Bounds on the complex permittivity of polycrystalline materials by analytic continuation.

An analytic continuation method for obtaining rigorous bounds on the effective complex permittivity ε * of polycrystalline composite materials is developed. It is assumed that the composite consists of many identical anisotropic crystals, each with a unique orientation. The key step in obtaining the bounds involves deriving an integral representation for ε *, which separates parameter information from geometrical information. Forward bounds are then found using knowledge of the single crystal permittivity tensor and mean crystal orientation. Inverse bounds are also developed, which recover information about the mean crystal orientation from ε *. We apply the polycrystalline bounds to sea ice, a critical component of the climate system. Different ice types, which result from different growth conditions, have different crystal orientation and size statistics. These characteristics significantly influence the fluid transport properties of sea ice, which control many geophysical and biogeochemical processes important to the climate and polar ecosystems. Using a two-scale homogenization scheme, where the single crystal tensor is numerically computed, forward bounds for sea ice are obtained and are in excellent agreement with columnar sea ice data. Furthermore, the inverse bounds are also applied to sea ice, helping to lay the groundwork for determining ice type using remote sensing techniques.

Characterization of Jamaican agro-industrial wastes. Part II, fatty acid profiling using HPLC: precolumn derivatization with phenacyl bromide.

This paper describes the determination of fatty acid composition of coffee, citrus and rum distillery wastes using reversed-phase high-performance liquid chromatography (RP-HPLC). Lipid extracts of the waste samples are derivatized with phenacyl bromide and their phenacyl esters are separated on a C8 reversed-phase column by using continuous gradient elution with water and acetonitrile. The presence of saturated and unsaturated fatty acids in quantifiable amounts in the examined wastes, as well as the high percentage recoveries, are clear indications that these wastes have potential value as inexpensive sources of lipids. The HPLC procedures described here could be adopted for further analysis of materials of this nature.

Dose titration of the clinical efficacy of intravenously administered flunixin meglumine in a reversible model of equine foot lameness.

REASONS FOR PERFORMING STUDY: There are no refereed controlled documentations of the skeletal analgesic efficacy of different dosages of flunixin meglumine (FM). OBJECTIVES: The objective of this experiment was to compare the efficacy of various dosages of FM with a negative control. The hypothesis was that higher doses would result in improved efficacy in a dose-dependent manner when tested in a reversible model of foot lameness. METHODS: Ten horses shod with adjustable heart bar shoes had weekly modified AAEP grade 4.0/5.0 lameness induced by tightening a set screw against the heart bar. Heart rate (HR) and lameness score (LS) were monitored by one double-blinded investigator at rest; every 20 min after lameness induction for 5 h and hourly for another 8 h. One hour after lameness induction, treatments were administered i.v. in a randomised order: negative control (isotonic saline: SAL) or FM at 0.55 (half-dose), 1.1 (single-dose) or 2.2 (double-dose) mg/kg bwt. Results were compared using RM ANOVA and Student-Newman-Keul's test with the level of significance set at P < 0.05. RESULTS: Compared to SAL, half-dose FM reduced HR at 2.33, 2.67, 4.0-8.0, and 10.0 h and LS at 1.33-12.0 h (P < 0.05). Single- and double-dose FM reduced HR from 0.67 to 12.0 h and LS from 1.0 to 12.0 h post administration (P < 0.05). Compared with half-dose FM, single- and double-dose LS were further decreased from 1.67 to 12.0 h post administration (P < 0.05). Mean peak and decaying plasma FM concentrations were different between dosages in a dose-dependent manner through 6 h post administration (P < 0.05). CONCLUSIONS: Flunixin meglumine administration affected dependent variables in a dose-dependent manner with half-dose FM clinically effective for a shorter period. Higher dosages did not perform differently from one another. POTENTIAL RELEVANCE: Practitioners must be aware that half-doses of FM are less efficacious than single doses but double doses are not more efficacious and yet are potentially more toxic.

Characterization of Jamaican agro-industrial wastes. Part I: characterization of amino acids using HPLC: pre-column derivatization with phenylisothiocyanate.

