bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth stimulation and chemotropic attraction of rat retinal ganglion cell axons in vitro by co‐cultured optic nerves, astrocytes and astrocyte conditioned medium
Authors: Lucius Ralph , Young Hans Peter , Tidow Susanne , Sievers Jobst
Published: January 2005

The effects of explants of optic nerves of different ontogenetic ages (P0‐P14, adult), and of cultured astrocytes of various ages on the neurite regeneration of rat retinal ganglion cells (RGC) were assessed in vitro, using a three‐dimensional culture system which allows the co‐cultivation of various explants. Both co‐cultured P0‐P12 optic nerves and astrocyte cultures from P2 cerebral cortex stimulated the regeneration of neurites from the retinal explants after 3 days in culture. By contrast, P14 and older explants of the optic nerve, astrocytes from P17 optic nerve and astrocytes that had previously been grown in culture for more than 6 weeks had no effect on RGC neurite outgrowth. Moreover, both the P0–P12 optic nerve explants and the astrocytes from P2 cerebral cortex also seemed to have a chemotropic effect on the regenerating neurites, because the latter were longer on the side facing the co‐explantat. The absence of a cellular bridge between retinal and optic nerve explants suggests that the effects are mediated by astroglia‐derived diffusible neurite growth promoting factors. Accordingly, astrocyte‐conditioned medium from P2 astrocytes also stimulated the outgrowth of neurites from the retinal explants. These findings show that immature astrocytes of a limited ontogenetic period release as yet unknown diffusible neurite growth‐promoting factors which stimulate the regeneration of neurites from retinal explants.
Chronic heart failure is associated with vascular remodeling of the brachial artery
Authors: Poelzl Gerhard , Frick Matthias , Huegel Heike , Lackner Benedikt , Alber Hannes F. , Mair Johannes , Herold Manfred , Schwarzacher Severin , Pachinger Otmar , Weidinger Franz
Published: January 2005

Aims:

Endothelial dysfunction has been shown to correlate with severity of congestive heart failure (CHF) and recent data suggest morphological changes of peripheral vasculature to be associated with the syndrome. We therefore investigated the hypothesis that vascular remodeling is associated with functional changes in peripheral conduit arteries and with systemic overexpression of ET‐1 in patients suffering from CHF.

Methods and results:

57 consecutive patients referred to the Innsbruck Heart Failure and Transplantation Program (EF=23±7%) and 16 matched controls (EF=60±5%) were studied. Flow‐mediated vasodilation (FMD), nitroglycerin‐mediated vasodilation (NMD), wall thickness (WT), and incremental elastic modulus (Einc) were assessed by high‐resolution ultrasound of the brachial artery. FMD (P=0.004) and NMD (P=0.02) were significantly higher in controls as compared to moderate and severe CHF patients. In contrast, brachial artery‐wall thickness (BA‐WT) was increased in severe CHF patients (P=0.038). BA‐WT was significantly correlated with both FMD (r=−0.28; P=0.049) and NMD (r=−0.38; P=0.003), and with the Einc (r=0.45, P=0.001). Lumen diameter was not different among groups. In patients with BA‐WT>0.31 mm, bigET‐1 was higher compared to BA‐WT<0.31 mm (P<0.05).

Conclusion:

CHF is associated with remodeling of the brachial artery, which is characterized by morphological, mechanical and functional changes of the vessel wall. Endothelin‐1 may play a role in the vascular remodeling process.
Extracellular copper ions regulate cellular prion protein (PrPC) expression and metabolism in neuronal cells
Authors: Toni Mattia , Massimino Maria Lina , Griffoni Cristiana , Salvato Benedetto , Tomasi Vittorio , Spisni Enzo
Published: January 2005

The physiological functions of cellular prion protein (PrPC) remain unclear. It has been demonstrated that PrPC is a copper binding protein and proposed that its functions could be strictly linked to copper metabolism and neuroprotection. The aim of this study was to clarify how extracellular copper modifies PrPC expression and metabolism in cultured neurones. We reported here that copper delivered at physiological concentrations significantly decreases PrPC mRNA expression in GN11 neurones. Moreover, copper increases the release of PrPC into the culture medium. These results indicate that extracellular copper strongly affects the amount of cellular PrP and might represent an interesting strategy to decrease the expression of PrPC in neurones and its conversion in the pathological isoform PrPSc.
Cortactin phosphorylation as a switch for actin cytoskeletal network and cell dynamics control
Authors: Lua Bee Leng , Low Boon Chuan
Published: January 2005

