Thermal poling of silica optical fibers using liquid electrodes.

Thermal poling is a well-known technique for inducing second-order nonlinearities in centrosymmetric silica optical fibers. However, some 25 years since its discovery, there still remain a number of issues that prevent the realization of very long length, highly efficient all-fiber nonlinear device applications that include frequency conversion or sources of polarization-entangled photon pairs. In this Letter, we report a thermal poling method that utilizes a novel range of liquid metal and aqueous electrodes embedded into the optical fibers. We demonstrate that it is possible to pole samples that are potentially meters in length, characterized by very low losses for efficient second-harmonic generation processes. The maximum estimated effective value of χ(2) (0.12 pm/V) obtained using mercury electrodes is the highest reported in periodically poled silica fibers.

Three-axis correction of distortion due to positional drift in scanning probe microscopy.

Two common sources of distortion in scanning probe microscopy are piezo creep and thermal drift, the latter caused by slow thermal expansions of materials in the sample and microscope due to small changes in temperature over the course of a scan. We present a technique for correcting distortion due to thermal drift along all three spatial axes, along with simultaneous correction of z-axis piezo creep. Our method works by comparing each scanned topographical image to a second, partial scan, taken immediately afterwards, on which the fast and slow scan axes have been reversed. We model the positional distortion as a low-order polynomial function in three dimensions, searching for the set of correctional coefficients that minimizes the root-mean-square difference between the two scans. We demonstrate in a variety of real-world and simulated tests that this technique can routinely reduce distortion from these effects by over 90%, often to a precision of better than a single pixel.

Deposition of high-quality HfO2 on graphene and the effect of remote oxide phonon scattering.

We demonstrate atomic layer deposition of high-quality dielectric HfO2 films on graphene and determine the magnitude of remote oxide surface phonon scattering in dual-oxide structures. The carrier mobility in these HfO2-covered graphene samples reaches 20,000 cm2/V s at low temperature. Distinct contributions to the resistivity from surface optical phonons in the SiO2 substrate and the HfO2 overlayer are isolated. At 300 K, surface phonon modes of the HfO2 film centered at 54 meV limit the mobility to approximately 20,000 cm2/V s.

Validity and reliability of the BOD POD® S/T tracking system.

BOD POD(®) self-testing (S/T) body composition tracking system is a practical assessment tool designed for use in the health and fitness industries. Relative to its parent counterpart, the BOD POD(®) S/T has received little research attention. The primary purpose was to determine the validity of the BOD POD(®) S/T against hydrostatic weighing and 7-site skinfolds. Secondary aim was to determine the within-day and between-day reliability of the BOD POD(®) S/T. After a period of equipment and testing accommodation, volunteer's (N=50) body composition (%BF) via 7-site skinfolds, BOD POD(®) S/T, and hydrostatic weighing were obtained on the second and third visits. BOD POD(®) S/T significantly overestimated %BF when compared to hydrostatic weighing and 7-site skinfolds. There was no statistical difference between 7-site skinfolds and hydrostatic weighing values. BOD POD(®) S/T reliability within-day and between-days were high. While the BOD POD(®) S/T body composition tracking system is deemed reliable both within-day and between-days, it did significantly overestimate %BF in comparison to hydrostatic weighing and skinfolds. Future research should be aimed at deriving a correction factor for this body composition assessment tool.

Interrelationships among thigh muscle co-contraction, quadriceps muscle strength and the aerobic demand of walking in children with cerebral palsy.