Jamaican agro-industries generate large quantities of wastes, which are either discarded or under-utilized. In order to evaluate the possible utilization of these wastes, it is necessary that the profiles of the major biochemical groups be developed. This paper describes the determination of the amino acid composition of coffee, citrus, and rum distillery wastes using a reversed-phase high-performance liquid chromatography method. Acid hydrolysates of the wastes are derivatized with phenylisothiocyanate. They are analyzed as their phenylthiocarbamyl derivatives and determined quantitatively using norleucine as the internal standard. The presence of all the 17 amino acids investigated, nine of which include those essential for animal nutrition, are observed in the samples investigated, suggesting a high quality of protein with implications in the formulation of animal feeds.

Collective dynamics of complex plasma bilayers.

A classical dusty plasma experiment was performed using two different dust grain sizes to form a strongly coupled asymmetric bilayer (two closely spaced interacting monolayers) of two species of charged dust particles. The observation and analysis of the thermally excited particle oscillations revealed the collective mode structure and dispersion (wave propagation) in this system; in particular, the existence of the theoretically predicted k=0 energy (frequency) gap was verified. Equilibrium molecular-dynamics simulations were performed to emulate the experiment, assuming Yukawa-type interparticle interaction. The simulations and analytic calculations based both on lattice summation and on the quasilocalized charge approximation approach are in good agreement with the experimental findings and help in identifying and characterizing the observed phenomena.

Collective excitations in electron-hole bilayers.

We report a combined analytic and molecular dynamics analysis of the collective mode spectrum of a bipolar (electron-hole) bilayer in the strong coupling classical limit. A robust, isotropic energy gap is identified in the out-of-phase spectra, generated by the combined effect of correlations and of the excitation of the bound dipoles. In the in-phase spectra we identify longitudinal and transverse acoustic modes wholly maintained by correlations. Strong nonlinear generation of higher harmonics of the fundamental dipole oscillation frequency and the transfer of harmonics between different modes is observed.

Testosterone regulates mRNA levels of calcium regulatory proteins in cardiac myocytes.

Gender-related differences in cardiac function have been described in the literature, but whether the presence of sex hormones is responsible for these differences remains unclear. This study was designed to determine whether testosterone regulates the gene expression of calcium regulatory proteins in rat heart, thus playing a role in gender-related differences in cardiac performance. Ventricular myocytes were isolated from two-day-old rats and treated with testosterone at varying duration; the levels of gene expression for the androgen receptor (AR) and major calcium regulatory proteins were determined by quantitative real-time PCR. Testosterone (1 microM) treatment induced a maximum increase in beta1-adrenergic receptor and L-type calcium channel mRNA levels following an eight hour exposure. Six hours testosterone treatment stimulated a 300-fold increase in androgen receptor message abundance, and Na/Ca exchanger mRNA levels reached a maximum level following twenty-four hour testosterone treatment. Taken together, these data provide the first evidence that testosterone regulates gene expression of the major calcium regulatory proteins in isolated ventricular myocytes, and may thus play a role in the gender-related differences observed in cardiac performance.

Dynamical structure functions, collective modes, and energy gap in charged-particle bilayers.

The dynamical properties of strongly coupled charged-particle bilayers are investigated by molecular dynamics (MD) simulation and theoretical analysis. The spectra of the current correlation functions show the existence of two (in-phase and out-of-phase) longitudinal and two (in-phase and out-of-phase) transverse collective modes. The out-of-phase modes possess finite frequencies at wave numbers k-->0, confirming the existence of the predicted long-wavelength energy gap in the bilayer system. A theoretical model based on an extended Feynman ansatz for the dynamical structure functions provides predictions on the strength of the collective modes that are verified by the MD experiment.

High-performance liquid chromatographic analysis of amino acids in ackee fruit with emphasis on the toxic amino acid hypoglycin A.

High-performance liquid chromatography is used to determine the amino acid content of ripe and unripe ackee fruit. Specific emphasis is placed on the level of the toxic amino acid hypoglycin A (hyp-A) in the unripe and ripe ackee fruit and seed. Unripe samples are found to contain significantly higher quantities (P < 0.05) of hyp-A when compared with ripe samples. Uncooked unripe fruit is found to contain 124.4 +/- 6.7 mg/100 g fresh weight and uncooked ripe fruit 6.4 +/- 1.1 mg/100 g fresh weight. The seed of the uncooked unripe fruit is found to contain 142.8 +/- 8.8 mg/100 g fresh weight, and the seed of uncooked ripe fruit has 106.0 +/- 5.4 mg/100 g fresh weight. Boiling fruit in water for approximately 30 min is efficient in removing hyp-A from the edible arilli; however, low levels of 0.54 +/- 0.15 mg/200 mL are detected in the water that was used to cook the ripe fruit. The average %recovery of the amino acids was 80.34%.

