Showing papers by "Sapienza University of Rome published in 2009"

Statistical physics of social dynamics

Abstract: Statistical physics has proven to be a fruitful framework to describe phenomena outside the realm of traditional physics. Recent years have witnessed an attempt by physicists to study collective phenomena emerging from the interactions of individuals as elementary units in social structures. A wide list of topics are reviewed ranging from opinion and cultural and language dynamics to crowd behavior, hierarchy formation, human dynamics, and social spreading. The connections between these problems and other, more traditional, topics of statistical physics are highlighted. Comparison of model results with empirical data from social systems are also emphasized.

Word sense disambiguation: A survey

Abstract: Word sense disambiguation (WSD) is the ability to identify the meaning of words in context in a computational manner. WSD is considered an AI-complete problem, that is, a task whose solution is at least as hard as the most difficult problems in artificial intelligence. We introduce the reader to the motivations for solving the ambiguity of words and provide a description of the task. We overview supervised, unsupervised, and knowledge-based approaches. The assessment of WSD systems is discussed in the context of the Senseval/Semeval campaigns, aiming at the objective evaluation of systems participating in several different disambiguation tasks. Finally, applications, open problems, and future directions are discussed.

Predicting survival after liver transplantation in patients with hepatocellular carcinoma beyond the Milan criteria: a retrospective, exploratory analysis

Abstract: Summary Background Patients undergoing liver transplantation for hepatocellular carcinoma within the Milan criteria (single tumour ≤5 cm in size or ≤3 tumours each ≤3 cm in size, and no macrovascular invasion) have an excellent outcome. However, survival for patients with cancers that exceed these criteria remains unpredictable and access to transplantation is a balance of maximising patients' chances of cure and organ availability. The aim of this study was to explore the survival of patients with tumours that exceed the Milan criteria, to assess whether the criteria could be less restrictive, enabling more patients to qualify as transplant candidates, and to derive a prognostic model based on objective tumour characteristics, to see whether the Milan criteria could be expanded. Methods Data on patients who underwent transplantation for hepatocellular carcinoma despite exceeding Milan criteria at different centres were recorded via a web-based survey completed by specialists from each centre. The survival of these patients was correlated retrospectively with the size of the largest tumour nodule, number of nodules, and presence or absence of microvascular invasion detected at pathology. Contoured multivariable regression Cox models produced survival estimates by means of different combinations of the covariates. The primary aim of this study was to derive a prognostic model of overall survival based on tumour characteristics, according to the main parameters used in the Tumour Node Metastasis classification. The secondary aim was the identification of a subgroup of patients with hepatocellular carcinoma exceeding the Milan criteria, who achieved a 5-year overall survival of at least 70%—ie, similar to the outcome expected for patients who meet the Milan criteria. Findings Over a 10-month period, between June 25, 2006, and April 3, 2007, data for 1556 patients who underwent transplantation for hepatocellular carcinoma were entered on the database by 36 centres. 1112 patients had hepatocellular carcinoma exceeding Milan criteria and 444 patients had hepatocellular carcinoma shown not to exceed Milan criteria at post-transplant pathology review. In the group of patients with hepatocellular carcinomas exceeding the criteria, the median size of the largest nodule was 40 mm (range 4–200) and the median number of nodules was four (1–20). 454 of 1112 patients (41%) had microvascular invasion and, for those transplanted outside the Milan criteria, 5-year overall survival was 53·6% (95% CI 50·1–57·0), compared with 73·3% (68·2–77·7) for those that met the criteria. Hazard ratios (HR) associated with increasing values of size and number were 1·34 (1·25–1·44) and 1·51 (1·21–1·88), respectively. The effect was linear for size, whereas for number of tumours, the effect tended to plateau above three tumours. The effect of tumour size and number on survival was mediated by recurrence (b=0·08, SE=0·12, p=0·476). The presence of microvascular invasion doubled HRs in all scenarios. The 283 patients without microvascular invasion, but who fell within the Up-to-seven criteria (hepatocellular carcinomas with seven as the sum of the size of the largest tumour [in cm] and the number of tumours) achieved a 5-year overall survival of 71·2% (64·3–77·0). Interpretation More patients with hepatocellular carcinoma could be candidates for transplantation if the current dual (yes/no) approach to candidacy, based on the strict Milan criteria, were replaced with a more precise estimation of survival contouring individual tumour characteristics and use of the up-to-seven criteria. Funding Specific funding was not used to do this study.

