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<jats:p>The optical and ultraviolet emission from the type II supernova SN 1987A is currently powered by the radioactive decay of titanium-44. In contrast, the emission from SN 1993J is dominated by radiation from the interaction of the supernova shock wave with a dense, stellar wind released before the explosion. The dense wind around SN 1987A was displaced by the fast wind from the compact progenitor star, and the interaction of the supernova with dense gas is now being detected at x-ray and radio wavelengths. The expected neutron stars or black holes at the centers of these supernovae are not yet significant power sources.</jats:p>

<jats:p>Spectroscopic and photometric evidence indicates that Type Ia supernovae (SNe Ia) are the thermonuclear explosions of accreting white dwarfs. However, the progenitor binary systems and hydrodynamical models for SNe Ia are still controversial. The relatively uniform light curves and spectral evolution of SNe Ia have led to their use as a standard candle for determining cosmological parameters, such as the Hubble constant, the density parameter, and the cosmological constant. Recent progress includes the calibration of the absolute maximum brightness of SNe Ia with the Hubble Space Telescope, the reduction of the dispersion in the Hubble diagram through the use of the relation between the light curve shape and the maximum brightness of SNe Ia, and the discovery of many SNe Ia with high red shifts.</jats:p>

<jats:p>Planetary nebulae are one of the few classes of celestial objects that are active in every part of the electromagnetic spectrum. These fluorescing and often dusty expanding gaseous envelopes were recently found to be quite complex in their dynamics and morphology, but refined theoretical models can account for these discoveries. Great progress was also made in understanding the mechanisms that shape the nebulae and the spectra of their central stars. In addition, applications for planetary nebulae have been worked out; for example, they have been used as standard candles for long-range distances and as tracers of the enigmatic dark matter.</jats:p>

<jats:p>Neutron stars and black holes can be studied by observation of the radiation produced as matter falls into their gravitational fields. X-ray binaries, which are systems consisting of a neutron star or black hole and a companion gaseous star, produce radiation in this manner. Recently, oscillations at frequencies near 1000 cycles per second have been detected from x-ray binaries. These oscillations are likely produced in regions of very strong gravitational fields within a few tens of kilometers of the compact star. The oscillations have been interpreted as evidence for the existence of an innermost stable orbit near a compact star, a key prediction of general relativity theory. The study of x-ray binaries has also advanced the search for definitive evidence of black holes. Recent developments in our understanding of accretion flows in x-ray binaries have provided evidence for the existence of event horizons in x-ray binaries thought to contain black holes.</jats:p>

<jats:p> Human fossil remains recovered from the TD6 level (Aurora stratum) of the lower Pleistocene cave site of Gran Dolina, Sierra de Atapuerca, Spain, exhibit a unique combination of cranial, mandibular, and dental traits and are suggested as a new species of <jats:italic>Homo—H. antecessor</jats:italic> sp. nov. The fully modern midfacial morphology of the fossils antedates other evidence of this feature by about 650,000 years. The midfacial and subnasal morphology of modern humans may be a retention of a juvenile pattern that was not yet present in <jats:italic>H. ergaster. Homo antecessor</jats:italic> may represent the last common ancestor for Neandertals and modern humans. </jats:p>

<jats:p>A high-capacity lithium-storage material in metal-oxide form has been synthesized that can replace the carbon-based lithium intercalation materials currently in extensive use as the negative electrode (anode) of lithium-ion rechargeable batteries. This tin-based amorphous composite oxide (TCO) contains Sn(II)-O as the active center for lithium insertion and other glass-forming elements, which make up an oxide network. The TCO anode yields a specific capacity for reversible lithium adsorption more than 50 percent higher than those of the carbon families that persists after charge-discharge cycling when coupled with a lithium cobalt oxide cathode. Lithium-7 nuclear magnetic resonance measurements evidenced the high ionic state of lithium retained in the charged state, in which TCO accepted 8 moles of lithium ions per unit mole.</jats:p>

<jats:p>A sonoluminescing bubble has been modeled as a thermally conducting, partially ionized, two-component plasma. The model shows that the measured picosecond pulse widths are due to electron conduction and the rapidly changing opacity of the plasma and that these mechanisms are also responsible for the absence of an “afterglow” subsequent to the sonoluminescence flash while the hot bubble expands and cools. The calculated spectra for sonoluminescing nitrogen and argon bubbles suggest that a sonoluminescing air bubble probably contains only argon, in agreement with a recent theoretical analysis.</jats:p>

<jats:p>Dense periodic arrays of holes and dots have been fabricated in a silicon nitride–coated silicon wafer. The holes are 20 nanometers across, 40 nanometers apart, and hexagonally ordered with a polygrain structure that has an average grain size of 10 by 10. Spin-coated diblock copolymer thin films with well-ordered spherical or cylindrical microdomains were used as the templates. The microdomain patterns were transferred directly to the underlying silicon nitride layer by two complementary techniques that resulted in opposite tones of the patterns. This process opens a route for nanometer-scale surface patterning by means of spontaneous self-assembly in synthetic materials on length scales that are difficult to obtain by standard semiconductor lithography techniques.</jats:p>

<jats:p> Members of the myocyte enhancer factor–2 (MEF2) family of MADS (MCM1, agamous, deficiens, serum response factor)–box transcription factors bind an A-T–rich DNA sequence associated with muscle-specific genes. The murine <jats:italic>MEF2C</jats:italic> gene is expressed in heart precursor cells before formation of the linear heart tube. In mice homozygous for a null mutation of <jats:italic>MEF2C</jats:italic> , the heart tube did not undergo looping morphogenesis, the future right ventricle did not form, and a subset of cardiac muscle genes was not expressed. The absence of the right ventricular region of the mutant heart correlated with down-regulation of the <jats:italic>dHAND</jats:italic> gene, which encodes a basic helix-loop-helix transcription factor required for cardiac morphogenesis. Thus, MEF2C is an essential regulator of cardiac myogenesis and right ventricular development. </jats:p>