Terahertz magnetoplasmon resonances in coupled cavities formed in a gated two-dimensional electron gas.

We report on both experiments and theory of low-terahertz frequency range (up to 400 GHz) magnetoplasmons in a gated two-dimensional electron gas at low (<4K) temperatures. The evolution of magnetoplasmon resonances was observed as a function of magnetic field at frequencies up to ∼400 GHz. Full-wave 3D simulations of the system predicted the spatial distribution of plasmon modes in the 2D channel, along with their frequency response, allowing us to distinguish those resonances caused by bulk and edge magnetoplasmons in the experiments. Our methodology is anticipated to be applicable to the low temperature (<4K) on-chip terahertz measurements of a wide range of other low-dimensional mesoscopic systems.

FCSlib: an open-source tool for fluorescence fluctuation spectroscopy analysis for mobility, number and molecular brightness in R.

SUMMARY: FCSlib is an open-source R tool for fluorescence fluctuation spectroscopy data analysis. It encompasses techniques such as Fluorescence Correlation Spectroscopy, Number and Brightness, Pair Correlation Function and Pair Correlation of Molecular Brightness. AVAILABILITY AND IMPLEMENTATION: Source code available at https://cran.r-project.org/web/packages/FCSlib/ for Linux, Windows and macOS platforms. Sample data as well as a user's guide are available at https://github.com/FCSlib/FCSlib. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Increasing the sensitivity of terahertz split ring resonator metamaterials for dielectric sensing by localized substrate etching.

We demonstrate a significant enhancement in the sensitivity of split ring resonator terahertz metamaterial dielectric sensors by the introduction of etched trenches into their inductive-capacitive gap area, both through finite element simulations and in experiments performed using terahertz time-domain spectroscopy. The enhanced sensitivity is demonstrated by observation of an increased frequency shift in response to overlaid dielectric material of thicknesses up to 18 µm deposited on to the sensor surface. We show that sensitivity to the dielectric is enhanced by a factor of up to ∼2.7 times by the incorporation of locally etched trenches with a depth of ∼3.4 µm, for example, and discuss the effect of the etching on the electrical properties of the sensors. Our experimental findings are in good agreement with simulations of the sensors obtained using finite element methods.

On-chip terahertz spectroscopic techniques for measuring mesoscopic quantum systems.

We present the self-aligned fabrication of on-chip devices in which waveguides, incorporating integrated photoconductive switches, are combined with two-dimensional electron systems to allow probing of the ultrafast (terahertz frequency range) properties of confined semiconductor systems, both at cryogenic temperatures and in high magnetic fields. We demonstrate the direct injection of on-chip terahertz pulses into the mesoscopic system by femtosecond, near infra-red laser excitation of in-plane photoconductive switches formed on an epitaxially grown, low-temperature GaAs layer, which is integrated monolithically with a GaAs∕AlGaAs heterostructure containing a two-dimensional electron system. Both the input and output terahertz signals of an on-chip waveguide are sampled by altering dynamically the photoconductive excitation∕detection arrangement in situ on a single device. We also demonstrate a new method for sub-Kelvin excitation and detection of on-chip terahertz frequency radiation in a (3)He∕(4)He dilution refrigerator that allows the photocurrent and detected terahertz transient to be mapped as function of the near-infrared excitation position at the emitter and the detector, respectively. Furthermore, we demonstrate transmission of terahertz transients through a two-dimensional electron system in a coplanar waveguide under magnetic field at temperatures as low as 200 mK.

Tracking sperm in three-dimensions.

Sperm motility, crucial for fertilization, has been mostly studied in two dimensions (2D) by recording their swimming trajectories near a flat surface. However, spermatozoa swim in three-dimensions (3D) to find eggs, with their speed being the main impediment to track them under realistic conditions. Here, we describe a novel method allowing 3D tracking and analysis of the trajectories of multiple free-swimming sperm. The system uses a piezo-electric device displacing a large focal distance objective mounted on a microscope to acquire 70 image stacks per second, each stack composed of 60 images that span a depth of 100 microm. With this method, 3D paths of multiple sperm in the same field could be visualized simultaneously during 1 s. Within the same sample we found that surface-confined sperm swam 25% slower, produced 3-fold fewer circular revolutions per second, and had trajectories of 134% greater radius of curvature than those sperm swimming freely in 3D.