Gait speed at usual pace as a predictor of adverse outcomes in community-dwelling older people an International Academy on Nutrition and Aging (IANA) Task Force

Abstract: Introduction: The use of a simple, safe, and easy to perform assessment tool, like gait speed, to evaluate vulnerability to adverse outcomes in community-dwelling older people is appealing, but its predictive capacity is still questioned. The present manuscript summarises the conclusions of an expert panel in the domain of physical performance measures and frailty in older people, who reviewed and discussed the existing literature in a 2-day meeting held in Toulouse, France on March 12-13, 2009. The aim of the IANA Task Force was to state if, in the light of actual scientific evidence, gait speed assessed at usual pace had the capacity to identify community-dwelling older people at risk of adverse outcomes, and if gait speed could be used as a single-item tool instead of more comprehensive but more time-consuming assessment instruments. Methods: A systematic review of literature was performed prior to the meeting (Medline search and additional pearling of reference lists and key-articles supplied by Task Force members). Manuscripts were retained for the present revision only when a high level of evidence was present following 4 pre-selected criteria: a) gait speed, at usual pace, had to be specifically assessed as a single-item tool, b) gait speed should be measured over a short distance, c) at baseline, participants had to be autonomous, community-dwelling older people, and d) the evaluation of onset of adverse outcomes (i.e. disability, cognitive impairment, institutionalisation, falls, and/or mortality) had to be assessed longitudinally over time. Based on the prior criteria, a final selection of 27 articles was used for the present manuscript. Results: Gait speed at usual pace was found to be a consistent risk factor for disability, cognitive impairment, institutionalisation, falls, and/or mortality. In predicting these adverse outcomes over time, gait speed was at least as sensible as composite tools. Conclusions: Although more specific surveys needs to be performed, there is sufficient evidence to state that gait speed identifies autonomous community-dwelling older people at risk of adverse outcomes and can be used as a single-item assessment tool. The assessment at usual pace over 4 meters was the most often used method in literature and might represent a quick, safe, inexpensive and highly reliable instrument to be implemented.

Systematic Pelvic Lymphadenectomy vs No Lymphadenectomy in Early-Stage Endometrial Carcinoma: Randomized Clinical Trial

Abstract: Results The median number of lymph nodes removed was 30 (interquartile range = 22 – 42) in the pelvic systematic lymphadenectomy arm and 0 (interquartile range = 0 – 0) in the no-lymphadenectomy arm ( P < .001). Both early and late postoperative complications occurred statistically significantly more frequently in patients who had received pelvic systematic lymphadenectomy (81 patients in the lymphadenectomy arm and 34 patients in the no-lymphadenectomy arm, P = .001). Pelvic systematic lymphadenectomy improved surgical staging as statistically significantly more patients with lymph node metastases were found in the lymphadenectomy arm than in the no-lymphadenectomy arm (13.3% vs 3.2%, difference = 10.1%, 95% confidence interval [CI] = 5.3% to 14.9%, P < .001). At a median follow-up of 49 months, 78 events (ie, recurrence or death) had been observed and 53 patients had died. The unadjusted risks for first event and death were similar between the two arms (hazard ratio [HR] for first event = 1.10, 95% CI = 0.70 to 1.71, P = .68, and HR for death = 1.20, 95% CI = 0.70 to 2.07, P = .50). The 5-year disease-free and overall survival rates in an intention-to-treat analysis were similar between arms (81.0% and 85.9% in the lymphadenectomy arm and 81.7% and 90.0% in the no-lymphadenectomy arm, respectively). Conclusion Although systematic pelvic lymphadenectomy statistically significantly improved surgical staging, it did