Caging of particles in one-component plasmas.

Strongly coupled Coulomb systems are characterized by localization ("caging") of particles trapped and oscillating in slowly fluctuating local potential wells. This observation constitutes the basic assumption underlying the quasilocalized charge approximation. Using molecular dynamics simulation we study the changes in the particles' surroundings (cages) in a classical three-dimensional one-component plasma. The results of our analysis show that at high coupling values, substantial changes occur only after several plasma oscillation cycles. We also analyze the oscillation frequencies of the caged particles and relate the decorrelation of the cages to the process of self-diffusion.

Dynamical theory of strongly coupled two-dimensional Coulomb fluids in the weakly degenerate quantum domain.

We study the problem of dynamical response and plasma mode dispersion in strongly coupled two-dimensional Coulomb fluids (2DCFs) in the weakly degenerate quantum domain. Adapting the nonlinear response function approach of Golden and Kalman [Phys. Rev. A 19, 2112 (1979)] to the 2DCF, we construct a self-consistent approximation scheme for the calculation of the density response functions and plasma mode dispersion at long wavelengths. The basic ingredients in the construction are (i). the first kinetic equation in the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy, (ii). the velocity-average-approximation (VAA) hypothesis, (iii.) the quadratic fluctuation-dissipation theorem, and (iv). the dynamical superposition approximation (DSA) closure hypothesis. The reliability of the VAA-DSA theory can be assessed by observing that the principal coupling correction to the 2D temperature-dependent Lindhard function is identified as being precisely the part of the third-frequency-moment sum-rule coefficient proportional to the potential energy.

Traumatic brain injury-induced changes in gene expression and functional activity of mitochondrial cytochrome C oxidase.

Traumatic brain injury (TBI) is documented to have detrimental effects on CNS metabolism, including alterations in glucose utilization and the depression of mitochondrial oxidative phosphorylation. Studies on mitochondrial metabolism have also provided evidence for reduced activity of the cytochrome oxidase complex of the electron transport chain (complex IV) after TBI and an immediate (lhr) reduction in mitochondrial state 3 respiratory rate, which can persist for up to 14 days postinjury. Using differential display methods to screen for differences in gene expression, we have found that cytochrome c oxidase II (COII), a mitochondrial encoded subunit of complex IV, is upregulated following TBI. Since COII carries a binding site for cytochrome c in the respiratory chain, and since it is required for the passage of chain electrons to molecular oxygen, driving the production of ATP, we hypothesized that metabolic dysfunction resulting from TBI alters COII gene expression directly, perhaps influencing the synaptic plasticity that occurs during postinjury recovery processes. To test this hypothesis, we documented COII mRNA expression and complex IV (cytochrome c oxidase) functional activity at 7 days postinjury, focusing on the long-term postinjury period most closely associated with synaptic reorganization. Both central fluid percussion TBI and combined TBI and bilateral entorhinal cortical lesion were examined. At 7 days survival, differential display, RT-PCR, and Northern blot analysis of hippocampal RNA from both TBI and combined insult models showed a significant induction of COII mRNA. This long-term elevation in COII gene expression was supported by increases in COII immunobinding. By contrast, cytochrome oxidase histochemical activity within tissue sections from injured brains suggested a reduction of complex IV activity within the TBI cases, but not within animals subjected to the combined insult. These differences in cytochrome c oxidase activity were supported by in vitro assay of complex IV using cerebral cortical and hippocampal tissues. Our present results support the hypothesis that COII is selectively vulnerable to TBI and that COII differences may indicate the degree of metabolic dysfunction induced by different pathologies. Taken together, such data will better define the role of metabolic function in long-term recovery after TBI.

Compressibility sum rule for the two-dimensional electron gas.

The authors establish formulas for the isothermal compressibility and long-wavelength static density-density response function of a weakly correlated two-dimensional electron gas in the 1<

Amino acid, fatty acid, and carbohydrate content of Artocarpus altilis (breadfruit).