Cortactin is an important molecular scaffold for actin assembly and organization. Novel mechanistic functions of cortactin have emerged with more interacting partners identified, revealing its multifaceted roles in regulating actin cytoskeletal networks that are necessary for endocytosis, cell migration and invasion, adhesion, synaptic organization and cell morphogenesis. These processes are mediated by its multi‐domains binding to F‐actin and Arp2/3 complex and various SH3 targets. Furthermore, its role in actin remodeling is subjected to regulation by tyrosine and serine/threonine kinases. Elucidating the mechanisms underlying cortactin phosphorylation and its functional consequences would provide new insights to various aspects of cell dynamics control.
A comparison of CAT Doppler and oscillometric Memoprint machines for non-invasive blood pressure measurement in conscious cats
Authors: Jepson Rosanne E. , Hartley Vivien , Mendl Michael , Caney Sarah ME , Gould David J
Published: January 2005

Indirect blood pressure measurements were compared in 28 conscious cats using Doppler and oscillometric blood pressure-measuring devices. Ten cats were used to compare Doppler measurements between two examiners and 18 cats were used to compare Doppler and oscillometric measurements. The Doppler machine obtained systolic and diastolic blood pressure readings in 100% and 51% of attempts, respectively. With the oscillometric machine, systolic and diastolic blood pressure readings were obtained in 52% of the attempts. With the Doppler, measures of mean systolic blood pressure between two examiners were positively correlated, but there was no correlation for diastolic blood pressure measures. When comparing the results obtained by Doppler and oscillometric machines there was no significant difference between mean systolic blood pressure readings, but the oscillometric machine produced significantly higher estimates of diastolic blood pressure. In both cases, the standard deviations for the oscillometric machine were considerably larger than those for the Doppler machine. The first reading of systolic blood pressure obtained with the Doppler machine was an excellent predictor of the mean of five readings, but this was not so for the oscillometric machine. It took less than 5 min to obtain five readings in 37.5% of cases with the Doppler machine but this was true for only 5% of cases with the oscillometric machine. Two cats with ophthalmological lesions consistent with systemic hypertension were identified. In these two patients, systolic blood pressure measurements were between 200 and 225 mmHg when measured by Doppler, and between 140 and 150 mmHg when measured by the oscillometric machine. This suggests that a lower reference range for normal systolic blood pressure values should be used for the oscillometric device.
Traditional forest protection and woodlots in the coastal savannah of Ghana
Authors: CAMPBELL MICHAEL O'NEAL
Published: January 2005

There is increased international interest in religiously based restrictions on land and forest stand use. However, the extent to which so-called sacred groves represent earlier forest ecosystems, and their possible role in biodiversity conservation, are interrelated and complex issues, and neglected in the context of Ghanaian savannahs, which are believed to be in transition from a forested past. Geographical information system (GIS) analysis of time-series images, aerial photographs, statistical analysis of ecological field data and social surveys were used to investigate the Ghanaian savannah. Sacred groves were found to be similar in plant species content and structure to the deciduous forest of southern Ghana. Between 1960 and 1996, these groves experienced far fewer forest losses than unprotected tree stands (<20%, as opposed to up to 100%). Non-sacred groves also contained lower plant species richness and higher numbers of invasive species such as neem (Azadirachta indica A. Juss). Sacred groves, while dependent on respect for religion, local cultural structures and individual peer pressure, offer a role that may support and also be supported by official conservation efforts.
Amphibians and reptiles in tropical rainforest fragments on Negros Island, the Philippines
Authors: ALCALA E.L. , ALCALA A.C. , DOLINO C.N.
Published: January 2005

