bluuebunny/crossref_metadata_2025_split huggingface dataset:
Secretagogues govern GH secretory-burst waveform and mass in healthy eugonadal and short-term hypogonadal men
Authors: Veldhuis Johannes D , Keenan Daniel M 
Published: August 2008

BackgroundGH pulses are putatively initiated by hypothalamic GH-releasing hormone (GHRH), amplified by GH-releasing peptide (GHRP), and inhibited by somatostatin (SS).ObjectiveTo ascertain how secretagogues control the waveform (time evolution of release rates) as well as the mass of secretory bursts.DesignWe quantified the shape of GH secretory bursts evoked by continuous combined i.v. infusion of maximally effective doses of GHRH and GHRP-2, and by bolus injection of each peptide after delivering l-arginine to restrain hypothalamic SS release in 12 healthy young men.MethodsA mathematically verified and experimentally validated variable-waveform deconvolution model was applied to intensively sampled GH time series.ResultsThe secretory-burst mode (time from burst onset to maximal secretion) was 19±0.69 min during saline infusion, and fell to a) 10.4±3.0 min during constant dual stimulation with GHRH/GHRP-2 (P<0.01), b) 14.6±1.8 min after l-arginine/GHRH (P<0.025), and c) 15.0±1.0 min after l-arginine/GHRH (P<0.01). Secretagogues augmented the mass of GH secreted in pulses by 44-, 42-, and 16-fold respectively, over saline (2.2±0.81 μg/l per h; P<0.001 for each). Pulse number and variability were unaffected. Applying the same methodology to ten other young men with acute leuprolide-induced hypogonadism yielded comparable waveform and mass estimates.ConclusionThe present analyses in men demonstrate that peptidyl secretagogues modulate not only the magnitude but also the time course of the GH-release process in vivo independently of the short-term sex-steroid milieu.
The Sound of Poetry / The Poetry of Sound: The 2006 MLA Presidential Forum
Authors: Perloff Marjorie , Dworkin Craig 
Published: August 2008

An onomatopoeic expression automatically entails the specification of what is being described. A pattering sound cannot come from a piece of wood. But when I was listening to [Peter Ablinger's Berlin sound] recordings, I sometimes couldn't tell whether a sound was coming from thunder or a sheet of metal. I wanted to represent the sound, not the person who was producing it, nor its metaphorical significance. It took me quite some time to come up with a solution: My solution was not to find a solution, but rather to enter into the crevice between sound and language and make countless little notes.—Yoko Tawada, “The Art of Being Synchronous”
Emergence of Patterned Stem Cell Differentiation Within Multicellular Structures
Authors: Ruiz Sami Alom , Chen Christopher S. 
Published: August 2008

Abstract
The ability of stem cells to differentiate into specified lineages in the appropriate locations is vital to morphogenesis and adult tissue regeneration. Although soluble signals are important regulators of patterned differentiation, here we show that gradients of mechanical forces can also drive patterning of lineages. In the presence of soluble factors permitting osteogenic and adipogenic differentiation, human mesenchymal stem cells at the edge of multicellular islands differentiate into the osteogenic lineage, whereas those in the center became adipocytes. Interestingly, changing the shape of the multicellular sheet modulated the locations of osteogenic versus adipogenic differentiation. Measuring traction forces revealed gradients of stress that preceded and mirrored the patterns of differentiation, where regions of high stress resulted in osteogenesis, whereas stem cells in regions of low stress differentiated to adipocytes. Inhibiting cytoskeletal tension suppressed the relative degree of osteogenesis versus adipogenesis, and this spatial patterning of differentiation was also present in three-dimensional multicellular clusters. These findings demonstrate a role for mechanical forces in linking multicellular organization to spatial differentials of cell differentiation, and they represent an important guiding principle in tissue patterning that could be exploited in stem cell-based therapies.
Disclosure of potential conflicts of interest is found at the end of this article.
Hillslope hydrological linkages: importance to ponds within a polar desert High Arctic wetland
Authors: Abnizova Anna , Young Kathy L. 
Published: August 2008