A study is conducted to determine the amino acid, fatty acid, and carbohydrate content of breadfruit using high-performance liquid chromatography (HPLC) and gas chromatography (GC). An HPLC method is used for the determination of amino acids and fatty acids in breadfruit. Representative amino acid samples are derivatized with phenylisothiocianate and the resulting phenylthiocarbamyl derivatives are separated on a reversed-phase column by gradient elution with a 0.05M ammonium acetate buffer and 0.01M ammonium acetate in acetonitrile-methanol-water (44:10:46, v/v). Representative fatty acid samples are derivatized with phenacyl bromide and the resulting fatty acid phenacyl esters are separated on a reversed-phase column by gradient elution with acetonitrile and water. Amino acid and fatty acid derivatives are detected by ultraviolet detection at 254 nm. The analysis of the carbohydrates in breadfruit employs a GC method. Carbohydrates are derivatized using trimethylchlorosilane and hexamethyldisilazane to form trimethylsilyl ethers. Compounds in the samples are separated by the temperature programming of a GC using nitrogen as the carrier gas. Percent recoveries of amino acids, fatty acids, and carbohydrates are 72.5%, 68.2%, and 81.4%, respectively. The starch content of the breadfruit is 15.52 g/100 g fresh weight.

In vivo regulation of Na/Ca exchanger expression by adrenergic effectors.

The Na/Ca exchanger encoded by the NCX1 gene plays an important role in calcium homeostasis in cardiac muscle. We previously identified three in vitro signaling pathways that are of major importance in the regulation of Na/Ca exchanger gene expression in neonatal cardiac myocytes, the protein kinase A (PKA) and protein kinase C (PKC) pathways, and intracellular Ca(2+). To determine whether these pathways are important in vivo, we stimulated the PKA and PKC pathways and examined functional expression of the Na/Ca exchanger in adult rat heart. After a 3- and 7-day treatment, norepinephrine (200 microg x kg(-1) x h(-1)), isoproterenol (150 microg x kg(-1) x h(-1)), and phenylephrine (200 microg x kg(-1) x h(-1)) each stimulated a significant increase in NCX1 mRNA levels (35-85%, P < 0.05). Norepinephrine also stimulated a 35% increase in protein abundance (P < 0.05), a 20% decrease in relaxation duration (P < 0.05), and a 25% reduction in the fluorescence decay constant (P < 0.05) after a 7-day treatment. We conclude that a 7-day treatment of alpha- and beta-adrenergic agonists increases the expression of functional Na/Ca exchangers in adult rat heart.

Combinations of clozapine and phencyclidine: effects on drug discrimination and behavioral inhibition in rats.

Phencyclidine (PCP) produces psychotomimetic effects in humans that resemble schizophrenia symptoms. In an effort to screen compounds for antipsychotic activity, preclinical researchers have investigated whether these compounds block PCP-induced behaviors in animals. In the present study, the atypical antipsychotic clozapine was tested in combination with an active dose of PCP in two-lever drug discrimination and mixed signalled-unsignalled differential-reinforcement-of-low-rates (DRL) procedures. PCP produced distinctive effects in each task: it substituted for the training dose in PCP discrimination and it increased the number of responses with short (<3 s) interresponse times as well as increasing overall response rates in the DRL schedule. Acute dosing with clozapine failed to alter the behavioral effects of PCP in either procedure even when tested up to doses that produced pharmacological effects alone. These results suggest that acute dosing with clozapine would not affect behaviors most closely associated with PCP intoxication. Further, they bring into question the utility of using PCP combination procedures in animals to screen for antipsychotic potential. Since chronic dosing is required for therapeutic efficacy of antipsychotics, future studies should focus on investigation of chronic dosing effects of these drugs in combination with PCP.

Separation of drug effects on timing and behavioral inhibition by increased stimulus control.

Impulsive behavior may represent, in part, a failure of behavioral inhibition (the ability to delay or inhibit a response). In this study, use of a multiple signaled-unsignaled differential-reinforcement-of-low-rates (DRL) 15-s schedule allowed examination of drug effects in conditions in which level of stimulus control differed. Results showed that whereas diazepam increased premature responding during signaled and unsignaled DRL components, amphetamine and delta9-tetrahydrocannabinol increased premature responding primarily during unsignaled components when timing was necessary for efficient performance on the task. In contrast, pimozide and desipramine increased long-delay responses across both components, resulting in longer mean interresponse times. Collectively, these results suggest that the use of different levels of stimulus control may aid in separation of drug effects on timing and other behavioral processes, including behavioral inhibition.

