Flat microwave spectra seen at X-class flares

We report peculiar spectral activity of four large microwave bursts as obtained from the Solar Arrays at the Owens Valley Radio Observatory during observations of X-class flares on 1990 May 24 and 1991 March 7, 8, and 22. Main observational points that we newly uncovered are: (1) flat flux spectra over 1–18 GHz in large amounts of flux ranging from 10² to 10⁴ s.f.u. at the maximum phase, (2) a common evolutionary pattern in which the spectral region of dominant flux shifts from high frequencies at the initial rise to low frequencies at the decaying phase, and (3) unusual time profiles that are impulsive at high frequencies but more extended at lower frequencies. In an attempt to elucidate these new properties, we carry out the model calculations of microwave spectra under assumptions of gyrosynchrotron mechanism and a dipole field configuration to reproduce the observational characteristics. Our results are summarized as follows. First, a flat microwave spectrum reaching up to 10²–10⁴ s.f.u. may occur in a case where a magnetic loop is extended to an angular size of ∼(0.7–7.0) × 10⁻⁷ sterad and contains a huge number (N(E > 10 keV) ∼ 10³⁶– 10³⁸) of nonthermal electrons with power-law index δ ∼ 3–3.5 over the entire volume. Second, the observed spectral activity could adequately be accounted for by the shrinking of the region of nonthermal electrons to the loop top and by the softening of the power-law spectrum of electrons in a time scale ranging 3–45 min depending on the event. Third, the extended microwave activity at lower frequencies is probably due to electrons trapped in the loop top where magnetic fields are low. Finally, we clarify the physical distinction between these large, extended microwave bursts and the gradual/post-microwave bursts often seen in weak events, both of which are characterized by long-period activity and broadband spectra

Isolated sequences from the linked Myf-5 and MRF4 genes drive distinct patterns of muscle-specific expression in transgenic mice

In developing mouse embryos, MyoD family regulatory genes are expressed specifically in muscle precursors and mature myofibers. This pattern, taken together with the well-established ability of MyoD family members to convert a variety of cell types to skeletal muscle, suggests a significant role for these genes in regulating skeletal myogenesis. The possibility that expression of these genes may be causally associated with segregation of the myogenic lineage from other mesodermal derivatives, or with the subsequent maintenance of muscle phenotypes at later times, raises the issue of how MyoD family genes are themselves regulated during development. In this work, we have initiated studies to identify DNA sequences that govern Myf-5 and MRF4 (herculin, myf-6) transcription. Myf-5 is the first of the MyoD family to be expressed in the developing mouse embryo, while MRF4 is the most abundantly expressed myogenic factor in postnatal animals. In spite of their strikingly divergent patterns of expression, Myf-5 and MRF4 are tightly linked in the mouse genome; their translational start codons are only 8.5 kilobases apart. Here, the 5' flanking regions of the mouse Myf-5 and MRF4 genes were separately linked to a bacterial β-galactosidase (lacZ) gene, and these constructs were each used to produce several lines of transgenic mice. Transgene expression was monitored by X-gal staining of whole embryos and by in situ hybridization of embryo sections. For the Myf-5/lacZ lines, the most intense transgene expression was in the visceral arches and their craniofacial muscle derivatives, beginning at day 8.75 post coitum (p.c.). This correlates with endogenous Myf-5 expression in visceral arches. However, while Myf-5 is also expressed in somites starting at day 8 p.c., transgene expression in the trunk is not observed until day 12 p.c. Thus, the Myf-5/lacZ construct responds to early Myf-5 activators in the visceral arches but not in the somites, suggesting that myogenic determination in the nonsomitic head mesoderm may be under separate control from that of the somitic trunk mesoderm. MRF4/lacZ lines displayed an entirely different pattern from Myf-5. Transgene expression appeared in muscles starting at day 16.5 p.c. and became increasingly prominent at later times. However, an early wave of myotomal expression that is characteristic of the endogenous MRF4 was not recapitulated by the transgene

Influence of the Cortical Midline Structures on Moral Emotion and Motivation in Moral Decision-Making