Arctic wetland environments are considered to be sensitive to ongoing climate change but they have received limited attention despite their ecological importance. To understand and quantify better the hydrologic processes which are leading to the sustainability and demise of High Arctic ponds, a water balance framework was employed on several ponds situated in two broad geomorphic areas near Creswell Bay, Somerset Island (72°43′N, 94°15′W). These ponds are also linked to an upland area through a range of linear features: stream, late-lying snowbeds and frost cracks. This study assesses the importance of these features with respect to the sustainability of these wetland ponds.
A pond's position in the moraine landscape was important in determining its connectivity to a nearby stream and late-lying snowbed. Close proximity to a stream draining a large upland snow-covered catchment ensures steady water levels during the snowmelt period. Once discharge slows, a late-lying snowbed continues to supply the pond and others nearby with meltwater. The deeply thawed, sandy coastal zone is characterized by frost cracks, which contribute to the patterned ground of this wetland zone. These cracks, when situated downslope of ponds, function primarily as ‘sinks’ and serve to deprive small and medium-sized ponds of water during dry periods, often leading to their desiccation.
Preparation and characterization of diethylnicotinamidium perchlorate
Authors: Ondrejkovičová Iveta , Mikloš Dušan , Štefániková Silvia 
Published: August 2008

AbstractThe title compound is the first example of N,N′-diethylnicotinamidium, [denaH]+, salt which has been characterized by X-ray analysis and IR spectra. [denaH]ClO4 was obtained from the reaction mixture prepared from N,N′-diethylnicotinamide (dena) and Fe(ClO4)3 in ethanol without any addition of HClO4. The proton required for protonation of dena is produced by hydrolysis of aquairon(III) cations. In the crystal structure, cations and anions are held together by ionic interactions. The cations are linked to each other by pyridinium-carbonyl N-H⋯O=C hydrogen bonds and an infinite linear chain along axis a is formed.
ICP MS analysis and classification of potable, spring, and mineral waters
Authors: Kraic Filip , Mocák Ján , Fiket Željka , Kniewald Goran 
Published: August 2008

AbstractNinety-three water samples were categorized into five classes as the tap, mineral, mineral carbonated, spring, and spring carbonated water, or, alternatively, into four or three categories — with all spring water samples together or as tap, mineral, and spring water, respectively. The samples originated from four European countries and thirty-one chemical descriptors (concentrations of contained elements) were used for their characterization. Analytical measurements were performed by mass spectrometry with inductively coupled plasma, allowing the determination of individual nuclides. Different water categories were characterized by chemometrical techniques, mainly by principal component analysis, cluster analysis, linear and quadratic discriminant analyses, correlation analysis, and ANOVA. Their role was to discover the nuclides important for distinct characterization of individual water categories as well as to assess the possibility of water samples from different countries being recognized from the increased/decreased content of some elements. The enhanced content of Cd, Cu, Zn, Bi, and Fe was characteristic for tap water samples, whilst mineral water samples were characterized by the elevated concentration of Sr, Li, B, Ni, Co, As, and Sb. The classification results were successful and close to 100 %, which was proved by the leave-one-out cross-validation procedure.
Application of Conceptual Rainfall-Runoff Model METQ for Simulation of Daily Runoff and Water Level: The case of the Lake Burtnieks Watershed
Authors: Apsīte Elga , Zīverts Ansis , Bakute Anda 
Published: August 2008

Application of Conceptual Rainfall-Runoff Model METQ for Simulation of Daily Runoff and Water Level: The case of the Lake Burtnieks Watershed
In this study a conceptual rainfall-runoff METQ model—the latest version METQ2007BDOPT—was applied to simulate the daily runoff and water level of the Lake Burtnieks watershed from 1990 to 1999. The model structure and parameters were basically the same as in the METQ98, with some additional improvements and semi-automatical calibration performance. Model calibration was done for four rivers and one lake gauging station. The results of calibration showed a good correlation between the measured and simulated daily discharges. The Nash-Sutcliffe efficiency R2 varied from 0.90 to 0.58 and correlation coefficient r from 0.95 to 0.83. The highest values of R2 = 0.90 and r = 0.95 were obtained for the River Salaca and the lowest R2 = 0.53 and r = 0.83 for Lake Burtnieks. We observed some relationships between the model parameter values and physiographic characteristic of the sub-catchments.
Experimental Study of Peat Humification Indicators
Authors: Šīre Jānis , Kļaviņš Māris , Purmalis Oskars , Melecis Viesturs 
Published: August 2008