The PRIAMO study: A multicenter assessment of nonmotor symptoms and their impact on quality of life in Parkinson's disease

Abstract: We performed a multicenter survey using a semistructured interview in 1,072 consecutive patients with Parkinson's disease (PD) enrolled during 12 months in 55 Italian centers to assess the prevalence of nonmotor symptoms (NMSs), their association with cognitive impairment, and the impact on patients' quality of life (QoL). We found that 98.6% of patients with PD reported the presence of NMSs. The most common were as follows: fatigue (58%), anxiety (56%), leg pain (38%), insomnia (37%), urgency and nocturia (35%), drooling of saliva and difficulties in maintaining concentration (31%). The mean number of NMS per patient was 7.8 (range, 0-32). NMS in the psychiatric domain were the most frequent (67%). Frequency of NMS increased along with the disease duration and severity. Patients with cognitive impairment reported more frequently apathy, attention/memory deficit, and psychiatric symptoms. Apathy was the symptom associated with worse PDQ-39 score but also presence of fatigue, attention/memory, and psychiatric symptoms had a negative impact on QoL. These findings further support a key role for NMS in the clinical frame of PD and the need to address them specifically in clinical trials using dedicated scales.

Concentration of Measure for the Analysis of Randomized Algorithms

Abstract: Randomized algorithms have become a central part of the algorithms curriculum based on their increasingly widespread use in modern applications. This book presents a coherent and unified treatment of probabilistic techniques for obtaining high- probability estimates on the performance of randomized algorithms. It covers the basic tool kit from the Chernoff-Hoeffding (CH) bounds to more sophisticated techniques like Martingales and isoperimetric inequalities, as well as some recent developments like Talagrand's inequality, transportation cost inequalities, and log-Sobolev inequalities. Along the way, variations on the basic theme are examined, such as CH bounds in dependent settings. The authors emphasize comparative study of the different methods, highlighting respective strengths and weaknesses in concrete example applications. The exposition is tailored to discrete settings sufficient for the analysis of algorithms, avoiding unnecessary measure-theoretic details, thus making the book accessible to computer scientists as well as probabilists and discrete mathematicians.

Analysis of high intensity activity in Premier League soccer

Abstract: The aim of the present investigation was to provide a detailed analysis of the high intensity running activity completed by elite soccer players during match-play A further aim of the study was to evaluate the importance of high intensity running activity to overall team success Observations on individual match performance measures were undertaken on 563 outfield players (median of 8 games per player; range=1-57) competing in the English Premier League from 2003/2004 to 2005/2006 using a computerised tracking system (Prozone, Leeds, England) High intensity activities selected for analysis included total high intensity running distance (THIR), total sprint distance (TSD) and the number and type of sprints undertaken Total high intensity running distance in possession and without possession of the ball was also analysed The THIR was dependant upon playing position with wide midfield (1,049+/-106 m) and central defenders (681+/-128 m) completing the highest and lowest distance respectively (p<0001) High intensity activity was also related to team success with teams finishing in the bottom five (919+/-128 m) and middle ten (917+/-143 m) league positions completing significantly more THIR compared with teams in the top five (885+/-113 m) (p=0003) The THIR and TSD also significantly declined during the 2nd half with the greatest decrements observed in wide midfield and attacking players (p<005) Both positional differences in high intensity activity and the observed change in activity throughout the game were also influenced by team success (p<005) The results of the present study indicate that high intensity activity in elite soccer match-play is influenced by both playing position and previous activity in the game These activity patterns are also dependant upon success of the team This may indicate that overall technical and tactical effectiveness of the team rather than high levels of physical performance per se are more important in determining success in soccer

Albumin-bound formulation of paclitaxel (Abraxane ABI-007) in the treatment of breast cancer.