The present study aims to examine the relationship between the cortical midline structures (CMS), which have been regarded to be associated with selfhood, and moral decision making processes at the neural level. Traditional moral psychological studies have suggested the role of moral self as the moderator of moral cognition, so activity of moral self would present at the neural level. The present study examined the interaction between the CMS and other moral-related regions by conducting psycho-physiological interaction analysis of functional images acquired while 16 subjects were solving moral dilemmas. Furthermore, we performed Granger causality analysis to demonstrate the direction of influences between activities in the regions in moral decision-making. We first demonstrate there are significant positive interactions between two central CMS seed regions—i.e., the medial prefrontal cortex (MPFC) and posterior cingulate cortex (PCC)—and brain regions associated with moral functioning including the cerebellum, brainstem, midbrain, dorsolateral prefrontal cortex, orbitofrontal cortex and anterior insula (AI); on the other hand, the posterior insula (PI) showed significant negative interaction with the seed regions. Second, several significant Granger causality was found from CMS to insula regions particularly under the moral-personal condition. Furthermore, significant dominant influence from the AI to PI was reported. Moral psychological implications of these findings are discussed. The present study demonstrated the significant interaction and influence between the CMS and morality-related regions while subject were solving moral dilemmas. Given that, activity in the CMS is significantly involved in human moral functioning

Tracking The Post-BBN Evolution Of Deuterium

The primordial abundance of deuterium produced during Big Bang Nucleosynthesis (BBN) depends sensitively on the universal ratio of baryons to photons, an important cosmological parameter probed independently by the Cosmic Microwave Background (CMB) radiation. Observations of deuterium in high-redshift, low-metallicity QSO Absorption Line Systems (QSOALS) provide a key baryometer, determining the baryon abundance at the time of BBN to a precision of 5%. Alternatively, if the CMB-determined baryon to photon ratio is used in the BBN calculation of the primordial abundances, the BBN-predicted deuterium abundance may be compared with the primordial value inferred from the QSOALS, testing the standard cosmological model. In the post-BBN universe, as gas is cycled through stars, deuterium is only destroyed so that its abundance measured anytime, anywhere in the Universe, bounds the primordial abundance from below. Constraints on models of post-BBN Galactic chemical evolution follow from a comparison of the relic deuterium abundance with the FUSE-inferred deuterium abundances in the chemically enriched, stellar processed material of the local ISM.Comment: 8 pages, 5 figures, to appear in the Proceedings of the Future Directions in Ultraviolet Spectroscopy Conferenc

Aerobic fitness impacts sympathoadrenal axis responses to concurrent challenges

The combination of mental and physical challenges can elicit exacerbated cardiorespiratory (CR) and catecholamine responses above that of a single challenge alone. Purpose This study examined the effects of a combination of acute mental challenges and physical stress on cardiorespiratory and catecholamine responses. Method Eight below-average fitness (LF VO2max = 36.58 +/- 3.36 ml(-1) kg(-1) min(-1)) and eight above-average fitness (HF VO2max = 51.18 +/- 2.09 ml(-1) kg(-1) min(-1)) participants completed an exercise-alone condition (EAC) session consisting of moderate-intensity cycling at 60% VO2max for 37 min, and a dual-challenge condition (DCC) that included concurrent participation in mental challenges while cycling. Result The DCC resulted in increases in perceived workload, CR, epinephrine, and norepinephrine responses overall. HF participants had greater absolute CR and catecholamine responses compared to LF participants and quicker HR recovery after the dual challenge. Conclusion These findings demonstrate that cardiorespiratory fitness does impact the effect of concurrent stressors on CR and catecholamine responses

A Suggested Criterion for Selecting between E-V and Stochastic Dominance Analysis Tools

Research Methods/ Statistical Methods,

Laboratory and field investigations of potential predation on early life stages of striped bass in the Pamunkey River, Virginia /

Predation is recognized as an important factor regulating survival of larval fishes and it is likely that both fish and invertebrate species are predators of striped bass eggs and larvae, yet few studies have documented such interactions in tidal freshwater systems. As a result, this study incorporated the following objectives: (1) determine kinds and relative abundances of potential fish and invertebrate predators of striped bass larvae through field surveys: (2) document acceptability of yolksac larvae as a prey item through laboratory experimentation with fish and invertebrate species: (3) establish preliminary estimates of consumption of yolksac larvae under laboratory conditions of varying prey density, prey consumption and container size: and (4) examine stomach contents of field collected target fish predators