Experimental Study of Peat Humification Indicators
An important parameter of organic matter in soils, peat, and fossil-carbon-containing deposits is their decomposition degree, which describes their transformation intensity—the humification degree of original living organic matter. In this article approaches to the analysis of humification degree are thoroughly described and14C dated peat columns extracted from several bogs in Latvia are investigated and compared. A new humification indicator is suggested: the ratio of the total amount of organic matter in peat in respect to the amount of humic substances.
Soil Pollution with Trace Elements in Territories of Military Grounds in Latvia
Authors: Kokorīte Ilga , Kļaviņš Māris , Šīre Jānis , Purmalis Oskars , Zučika Aija 
Published: August 2008

Soil Pollution with Trace Elements in Territories of Military Grounds in LatviaContamination of land used for military activities can significantly differ from that of municipal and industrial land, both in the intensity and type. Largely this is due to the intensity of activities even in a comparatively large surface area, and also by use of substances and materials not common in civil practice. Pollution from military grounds can affect not only soldiers, but also adjacent territories and water resources. In this study, concentrations of trace elements in the soil, water and higher vegetation in former Soviet army military territories were surveyed. The presence of point sources was found, and in a few cases the pollution is intensively spreading into deeper soil horizons and groundwater.
Potential Impact of Climate Change on Aquatic Vegetation of River Salaca, Latvia
Authors: Grīnberga Laura , Spriņge Gunta 
Published: August 2008

Potential Impact of Climate Change on Aquatic Vegetation of River Salaca, Latvia
Species diversity and cover of aquatic macrophytes were investigated in the River Salaca in 2007. In total 24 different taxa were found. Schoenoplectus lacustris was the dominant species, Sagittaria sagittifolia, Nuphar lutea, Nymphaea candida, Butomus umbellatus and different Potamogeton species were frequent. Cover of macrophytes varied in the river between 10-90%, maximum in-stream cover reached in rapidly flowing sites. Comparison of total cover of macrophytes in 1986 and 2002 surveys of several stretches was done. Causes for the changes are discussed. The increasing growth of aquatic vegetation in the River Salaca have been related to climatic factors—higher mean annual air temperatures, earlier springs and decrease in the period of ice cover in winter.
Landscape Ecological Structure in the Eastern Part of the North Vidzeme Biosphere Reserve, Latvia
Authors: Tērauds Aivars , Nikodemus Oļgerts , Rasa Inga , Bells Simons 
Published: August 2008

Landscape Ecological Structure in the Eastern Part of the North Vidzeme Biosphere Reserve, Latvia
Latvia is a country where the forest area has increased and habitat fragmentation has reversed compared with many other European countries. In order to examine the effect of this expansion on biodiversity, vegetation maps dating from 2002 and the years 1930-1936 were used for comparative landscape structure analyses while archive materials from forest plans, and data from the national forest management database were used for land use analysis. Four landscape ecoregions in the eastern side of the North Vidzeme Biosphere Reserve were selected for analysis. Landscape structure indicators derived from landscape ecology were used for the ecological assessment of land use changes. The total number of forest patches had decreased over the study period, but mean patch size had increased for all types of landscape element. This general change was found to vary between different landscape units in the study area. The biggest change in the area of forest patches occurred in the Rūjiena drumlin field, where the amount of forest patches decreased least and forest area increased the most. This study showed that the internal structure of the forest matrix changed substantially. This finding has implications for biodiversity protection if this trend of land use change continues.
Effect of Burst Frequency and Duration of Kilohertz-Frequency Alternating Currents and of Low-Frequency Pulsed Currents on Strength of Contraction, Muscle Fatigue, and Perceived Discomfort
Authors: Laufer Yocheved , Elboim Michal 
Published: August 2008

