Chemical changes in the adductor muscle of the cheliped of the crayfish in relation to the double motor innervation

Work from this laboratory has shown that a number of the striated muscles of the legs of the crayfish show a typical motor innervation (1). Such muscles are innervated by two motor fibers only, each causing a different type of contraction. One of these, resulting from stimulation of the thicker fiber, is termed the "fast" contraction, while the other is called the "slow." Both anatomical evidence and physiological experiments indicate that each muscle fiber is innervated by these two axons and that both contractions occur in the same muscle fibers (2, 3). The most striking difference between the two contractions is found in the adductor muscle of the cheliped of the crayfish. In this case, a single impulse in the thicker motor fiber causes a twitch-like contraction, and the system behaves in almost all respects as does a single motor unit of a vertebrate muscle: single shocks of different strengths give twitches of a considerable strength and a constant height, and during tetanic contraction the action currents are all of the same magnitude. In contrast to this, single shocks given to the thinner fiber produce no visible response in the muscle, but faradic stimulation causes action currents which grow in height and a contraction with a long latent period. The action currents in this case are always much smaller than those of the fast contraction. The chemical changes occurring in the adductor muscle of the cheliped of the crayfish Cambarus clarkii during these two types of contraction were investigated in order to obtain evidence on two possible mechanisms by which the two contractions might occur in the same muscle fiber. In the first place, two contractile substances might be present, a "phasic" and a "tonic" one, analogous to those supposed by Botazzi (4) in the vertebrate striated muscle, or the same substance might contract in both cases, the difference between the contractions being due solely to differences in the transmission mechanism between the nerve impulse and the contractile substance. Methods were devised for the rapid removal of the stimulated cheliped to liquid air and for the analysis of the frozen muscle tissue. The changes in phosphate and in lactic acid content were used as indices of the chemical changes occurring

House (centric) societies on the prehistoric Greek mainland

The concept of 'House Societies' was introduced by Levi-Strauss. It not only considers the social aspects of houses and households, but also the economic and political ones. By so doing, one gains a much more complete understanding of how a community is structured and organized, and how changes can slowly unfold within seemingly static communities. In this article it is argued that Early Helladic III and early Middle Helladic communities on the Greek mainland can be considered proto-house societies, while House Societies proper do emerge at some places during the later Middle Helladic and Late Helladic I periods. The arguments are based on an analysis of domestic architecture, mortuary practices and the domestic economy. These indicate that the concept of property became more important during the Middle Helladic period. The house was perpetuated through rebuilding and mortuary practices, thereby referencing the concept of kinship, in order to transmit property. Such habits define House Societies

The dangers of neglecting non-financial conflicts of interest in health and medicine

Non-financial interests, and the conflicts of interest that may result from them, are frequently overlooked in biomedicine. This is partly due to the complex and varied nature of these interests, and the limited evidence available regarding their prevalence and impact on biomedical research and clinical practice. We suggest that there are no meaningful conceptual distinctions, and few practical differences, between financial and non-financial conflicts of interest, and accordingly, that both require careful consideration. Further, a better understanding of the complexities of non-financial conflicts of interest, and their entanglement with financial conflicts of interest, may assist in the development of a more sophisticated approach to all forms of conflicts of interest.NHMRC Project Grant (APP1059732)

Status, respect and stigma: a qualitative study of non-financial interests in medicine

Conflicts of interest (COI) in health and medicine have been the source of considerable public and professional debate. Much of this debate has focused on financial, rather than non-financial COI, which is a significant lacuna because non-financial COI can be just as influential as financial COI. In an effort to explore the nature and effects of non-financial, as well as financial COI, we conducted semi-structured interviews with 11 Australian medical professionals regarding their experiences of, and attitudes towards, COI. We found that this group of medical professionals saw non-financial interests—most notably the pursuit of status and respect, and the avoidance of stigma—as potentially conflicting with other important interests (such as patient care).NHMRC Career Development Fellowship (APP1036539

A new chiral electro-optic effect: Sum-frequency generation from optically active liquids in the presence of a dc electric field