Characterization of the ethanol-inducible alc gene-expression system in Arabidopsis thaliana.

Controlled expression of transgenes in plants is key to the characterization of gene function and the regulated manipulation of growth and development. The alc gene-expression system, derived from the filamentous fungus Aspergillus nidulans, has previously been used successfully in both tobacco and potato, and has potential for use in agriculture. Its value to fundamental research is largely dependent on its utility in Arabidopsis thaliana. We have undertaken a detailed function analysis of the alc regulon in A. thaliana. By linking the alcA promoter to beta-glucuronidase (GUS), luciferase (LUC) and green fluorescent protein (GFP) genes, we demonstrate that alcR-mediated expression occurs throughout the plant in a highly responsive manner. Induction occurs within one hour and is dose-dependent, with negligible activity in the absence of the exogenous inducer for soil-grown plants. Direct application of ethanol or exposure of whole plants to ethanol vapour are equally effective means of induction. Maximal expression using soil-grown plants occurred after 5 days of induction. In the majority of transgenics, expression is tightly regulated and reversible. We describe optimal strategies for utilizing the alc system in A. thaliana.

Transcription inhibition induced by modified triple helix-forming oligonucleotides: a quantitative assay for evaluation in cells.

Oligonucleotides can bind to double-stranded DNA in a sequence-specific manner to form triple helices. Uniformly modified, pyrimidine-rich oligodeoxyribonuclotides containing internucleosidic N3'-P5' phosphoramidate linkages are known to form very stable triplexes with their DNA target. Psoralen-conjugated triple helix-forming oligonucleotides (Pso-TFOs) can additionally be photo-induced to become irreversibly bound to their targeted DNA sequence. Here, we have examined the ability of various 15-mer phosphoramidate TFOs targeted to the HIV-1 polypurine tract (PPT) sequence to prevent transcription elongation in cell cultures; the PPT sequence has been cloned in the transcribed region of a reporter firefly luciferase gene (luc) and transient expression experiments performed. We show that the level of transcription inhibition of the reporter gene in cells perfectly correlates with the amount of covalent triplex at the PPT site. The efficacy of non-covalent triplexes (either omitting the irradiation step with the psoralen conjugate, or using the unsubstituted oligonucleotide) has been studied in our expression system; the oligonucleotides were introduced into living cells by cationic lipid-mediated delivery or directly into the cell nucleus by microinjection. This experimental approach allowed us to evaluate the intrinsic activity of triplexes as transcriptional inhibitors; transcription elongation was inhibited in cells in a sequence-dependent and concentration-dependent manner. This experimental system is convenient for quantitative and fast evaluation of new chemistries of antigene oligonucleotides as inhibitors of gene expression in cells and in vivo.

Prokinetic effects of erythromycin after antimotion sickness drugs.

