The Origin of the Electromagnetic Interaction in Einstein's Unified Field Theory with Sources

Einstein's unified field theory is extended by the addition of matter terms in the form of a symmetric energy tensor and of two conserved currents. From the field equations and from the conservation identities emerges the picture of a gravoelectrodynamics in a dynamically polarizable Riemannian continuum. Through an approximate calculation exploiting this dynamical polarizability it is argued that ordinary electromagnetism may be contained in the theory.Comment: 8 pages. Misprint in eq. 15 correcte

The Electrostatics of Einstein's Unified Field Theory

When sources are added at their right-hand sides, and g_{(ik)} is a priori assumed to be the metric, the equations of Einstein's Hermitian theory of relativity were shown to allow for an exact solution that describes the general electrostatic field of n point charges. Moreover, the injunction of spherical symmetry of g_{(ik)} in the infinitesimal neighbourhood of each of the charges was proved to yield the equilibrium conditions of the n charges in keeping with ordinary electrostatics. The tensor g_{(ik)}, however, cannot be the metric of the theory, since it enters neither the eikonal equation nor the equation of motion of uncharged test particles. A physically correct metric that rules both the behaviour of wave fronts and of uncharged matter is the one indicated by H\'ely. In the present paper it is shown how the electrostatic solution predicts the structure of the n charged particles and their mutual positions of electrostatic equilibrium when H\'ely's physically correct metric is adopted.Comment: 15 pages. Misprints corrected. To appear in General Relativity and Gravitatio

A review of 71 cases of infected total knee arthroplasty: mid-term to long-term follow-up

Departamentul de Chirurgie Ortopedică și Reabilitare, Universitatea Tech din Texas, Centrul de Știinţe ale Sănătaţii, Școala de Medicină Paul L. Foster, El Paso, Texas, Statele Unite ale Americii, Departamentul de Chirurgie Ortopedică, Spitalul General Buffalo, Universitatea de Stat din New York, Buffalo, New York, Statele Unite ale Americii, Departamentul de Chirurgie Ortopedică a Universităţii Harvard, Spitalul General Massachusetts, Boston, Statele Unite ale AmericiiIntroducere. În cadrul acestui studiu au fost evaluate caracteristici și rezultate la termen mediu și lung ale cazurilor de artroplastie totală de genunchi (ATG) și ale infecţiilor asociate cu acestea, care au fost tratate prin diferite metode. Material și metode. Studiul retrospectiv reflectă rezultatele a 71 de cazuri de ATG, infectate și tratate în perioada august 1993 – august 2005. Datele colectate includ înregistrări medicale cu privire la sexe, clasificarea infecţiilor periprotetice (IPP), comorbiditatea pacienţilor, criteriile de diagnostic ale IPP, rezultatele microbiologice și histopatologice, tratamentele chirurgicale și antimicrobiene, modalitaţile de tratament, complicaţiile, consecinţele, precum și rezultatele tratamentului. Nivelul de evidenţă: nivel terapeutic III. Rezultate. Vârsta medie a pacienţilor a constituit 70 de ani (extreme, 43–88 de ani). Mediana duratei de supraveghere – 10,8 ani (extreme, 5 – 20 de ani). Treizeci și trei (46,5%) de pacienţi au prezentat multipli factori de risc pentru IPP. Principalii patogeni izolaţi au fost stafilococii coagulazo-negativi – 26 (37%), Staphylococcus aureus – 16 (22,4%). Metodele de tratament ale ATG infectate au fost: înlocuirea în două etape – 59 (83%) de cazuri, debridare și retenţie – 5 (7,2%) cazuri, artrodeza – 5 (7,2%) cazuri, excizie-artroplastie – 2 (2,8%) cazuri. La sfârșitul perioadei de supraveghere, 17 genunchi (24%) au suportat intervenţie repetată, dintre care 10 (14%) – îndepărtarea componentelor din cauza reinfectării. Doi genunchi s-au reinfectat de 3 ori, trei genunchi – de două ori. Prima reintervenţie după reinfectare a fost efectuată după 1,2 ani (mediana), cu extreme cuprinse între 0,04 și 2,5 ani. Analiza curbelor Kaplan-Meier „de supravieţuire” a constatat că la 5 ani fără reintervenţie au ajuns 90,5% (95% CI între 85,3% și 96,1%) dintre pacienţi, iar la 10 ani – 82% (95% CI între 70,3% și 94,5%). Scorurile Asociaţiei Genunchiului (engl. Knee Society score): scorurile de durere, scorurile funcţionale, amplituda mișcării (engl. range of motion, ROM) – îmbunătăţite. Concluzii. Tratamentul ATG infectate este o sarcină dificilă, cu rezultate nesatisfăcătoare la termen mediu și lung. Aproximativ fiecare al patrulea pacient a necesitat o reintervenţie, iar 14% dintre pacienţi s-au reinfectat în primii 2,5 ani. Jumă- tate dintre pacienţii cu reinfecţie a ATG s-au reinfectat din nou. În majoritatea cazurilor, pacienţii s-au reinfectat cu același microorganism, dar mai virulent. Tratamentul unei ATG infectate ar putea fi ales în funcţie de tipul de infecţie (acută sau cronică), durata ei, stabilitatea implantului, specia agentului patogen, calitatea și integritatea osului și ţesutului moale.Introduction. In the present study, the characteristics and mid-term to long-term outcomes of total knee arthroplasty (TKA) associated infections treated with different types of approaches were evaluated. Material and methods. A retrospective study of the results of 71 infected TKA treated between August 1993 and August 2005. The data included medical records, gender, periprosthetic infection (PPI) classification, patients’ comorbidities, PPI diagnostic criteria, microbiology and histopathology results, surgical and antimicrobial therapy, treatment modality, complications, follow up, and treatment results. Level of Evidence: Therapeutic Level III. Results. Median age was 70 years (range, 43–88). Median follow-up 10.8 years (range, 5–20). Thirty-three patients had multiple risk-factors for PPI. The main pathogens isolated were Coagulase-negative staphylococci 26 (37%), Staphylococcus aureus 16 (22.4%). The treatment methods of TKA infection were two-stage exchange in 59 (83%), debridement and retention – 5 (7.2%), arthrodesis – 5 (7.2%), excision arthroplasty 2 (2.8%). At final follow up, 17 knees (24%) had required reoperation: 10 knees (14%) – component removal for reinfection. Two knees were reinfected 3 times, three knees – two times. The median time to first reoperation for reinfection was 1.2 years (range, 0.04–2.5 years). By Kaplan-Meier survival analysis the estimated survivals free of reoperation for infection were 90.5% (95% confidence intervals, 85.3% to 96.1%) at 5 years and 82% (95% confidence intervals, 70.3% to 94.5%) at 10 years. The Knee Society scores: Pain scores, Functional scores, ROM improved. Conclusions. TKA infections treatment is a difficult task leading to a high rate of unsatisfactory mid-term and longterm results. About one forth of patient require reoperation, 14% become reinfected in first 2.5 years. Half of reinfected patients get reinfected repeatedly. In most cases patients are reinfected with the same microorganism but more virulent. TKA infection treatment option should be chosen according to the type of infection (acute or chronic), the duration of infection, the stability of the implant, the type of microorganism causing infection, bone quality and integrity, and the quality of the soft-tissue