Abstract: Breast cancer is the most common type of malignancy diagnosed in women. In the metastatic setting this disease is still uncurable. Taxanes represent an important class of antitumor agents which have proven to be fundamental in the treatment of advanced and early-stage breast cancer, but the clinical advances of taxanes have been limited by their highly hydrophobic molecular status. To overcome this poor water solubility, lipid-based solvents have been used as a vehicle, and new systemic formulations have been developed, mostly for paclitaxel, which are Cremophor-free and increase the circulation time of the drug. ABI-007 is a novel, albumin-bound, 130-nm particle formulation of paclitaxel, free from any kind of solvent. It has been demonstrated to be superior to an equitoxic dose of standard paclitaxel with a significantly lower incidence of toxicities in a large, international, randomized phase III trial. The availability of new drugs, such as Abraxane, in association with other traditional and non-traditional drugs (new antineoplastic agents and targeted molecules), will give the oncologist many different effective treatment options for patients in this setting.

Surface hydrophobin prevents immune recognition of airborne fungal spores

Abstract: The air we breathe is filled with thousands of fungal spores (conidia) per cubic metre, which in certain composting environments can easily exceed 10(9) per cubic metre. They originate from more than a hundred fungal species belonging mainly to the genera Cladosporium, Penicillium, Alternaria and Aspergillus. Although these conidia contain many antigens and allergens, it is not known why airborne fungal microflora do not activate the host innate immune cells continuously and do not induce detrimental inflammatory responses following their inhalation. Here we show that the surface layer on the dormant conidia masks their recognition by the immune system and hence prevents immune response. To explore this, we used several fungal members of the airborne microflora, including the human opportunistic fungal pathogen Aspergillus fumigatus, in in vitro assays with dendritic cells and alveolar macrophages and in in vivo murine experiments. In A. fumigatus, this surface 'rodlet layer' is composed of hydrophobic RodA protein covalently bound to the conidial cell wall through glycosylphosphatidylinositol-remnants. RodA extracted from conidia of A. fumigatus was immunologically inert and did not induce dendritic cell or alveolar macrophage maturation and activation, and failed to activate helper T-cell immune responses in vivo. The removal of this surface 'rodlet/hydrophobin layer' either chemically (using hydrofluoric acid), genetically (DeltarodA mutant) or biologically (germination) resulted in conidial morphotypes inducing immune activation. All these observations show that the hydrophobic rodlet layer on the conidial cell surface immunologically silences airborne moulds.

The prevalence of lower urinary tract symptoms (LUTS) in the USA, the UK and Sweden: results from the Epidemiology of LUTS (EpiLUTS) study.

Abstract: OBJECTIVE To estimate and compare the prevalence and associated bother of lower urinary tract symptoms (LUTS) in the general populations of the USA, UK and Sweden using current International Continence Society (ICS) definitions, as no previous population-based studies evaluating the prevalence of LUTS in the USA, using the 2002 ICS definitions, have been conducted. SUBJECTS AND METHODS This cross-sectional, population-representative survey was conducted via the Internet in the USA, the UK and Sweden. Members of Internet-based panels were randomly selected to receive an e-mailed invitation to participate. If interested, respondents selected a link to an informed consent page, followed by the survey. Participants were asked to rate how often they experienced individual LUTS during the previous 4 weeks, on a five-point Likert scale, and, if experienced, how much the symptom bothered them. Descriptive statistics were used to summarize and present the data. RESULTS Responses rates for the USA, the UK and Sweden were 59.6%, 60.6% and 52.3%, respectively, with a final sample of 30 000 (USA 20 000; UK 7500; Sweden 2500). The mean age (range) of the participants was 56.6 (40–99) years; the mean percentages for race were 82.9% white, 6.7% black, 6.0% Hispanic and 4.4% Asian/other. The prevalence of LUTS was defined by two symptom frequency thresholds, i.e. at least ‘sometimes’ and at least ‘often’ for all LUTS except incontinence, where frequency thresholds were at least ‘a few times per month’ and at least ‘a few times per week’. The prevalence of at least one LUTS at least ‘sometimes’ was 72.3% for men and 76.3% for women, and 47.9% and 52.5% for at least ‘often’ for men and women, respectively. For most LUTS, at least half of the participants were bothered ‘somewhat’ or more using a frequency threshold of at least ‘sometimes’. For a threshold of at least ‘often’, ‘somewhat’ or more bother was reported by ≥70% of participants except for terminal dribble in men and split stream in women. CONCLUSION In this large population study of three countries, LUTS are highly prevalent among men and women aged >40 years. In general, LUTS experienced ‘often’ or more are bothersome to most people.