Motion sickness and the antimotion sickness drugs scopolamine (SCP) and promethazine (PMZ) inhibit gastric emptying (GE). This study was conducted to determine if erythromycin would exert its well-known prokinetic effects in normal and motion-sick subjects given antimotion sickness drugs. Fifteen fasted volunteers (11 males, 4 females) participated in the study. In control tests, 8 subjects were given intramuscular (i.m.) saline (SAL, 0.5 ml), SCP (0.1 mg), or PMZ (25 mg). GE of liquid (300 ml) containing 1 mCi of Tc 99m diethylenetriaminepentaacetic acid (DTPA) was measured by sequential gastric scintigraphy 30 minutes after i.m. treatments. In other tests, GE was measured in 8 subjects after each i.m. treatment, followed 10 minutes later by 200 mg of erythromycin ethylsuccinate (ESS) suspension given orally. In a third group of tests, 7 subjects received an i.m. treatment, oral EES 10 minutes later, and were then brought to an advanced level of motion sickness short of vomiting. To induce motion sickness, blindfolded subjects made timed head movements while seated in a rotating chair. GE was measured immediately after rotation. GE half-life, rate constant, area under the curve (AUC), and lag time were calculated using conventional mathematical methods for analyzing exponential rate processes. GE parameters calculated for normal and motion-sick subjects given antimotion sickness drugs and EES were compared with those from subjects given i.m. treatments (control) only. In normal subjects, EES significantly (p < 0.05) increased the GE rate constant for all i.m. treatments and reduced the AUC for SAL, SCP, and PMZ by 49% (p < 0.05), 44% (p < 0.05), and 69% (p < 0.01), respectively. In motion-sick subjects, lag time was significantly (p < 0.05) increased, and the rate constant and AUC values were unchanged from control for all i.m. treatments. The authors conclude that oral EES reverses the gastrostatic actions of the antimotion sickness drugs but does not affect the inhibition of gastric emptying associated with motion sickness. The results suggest that motion sickness and antimotion sickness drugs reduce GE through different mechanisms.

Targeted inhibition of transcription elongation in cells mediated by triplex-forming oligonucleotides.

Triple-helix-forming oligonucleotides (TFOs) bind in the major groove of double-stranded DNA at oligopyrimidine small middle dotoligopurine sequences and therefore are candidate molecules for artificial gene regulation, in vitro and in vivo. We recently have described oligonucleotide analogues containing N3'-P5' phosphoramidate (np) linkages that exhibited efficient inhibition of transcription elongation in vitro. In the present work we provide conclusive evidence that np-modified TFOs targeted to the HIV-1 polypurine tract (PPT) sequence can inhibit transcriptional elongation in cells, either in transient or stable expression systems. The same constructs were used in transient expression assays (target sequence on transfected plasmid) and in the generation of stable cell lines (target sequence integrated into cellular chromosomes). In both cases the only distinguishable feature between the cellular systems is the presence of an insert containing the wild-type PPT/HIV-1 sequence, a mutated version with two mismatches, or the absence of the insert altogether. The inhibitory action induced by np-TFOs was restricted to the cellular systems containing the complementary wild-type PPT/HIV-1 target, and consequently can be attributed only to a triple-helix-mediated mechanism. As a part of this study we also have applied an imaging technique to quantitatively investigate the dynamics of TFO-mediated specific gene silencing in single cells.

Real-time imaging of gene expression in single living cells.

Recent advances in reporter gene technologies are now allowing us to image gene transcription at the single cell level, using either fluorescence or luminescence microscopy. Here, the basis of these techniques is outlined and their advantages and disadvantages in various biological systems are discussed.

Dynamic changes in prolactin promoter activation in individual living lactotrophic cells.