To elucidate effects of fragmentation and degradation of tropical rainforest on Negros Island (Philippines) on tropical herpetofauna, nine tropical rainforest fragments (eight limestone and one non-limestone), ranging in area from five to 122 ha (total area = 352 ha) in south-western Negros were surveyed using cruising and quadrat sampling methods, between December 2001 and October 2002. A 14-ha limestone plantation forest served as a reference site. Ten to fifteen of the total 61 species (16.4–24.6%) expected in the nine forest fragments (taken as a whole) had been lost in the previous 50 years. These species are known to occur in the tropical rainforest on Cuernos de Negros and environs in south-eastern Negros Island at altitudes <500 m above sea level. The factors responsible for the loss of these species appear to be (1) removal of large trees, which decreases canopy cover causing physical changes; and (2) forest fragmentation, which increases the edge areas. However, it is not possible to separate the effects of each of these two factors. The main factor that was correlated with the number of species in the limestone forest fragments appeared to be area. Two species of frogs appeared to be represented by relatively moderate population densities: the Negros cave frog (Platymantis spelaeus) and the common forest frog (Platymantis dorsalis). The burrowing skink (Brachymeles boulengeri taylori) also exhibited a relatively higher density than the other burrowing species of skinks. The other herpetofaunal species exhibited low population densities.
Archaeology, biology and conservation on islands in the Gulf of California
Authors: BOWEN THOMAS
Published: January 2005

Urgent threats to the Gulf of California ecosystem from modern human activity obscure the fact that humans have interacted with native plants and animals for millennia. Archaeological and historical evidence suggests that indigenous peoples occupied both sides of the Gulf some 13 000 calendar years ago and that they eventually inhabited six major islands and visited most smaller ones. Biologists have increasingly realized that these peoples probably played a role in shaping island biotic communities extant today. How much of a role is unknown, but the best places to find evidence may be archaeological sites, which often contain remains of plants and animals directly used by prehistoric peoples. The opportunity to investigate the interaction between early humans and island biota may be lost because modern island visitors endanger sites. Many people, whether boaters, ecotourists, government officials, scientists or artefact collectors, enjoy picking up artefacts. Small surface sites, with exposed remains, can be completely denuded in minutes. Visitors to small islands can obliterate entire archaeological records, thereby creating the illusion of pristine islands. This problem is bound to worsen as Mexico implements Escalera Náutica, a chain of marinas specifically intended to multiply manyfold the boating population. The Mexican government's management plan for Gulf islands, published in 2000, recognizes only a general need to manage cultural resources. Specific mechanisms for protecting sites should be developed. These should educate visitors about the importance of the archaeological record and the destructiveness of collecting. They should also provide adequate enforcement of Mexico's existing antiquities laws. Conserving the archaeological resources may be the best way of preserving biological data essential to island biogeographers and ecologists.
How useful are urban island ecosystems for defining invader patterns?
Authors: CLERGEAU PHILIPPE , CROCI SOLÈNE , JOKIMÄKI JUKKA
Published: January 2005

Biological invasions are pervasive, alter ecosystem sustainability, and can reduce native biological diversity (Vitousek et al. 1996). Ecologists are scrambling to predict where and when new invaders may strike (Lodge 1993; Fagan et al. 2002). Urbanization has created a number of new ecological niches which, after remaining empty for some time, are increasingly being colonized or invaded by vertebrates (Erz 1966). One of the major disputes in evolutionary biology concerns the rate at which species evolve to occupy new niches (Diamond 1986). How quickly are animals adapting to these new habitats and what makes them successful colonists?
Livelihood gains and ecological costs of non-timber forest product dependence: assessing the roles of dependence, ecological knowledge and market structure in three contrasting human and ecological settings in south India
Authors: SHAANKER R. UMA , GANESHAIAH K.N. , KRISHNAN SMITHA , RAMYA R. , MEERA C. , ARAVIND N.A. , KUMAR ARVIND , RAO DINESH , VANARAJ G. , RAMACHANDRA J. , GAUTHIER REMI , GHAZOUL JABOURY , POOLE NIGEL , REDDY B.V. CHINNAPPA
Published: January 2005

Non-timber forest products (NTFPs) constitute the single largest determinant of livelihoods for scores of forest fringe communities and poor people in the tropics. In India over 50 million people are believed to be directly dependent upon NTFPs for their subsistence. However, such human dependence on NTFPs for livelihood gains (win) has most frequently been at a certain ecological cost (lose). If livelihoods are to be maintained, the existing ‘win-lose’ settings have to be steered to a ‘win-win’ mode, otherwise, there could be severe erosion of the biological resources and loss of livelihoods (‘lose-lose’). Examining the dependence of forest fringe communities on NTFPs at three sites in south India with contrasting human and ecological settings, three key factors (extent of dependence on NTFPs, indigenous ecological knowledge and market organization) are likely to constrain reaching the win-win situation. How these factors shape the ecological cost of harvesting NTFPs at the three sites is examined. Within the parameter space of these factors, it is possible to predict outcomes and associations that will conform to win-win or win-lose situations. Empirical data derived from the three study sites demonstrate the causality of the observed associations. The key for long-term livelihood gains lies in reducing the ecological cost. Certain interventions and recommendations that could optimize the balance between livelihood gains and ecological cost are proposed.
Propagation of the October/November 2003 CMEs through the heliosphere
Authors: Richardson J. D. , Wang C. , Kasper J. C. , Liu Y.
Published: January 2005