Peer Effects and Social Networks in Education

Abstract: This paper studies whether structural properties of friendship networks affect individual outcomes in education. We first develop a model that shows that, at the Nash equilibrium, the outcome of each individual embedded in a network is proportional to her Katz-Bonacich centrality measure. This measure takes into account both direct and indirect friends of each individual but puts less weight to her distant friends. We then bring the model to the data by using a very detailed dataset of adolescent friendship networks. We show that, after controlling for observable individual characteristics and unobservable network specific factors, the individual’s position in a network (as measured by her Katz-Bonacich centrality) is a key determinant of her level of activity. A standard deviation increase in the Katz-Bonacich centrality increases the pupil school performance by more than 7 percent of one standard deviation.

Models for Evaluating and Planning City Logistics Systems

Abstract: City logistics aims to reduce the nuisances associated to freight transportation in urban areas while supporting their economic and social development. The fundamental idea is to view individual stakeholders and decisions as components of an integrated logistics system. This implies the coordination of shippers, carriers, and movements as well as the consolidation of loads of several customers and carriers into the same environment-friendly vehicles. City logistics explicitly aims to optimize such advanced urban transportation systems. We focus on a challenging city logistics planning issue, the integrated short-term scheduling of operations and management of resources, for the general case involving a two-tiered distribution structure. We investigate the main issues related to the problem, introduce a new problem class, propose both a general model and formulations for the main system components, and identify promising solution avenues.

Bright Active Galactic Nuclei Source List from the First Three Months of the Fermi Large Area Telescope All-Sky Survey

Abstract: The first three months of sky-survey operation with the Fermi Gamma Ray Space Telescope (Fermi) Large Area Telescope (LAT) reveals 132 bright sources at |b|>10 deg with test statistic greater than 100 (corresponding to about 10 sigma). Two methods, based on the CGRaBS, CRATES and BZCat catalogs, indicate high-confidence associations of 106 of these sources with known AGNs. This sample is referred to as the LAT Bright AGN Sample (LBAS). It contains two radio galaxies, namely Centaurus A and NGC 1275, and 104 blazars consisting of 57 flat spectrum radio quasars (FSRQs), 42 BL Lac objects, and 5 blazars with uncertain classification. Four new blazars were discovered on the basis of the LAT detections. Remarkably, the LBAS includes 10 high-energy peaked BL Lacs (HBLs), sources which were so far hard to detect in the GeV range. Another 10 lower-confidence associations are found. Only thirty three of the sources, plus two at |b|>10 deg, were previously detected with EGRET, probably due to the variable nature of these sources. The analysis of the gamma-ray properties of the LBAS sources reveals that the average GeV spectra of BL Lac objects are significantly harder than the spectra of FSRQs. No significant correlation between radio and peak gamma-ray fluxes is observed. Blazar log N - log S and luminosity functions are constructed to investigate the evolution of the different blazar classes, with positive evolution indicated for FSRQs but none for BLLacs. The contribution of LAT-blazars to the total extragalactic gamma-ray intensity is estimated.

Common variants at five new loci associated with early-onset inflammatory bowel disease.

