Transform-Limited-Pulse Representation of Excitation with Natural Incoherent Light

We study the natural excitation of molecular systems, applicable to, for example, photosynthetic light-harvesting complexes, by natural incoherent light. In contrast with the conventional classical models, we show that the light need not have random character to properly represent the resultant linear excitation. Rather, thermal excitation can be interpreted as a collection of individual events resulting from the system's interaction with individual, deterministic pulsed realizations that constitute the field. The derived expressions for the individual field realizations and excitation events allow for a wave function formalism, and therefore constitute a useful calculational tool to study dynamics following thermal-light excitation. Further, they provide a route to the experimental determination of natural incoherent excitation using pulsed laser techniques.Comment: 5 pages, 3 figures, 1 page supplementary information. Comments welcom

Calcium Pyrophosphate Crystal Deposition: The Effect of Soluble Iron in a Kinetic Study Using a Gelatin Matrix Model

The kinetics of calcium pyrophosphate dihydrate (CPPD) crystal growth was studied by allowing calcium and pyrophosphate (PPi-4) ions to diffuse through a denatured collagen matrix (biological grade gelatin) in the presence of either ferric or ferrous ions. Ferric and, to some extent, ferrous ions blocked the migration of the PPi-4 diffusion gradient. This retardation in the [PPi-4] gradient led to numerous changes in the patterns of CPPD crystal formation. At the initial stages of crystal growth, the iron ions induced more crystal growth compared to control. At later incubation times, ferrous and ferric ions enhanced crystal growth at the expense of crystal nucleation. The presence of both ferrous and ferric ions resulted in the more rapid formation of the two crystals observed in vivo, triclinic CPPD and monoclinic CPPD. Further, both ferrous and ferric ions also reduced the solubility of the crystalline material in the broad diffuse band which formed when the Ca+2 and PPi-4 gradients first met. In this system, the presence of either ferrous or ferric ions increased the amount of hydroxyproline included in the crystalline precipitates. Iron was also incorporated into the crystals, particularly into the triclinic CPPD and monoclinic CPPD crystals

Calcium Pyrophosphate Crystal Deposition: The Effect of Monosodium Urate and Apatite Crystals in a Kinetic Study Using a Gelatin Matrix Model

The kinetics of calcium pyrophosphate dihydrate (CPPD) crystal growth was studied by allowing calcium and pyrophosphate (PPi-4) ions to diffuse through a denatured collagen matrix (biological grade gelatin) in the presence of either monosodium urate monohydrate (MSU) or hydroxyapatite (HA) crystals. In this in vitro model system, MSU crystals significantly altered the kinetics of PPi-4 ionic diffusion through the gelatin matrix by allowing the [PPi-4] gradient to fall off much more rapidly, suggesting an increased level of scavenging of PPi-4 ions into crystalline materials. Even more significantly, the presence of MSU crystals markedly influenced the crystal growth morphology of triclinic CPPD, producing that observed in vivo. A large number of epitaxially dimensional matches between MSU and triclinic (t) and monoclinic (m) CPPD were identified, suggesting that MSU crystals can epitaxially induce CPPD crystal growth. This finding supports the hypothesis that the association of urate gout and CPPD crystal deposition disease is based on the nucleating potential of MSU crystals for CPPD crystal growth. In contrast, the HA crystal structure did not appear to serve as a nucleating agent for CPPD crystals. However, HA crystals did serve as effective traps for PPi-4 ions and their presence led to more stable CPPD crystal growth

Calcium Pyrophosphate Crystal Deposition: A Kinetic Study Using a Type I Collagen Gel Model

Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease is characterized by deposits of triclinic (t) and monoclinic (m) CPPD crystals in articular and fibrocartilage. Many investigators have attempted to model CPPD crystal growth using both solution and a variety of gel systems. We have investigated the effect of type I collagen fibrils on CPPD crystal nucleation and growth using an ionic diffusion model. Collagen was isolated from porcine menisci using a pepsin solubilization procedure and gelled in three layers, with one containing 10 mM pyrophosphate (PPi) plus physiologic ions, the middle containing only the ions, while the third contained 25 mM Ca plus physiologic ions. Initially, amorphorous calcium pyrophosphate formed at the Ca-PPi interface. Monoclinic CPPD crystallized in 6 weeks when the [Ca] was between 2 and 3 mM and the [PPi] was between 50 and 75 μM. At 13 weeks, t-CPPD formed when the [Ca] was also between 2 and 3 mM, but the PPi was less than 25 μM. One of the most striking differences between this system and all previous solution and gel model systems is the total absence of orthorhombic calcium pyrophosphate tetrahydrate (o-CPPT) from the gels made of collagen fibrils in near native conformation. Further, crystals of t-CPPD appear as large single crystals with the classic prismatic growth habit observed in vivo, and crystals of m-CPPD also evidence the in vivo rod habit. In contrast, the crystal growth habits of t-CPPD, m-CPPD, and o-CPPT grown in all of the other model systems never matched that observed in vivo. When compared to the previous studies, these results, particularly the crystal growth habit data, suggest that the native collagen fibrils themselves can nucleate CPPD crystal formation

Unexpected stimulation of mitochondrial ADP-ribosylation by cyanide

AbstractCyanide, the classical inhibitor of the mitochondrial respiratory chain at site III, stimulates ADP-ribosylation of a number of mitochondrial proteins, the major protein being the 50–55 kDa band. Sodium azide, sharing the same inhibitory site, does not have the same effect. Rotenone or antimycin A have no influence on mitochondrial ADP-ribosylation. Data suggest that no apparent correlation exists between oxidoreductase function and protein ADP-ribosylation. Purified nuclear poly(ADP-ribose) polymerase activity was not affected by cyanide. The cyanide effect on mitochondrial ADP-ribosylation seems intriguing and may be attributed to NAD+ -CN complex formation, since NAD reacts with cyanide at pH > 8 with N-substituted nicotinamide which may prevent inhibition of ADP-ribosylation

A model for mode-locking in quantum dot lasers

We propose a model for passive mode-locking in quantum dot laser and report on specific dynamical properties of the regime which is characterized by a fast gain recovery. No Q-switching instability has been found accompanying the mode-locking. Bistability can occur between the mode-locking regime and zero intensity steady state

Nondestructive interaction-free atom-photon controlled-NOT gate

We present a probabilistic (ideally 50%) nondestructive interaction-free atom-photon controlled-NOT gate, where nondestructive means that all four outgoing target photon modes of the gate are available and feed-forwardable. Individual atoms are controlled by a stimulated Raman adiabatic passage transition and photons by a ring resonator with two outgoing ports. Realistic estimates we obtain for ions confined in a Paul trap around which the resonator is mounted show that a strong atom-photon coupling can be achieved. It is also shown how the resonator can be used for controlling superposition of atom states.Comment: 20 pages, 5 figures, Web page: http://m3k.grad.hr/pavici

Offshoring and the State of American Manufacturing

The rapid growth of offshoring has sparked a contentious debate over its impact on the U.S. manufacturing sector, which has recorded steep employment declines yet strong output growth—a fact reconciled by the notable gains in manufacturing productivity. We maintain, however, that the dramatic acceleration of imports from developing countries has imparted a significant bias to the official statistics. In particular, the price declines associated with the shift to low-cost foreign suppliers generally are not captured in input cost and import price indexes. To assess the implications of offshoring bias for manufacturing productivity and value added, we implement the bias correction developed by Diewert and Nakamura (2009) to the input price index in a growth accounting framework, using a variety of assumptions about the magnitude of the discounts from offshoring. We find that from 1997 to 2007 average annual multifactor productivity growth in manufacturing was overstated by 0.1 to 0.2 percentage point and real value added growth by 0.2 to 0.5 percentage point. Furthermore, although the bias from offshoring represents a relatively small share of real value added growth in the computer and electronic products industry, it may have accounted for a fifth to a half of the growth in real value added in the rest of manufacturing