Adrenergic stimulation regulates Na(+)/Ca(2+)Exchanger expression in rat cardiac myocytes.

The Na/Ca exchanger protein encoded by the NCX1 gene provides the predominant mechanism for calcium efflux during cardiac relaxation. Because beta -adrenergic stimulation increases expression of Ca(2+)channels (Ca(2+)influx) in cardiac myocytes, we tested the hypothesis that isoproterenol would concomitantly augment expression of NCX1. Four hour treatment of neonatal myocytes with isoproterenol significantly increased NCX1 gene and protein expression, and increased the rate of transcript initiation. Alpha-adrenergic stimulation significantly decreases NCX1 mRNA levels. Calcium transient measurements revealed that for cells that had been pretreated with isoproterenol there was a faster relaxation rate of the Ca(2+)transient in the presence of thapsigargin, indicating an enhanced rate of intracellular Ca(2+)removal. We conclude that effectors that increase calcium channel expression in neonatal myocytes also augments NCX1 gene and protein expression over a similar time course, and that this is due to enhanced NCX1 transcription. The regulation of expression of NCX1 by adrenergic pathways may play an important role in regulation of excitation-contraction coupling in cardiac myocytes.

Cardiac enhancer activity of the homeobox gene tinman depends on CREB consensus binding sites in Drosophila.

The Drosophila homeobox gene tinman plays a critical role in subdividing the early mesoderm. In particular, tinman is absolutely required for formation of the heart and visceral mesoderm. tinman expression is initiated throughout the mesoderm of the trunk region under the control of the bHLH transcription factor encoded by the twist gene, a determinant of all mesoderm. Later, tinman expression is restricted to the dorsal portion of the mesoderm, a process that is directed by decapentaplegic (dpp) whose product (a TGF-beta-related protein) is secreted by the overlaying ectoderm. Further restriction of tinman expression to the cardiac progenitors, in which it will persist throughout development, involves the secreted segmentation gene product encoded by wingless (wg, a Drosophila Wnt gene). Here, we show that strong early expression depends on the synergistic action of an enhancer element at the 5' end of the gene in conjunction with an element in the first intron. Moreover, two distinct enhancer regions are responsible for tinman expression in the heart: one region confers expression in the heart-tube-associated pericardial cells, the other element drives expression in the contractile, myocardial cells. The latter element contains two CREB consensus binding sites that are essential for cardiac-specific expression. genesis 26:55-66, 2000.

Sternocleidomastoid imbalance versus congenital muscular torticollis: their relationship to positional plagiocephaly.

OBJECTIVE: The purpose of this study was to investigate the existence of sternocleidomastoid (SCM) imbalance in a plagiocephalic population and further clinically describe its difference, if any, from congenital muscular torticollis (CMT). If SCM imbalance is different from CMT, then the development of terminology and a differential diagnosis may allow early recognition and intervention and possible prevention of positional plagiocephaly in the first place. DESIGN: This was a retrospective, random review of 100 patients referred for orthotic correction of their positional plagiocephaly. SETTING: The data was collected in a private orthotic clinic and was directed by a physical therapist. The patients were seen on a weekly or biweekly basis. PATIENTS: Eighty-three patients diagnosed with positional plagiocephaly that were referred for Dynamic Orthotic Cranioplasty during 1996 were studied. RESULTS: Sixty-four percent of the sample was identified as having SCM imbalance and 12% was diagnosed with CMT. There were no statistically significant differences between the characteristics of these two groups in relation to the etiological factors of positional plagiocephaly. The only observed difference was related to symptoms of the neck itself. CONCLUSIONS: Seventy-six percent of the sample was found to have some degree of SCM dysfunction, whether it be SCM imbalance or CMT. The finding that over three quarters of our population suffers from some form of SCM dysfunction, either SCM imbalance or CMT, suggests that any degree of SCM dysfunction may act as a precursor to positional plagiocephaly and therefore should be recognized and treated at the earliest opportunity.