Beyond the frame rate: Measuring high-frequency fluctuations with light intensity modulation

Power spectral density measurements of any sampled signal are typically restricted by both acquisition rate and frequency response limitations of instruments, which can be particularly prohibitive for video-based measurements. We have developed a new method called Intensity Modulation Spectral Analysis (IMSA) that circumvents these limitations, dramatically extending the effective detection bandwidth. We demonstrate this by video-tracking an optically-trapped microsphere while oscillating an LED illumination source. This approach allows us to quantify fluctuations of the microsphere at frequencies over 10 times higher than the Nyquist frequency, mimicking a significantly higher frame rate.Comment: 4 pages, 2 figure

Simple Rings and Degree Maps

For an extension A/B of neither necessarily associative nor necessarily unital rings, we investigate the connection between simplicity of A with a property that we call A-simplicity of B. By this we mean that there is no non-trivial ideal I of B being A-invariant, that is satisfying AI \subseteq IA. We show that A-simplicity of B is a necessary condition for simplicity of A for a large class of ring extensions when B is a direct summand of A. To obtain sufficient conditions for simplicity of A, we introduce the concept of a degree map for A/B. By this we mean a map d from A to the set of non-negative integers satisfying the following two conditions (d1) if a \in A, then d(a)=0 if and only if a=0; (d2) there is a subset X of B generating B as a ring such that for each non-zero ideal I of A and each non-zero a \in I there is a non-zero a' \in I with d(a') \leq d(a) and d(a'b - ba') < d(a) for all b \in X. We show that if the centralizer C of B in A is an A-simple ring, every intersection of C with an ideal of A is A-invariant, ACA=A and there is a degree map for A/B, then A is simple. We apply these results to various types of graded and filtered rings, such as skew group rings, Ore extensions and Cayley-Dickson doublings.Comment: 17 page

Universal Toda brackets of ring spectra

We construct and examine the universal Toda bracket of a highly structured ring spectrum R. This invariant of R is a cohomology class in the Mac Lane cohomology of the graded ring of homotopy groups of R which carries information about R and the category of R-module spectra. It determines for example all triple Toda brackets of R and the first obstruction to realizing a module over the homotopy groups of R by an R-module spectrum. For periodic ring spectra, we study the corresponding theory of higher universal Toda brackets. The real and complex K-theory spectra serve as our main examples.Comment: 38 pages; a few typos corrected, to appear in Trans. Amer. Math. So

Fulgenzio e la cultura scritta in Sardegna agli inizi del VI secolo

Fulgenzio, vescovo di Ruspe, e il papa Gregorio Magno hanno illuminato, nel VI secolo, le punte estreme di una parabola che inizia in Sardegna con il potere piuttosto distaccato e permissivo del re vandalo Trasamondo per chiudersi più tardi, in pieno dominio bizantino, quando l'imperatore Maurizio, pur impegnato nella difesa delle terre dell'impero dai Longobardi di Agilulfo, non manca di far sentire tutto il peso dell'efficienza fiscale della sua burocrazia. In particolare, per il ricercatore interessato allo stato della cultura scritta in questo periodo, riveste un più immediato interesse l'esame della Vita e dell'opera del vescovo africano, anche alla luce delle ipotesi che si possono avanzare sulla situazione culturale dell'area cagliaritana nel primo ventennio del VI secolo. Si tratta di un ulteriore contributo, seppur necessariamente ristretto, indirizzato a una regione della quale si è finora parlato, quasi esclusivamente, per sottolinearne la chiusura e l'isolamento

Immunohistochemical study of the BMPs and their extracellular antagonists in osteoarthritic human knee joint

The osteophytes are bone spurs overgrowing the edge of the articular cartilage during the course of osteoarthritis (OA). The cellular mechanism of their development and growth resembles the intramembranous and endochondral bone development during embrional and postnatal normal bone development, growth, modeling, remodeling and repair. The role of BMPs in bone development and metabolism is well documented and the members of the BMPs molecular network were recognized as important factors which could modulate new bone development and growth of osteophytes. The purpose of this study is to analyze the cooexpression of the most potent osteoinductive members of the BMP family (BMP-2, -4 and -7) and their extracellular antagonists gremlin, noggin, chordin, follistatin in order to establish their role during degenerative process of the synovial joints and growth of osteophyte. In this study, the BMP-2, BMP-4, BMP-7, gremlin, noggin, chordin, follistatin expressions were analyzed in joint tissues from OA patients and from healthy individuals by immunohistochemistry and Western blot. The immunohistochemistry showed different localization pattern of BMPs and BMP extracellular antagonists expressions in OA vs. normal joint tissues. In osteophyte, BMP-2 was not detected, while BMP-4 and BMP-7 were positive in hypertrophyc chondrocytes and osteocytes at the sites of endochondral bone development. BMP-7 was strongly positive, while BMP-4 was negative in synovial membrane of OA joints. Gremlin, chordin and noggin were found in chondrocytes, osteoblasts of the osteophytic bone and synovial epithelium, while follistatin was found in chondrocytes, blood vessels and synovial epithelium. Our result demonstrate the significant differences in BMPs and their antagonists expression in normal tissues compare to joint tissue affected by OA and revealed how molecular balance of the local growth factors such as BMPs and their antagonists could be disturbed during degenerative processes. Also, these findings suggest the potent role of these molecular factors in pathogenesis of the OA and/or during growth and development of the human knee joint osteophytes