Environmental degradation and indeterminacy of equilibrium selection

This paper analyzes an intertemporal optimization problem in which agents derive utility from three goods: leisure, a public environmental good and the consumption of a produced good. The global analysis of the dynamic system generated by the optimization problem shows that global indeterminacy may arise: given the initial values of the state variables, the economy may converge to different steady states, by choosing different initial values of the control variable

Consumption of private goods as substitutes for environmental goods in an economic growth model

We analyze growth dynamics in an economy where a private good can be consumed as a substitute for a free access environmental good. In this context we show that environmental deterioration may be an engine of economic growth. To protect themselves against environmental deterioration, economic agents are forced to increase their labour supply to increase the production and consumption of the private good. This, in turn, further depletes the environmental good, leading economic agents to further increase their labour supply and private consumption and so on. This substitution process may give rise to self-enforcing growth dynamics characterized by a lack of correlation between capital accumulation and private consumption levels, on one side, and economic agents’ welfare, on the other. Furthermore, we show that agents’ self-protection consumption choices can generate indeterminacy; that is, they can give rise to the existence of a continuum of (Nash) equilibrium orbits leading to the same attracting fixed point or periodic orbit

Bowling alone but tweeting together: the evolution of human interaction in the social networking era

The objective of this paper is to theoretically analyze how human interaction may evolve in a world characterized by the explosion of online networking and other Web-mediated ways of building and nurturing relationships. The analysis shows that online networking yields a storage mechanism through which any individual contribution—e.g. a blog post, a comment, or a photo—is stored within a particular network and ready for virtual access by each member who connects to the network. When someone provides feedback, for example by commenting on a note, or by replying to a message, the interaction is finalized. These interactions are asynchronous, i.e. they allow individuals to relate in different moments, whenever they have time to. When the social environment is poor of participation opportunities and/or the pressure on time increases (for example due to the need to increase the working time), the stock of information and ties stored in the Internet can help individuals to defend their sociability

The {\gamma} Dor stars as revealed by Kepler : A key to reveal deep-layer rotation in A and F stars

The {\gamma} Dor pulsating stars present high-order gravity modes, which make them important targets in the intermediate-and low-mass main-sequence region of the Hertzsprung-Russell diagram. Whilst we have only access to rotation in the envelope of the Sun, the g modes of {\gamma} Dor stars can in principle deliver us constraints on the inner layers. With the puzzling discovery of unexpectedly low rotation rates in the core of red giants, the {\gamma} Dor stars appear now as unique targets to explore internal angular momentum transport in the progenitors of red giants. Yet, the {\gamma} Dor pulsations remain hard to detect from the ground for their periods are close to 1 day. While the CoRoT space mission first revealed intriguing frequency spectra, the almost uninterrupted 4-year photometry from the Kepler mission eventually shed a new light on them. It revealed regularities in the spectra, expected to bear signature of physical processes, including rotation, in the shear layers close to the convective core. We present here the first results of our effort to derive exploitable seismic diagnosis for mid- to fast rotators among {\gamma} Dor stars. We confirm their potential to explore the rotation history of this early phase of stellar evolution.Comment: 4 pages, 1 figure, proceedings of the 22nd Los Alamos Stellar Pulsation Conference, "Wide-field variability surveys: a 21st-century perspective" held in San Pedro de Atacama, Chile, Nov. 28-Dec. 2, 201