Abstract: The inflammatory bowel diseases (IBD) Crohn's disease and ulcerative colitis are common causes of morbidity in children and young adults in the western world. Here we report the results of a genome-wide association study in early-onset IBD involving 3,426 affected individuals and 11,963 genetically matched controls recruited through international collaborations in Europe and North America, thereby extending the results from a previous study of 1,011 individuals with early-onset IBD. We have identified five new regions associated with early-onset IBD susceptibility, including 16p11 near the cytokine gene IL27 (rs8049439, P = 2.41 x 10(-9)), 22q12 (rs2412973, P = 1.55 x 10(-9)), 10q22 (rs1250550, P = 5.63 x 10(-9)), 2q37 (rs4676410, P = 3.64 x 10(-8)) and 19q13.11 (rs10500264, P = 4.26 x 10(-10)). Our scan also detected associations at 23 of 32 loci previously implicated in adult-onset Crohn's disease and at 8 of 17 loci implicated in adult-onset ulcerative colitis, highlighting the close pathogenetic relationship between early- and adult-onset IBD.

What Makes Oral History Different

Abstract: Back in 1960–61,I was an American Field Service foreign exchange student at Westchester High School here in Los Angeles—which still exists, although it has been almost swallowed up by the airport. And I had this wonderful experience of being an Italian in Los Angeles. Part of this was listening to the Italian radio station from “la bellissima citta di San Pedro” on Sundays. Every Italian boy lives the day of Sunday in anxiety, waiting for the soccer results. The great privilege here was that, thanks to the time difference, by 10:00 a.m. Pd know the scores—and my Sunday anxiety was replaced by Sunday despair.

Randomized study on the efficacy of immunosuppressive therapy in patients with virus-negative inflammatory cardiomyopathy: the TIMIC study

Abstract: Aims To evaluate the efficacy of immunosuppression in virus-negative inflammatory cardiomyopathy. Methods and results This randomized, double-blind, placebo-controlled study included 85 patients with myocarditis and chronic (>6 months) heart failure unresponsive to conventional therapy, with no evidence of myocardial viral genomes. Patients received either prednisone 1 mg kg–1 day–1 for 4 weeks followed by 0.33 mg kg–1 day–1 for 5 months and azathioprine 2 mg kg–1 day–1 for 6 months (43 patients, Group 1) or placebo (42 patients, Group 2) in addition to conventional therapy for heart failure. Primary outcome was the 6 month improvement in left-ventricular function. Group 1 showed a significant improvement of left-ventricular ejection fraction and a significant decrease in left-ventricular dimensions and volumes compared with baseline. None of Group 2 patients showed improvement of ejection fraction, that significantly worsened compared with baseline. No major adverse reaction was registered as a result of immunosuppression. Conclusion These data confirm the efficacy of immunosuppression in virus-negative inflammatory cardiomyopathy. Lack of response in 12% of cases suggests the presence of not screened viruses or mechanisms of damage and inflammation not susceptible to immunosuppression.

Roma-BZCAT: A multifrequency catalogue of Blazars

Abstract: We present a new catalogue of blazars based on multi-frequency surveys and on an extensive review of the literature. Blazars are classified as BL Lacertae objects, as flat spectrum radio quas ars or as blazars of uncertain/transitional type. Each object is identified by a root name, coded as BZB, BZQ and BZU for these three subclasses respectively, and by its coordinates. This catalogue i s being built as a tool useful for the identification of the extragala ctic sources that will be detected by present and future experiments for X and gamma-ray astronomy, like Swift, AGILE, Fermi-GLAST and Simbol-X. An electronic version is available from the ASI Science Data Center web site at http://www.asdc.asi.it/bzcat.