The solar storms of late October, early November 2003 generated many ICMEs. The Wind, ACE, Ulysses, Cassini, Voyager 2, and Voyager 1 spacecraft are distributed throughout the heliosphere and observe the effects of these ICMEs. We investigate whether these ICMEs form a global merged interaction region. WIND, ACE, and IMP 8 data are combined to produce a plasma and magnetic field data set for these solar events at 1 AU. We use this data set as input to a 1‐D MHD model, propagate the solar wind outward, and then compare our predictions with observations. The arrival times of ICMEs at Ulysses, Cassini, and Voyager 2 are consistent with the outward motion of a shell of ICME material; Voyager 1, however, sees no evidence of these ICMEs. These results are consistent with the creation of a large, but not complete, shell of outward‐moving material and suggest true GMIRs are rare.
Surface bidirectional reflectance and albedo properties derived using a land cover–based approach with Moderate Resolution Imaging Spectroradiometer observations
Authors: Luo Yi , Trishchenko Alexander P. , Latifovic Rasim , Li Zhanqing
Published: January 2005

Surface bidirectional reflectance distribution function (BRDF) and albedo maps are derived from Moderate Resolution Imaging Spectroradiometer (MODIS) multiday surface reflectance composites with a 500‐m spatial resolution (MODIS product MOD09A1/MYD09A1). The proposed method dubbed land cover–based fitting employs the processing of clear‐sky reflectance data for similar land cover types and takes into account the magnitude of normalized difference vegetation index (NDVI). The BRDF is derived through the fitting of pixel data sorted into small bins according to the values of angular variables and NDVI. Robust statistical processing is applied to reduce the influence of noise and outliers. This method increases the success rate of the fitting process and enables more accurate monitoring of surface temporal changes during periods of rapid spring vegetation green up and autumn leaf fall, as well as changes due to agricultural practices and snow cover variations. The approach is specifically applied over the Atmospheric Radiation Measurement Program Southern Great Plains area. Results are compared to alternative BRDF/albedo products, such as the MOD43 albedo and Multiangle Imaging Spectroradiometer surface products that are derived through a pixel‐based fitting process. A good agreement was generally found between different data sets. For example, the average biases in the visible and near‐infrared bands are usually less than 0.01 and 0.02, respectively, and correlation coefficients are typically larger than 0.80. An analysis of these differences identifies some unique advantages of the proposed method, such as the ability to capture rapidly changing surface properties and an increased performance in the case of reduced number of clear‐sky observations because of frequent cloudy conditions. Results suggest that the developed land cover–based methodology is valuable for the purpose of surface BRDF and albedo mapping using MODIS observations.
HF propagation in a wideband ionospheric fluctuating reflection channel: Physically based software simulator of the channel
Authors: Gherm V. E. , Zernov N. N. , Strangeways H. J.
Published: January 2005

A wideband HF simulator has been constructed on the basis of a detailed physical model of propagation which can generate a time realization of the HF wideband channel for any HF carrier frequency, bandwidth, transmitter receiver path and background, and stochastic (irregularity) ionosphere models. To accomplish this, a comprehensive solution has been obtained on the basis of the complex phase method (Rytov's method) to the problem of HF wave propagation for the most general case of a three‐dimensional (3‐D) inhomogeneous ionosphere with time‐varying electron density fluctuations. A simulation is presented for a 1000 km path for which E and low‐ and high‐angle F mode paths exist. The time‐varying field owing to each of these paths is summed at the receiving location, enabling the calculation of the scattering function and also the time realization of the received signal shown as a function of both fast and slow time.
The Structural Characteristics of Certain Silver Films
Authors: Essig Sanford F.
Published: January 2005

The structural characteristics of three types of silver films which have found general use as photocathode bases in television image analyzers and similar electronic devices are discussed. They are classified as mosaics and translucent films. Two types of mosaics are discussed, (1) the reduced oxide dust film, and (2) the agglomerated sputtered or evaporated film. A characteristic of the first is a wide range in particle size (<1−30μ in films photographed), those below 3 microns being greatest in number. A critical temperature, approx. 600°C, is observed in reduction of the oxide films above which there is a distinct liquid phase in the silver-silver oxide system resulting in a radical change in the final film structure.

