Amino acid profiles and liposomes: Their role as chemosensory information carriers in the marine environment

Yellowfin tuna enhance their hunting success in the vast pelagic environment by using their sense of smell to detect intact (uninjured) prey that are beyond visual range. However, the olfactory cues that tuna use would normally face huge and rapid dilution in the open ocean. We demonstrate that these prey odors are complexed within biologically derived lipid structures that probably delay the dilution of the amino acids to subthreshold concentrations and provide persistent arousal and search cues for the tuna. This may be the first demonstration of an extracorporeal biological function for liposomes. Tuna may also form chemical search images to maximize feeding efficiency. We demonstrate that the amino acid profiles of various prey species are consistent over time and between schools, which makes the formation of search images feasible.     

A modification of broyden's method for the solution of sparse systems—with application to distillation problems described by nonideal thermodynamic functions

An algorithm that permits Broyden's method to be used for the solution of large systems of algebraic equations with sparse Jacobians is presented. The new procedure is compared to Schubert's modification of Broyden's method and to the Newton-Raphson method by solving an extractive distillation problem. It is demonstrated that the new procedure is competitive with Schubert's method when it is necessary to evaluate Jacobian matrices numerically.     

Determination of Both Mesopores and Macropores in Three-Dimensional Ordered Porous Materials by Nitrogen Adsorption

Three-dimensionally ordered silica structures containing both mesopores and macropores are created using polystyrene coacervate spheres with a diameter of ca. 146 nm. The close-packed polystyrene coacervate spheres are intercalated with tetraethyl orthosilicate. The spheres are removed by calcination leaving an inverse silica replica with a spherical macropore cavity diameter of 110 nm. Due to the nature of these porous structures, pores leading into the macropore cavity are in the mesopore regime, 40 nm in diameter. The nitrogen adsorption data described in the following paper gives a pore size for both the macropore cavity and the mesopore openings leading into the cavity. The pore sizes as determined by nitrogen sorption are in good agreement with the pore sizes observed by scanning electron microscopy. Mercury intrusion porosimetry results confirm the size of the mesopore openings leading into the macropore cavity, however due to destruction of the sample upon intrusion, extrusion results can not be obtained to determine main cavity diameters. As a result, nitrogen sorption may be a viable option for determining pore sizes with these three-dimensionally ordered materials containing both mesopores and macropores.     

Natural and unnatural silks

Natural silk is an important biopolymer with huge potential as it combines superb mechanical properties with environmentally sensitive production methods. Native silk dope taken straight from the gland can easily and without chemical assistance be drawn into strong fibres. Artificial silk fibres, on the other hand, rely on spinning dopes typically ‘reconstituted’ from natural silk fibres by strong chaotropic agents. Such fibres do not form readily, and often require chemical post-spin treatment for stabilisation. In addition these fibres tend to be brittle, and so far have been unable to match native fibres. Here we present novel rheometric data to argue that native and reconstituted silkworm silk dope differ in kind, not just in degree. While native silks behave like typical molten polymers, reconstituted silks do not. We conclude that rheology provides a powerful tool in the quest to learn from the Nature's polymer fibre technology.     

The dielectric properties of glass-ceramic-on-metal substrates for microelectronics packaging

The dielectric properties of some glass-ceramic-on-metal substrates have been determined over the frequency range 500 Hz to 5 MHz using a.c. bridge techniques. The substrates consisted of cordierite-based glass-ceramics screen printed on molybdenum. For glass layers of thickness greater than 100 m both the permittivity, and the dielectric loss, , are frequency independent over this frequency range at room temperature giving the value of =6.5 and tan =8×10^–3; the room-temperature data are consistent with the universal law of dielectric response. The variation of permittivity with temperature has also been examined and, below 120 °C, the temperature coefficient [(–1) (+2)]^–1 (/T)_p, was found to be 1.3×10^–5 K^–1. The results are compared with those previously reported for Al₂O₃ and AIN substrates.     

Effect of energetic electron and proton bombardment on the reflectance of silicon-carbide mirrors in the extreme-ultraviolet region

Chemical-vapor-deposited silicon-carbide mirrors were exposed to bombardment by 95-keV electrons and 100-keV protons with accumulated fluxes comparable with those expected in low-altitude Earth orbit for simulated periods of as many as 5 years. The reflectances of four mirrors were measured at five wavelengths (58.4, 73.6, 104.8, 121.6, and 161 nm) and at 11 angles of incidence from 5° to 80°. The electron and proton exposure resulted in no significant change in the reflectances of the mirrors.     