Bovine lactoferrin supplementation for prevention of late-onset sepsis in very low-birth-weight neonates: A randomized trial

Abstract: Context Sepsis is a common and severe complication in premature neonates, particularly those with very low birth weight (VLBW) ( Objective To establish whether bovine lactoferrin (BLF), alone or in combination with LGG, reduces the incidence of late-onset sepsis in VLBW neonates. Design, Setting, and Patients Prospective, multicenter, double-blind, placebo-controlled, randomized trial conducted in 11 Italian tertiary neonatal intensive care units. Patients were 472 VLBW infants enrolled from October 1, 2007, through July 31, 2008, and assessed until discharge for development of sepsis. Intervention Infants were randomly assigned to receive orally administered BLF (100 mg/d) alone (n = 153), BLF plus LGG (6 × 10 9 colony-forming units/d) (n = 151), or placebo (n = 168) from birth until day 30 of life (day 45 for neonates Main Outcome Measure First episode of late-onset sepsis, ie, sepsis occurring more than 72 hours after birth with isolation of any pathogen from blood or from peritoneal or cerebrospinal fluid. Results Demographic, clinical, and management characteristics of the 3 groups were similar, including type of feeding and intake of maternal milk. Incidence of late-onset sepsis was significantly lower in the BLF and BLF plus LGG groups (9/153 [5.9%] and 7/151 [4.6%], respectively) than in the control group receiving placebo (29/168 [17.3%]) (risk ratio, 0.34; 95% confidence interval, 0.17-0.70; P = .002 for BLF vs control and risk ratio, 0.27; 95% confidence interval, 0.12-0.60; P Conclusion Compared with placebo, BLF supplementation alone or in combination with LGG reduced the incidence of a first episode of late-onset sepsis in VLBW neonates. Trial Registration isrctn.org Identifier: ISRCTN53107700

Amino acid composition and sequence of dermorphin, a novel opiate‐like peptide from the skin of phyllomedusa sauvagei

Abstract: Dermorphin, a heptapeptide with very potent opiate-like activity, has been isolated from methanol extracts of the skin of the South American frog Phyllomedusa sauvagei. The amino acid sequence of the peptide is: H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2. Dermorphin presents striking differences from the known enkephalins; it offers a surprising example of a peptide from Vertebrata containing a D-amino acid residue in its sequence.

On the stationarity of annual flood peaks in the continental United States during the 20th century

Abstract: [1] Annual peak discharge records from 50 stations in the continental United States with at least 100 years of record are used to investigate stationarity of flood peaks during the 20th century. We examine temporal trends in flood peaks and abrupt changes in the mean and/or variance of flood peak distributions. Change point analysis for detecting abrupt changes in flood distributions is performed using the nonparametric Pettitt test. Two nonparametric (Mann-Kendall and Spearman) tests and one parametric (Pearson) test are used to detect the presence of temporal trends. Generalized additive models for location, scale, and shape (GAMLSS) are also used to parametrically model the annual peak data, exploiting their flexibility to account for abrupt changes and temporal trends in the parameters of the distribution functions. Additionally, the presence of long-term persistence is investigated through estimation of the Hurst exponent, and an alternative interpretation of the results in terms of long-term persistence is provided. Many of the drainage basins represented in this study have been affected by regulation through systems of reservoirs, and all of the drainage basins have experienced significant land use changes during the 20th century. Despite the profound changes that have occurred to drainage basins throughout the continental United States and the recognition that elements of the hydrologic cycle are being altered by human-induced climate change, it is easier to proclaim the demise of stationarity of flood peaks than to prove it through analyses of annual flood peak data.

A Multistage Processing Algorithm for Disturbance Removal and Target Detection in Passive Bistatic Radar

Abstract: The paper examines the problem of cancellation of direct signal, multipath and clutter echoes in passive bistatic radar (PBR). This problem is exacerbated as the transmitted waveform is not under control of the radar designer and the sidelobes of the ambiguity function can mask targets including those displaced in either (or both) range and Doppler from the disturbance. A novel multistage approach is developed for disturbance cancellation and target detection based on projections of the received signal in a subspace orthogonal to both the disturbance and previously detected targets. The resulting algorithm is shown to be effective against typical simulated scenarios with a limited number of stages, and a version with computational savings is also introduced. Finally its effectiveness is demonstrated with the application to real data acquired with an experimental VHF PBR system.