Dynamics of Money and Income Distributions

We study the model of interacting agents proposed by Chatterjee et al that allows agents to both save and exchange wealth. Closed equations for the wealth distribution are developed using a mean field approximation. We show that when all agents have the same fixed savings propensity, subject to certain well defined approximations defined in the text, these equations yield the conjecture proposed by Chatterjee for the form of the stationary agent wealth distribution. If the savings propensity for the equations is chosen according to some random distribution we show further that the wealth distribution for large values of wealth displays a Pareto like power law tail, ie P(w)\sim w^{1+a}. However the value of $a$ for the model is exactly 1. Exact numerical simulations for the model illustrate how, as the savings distribution function narrows to zero, the wealth distribution changes from a Pareto form to to an exponential function. Intermediate regions of wealth may be approximately described by a power law with $a>1$. However the value never reaches values of \~ 1.6-1.7 that characterise empirical wealth data. This conclusion is not changed if three body agent exchange processes are allowed. We conclude that other mechanisms are required if the model is to agree with empirical wealth data.Comment: Sixteen pages, Seven figures, Elsevier style file. Submitted to Physica

Clinical improvement after treatment with VEGF165 in patients with severe chronic lower limb ischaemia

The present study focuses on the application of a therapeutic strategy in patients with chronic severe lower limb ischaemia using a plasmid vector encoding the vascular endothelial growth factor (phVEGF165). It has been shown that VEGF promotes neo-vascularization and blood vessel network formation and thus might have the ability to improve blood-flow at the level of the affected limbs. However, little information is available regarding the necessary level of expression of VEGF and its possible related adverse effects. We have subcloned VEGF165isoform into pCMV-Script expression vector (Stratagene) under the control of the CMV promoter. Three patients with chronic ischaemia of the lower limb, considered as not suitable for surgical re-vascularization, received intramuscular injection with 0.5 ml saline solution containing 1011 copies of VEGF165 plasmid. The clinical evolution has been monitored by angiography and estimated by walking time on the rolling carpet (Gardner protocol). Two months after therapy, all three patients showed complete relief of rest pain, improvement of ischaemic ulcer lesions and increased walking distance on the rolling carpet most probably due to appearance of newly formed collateral vessels

Double power laws in income and wealth distributions

Close examination of wealth distributions reveal the existence of two distinct power law regimes. The Pareto exponents of the super-rich, identified for example in rich lists such as provided by Forbes are smaller than the Pareto exponents obtained for top earners in income data sets. Our extension of the Slanina model of wealth is able to reproduce these double power law features.Comment: 10 pages, 4 figures, conference APFA6, Lisboa, July 200

Measuring social dynamics in a massive multiplayer online game

Quantification of human group-behavior has so far defied an empirical, falsifiable approach. This is due to tremendous difficulties in data acquisition of social systems. Massive multiplayer online games (MMOG) provide a fascinating new way of observing hundreds of thousands of simultaneously socially interacting individuals engaged in virtual economic activities. We have compiled a data set consisting of practically all actions of all players over a period of three years from a MMOG played by 300,000 people. This large-scale data set of a socio-economic unit contains all social and economic data from a single and coherent source. Players have to generate a virtual income through economic activities to `survive' and are typically engaged in a multitude of social activities offered within the game. Our analysis of high-frequency log files focuses on three types of social networks, and tests a series of social-dynamics hypotheses. In particular we study the structure and dynamics of friend-, enemy- and communication networks. We find striking differences in topological structure between positive (friend) and negative (enemy) tie networks. All networks confirm the recently observed phenomenon of network densification. We propose two approximate social laws in communication networks, the first expressing betweenness centrality as the inverse square of the overlap, the second relating communication strength to the cube of the overlap. These empirical laws provide strong quantitative evidence for the Weak ties hypothesis of Granovetter. Further, the analysis of triad significance profiles validates well-established assertions from social balance theory. We find overrepresentation (underrepresentation) of complete (incomplete) triads in networks of positive ties, and vice versa for networks of negative ties...Comment: 23 pages 19 figure