The firefly luciferase gene has become widely used as a convenient reporter for studies of gene promoter regulation. Very recently, the development of ultralow-light imaging cameras has enabled the quantitative digital imaging of light signals resulting from luciferase activation in the presence of luciferin substrate. We have applied this technology to the study of PRL promoter activation in individual pituitary tumor cells to study the temporal and spatial characteristics of the expression of a well-characterized pituitary hormone gene. Rat pituitary GH3 cells were transfected by lipofection with a luciferase reporter gene linked to 5000 bp from the human PRL gene 5'-flanking region. A series of stably transfected cell clones were generated, and one of these was chosen for detailed study on the basis of appropriate regulation of high-level luciferase expression by a series of known stimuli including TRH, forskolin, the calcium channel agonist Bay K8644, and basic fibroblast growth factor (bFGF). These cells were subjected to direct imaging of luciferase activity using a Hamamatsu photon-counting camera linked to a Zeiss Axiovert microscope with an Argus-50 image processor. Cells were exposed to 1 mM luciferin, and images were integrated over 30-min periods for up to 72 h. The total photon count over a given field settled to steady levels within 10 h and then remained constant for over 55 h. Addition of forskolin, TRH, or bFGF increased the total photon count of fields of 20-100 cells by 2- to 4-fold consistent with previous data from transient expression assays using the human PRL promoter. Individual cells, on the other hand, showed marked marked temporal and spatial heterogeneity and variability of luciferase expression when studied at 3-h intervals. Unstimulated cells showed variable luciferase expression with up to 40-fold excursions in photon counts per single cell area within 12-h periods. Stimulation of cells with either TRH, forskolin, or bFGF resulted in smooth increases in photon output over fields of 20-100 cells, but again individual cell responses differed widely, with some cells showing slow progressive rises in photon output, others showing phasic or transient responses, and yet others showing no response. In conclusion, we found a surprising degree of heterogeneity and temporal variability in the level of gene expression in individual living pituitary tumor cells over long periods of time, with markedly divergent responses to hormonal or intracellular stimulation. The use of stably transfected clonal cell lines with extended periods of reporter gene imaging offers a valuable insight into control of gene expression in living cells in real time.

The nutritive value of stackburned yellow maize for livestock: tests in vitro and in broiler chicks.

Difference in the nutritive value of four grades of stackburned yellow maize, obtained from a single storage unit in Mozambique, were examined. Samples were analysed for chemical composition, and subjected to the following in vitro assays for estimating digestibility: total dietary fibre and pancreatin for non-ruminants, and gas production using sheep rumen fluid for ruminant livestock. Samples were also fed to broiler chicks at 600 g/kg diet in a growth trial. There were no significant differences in crude protein contents of the maize samples, but there was evidence for the development of Maillard reaction products. Detectable amino acids were lower in discoloured maize, with decreases of 52% in lysine, 35% in arginine, and 15% in glycine concentration in the most severely discoloured sample compared with control. Total starch, reducing sugar, acid-detergent fibre and amylase-neutral-detergent fibre values increased, while total non-reducing sugar content decreased with increased discolouration. Total dietary fibre and pancreatin assays indicated a lowering in digestibility of maize with increasing discolouration. Weight gain of chicks (P = 0.0228), efficiency of feed utilization (P = 0.0009) and the metabolizable energy value of diets decreased (P < 0.0001) with increasing stackburn discolouration. There were no significant effects on N retention of diets. In vitro fermentation using sheep rumen fluid showed a linear decrease in gas production with increasing maize discolouration, indicating a reduction in rumen degradability with stackburn.

Habituation and motion sickness.

The vestibular, cerebellar, and reticular systems are central in importance, in motion sickness and habituation, to the effects of motion. Nuclear medicine single photon emission computed tomography (SPECT) studies of cerebral blood flow and power spectral electroencephalographic recordings during motion sickness were used to determine alterations in the central nervous system. The rotating chair with and without visual stimulation was used to study the rate of habituation and the effect of antimotion sickness medications on this rate. An increase of theta waves over the frontal cortex indicated a decreased activation of the higher centers during motion sickness. Motion sickness also produces an increase of blood flow in the central cerebellum that has connections to the reticular system. This increase in cerebellar activity is relayed to the reticular system whereby neural recruitment builds up to trigger the vomiting center, producing motion sickness. Habituation may be a conditioned compensatory activation of the reticular neurons that prevents this disruption of normal activation. The rate of habituation when motion sickness was prevented by scopolamine was slowed, indicating that, if the central nervous system is not challenged by disruption of normal activation, it does not produce the compensatory reactions that result in habituation.

Effects of motion sickness and antimotion sickness drugs on gastric function.