The purpose of this study was to quantify interrelationships among thigh muscle co-contraction, quadriceps muscle strength, and the aerobic demand of walking in 13 children with spastic hemiplegic cerebral palsy (CP). During Session 1, subjects were familiarized with testing procedures, given five minutes of treadmill walking practice, and completed quadriceps muscle strength testing. In Session 2, subjects performed three 5-min walking bouts on the treadmill at 0.67 m x s(-1) to further accommodate to treadmill ambulation. During Session 3, resting VO2 was measured and subjects walked at 0.67, 0.89, and 1.12 m x s(-1) for five minutes while oxygen uptake (VO2) and thigh muscle co-contraction data were collected. Results demonstrated that no significant relationship existed between net VO2 and measures of thigh muscle co-contraction or quadriceps muscle strength. In addition, thigh muscle co-contraction was not shown to be associated with quadriceps muscle strength. Collectively, thigh muscle co-contraction and quadriceps muscle strength explained 13. 5%, 6.2%, and 2.2% of the variance in VO2 at 0.67, 0.89, and 1.12 m x s(-1), respectively. Viewed in concert, these results suggest that the walking energy expenditure of children with spastic hemiplegic CP is not influenced by the level of thigh muscle co-contraction or quadriceps muscle strength.

An in situ gamma-ray spectrometry intercomparison.

This paper provides the results of an in situ gamma-ray spectrometry intercomparison that was held from 18-21 October 1999, in Grand Junction, CO. This intercomparison was a collaborative effort between the U.S. Department of Energy's Environmental Measurements Laboratory and the U.S. Environmental Protection Agency's Office of Radiation and Indoor Air. It featured measurements of a background location and the Walker Field Calibration Pads. In this paper, the in situ gamma-ray measurements of the background location were compared to soil samples, and the in situ measurements of the Walker Field Calibration Pads were compared to corrected reference values. The results showed that 84% of the in situ gamma-ray measurements of 226Ra, 232Th, and 40K at the background location fell within 20% of the soil sample mean. Similarly, in situ gamma-ray measurements of the Walker Field Calibration Pads showed that 77% of the in situ concentrations fell within 20% of the corrected reference values.

Metabolic accommodation of young children to treadmill walking.

Few data exist concerning the reproducibility of stable oxygen uptake (VO(2)) values during level treadmill walking in young able-bodied children. To address this issue, 41 able-bodied 6-year-olds (19 boys, 22 girls, X height=117.2+/-4.7 cm, X body mass=21.8+/-2.5 kg) were tested on two occasions. In session 1, subjects were familiarized with the laboratory environment and performed 5 min of level treadmill walking at 1.34 m s(-1). During session 2, each child completed 30 min (three 10-min trials) of level treadmill walking at 1.34 m s(-1). For each 10-min trial, mean VO(2) was determined by averaging VO(2) values obtained from analysis of two 2-min expired gas samples. While the mean VO(2) for trial 1 was higher than values recorded for trials 2 and 3, effect sizes corresponding to these differences were low (

Stability of running economy in young children.

Few studies have been conducted documenting the length of time required for young children to achieve stable measures of running economy. Hence the purpose of this study was to quantify within- and between-day stability in running economy among young children. To address this issue, 30 6-year olds (16 girls, 14 boys) completed three test sessions within a 2 wk period. During Sessions 1 and 2 subjects performed three 5 min level treadmill runs at 2.23 m x sec(-1). During Session 2 expired air was collected during the last 2 min of each 5 min run (R1, R2, R3) and analyzed to determine VO2. In Session 3 subjects completed a single 5 min run (R4) at 2.23 m x sec(-1) and VO2 was measured during the last 2 min of running. Data analysis revealed no significant difference (p>0.05) in absolute or relative VO2 across trials. The average coefficient of variation for both absolute and relative VO2 among runs completed in Session 2 was 2.17 %, and the mean coefficient of variation for VO2 between R4 and the average VO2 of R1, R2, and R3 was 2.51 % and 2.35% for absolute and relative VO2, respectively. Moreover intraclass correlation coefficients for absolute and relative VO2 across all runs were 0.99 and 0.96, respectively. Viewed in concert, these results suggest that following 15 minutes of level treadmill running practice, stable within- and between-day measures of running economy can be obtained in young, prepubescent children.

Autoradiographic localization of dihydrotestosterone and testosterone concentrating neurons in the brain of the oyster toadfish.