Effect of aliskiren on post-discharge outcomes among diabetic and non-diabetic patients hospitalized for heart failure: insights from the ASTRONAUT trial

Aims The objective of the Aliskiren Trial on Acute Heart Failure Outcomes (ASTRONAUT) was to determine whether aliskiren, a direct renin inhibitor, would improve post-discharge outcomes in patients with hospitalization for heart failure (HHF) with reduced ejection fraction. Pre-specified subgroup analyses suggested potential heterogeneity in post-discharge outcomes with aliskiren in patients with and without baseline diabetes mellitus (DM). Methods and results ASTRONAUT included 953 patients without DM (aliskiren 489; placebo 464) and 662 patients with DM (aliskiren 319; placebo 343) (as reported by study investigators). Study endpoints included the first occurrence of cardiovascular death or HHF within 6 and 12 months, all-cause death within 6 and 12 months, and change from baseline in N-terminal pro-B-type natriuretic peptide (NT-proBNP) at 1, 6, and 12 months. Data regarding risk of hyperkalaemia, renal impairment, and hypotension, and changes in additional serum biomarkers were collected. The effect of aliskiren on cardiovascular death or HHF within 6 months (primary endpoint) did not significantly differ by baseline DM status (P = 0.08 for interaction), but reached statistical significance at 12 months (non-DM: HR: 0.80, 95% CI: 0.64-0.99; DM: HR: 1.16, 95% CI: 0.91-1.47; P = 0.03 for interaction). Risk of 12-month all-cause death with aliskiren significantly differed by the presence of baseline DM (non-DM: HR: 0.69, 95% CI: 0.50-0.94; DM: HR: 1.64, 95% CI: 1.15-2.33; P < 0.01 for interaction). Among non-diabetics, aliskiren significantly reduced NT-proBNP through 6 months and plasma troponin I and aldosterone through 12 months, as compared to placebo. Among diabetic patients, aliskiren reduced plasma troponin I and aldosterone relative to placebo through 1 month only. There was a trend towards differing risk of post-baseline potassium ≥6 mmol/L with aliskiren by underlying DM status (non-DM: HR: 1.17, 95% CI: 0.71-1.93; DM: HR: 2.39, 95% CI: 1.30-4.42; P = 0.07 for interaction). Conclusion This pre-specified subgroup analysis from the ASTRONAUT trial generates the hypothesis that the addition of aliskiren to standard HHF therapy in non-diabetic patients is generally well-tolerated and improves post-discharge outcomes and biomarker profiles. In contrast, diabetic patients receiving aliskiren appear to have worse post-discharge outcomes. Future prospective investigations are needed to confirm potential benefits of renin inhibition in a large cohort of HHF patients without D

ARTYKUŁ ORYGINALNYZwiązek pomiędzy elektrofizjologicznymi i echokardiograficznymi parametrami sprzyjającymi migotaniu przedsionków u chorych bez organicznej choroby serca