Combined effects of a parasite, QPX, and the harmful-alga, Prorocentrum minimum on northern quahogs, Mercenaria mercenaria

Northern quahogs, Mercenaria mercenaria (L.), frequently are infected with the parasite Quahog Parasite Unknown (QPX, Labyrintohomorpha, Thraustochytriales), which can cause morbidity and mortality of the quahogs. Possible interactions between this parasitic disease and exposure to the harmful dinoflagellate Prorocentrum minimum in M. mercenaria were studied experimentally. Quahogs from Massachusetts with variable intensity of QPX infection were exposed, under controlled laboratory conditions, to cultured P. minimum added to the natural plankton at a cell density equivalent to a natural bloom. After 5 days of exposure, individual clams were diagnosed histologically to assess prevalence and intensity of parasitic infection, as well as other pathological conditions. Further, cellular defense status of clams was evaluated by analyzing hemocyte parameters (morphological and functional) using flow-cytometry. Exposure of quahogs to P. minimum resulted in: a lower percentage of phagocytic hemocytes, higher production of reactive oxygen species (ROS), larger hemocyte size, more-numerous hemocytic aggregates, and increased numbers of hemocytes in gills accompanied by vacuolation and hyperplasia of the water-tubular epithelial cells of the gills. Quahogs had a low prevalence of QPX; by chance, the parasite was present only in quahogs exposed to P. minimum. Thus, the effect of QPX alone on the hemocyte parameters of quahogs could not be assessed in this experiment, but it was possible to assess different responses of infected versus non-infected quahogs to P. minimum. QPX-infected quahogs exposed to P. minimum had repressed percentage of phagocytic hemocytes, consistent with immuno-modulating effect of P. minimum upon several molluscan species, as well as smaller hemocytes and increased hemocyte infiltration throughout the soft tissues. This experiment demonstrates the importance of considering interactive effects of different factors on the immunology and histopathology of bivalve shellfish, and highlights the importance of considering the presence of parasites when bivalves are subjected to harmful-algal blooms

Stock Repurchases And False Signals

Each year many firms repurchase shares of their common stock. Research evidence shows that when firms announce the repurchase of common stock, their share prices typically rise.  Numerous studies attribute these increases to a signaling effect.  But some firms that announce their intention of repurchasing shares of common stock either repurchase no shares at all or repurchase fewer shares than initially announced. Although the practice of firms intentionally announcing the repurchase of more shares than they expect to repurchase is illegal, the expected increase in share prices may give firms an incentive to make such false announcements. This study surveys top financial executives to learn the extent that firms repurchase fewer shares than announced, identify the reasons for this activity, and learn how managers view this activity.  We surveyed 642 firms that conducted common stock repurchases from January 1998 to September 1999.  Based on 218 responses, we find that while managers are uncertain about the legality of this activity, they believe that the intentional repurchase of fewer shares than announced is unethical, sends a false signal to the market, and damages the firm’s credibility with its stockholders.  Managers also believe that firms repurchasing fewer shares than announced should publicly reveal both the reason for not repurchasing all shares and the amount by which the repurchase fell short of the firm’s announced intentions.  Despite these beliefs, managers report that repurchasing fewer shares than announced is a common practice

Kinetic Signatures and Intermittent Turbulence in the Solar Wind Plasma

A connection between kinetic processes and intermittent turbulence is observed in the solar wind plasma using measurements from the Wind spacecraft at 1 AU. In particular, kinetic effects such as temperature anisotropy and plasma heating are concentrated near coherent structures, such as current sheets, which are non-uniformly distributed in space. Furthermore, these coherent structures are preferentially found in plasma unstable to the mirror and firehose instabilities. The inhomogeneous heating in these regions, which is present in both the magnetic field parallel and perpendicular temperature components, results in protons at least 3-4 times hotter than under typical stable plasma conditions. These results offer a new understanding of kinetic processes in a turbulent regime, where linear Vlasov theory is not sufficient to explain the inhomogeneous plasma dynamics operating near non-Gaussian structures.Comment: 4 pages, 3 figures, submitted to Physical Review Letter