BackgroundLow-frequency pulsed currents (LPCs) and kilohertz-frequency alternating currents (KACs) are used clinically to augment muscle contractions. Treatment effectiveness may be enhanced by selecting stimulation parameters that evoke the strongest contractions with minimal discomfort and fatigue.ObjectiveThe objective of this study was to compare maximally induced strength (force-producing capacity) of contractions, muscle fatigue, and discomfort associated with an LPC and with 3 KACs differing in frequency and duration of burst modulation.DesignThis was a repeated-measures trial, with randomized order of current presentation.SettingThe study was conducted in the physical therapy laboratory at the University of Haifa.SubjectsTwenty-six volunteers without impairments, with a mean age of 27.4 years (SD=5.0, range=21–45), participated.InterventionAll currents were applied in separate sessions to the wrist extensors of each subject. Currents consisted of an LPC with a 50-Hz pulse frequency and 3 KACs with a 2.5-kHz carrier frequency, including the “Russian current” (RC) burst modulated at 50 Hz with 25 cycles per burst and 2 currents burst modulated at 20 or 50 Hz with 10 cycles per burst.MeasurementThe maximal electrically induced isometric force, the force integral of 21 electrically induced consecutive contractions, and the degree of discomfort were recorded.ResultsForce of contraction was not affected by type of current. The LPC was least fatiguing, and the RC was most fatiguing, with the 2 other KACs having an intermediate effect. Degree of discomfort was higher with the KAC modulated at 20 Hz.ConclusionsWhen comfort, strength, and fatigue are considered jointly, the LPC is advantageous. Electrically induced fatigue is affected by the number of cycles per second, rather than the number of bursts per second.
Superheavy Elements – Chemistry and Spectroscopy
Authors: Kaldor Uzi 
Published: August 2008

AbstractSuperheavy elements, a somewhat loose term usually applied to elements with atomic number above 100, exhibit chemical and spectroscopic properties that are not necessarily extrapolations of lighter elements in the same group of the periodic table. This behavior is caused by relativity, which already affects heavy elements (e.g., changing transition energies in gold by as much as 4 eV), and is more important for the superheavy atoms. These elements are produced in accelerators in minute quantities and have short lifetimes, making experimental studies very difficult and costly. Chemical experiments involving the heavier elements are of the ‘one‐atom‐at‐a‐time’ type. Input from theory is crucial in guiding the experimentalist in the search for data.The various theoretical and computational methods used to study these elements are described, and representative results given. For atoms, one can use highly accurate methods: starting from the four‐component Dirac–Coulomb–Breit Hamiltonian, correlation may be included by the most powerful tools of quantum chemistry. In particular, the relativistic Fock‐space coupled cluster (CC) approach reproduced numerous energy levels of heavy elements with an accuracy of a few hundredths of an eV, and provides therefore a reliable tool for predicting yet unknown levels of superheavy elements, as well as their ground state electron configurations. Molecules present a more difficult computational challenge, and more approximate methods, relying on effective core potentials or density functionals, are often used. Molecular properties such as volatility or adsorption energies, which are needed to guide experimentalists in tracing the compounds produced when atoms synthesized in the accelerator are reacted with various chemicals, are calculated, providing invaluable help in determining the existence and properties of the superheavy elements.
Voltage Measurement
Authors: Eren Halit 
Published: August 2008

Abstract
Signals generated by the sensors and transducers from physical variables are mostly in the voltage form. Examples are found in thermocouples, strain gauges, chemical sensors, electrochemical probes, biological sensors, and so on. Voltage magnitudes produced by these sensors are small requiring specialized signal conditioning circuits in the form of electrical bridges, amplifiers, filters, multiplexers, analog‐to‐digital converters, and so on. Once converted to digital forms, information about the physical variable can be stored or processed by computers. This article introduces the main methods used for voltage measurement.
Capacitance and Inductance Measurement
Authors: Liguori Consolatina 
Published: August 2008