Vertebrate species with male mating calls or songs tend to have sexually dimorphic sonic neurons that concentrate gonadal steroids. The distribution of [3H]dihydrotestosterone- and testosterone-concentrating neurons was examined in oyster toadfish (Opsanus tau), males of which produce a courtship boatwhistle call. Labeled cells in the forebrain were found in the posterior nucleus of the dorsal telencephalon (Dp), a pallial structure, the supracommissural nucleus of the ventral telencephalon (Vs), nucleus propticus parvocellularis anterior (PPa) and other preoptic nuclei, the ventral, dorsal and caudal hypothalamus. Positive brainstem areas included the optic tectum, torus semicircularis, nucleus lateralis valvula, a periventricular nucleus of the rostral medulla and the inferior reticular formation. Compared to estrogen, androgens labeled fewer sites in the forebrain and more in the brainstem. Two of the positive sites, Vs and PPa, have been implicated in boatwhistle production. Many sites that connect to these areas in teleosts likewise concentrate steroids. Unlike the situation in frogs, birds, and one other teleost, the toadfish sonic motor nucleus did not concentrate androgens. Androgen labeling in the posterior nucleus of the dorsal telencephalon represents the first autoradiographic demonstration of steroid concentration in the pallium of a teleost forebrain.

Effect of graded epinephrine infusion on blood lactate response to exercise.

In an attempt to determine whether the lactate threshold (LT) is the result of a sudden increase in plasma epinephrine (Epi), eight healthy college-aged males (22.4 +/- 0.4 yr) were recruited to perform three cycle ergometer exercise tests. Each subject performed a graded exercise test (GXT) to determine LT, Epi threshold, and norepinephrine threshold (64.6 +/- 2.4, 62.5 +/- 2.4, and 60.8 +/- 4.3% peak oxygen uptake, respectively). Each subject also completed, in random order, two 30-min submaximal (20% peak oxygen uptake below LT) exercise tests. During one test, graded Epi infusions were carried out at rates of 0.02-0.12 micrograms.kg-1.min-1; the other served as a control test. Infusion resulted in plasma Epi concentrations similar to those observed during GXT. The increase in blood lactate with Epi infusion was significantly greater than that during the control test (3.0 +/- 0.3 vs. 1.4 +/- 0.1 mmol/l at minute 30) but did not approach levels exhibited during GXT. We suggest an interaction of the increasing plasma Epi with other factors may be responsible for the sudden increase in blood lactate during graded exercise.

Autoradiographic localization of estrogen-concentrating cells in the brain and pituitary of the oyster toadfish.

We examined the distribution of [3H] estradiol-concentrating neurons in gonadectomized male and female oyster toadfish (Opsanus tau) by thaw-mount autoradiography. Compared to other teleosts studied in this fashion, the toadfish is of interest because of its reliance on male sound production during courtship. Labeled cells were found in the pars distalis of the pituitary and in periventricular midline regions of the forebrain. These included the ventral, supracommissural and posterior nuclei of the ventral telencephalon, nucleus preopticus parvocellularis anterior, the ventral, lateral, dorsal and caudal hypothalamus, and the periventricular nucleus of the posterior tuberculum of the thalamus. For the first time in a teleost, estrogen-concentrating cells were recorded in the brainstem, in sites including the optic tectum and torus semicircularis. In contrast to a previous study with testosterone, two prominent nuclei in the medulla were negative. With some additions, the distribution of estrogen-concentrating neurons conformed to the general pattern in other teleosts.

Real-time landslide warning during heavy rainfall.

A real-time system for issuing warnings of landslides during major storms is being developed for the San Francisco Bay region, California. The system is based on empirical and theoretical relations between rainfall and landslide initiation, geologic determination of areas susceptible to landslides, real-time monitoring of a regional network of telemetering rain gages, and National Weather Service precipitation forecasts. This system was used to issue warnings during the storms of 12 to 21 February 1986, which produced 800 millimeters of rainfall in the region. Although analysis after the storms suggests that modifications and additional development are needed, the system successfully predicted the times of major landslide events. It could be used as a prototype for systems in other landslide-prone regions.