This study examined the effects of motion sickness and antimotion sickness drugs on gastric emptying (GE). Drugs were tested in normal and motion sick subjects. To induce motion sickness, subjects performed head movements while seated in a rotating chair. Gastric emptying of liquid (300 mL) was determined by nuclear medicine techniques, whereas gastric electrical activity, the electrogastrogram (EGG), was monitored from surface (cutaneous) electrodes positioned over the abdominal area. Gastric emptying was severely inhibited at the peak of motion sickness symptoms, but returned to normal 15 minutes later when symptoms abated. In normal (non-motion sick) subjects intramuscular (IM) scopolamine (0.1 mg) and IM promethazine (25 mg) inhibited GE, whereas erythromycin ethylsuccinate (EES) suspension (200 mg) given orally increased GE. When administered to motion sick subjects, IM scopolamine and IM promethazine added slightly, but not significantly, to the inhibition of GE already present. Oral EES did not significantly alter GE in motion sick subjects. Although EGG frequency remained within normal limits (approximately 2.5-3.5 cpm) after liquid ingestion in both normal and motion sick subjects, EGG amplitude was differentially affected in the two groups. Electrogastrogram amplitude increased twofold to fourfold after liquid ingestion in normal, but not in motion sick subjects. The results suggest that (1) maximal inhibition of GE is coincident with peak motion sickness symptoms, (2) both IM scopolamine and IM promethazine inhibit GE in normal subjects, but do not add significantly to the inhibition of GE already established during motion sickness, (3) orally administered erythromycin enhances GE in normal, but not in motion sickness subjects, and (4) the normal stimulatory effect of liquid ingestion on gastric motility does not occur in motion sick subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Interspecies differences and variability with time of protein precipitation activity of extractable tannins, crude protein, ash, and dry matter content of leaves from 13 species of Nepalese fodder trees.

Dry matter, ash, crude protein, and protein precipitation activity (PPA) of 13 Nepalese tree fodder species were monitored in dried samples prepared monthly between November 1990 and May 1991, and additionally in November 1991, covering the season when they are particularly important as fodder. Monthly levels of dry matter, ash, and crude protein were fairly stable except when there was new leaf growth, although year to year differences in dry matter were found inBrassaiopsis hainla (Bh),Dendrocalamus strictus (Ds),Ficus roxburghii (Fr), andQuercus semecarpifolia (Qs). Tannin PPA fluctuated considerably inArtocarpus lakoocha (Al),Ficus glaberrima (Fg),F. nerrifolia (Fn), Fr,F. semicordata (Fs),Litsea polyantha (Lp), andPrunus cerasoides (Pc), and to a lesser extent in Bh,Castanopsis indica (Ci),C. tribuloides (Ct),Quercus lamellosa (Ql), and Qs. Similar fluctuations in PPA were observed in fresh leaf samples taken weekly. Ds did not have any detectable PPA. Trends in PPA fluctuation were generally similar for trees located at similar altitudes. Fr, Pc, Al, Fn, Ql, and Ci had falling PPAs before shedding leaves. Some of the fluctuations in Fr, Fs, Fg, Pc, and Lp were apparently due to changes in the extractability and quantity of condensed tannins. These fluctuations in PPA may affect the nutritive value of the fodders.

The Seattle appropriate level of care survey: health status and health services use in ambulatory persons with AIDS.

We surveyed 77 persons with AIDS, their physicians and their social workers during the autumn of 1987 to ascertain health status and to quantify use of health services in Seattle, Washington. Participants included the majority (59%) of persons living with AIDS in the area. Information was gathered regarding demography, health status, functional status, medical history and the use of health services. The validity of self-assessed general health was corroborated by the physician-rated Karnovsky score (kappa = 0.59), by social worker assessment (kappa = 0.41), and by correlation with functional status (r = 0.6-0.8). We found more frequent use of health services (categorized into skilled services, chore services and physician services) among AIDS patients who were dependent in basic and instrumental daily activities, had low income, had poor self-assessed general health, lived alone or lacked an available support person at home. These associations persisted in multivariate analyses, and accounted for 6-23% of the variability in service use. We conclude that health and functional status of persons with AIDS can be estimated via mailed questionnaires and accounts for a modest amount of the variability in use of health services.