Abstract
Capacitance and inductance measurement techniques are intensively used in industrial and scientific applications. In fact, along with resistors, capacitors, and inductors, which are basically components with the propriety of capacitance and inductance respectively, are widely used in circuits for realizing a wide range of electrical and electronic apparatus and instruments. Consequently, the need for capacitance and inductance measurements arises in the characterization, design evaluation, and production test of relevant components and in the circuit modeling of electrical apparatus. Furthermore, these measurements are important since some physical quantities (e.g. humidity, displacement, pressure etc.) are transduced in capacitance or inductance.
Chromatography
Authors: Paull Brett 
Published: August 2008

Abstract

Chromatography is a physical method of separation in which compounds are separated due to differences in their distribution between two phases, namely, a mobile phase and a stationary phase. In column chromatography, the stationary phase is immobilized within columns of various dimensions and the mobile phase, which can be either a gas or a liquid, carries the solute compounds through the stationary phase. The variety of instrumentation employed to carry out chromatographic separations are collectively termed
chromatographs
and all consist of a mobile phase delivery system, a sample/solute injection system, the chromatographic column itself, and a detector to monitor the separation over time and to record the separation in the form of a chromatogram.
Transducer Fundamentals
Authors: Regtien Paul P.L. 
Published: August 2008

Abstract
Transducers (sensors, actuators) are based on physical effects, allowing the conversion of energy (signals) from one domain to another. Most important for measurement instruments are input transducers (or sensors). Their function is the conversion of information about a particular (physical) quantity into an electrical quantity, with preservation of the information as a major issue. This section describes general properties of transducers, with emphasis on nomenclature, structure, physical basis, and performance specification.
Systematic Description of Sensors
Authors: Regtien Paul P.L. 
Published: August 2008

Abstract
There are an overwhelming number of sensors available, for almost every quantity that has to be measured, based on many different physical principles, in a wide variety of shapes and sizes, and for all kinds of applications and conditions. To find a way through this sensor jungle, a clear and systematic description of sensors would be very helpful. This article presents a description following a systematic approach. Such a systematic presentation may help designers and users of sensors to get a clear overview of the major sensor concepts, to obtain a better understanding of their basic operation and performance, and to facilitate sensor selection.
Ultrasonic Sensors
Authors: Lesniewski Peter J. 
Published: August 2008

Abstract

The detailed description of piezoelectric sensor technology presented here includes tensor wave formulation and transduction relations, review of sensor material properties, technologies and measurement principles such as resonant, and delay time. Also provided is information on alternative sensing methods and the main shortcomings of typical sensors. Refer to
Ultrasonic Instrumentation Principles
and
Ultrasonic Instrumentation Design
for application detail.
Signals in the Presence of Noise
Authors: Burdett Richard 
Published: August 2008

Abstract
A measurement system begins with sensing stages that couple to relevant measurands of the system under study. The power level of the wanted information‐bearing signals formed by the sensors is often very low and may be swamped by the interfering noise signals that are present. Careful attention to sensor and circuit design and assembly, plus use of certain signal processing methods, makes it possible to greatly enhance the original signal‐to‐noise ratio to usable levels. This first article of the group on signal‐to‐noise improvement introduces the issues involved that are developed in later articles of this section.
Outline of Purpose of Analog Data Filters
Authors: McGhee Joseph 
Published: August 2008

Abstract
Active analog data filters are outlined in this block, commencing with a description of the role of active signal filters. A description of the signal parameters to be selected and the interference effects to be filtered out is given. Active filter types are classified and their applications are briefly described. A comparison between active analog and digital filters is given. Active filter design methodology is described and some suppliers of universal active analog filter modules are given.
Z‐Transforms
Authors: Bousbaine Amar 
Published: August 2008

Abstract

The z‐transform plays a major role in engineering practice. It is used to study the system characteristics and the derivation of the computational structures for implementing discrete time systems on computers. The most important aspects of the z‐transform are presented, that is, characteristics of signals in terms of their pole‐zero diagram, ROC, causality and stability, and impulse response. More importantly, applications of the z‐transform in signal processing are discussed, which covers the computation of the frequency response, and the stability of the discrete time systems. Detailed applications of the z‐transform are covered in (
General Performance of the Digital Filter
;
Low‐, High‐, and Band‐pass Digital Filters
;
Finite Infinite Impulse Response (IIR) Digital Filters
; and
Finite Impulse Response (FIR) Digital Filters
).