Background: The electroanatomical substrate of dilated atria is characterised by increased non-uniform anisotropy and macroscopic slowing of conduction, which promote reentrant circuits. Aim: To analyse the relationship between electrophysiological properties of atria and echocardiographic markers of dilatation and increased filling pressure. Methods: The study group consisted of 79 patients without structural heart disease, aged 53&#177;22 years, who were referred for electrophysiological study. In order to examine the atrial electrophysiological characteristics we studied interatrial conduction time (iaCT), double potentials and fragmented atrial activity during premature stimulation of the high right atrium (HRA). The analysed parameters included: duration of atrial activity, baseline iaCT (iaCTb) between HRA and distal coronary sinus (CS), iaCT during HRA pacing S1S1 600 ms (iaCTS1), maximum prolongation of iaCT during S2 and S3 delivery (iaCTS2, iaCTS3). We also calculated the decremental index (DI)=iaCT S3- iaCTS1/iaCTS1%. The following echocardiographic parameters were assessed: left atrial (LA) dimensions, surface (LAs), volume using ellipse formula (LAv), right surface (RAs), total atrial surface (TAs=LAs+RAs), and global myocardial index (GMI). Results: Patients were divided into two groups. Group 1 consisted of 37 patients with evidence of slow atrial conduction (atrial fragmentation/iaCTb>80ms/DI>50%/double atrial potentials), whereas group 2 was composed of 42 patients without slow conduction properties. There were no significant differences concerning age, body mass index or LA parasternal dimensions between the groups. Thirty-seven patients, of whom 32 were from group 1, had documented episodes of paroxysmal atrial fibrillation. GMI, LAs, LAv and TAs values were significantly higher in patients from group 1 than in group 2 subjects. A statistically significant linear correlation between iaCTb and TAs (r=0.52 pWstęp: Elektroanatomiczne parametry sprzyjające występowaniu migotania przedsionków (AF) u chorych z powiększonym lewym przedsionkiem (LA) polegają na anizotropii i zwolnieniu przewodzenia, co stanowi podłoże nawrotnych arytmii. Cel: Zbadanie związku pomiędzy elektrofizjologicznymi właściwościami przedsionków a powiększeniem przedsionka i zwiększonym ciśnieniem napełniania. Metodyka: Grupę badaną stanowiło 79 chorych bez organicznej choroby serca w średnim wieku 53&#177;22 lata, którzy zostali zakwalifikowani do wykonania inwazyjnego badania elektrofizjologicznego. Podczas stymulacji programowanej prawego przedsionka (HRA) oceniano takie parametry elektrofizjologiczne jak czas przewodzenia międzyprzedsionkowego (iaCT) i występowanie podwójnych potencjałów oraz fragmentację potencjałów przedsionkowych. W szczególności oceniano czas pobudzenia przedsionków, podstawowy iaCT (iaCTb) pomiędzy HRA a dystalnym odcinkiem zatoki wieńcowej (CS), iaCT podczas stymulacji HRA o długości cyklu S1-S1 600 ms (iaCTS1) i maksymalne wydłużenie iaCT po bodźcach przedwczesnych S2 i S3 (iaCTS2, iaCTS3). Obliczono także indeks zwolnienia przewodzenia (ang. decremental index) (DI)=iaCTS3-iaCTS1/iaCTS1%. Parametry hemodynamiczne, oceniane przy pomocy echokardiografii, obejmowały ocenę wielkości LA, powierzchni LA (LAs), objętości LA przy użyciu wzoru elipsowego (LAv), powierzchni RA (RAs), całkowitej powierzchni przedsionków (TAs=LAs+RAs) oraz globalnego indeksu sercowego (GMI). Wyniki: Chorych podzielono na dwie grupy w zależności od zmierzonych parametrów elektrofizjologicznych. Grupę 1 stanowiło 37 chorych ze zwolnionym przewodzeniem (fragmentacja potencjałów przedsionkowych, iaCTb >80 ms, DI >50% lub obecność podwójnych potencjałów), podczas, gdy grupę 2 stanowiło 42 chorych bez zaburzeń przewodzenia w przedsionkach. Obie grupy nie różniły się istotnie pod względem wieku, indeksu masy ciała lub wymiarami LA. U 37 chorych (w tym 32 pacjentów z grupy 1) występowały w przeszłości udokumentowane napady AF. Wartości GMI, LAs, LAv i TAs były istotnie większe w grupie 1 niż w grupie 2. Wykazano istotną liniową korelację pomiędzy iaCTb i TAs (r=0.52,

Um novo índice de doppler tecidual para a predição de fibrilação atrial futura em pacientes com insuficiência cardíaca