Dimerization/docking domain of the type Ialpha regulatory subunit of cAMP-dependent protein kinase. Requirements for dimerization and docking are distinct but overlapping

Based on increasing evidence that the type I R subunits as well as the type II R subunits localize to specific subcellular sites, we have carried out an extensive characterization of the stable dimerization domain at the N terminus of RIalpha. Deletion mutants as well as alanine scanning mutagenesis were used to delineate critical regions as well as particular amino acids that are required for homodimerization. A set of nested deletion mutants defined a minimum core required for dimerization. Two single site mutations on the C37H template, RIalpha(F47A) and RIalpha(F52A), were sufficient to abolish dimerization. In addition to serving as a dimerization motif, this domain also serves as a docking surface for binding to dual specificity anchoring proteins (D-AKAPs) (Huang, L. J., Durick, K., Weiner, J. A., Chun, J., and Taylor, S. S. (1997) J. Biol. Chem. 272, 8057-8064; Huang, L. J., Durick, K., Weiner, J. A., Chun, J., and Taylor, S. S. (1997) Proc. Natl. Acad. Sci. U. S. A. 94, 11184-11189). A similar strategy was used to map the sequence requirements for anchoring of RIalpha to D-AKAP1. Although dimerization appears to be essential for anchoring to D-AKAP1, anchoring can also be abolished by the following single site mutations: C37H, V20A, and I25A. These sites define "hot spots" for the anchoring surface since each of these dimeric proteins are deficient in binding to D-AKAP1. In contrast to earlier predictions, the alignment of the dimerization/docking domains of RIalpha and RII show striking similarities yet subtle differences not only in their secondary structure (Newlon, M. G., Roy, M., Hausken, Z. E., Scott, J. D., and Jennings. P. A. (1997) J. Biol. Chem. 272, 23637-23644) but also in the distribution of residues important for both docking and dimerization functions.     

Tennessee's failed managed care program for mental health and substance abuse services

In July 1996, Tennessee initiated a managed mental health and substance abuse program called TennCare Partners. This publicly funded "carve-out" experiment started chaotically and soon deteriorated into a crisis. Many patients did not receive care or lost continuity of care, and the traditional "safety net" mental health system nearly disintegrated. This qualitative case study sought to ascertain the impact of the TennCare Partners program. It points out that the program's difficulties stemmed directly from a flawed design that spread funds previously earmarked for severely mentally ill patients across the entire Medicaid population. States contemplating similar reforms should strive to protect vulnerable patients by risk-adjusting capitation payments and by focusing resources on care for severely mentally ill persons. States should also minimize program complexity and ensure the accountability of managed care networks for their patients' behavioral health care needs.     

Temporal processing of the pitch of complex tones

The effect of tone duration on fundamental frequency (F0) discrimination is greater for complexes containing unresolved harmonics than for those containing resolved harmonics [Plack and Carlyon, J. Acoust. Soc. Am. 98, 1355-1364 (1995)]. Three experiments explored this effect further. The first experiment measured sensitivity (as d') to fundamental frequency (F0) differences for two complexes, both with an F0 of 250 Hz. The first complex was low-pass filtered at 1875 Hz to create a resolved complex and the second was bandpass filtered between 5500 and 7500 Hz to create an unresolved complex. The harmonics for the resolved complex were selected so that no two harmonics were the same between the two observation intervals. Performance for both complexes was measured for tone durations of 20, 40, 80, and 160 ms. For the unresolved complex, the effect of duration was greater than that for the resolved complex and greater than the predictions of a "multiple-looks" model assuming either peripheral (before sampling) or central (after combining samples) sources of variance. The second experiment replicated these results using an F0 of 62.5 Hz with the cutoff frequencies of the bandpass filters divided by four, confirming that the effect is related to resolvability and not to spectral region. In the final experiment, F0 discrimination for pairs of complexes separated by a temporal gap was measured relative to that for one complex. Performance for the resolved and unresolved complexes was similar: Very little effect of gap duration was observed and the results were consistent with the predictions of the peripheral-variance multiple-looks model. Taken together, the results suggest that the pitch mechanism for resolved harmonics uses a relatively short sampling window of around 20 ms, while the mechanism for unresolved harmonics may use a more complex strategy for optimizing the combination of information over time, perhaps involving a flexible integration time.     

Evolution of the trappin multigene family in the Suidae

The purpose of the study was to examine the effects of manipulating lung volume (LV) on phonatory and articulatory kinematic behavior during sentence production in healthy adults. Five men and five women repeated the sentence "I sell a sapapple again" under five LV conditions. These included (1) speaking normally, (2) speaking after exhaling most of the air from the lungs, (3) speaking at end expiratory level (EEL), (4) speaking after a maximal inhalation, and (5) speaking after a maximal inhalation while attempting to maintain as normal a mode of speech as possible. From a multichannel recording, measures were made of LV, sound pressure level (SPL), fundamental frequency (F0) and semitone standard deviation (STSD), and upper and lower lip displacements and peak velocities. When compared with the reference condition, the sentence was spoken significantly more quickly at the lowest LV. SPL increased significantly for the high LV condition, as did the women's F0 and STSD. Upper lip displacements and peak velocities generally decreased for LVs other than the reference condition. Lower lip movements showed inconsistent changes as a function of LV. Adjustments to the LV for speech led to SPL and F0 changes consistent with a coordinated control of the respiratory system and the larynx. However, less consistent effects were observed in the articulatory kinematic measures, possibly because of a less direct biomechanical and neural control linkage between respiratory and articulatory structures.