Dihydrotestosterone induces a sexual dimorphism in estrogen uptake by specific anterior pituitary cell types in vivo.

Castrated male and female rats pretreated with dihydrotestosterone (DHT) were injected i.v. with 3H-estradiol (E2). Nuclear uptake and retention of 3H-E2 was measured in each of five cell types of the anterior pituitary gland using a combined quantitative autoradiographic and immunocytochemical procedure. In non-pretreated groups, each cell type bound a characteristic amount of ligand but no sex differences were apparent. DHT pretreatment, however, caused a significant decrease in 3H-E2 retention by gonadotrophs in both males and females. The treatment also caused a decrease in binding by lactotrophs and somatotrophs, but only in the females. No other cell types were altered. Thus, androgen appears to modulate E2 binding and retention by pituitary cells in both a cell-type and sex-dependent manner. Our results also indicate that the inhibitory effects of androgens on E2 binding by the pituitary gland is more complex than can be explained by simple competition for the estrogen receptor.

Prostate adenocarcinoma: effects of castration on in situ androgen uptake by individual cell types.

The cellular distribution of androgen uptake was investigated in normal prostate and in Dunning R3327H prostate tumors in Copenhagen rats in vivo at different time intervals after castration. Quantitative dry-autoradiography was used to demonstrate which cell types have androgen binding, and to quantify the amount of androgen binding per cell type during initial castration-induced tumor regression and subsequent tumor relapse. Regardless of time after castration, tumor stromal nuclei had significantly more 3H-dihydrotestosterone (DHT) labelling than did tumor epithelial nuclei (p less than .001). On the other hand, prostate gland epithelial nuclei showed more 3H-DHT binding than prostate gland stromal nuclei. Tumor stromal nuclei had greater DHT uptake than any other cell type measured in the tumor or in secondary sex organs at all times after castration. Different cell types responded differently to castration. The 3H-DHT uptake measured in tumor stromal nuclei after castration showed that one day after castration 14.6 +/- 2.1 silver grains were present, 14 days after castration 9.3 +/- 2.4 were seen, and 50 days after castration 18.9 +/- 1.8 were present. This significant increase from 14 days to 50 days is not seen in the other cell types. This study gives insight into the cellular androgen receptor distribution in normal and malignant rat prostate tissue.

Laser fluorescence velocimeter.

A new technique is described in which fluid flow velocity can be determined using the laser-induced fluorescence (LIF) signal produced by a space and time modulated excitation. The modulated excitation is produced by a crossed-beam probe volume similar to those commonly employed in particle-scattering laser Doppler velocimeters (LDV). The technique relies on a flow-induced variation of the visibility and phase of the fluorescence signal that results from the finite lifetime for fluorescence decay of the excited species. A simple, infinite reservoir model is presented to illustrate the technique and to identify the controlling parameters.

The ontogeny of the mouse estrogen receptor: the pelvic region.

The appearance of estrogen receptors was examined during the course of fetal and neonatal development in the pelvic region of the mouse; 3H-diethylstilbestrol (DES) was administered via the maternal circulation to developing mice on days 4, 7, 10, 13, 14, 15, and 17 of gestation or to neonates on the day of birth. Localization of the ligand was monitored autoradiographically. The earliest appearance of estrogen receptors occurred in the mesenchyme around the genital ducts on day 13 of pregnancy. On subsequent days, estrogen-concentrating cells appeared in certain mammary-gland cells, connective-tissue strands, in perichondrium associated with specific developing bones, skin, interstitial tissue of the testis, in a sheath of cells surrounding the colon, and in the urethra. The significance of cells containing estrogen receptors in these locations is discussed in reference to a transplacental action of estrogens and the clinical ramifications of DES.