Effectiveness and duration of intramuscular antimotion sickness medications.

Motion sickness inhibits gastric motility, making the oral route ineffective for medications. The intramuscular route is an effective alternative. The rotating chair was used to produce the M 111 level of motion sickness on the Graybiel Symptom Scale. The intramuscular medications given 30 minutes before rotation were compared with placebo (saline, 1 mL) for effectiveness and duration in increasing the number of tolerated head movements. Average placebo number of head movements was 294. Promethazine 25 mg increased head movements by 78% (P < .05), with a duration of 12 hours. Scopolamine 0.2 mg increased head movements by 91% (P < .05), with a duration of 4 hours. The effect of caffeine 250 mg and ephedrine 25 mg was not significant. When combined with scopolamine, ephedrine produced an 32% additive effect. Scopolamine 0.08 mg, 0.1 mg, and 0.2 mg and also promethazine 12.5 mg and 25 mg were significant (P < .05). Promethazine appears to be the drug of choice for intramuscular use because of a longer duration and a high level of effectiveness. Scopolamine was of high effectiveness, but had a duration of 4 hours. It was eight times as potent by the intramuscular as by the oral route.

Effects of ginger on motion sickness susceptibility and gastric function.

This study was designed to evaluate the antimotion sickness activity of ginger root (Zingiber officinale) and to characterize the effects of ginger on gastric function. Twenty-eight human volunteers participated in the project. Subjects made timed head movements in a rotating chair until they reached an endpoint of motion sickness short of vomiting (malaise III or M-III). Each subject was tested with either ginger or scopolamine and a placebo. A substance was judged to possess antimotion sickness activity if it allowed a greater number of head movements compared to placebo control. Gastric emptying of a liquid was measured by nuclear medicine techniques in normal and motion sick subjects. Gastric electrical activity was monitored by cutaneous (surface) electrodes positioned over the abdominal area. Powder ginger (whole root, 500 or 1,000 mg) or fresh ginger root (1,000 mg) provided no protection against motion sickness. In contrast, subjects performed an average of 147.5 more head movements (p less than 0.01) after scopolamine (0.6 mg p.o.) than after placebo. The rate of gastric emptying was significantly (p less than 0.05) slowed when tested immediately after M-III but was inhibited less when tested 15 min after M-III. Powdered ginger (500 mg) had no effect on gastric emptying in normal or motion-sick subjects. Gastric motility was also changed during motion sickness. The frequency of the electrogastrogram (EGG) was increased after M-III (tachygastria) and the normal increase in EGG amplitude after liquid ingestion was reduced in motion sick subjects. Although powdered ginger (500 mg) partially inhibited tachygastria in motion sickness, it did not enhance the EGG amplitude in motion sick subjects. We conclude that ginger does not possess antimotion sickness activity, nor does it significantly alter gastric function during motion sickness.

Differential effects of scopolamine and amphetamine on microcomputer-based performance tests.

Scopolamine (1.0 mg) and d-amphetamine (10 mg) were administered alone and in combination to 16 subjects (medical students), randomly assigned to testing sessions in a fully crossed-over (Latin square) within-subjects design. After being practiced to stability, 9 performance tests from a menu of portable microcomputer-based tests were administered double-blind over 4 weekly treatments (including a placebo). Differential effects of drugs on performance were found. Motor and perceptual speed tests appeared enhanced by d-amphetamine and not degraded by scopolamine. Two of the five cognitive tests showed reductions with scopolamine. The findings are discussed in connection with using a menu of performance tests that can have diagnostic significance for assessment of drug treatments. The effects of scopolamine in this study and others are considered in terms of a model which implies that magnitude of performance deficit depends on performance type (cognitive, motor, self-report) and dosage level. Applying the model, we offer the following summary: below 0.15 mg scopolamine is without any effect; below 0.50 mg, the effect is limited, but can be revealed by some sensitive, complex performance tests and self-report; above 1.0 mg, the effect is likely to impact on operational efficiency.