The process of agglomeration is traced from the continuous through the mosaic state in the second type film. The characteristics are a smaller and more uniform particle size than the reduced oxide type. Particle size and spacing is readily controlled and reproduced. The range in initial thickness of films investigated is approximately 0.01−0.2 microns.

The third type or translucent film is a composite consisting of a silver mosaic superposed on an electrically conducting film of relatively high light transmission. Platinum is chosen as the most suitable metal for this subfilm and is protected from destructive forces such as oxidation and alloying with the silver mosaic by an intermediate film of silica or aluminum oxide.
Electrical and Luminescent Properties of Phosphors Under Electron Bombardment
Authors: Nottingham Wayne B.
Published: January 2005

A tube using a cathode-ray type of electron gun has been used to study the properties of five phosphor samples using four different materials. These were (1) zinc-orthosilicate (2) calcium-tungstate (3) zinc-sulfide: cadmium-sulfide and (4) zinc-sulfide. The first three showed saturation effects with current density definitely greater than the last, and the first two have maximum potentials as limited by secondary emission of 6500 and 5000 volts respectively. For these, the light output per unit electron current increased with the square of the voltage, while it increased with the 2.8 power of the voltage for the zinc-sulfide. A simple power law does not hold for the zinc-sulfide: cadmium-sulfide which shows a maximum light output at 8000 volts. All of the sulfides had such good secondary emission properties that the maximum limiting potential was well above 10,000 volts.
X-Ray Study of Menthol
Authors: Sidhu S. S.
Published: January 2005

The stable α-form of menthol crystallizes in the hexagonal form with an axial ratio of 1.635; a0=11.82±0.02A; number of molecules per unit cell is eight and the calculated specific gravity is 0.885. The diffraction data presented here should be useful in the study of inversion phenomena in menthol by x-ray methods.
The Filtration of Sound. II.
Authors: Lindsay R. B.
Published: January 2005

In this second article on the Filtration of Sound, Professor Lindsay describes particularly filtration in solid media. It contains also a survey of recent developments.
Electrolytic Polishing
Authors: Elmore W. C.
Published: January 2005

An investigation of the electrolytic polishing of copper by the Jacquet method has thrown new light on the mechanism responsible for the polishing action. From a study of the voltage-current curves it is concluded that when conditions are right for polishing the concentration of dissolved copper at the anode is the highest possible. Accordingly the concentration gradient which exists at the anode limits the rate at which copper can dissolve,i.e., diffuse into the bulk of the electrolyte (orthophosphoric acid). Since there is greater diffusion from raised areas of the anode because of steeper concentration gradients near them, the surface will become progressively more nearly level. The surface does not etch for the concentration gradient alone controls the rate of solution. Details are given for the electrolytic polishing of iron with an orthophosphoric acid electrolyte. A convenient form of cell for electrolytic polishing is described.
The Temperature of High Pressure Arcs
Authors: Suits C. G.
Published: January 2005

From measured values of arc gradient E (v cm−1) and current density I (amp. cm−2) the arc temperature is calculated for nitrogen in the pressure range 1–30 atmospheres and current range 1–10 amperes, and in hydrogen at one atmosphere pressure for the current range 1–10 amperes.
Matrix Theory of Oscillatory Networks
Authors: Pipes Louis A.
Published: January 2005

Starting with the energy functions of a general, linear, bilateral, resistanceless, lumped network the canonical equations of the circuit are obtained. These equations are solved in a general form taking into account applied electromotive forces and initial charges and currents by a matrix multiplication process. It is shown how the matrix multiplication process replaces the usual ``frequency equation'' which determines the normal modes of the system. Initial charges and currents in the various component parts of the network are considered for generality. The method given appears to have some computational advantages in certain classes of problems over the method of the ``Heaviside calculus.'' The discussion is concluded with a discussion of normal coordinates and an illustrative numerical example is given. Since oscillatory networks are used extensively in communication engineering it is hoped that the present discussion will be of value. Since, if the circuit has a small amount of resistance present it may be shown that periods of oscillation are affected only by the squares of small quantities, it is seen that the method given is applicable to many technical problems. A method is given by which the attenuation due to the presence of small resistances in the system may be readily calculated.
Piezoelectric Versus Mechanical Spring Pressure Gauge
Authors: Webster R. Alden
Published: January 2005