We report the observation of sum-frequency signals that depend linearly on an applied electrostatic field and that change sign with the handedness of an optically active solution. This recently predicted chiral electro-optic effect exists in the electric-dipole approximation. The static electric field gives rise to an electric-field-induced sum-frequency signal (an achiral third-order process) that interferes with the chirality-specific sum-frequency at second-order. The cross-terms linear in the electrostatic field constitute the effect and may be used to determine the absolute sign of second- and third-order nonlinear optical susceptibilities in isotropic media.Comment: Submitted to Physical Revie

Activated Transport in the individual Layers that form the νT\nu_T=1 Exciton Condensate

We observe the total filling factor $\nu_{T}$=1 quantum Hall state in a bilayer two-dimensional electron system with virtually no tunnelling. We find thermally activated transport in the balanced system with a monotonic increase of the activation energy with decreasing $d/\ell_B$ below 1.65. In the imbalanced system we find activated transport in each of the layers separately, yet the activation energies show a striking asymmetry around the balance point. This implies that the gap to charge-excitations in the {\em individual} layers is substantially different for positive and negative imbalance.Comment: 4 pages. 4 figure

Fluctuations of radiation from a chaotic laser below threshold

Radiation from a chaotic cavity filled with gain medium is considered. A set of coupled equations describing the photon density and the population of gain medium is proposed and solved. The spectral distribution and fluctuations of the radiation are found. The full noise is a result of a competition between positive correlations of photons with equal frequencies (due to stimulated emission and chaotic scattering) which increase fluctuations, and a suppression due to interaction with a gain medium which leads to negative correlations between photons. The latter effect is responsible for a pronounced suppression of the photonic noise as compared to the linear theory predictions.Comment: 7 pages, 5 figures; expanded version, to appear in Phys. Rev.

Exciton condensate at a total filling factor of 1 in Corbino 2D electron bilayers

Magneto-transport and drag measurements on a quasi-Corbino 2D electron bilayer at the systems total filling factor 1 (v_tot=1) reveal a drag voltage that is equal in magnitude to the drive voltage as soon as the two layers begin to form the expected v_tot=1 exciton condensate. The identity of both voltages remains present even at elevated temperatures of 0.25 K. The conductance in the current carrying layer vanishes only in the limit of strong coupling between the two layers and at T->0 K which suggests the presence of an excitonic circular current

Light scattering from an amplifying medium bounded by a randomly rough surface: A numerical study

We study by numerical simulations the scattering of $s$-polarized light from a rough dielectric film deposited on the planar surface of a semi-infinite perfect conductor. The dielectric film is allowed to be either active or passive, situations that we model by assigning negative and positive values, respectively, to the imaginary part $\epsilon_2$ of the dielectric constant of the film. We study the reflectance ${\cal R}$ and the total scattered energy ${\cal U}$ for the system as functions of both $\epsilon_2$ and the angle of incidence of the light. Furthermore, the positions and widths of the enhanced backscattering and satellite peaks are discussed. It is found that these peaks become narrower and higher when the amplification of the system is increased, and that their widths scale linearly with $\epsilon_2$. The positions of the backscattering peaks are found to be independent of $\epsilon_2$, while we find a weak dependence on this quantity in the positions of the satellite peaks.Comment: Revtex, 9 pages, 9 figure

Mode suppression in the non-Markovian limit by time-gated stimulated photon echo

It is demonstrated that enhanced mode suppression in stimulated photon echo experiments can be obtained by diagonal time gating of the echo. This technique is especially important when the optical dynamics of the system is non-Markovian. A two-mode Brownian oscillator model is used to analyze the effect of time gating on the stimulated photon echo. The method is demonstrated on a dye solution of DTTCI in ethylene glycol at room temperature. Experimentally, time gating of the echo is accomplished by means of femtosecond phase-locked heterodyne detected stimulated photon echo. The vibrational dynamics in this system are explored by conventional stimulated photon echo experiments, Especially stimulated photon echo-maximum shift measurements are found to be particularly useful. (C) 1996 American Institute of Physics