FUNDAMENTO: O aparecimento de Fibrilação Atrial (FA) em pacientes com Insuficiência Cardíaca (IC) está em geral associado a uma alta ocorrência de complicações cardiovasculares. Constatou-se que a relação E/(E' × S') (E = velocidade transmitral diastólica inicial, E' = velocidade diastólica inicial no anel mitral e S = velocidade sistólica no anel mitral) reflete a pressão de enchimento do ventrículo esquerdo. Objetivo: Investigamos se E/(E' × S') poderia ser um preditor de FA de início recente em pacientes com IC. MÉTODOS: Foram analisados 113 pacientes consecutivos hospitalizados com IC, em ritmo sinusal, após o tratamento médico adequado. Os pacientes com histórico de FA, imagens ecocardiográficas inadequadas, cardiopatia congênita, ritmo acelerado, doença valvar primária significativa, síndrome coronariana aguda, revascularização coronária durante o seguimento, doença pulmonar ou insuficiência renal grave não foram incluídos. E/(E' × S') foi determinado utilizando a média das velocidades das bordas septal e lateral do anel mitral. A meta principal do estudo foi a FA de início recente. RESULTADOS: Durante o período de seguimento (35,7 ± 11,2 meses), 33 pacientes (29,2%) desenvolveram FA. A média de E/(E' × S') foi de 3,09 ± 1,12 nesses pacientes, ao passo que foi de 1,72 ± 1,34 no restante (p 2,2. A FA de início recente foi maior em pacientes com E/(E' × S') > 2,2 que em pacientes com E/(E' × S') < 2,2 [29 (59,1%) versus 4 (6,2%), p < 0,001]. Na análise multivariada de Cox incluindo as variáveis que previram FA em análise univariada, a relação E/(E' × S') foi o único preditor independente de FA de início recente (relação de risco = 2,26, 95% de intervalo de confiança = 1,25 - 4,09, p = 0,007). CONCLUSÃO: Em pacientes com IC, a relação E/(E' × S') parece ser um bom preditor de FA de início recente

Health care-associated native valve endocarditis: importance of non-nosocomial acquisition.

BACKGROUND: The clinical profile and outcome of nosocomial and non-nosocomial health care-associated native valve endocarditis are not well defined. OBJECTIVE: To compare the characteristics and outcomes of community-associated and nosocomial and non-nosocomial health care-associated native valve endocarditis. DESIGN: Prospective cohort study. SETTING: 61 hospitals in 28 countries. PATIENTS: Patients with definite native valve endocarditis and no history of injection drug use who were enrolled in the ICE-PCS (International Collaboration on Endocarditis Prospective Cohort Study) from June 2000 to August 2005. MEASUREMENTS: Clinical and echocardiographic findings, microbiology, complications, and mortality. RESULTS: Health care-associated native valve endocarditis was present in 557 (34%) of 1622 patients (303 with nosocomial infection [54%] and 254 with non-nosocomial infection [46%]). Staphylococcus aureus was the most common cause of health care-associated infection (nosocomial, 47%; non-nosocomial, 42%; P = 0.30); a high proportion of patients had methicillin-resistant S. aureus (nosocomial, 57%; non-nosocomial, 41%; P = 0.014). Fewer patients with health care-associated native valve endocarditis had cardiac surgery (41% vs. 51% of community-associated cases; P &lt; 0.001), but more of the former patients died (25% vs. 13%; P &lt; 0.001). Multivariable analysis confirmed greater mortality associated with health care-associated native valve endocarditis (incidence risk ratio, 1.28 [95% CI, 1.02 to 1.59]). LIMITATIONS: Patients were treated at hospitals with cardiac surgery programs. The results may not be generalizable to patients receiving care in other types of facilities or to those with prosthetic valves or past injection drug use. CONCLUSION: More than one third of cases of native valve endocarditis in non-injection drug users involve contact with health care, and non-nosocomial infection is common, especially in the United States. Clinicians should recognize that outpatients with extensive out-of-hospital health care contacts who develop endocarditis have clinical characteristics and outcomes similar to those of patients with nosocomial infection. PRIMARY FUNDING SOURCE: None

Evidence for an isomer in 76Ni^{76}Ni

In the experiment performed at the LISE2000 spectrometer at GANIL neutron-rich nickel isotopes were studied by microsecond isomer spectroscopy. Evidence for an isomer in 76Ni is found, consistently with the shell model prediction of an 8 + state of $\nu (g_{9/2})^2$ structure