Estrogen uptake capacity of individual pituitary cell types from male and female rats one, fourteen and fifty days after castration.

A quantitative autoradiographic technique was combined with immunocytochemical staining to compare 3H-estrogen uptake in individual pituitary cell types 1, 14 or 50 days after castration in both male and female rats. Silver grains were counted over nuclei of immunocytochemically stained cells and means were computed for each cell type. The order of labelling intensity for all groups was gonadotropes greater than or equal to lactotropes = somatotropes greater than thyrotropes = corticotropes. In male rats 3H-estrogen uptake capacity in all of these cell types remained unchanged over the post-castration interval. Only gonadotropes from female rats demonstrated a significant change in estrogen uptake capacity over the intervals examined. Uptake in these cells increased by 137% between 1 and 50 days after ovariectomy. At both 14 and 50 days post-ovariectomy, gonadotropes concentrated significantly more radioactive label than either lactotropes or somatotropes. One day after castration, gonadotropes from females concentrated less 3H-estrogen than males while at 50 days after castration they concentrated significantly more than gonadotropes from male rats.

Calcium, cAMP, and dopamine affect single mammotrophs assayed by hemolytic plaques.

We investigated the effects of dopamine, forskolin, and maitotoxin on prolactin release from individual rat and monkey mammotrophs. Forskolin increases cAMP levels, whereas maitotoxin amplifies the influx of extracellular calcium. Prolactin secretion from single mammotrophs was visualized by the reverse hemolytic plaque assay and then quantified by measuring the proportion of plaque-forming cells and the mean plaque area. In the presence of dopamine alone both the plaque proportion and mean area of the plaques formed by rat mammotrophs decreased by 50 and 40%, respectively. This inhibition of secretion was blocked by the dopaminergic antagonist spiperone as well as forskolin and maitotoxin. Forskolin and maitotoxin alone significantly elevated both the proportion (+30%) and area (+180% for forskolin and +250% for maitotoxin) of the plaques. These actions of maitotoxin were neutralized by D-600, a calcium channel blocker. All of these agents induced similar trends with monkey prolactin cells. We conclude that single mammotrophs in culture respond to perturbations in a differential manner and in a way predicted by earlier results based on macropopulation measurements.

Binding of [3H]aldosterone to a single population of cells within the rat epididymis.

Using the dry-mount autoradiographic technique, a single population of cells within the rat epididymis, the clear cells, have been shown to bind [3H]aldosterone at a nuclear site. Competitive binding experiments demonstrated that aldosterone was more potent than desoxycorticosterone than testosterone in reducing the nuclear uptake of radioactive aldosterone. Furthermore, the other epididymal cells (principal and basal cells) in all regions of the epididymis were not significantly labelled; occasional labelling was noted in some endothelial and stromal cells. It is suggested that aldosterone may play a role in controlling the intracellular and transcellular movement of ions and water necessary for concentrating absorbed macromolecules in the clear cell.

The ontogeny of estrogen receptors: brain and pituitary.

This study examines the prenatal and neonatal development of estrogen receptors in the central nervous system of the mouse. [3H]Diethylstilbestrol (DES) was injected into pregnant mice on days 4, 7, 10, 13, 14, 15 and 17 of gestation or into neonates. DES is an estrogen agonist that circumvents the alpha-fetoprotein barrier, thereby gaining access to intracellular estrogen receptors. Sixty minutes after injection whole embryos, fetuses or neonates were rapidly frozen and processed for autoradiography. Although the transplacental movement of the isotope was confirmed in all age groups evidence for nuclear estrogen receptors was not seen in the brain until day E14. On this day a few labeled cells first appeared in the basal hypothalamus, preoptic area, amygdala, midbrain and spinal cord. The number and the labeling intensity of target cells increased in each of these areas on days E15, E17 and P0. The first appearance of estrogen receptors closely follows the reported birthdates of neurons in these regions.