they solved practical problems at work. Both what they learned and how they learned was task‐driven. Contextual factors such as choice of tasks and social access to expertise within the company were important factors in their learning. The only influence outside work that was repeatedly named as significant on the acquisition of scientific competence was extensive tinkering experience. Understanding the successful acquisition of scientific competence within communities such as this one suggests that certain features of these communities may be useful for school science communities as well. © 2002 Wiley Periodicals, Inc. Sci Ed 86:756–782, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10034