That difficulties in the use of various types of pressure gauges warrant meticulous scrutiny in the rendering of an accurate pressure-time curve has advanced each type of gauge for particular work. In powder gas and internal combustion engine gas pressures the spring type and piezoelectric type offer great possibilities with the first a self-contained unit and the latter a charge-collecting device, and with the former following the true curve by an admitted time lag and the latter assumed to be responding instantaneously. Sparse comparative records of the two show the case to be more nearly the reverse of what the popular assumption leads one to believe. Fuller data are needed to determine the comparative lagging characteristics of both types.
Light Output and Secondary Emission Characteristics of Luminescent Materials
Authors: Martin S. T. , Headrick L. B.
Published: January 2005

Light output and screen potential data are given for zinc sulphide, calcium tungstate, willemite and several other silicate phosphors sprayed (from suspension) on Nonex glass and bombarded by electrons. The bombarding voltage range from 0.5 to 10 kilovolts is covered. The limiting potentials of willemite and other zinc silicate screens fall in the range from 6 to more than 10 kilovolts depending on the conditions of exhaust and preparation. The limiting potentials of two zinc sulphides fall in the range from 6 to 9 kilovolts while calcium tungstate has a limiting potential usually less than 5 kilovolts. Light output as a function of screen voltage over the range from 0.5 to 10 kilovolts is shown to follow a law of the form: L=Af(i)Vn,where L is intensity of light, i is current density, V is electron energy at the screen in kilovolts, and A is a constant. The data show that n<2 for willemite or other zinc silicates, n=2 for sulphides, and n>2 for calcium tungstate and a fused layer of willemite. Analysis and comparison of the light output current density characteristic and the persistence characteristic shows that a definite relation exists between them in the case of silicate phosphors. The function of current density may be represented by f(i)=Ai(1−(a/(a+b))e−α/Bi−(b/(a+b))e−γ/Bi). The constant α and γ are those appearing in the persistence characteristics of the material as: L=(a/(a+b))e−αt+(b/(a+b))e−γt,a formula which expresses well the persistence of silicate screens.
A High Frequency Oscillator and Amplifier
Authors: Varian Russell H. , Varian Sigurd F.
Published: January 2005

A d.c. stream of cathode rays of constant current and speed is sent through a pair of grids between which is an oscillating electric field, parallel to the stream and of such strength as to change the speeds of the cathode rays by appreciable but not too large fractions of their initial speed. After passing these grids the electrons with increased speeds begin to overtake those with decreased speeds ahead of them. This motion groups the electrons into bunches separated by relatively empty spaces. At any point beyond the grids, therefore, the cathode-ray current can be resolved into the original d.c. plus a nonsinusoidal a.c. A considerable fraction of its power can then be converted into power of high frequency oscillations by running the stream through a second pair of grids between which is an a.c. electric field such as to take energy away from the electrons in the bunches. These two a.c. fields are best obtained by making the grids form parts of the surfaces of resonators of the type described in this Journal by Hansen.
Studies in Lubrication IV. The Experimental Variation of the Coefficient of Friction with the Strength of the Lubricant Source for a Complete Journal Bearing
Authors: Morgan F. , Muskat M.
Published: January 2005

The experimental study of the lubrication of a complete journal bearing has been extended, emphasis being placed upon the role played by the position and strength of the lubricant source upon the coefficient of friction. As predicted theoretically, the friction on the bearing has been found to increase with increasing source strength and to be somewhat higher when the source is at the crown than when at the base (region of highest load) of the bearing. It has also been found that when the source is at the base, where it aids the journal rotation effects in supporting the load, the bearing may be successfully operated at much lower speeds and higher loads than when it is at the crown without encountering the usual thin film phenomena. Moreover, for this case, there exists a critical value of the source strength at which the journal and bearing are concentric and the coefficient of friction is given by the simple Petroff theory. The experimental results confirm qualitatively all the predictions of the hydrodynamic theory previously developed. Quantitatively, experiment and theory also agree for small values of the source strength and high values of the Sommerfeld variable, and especially when the source is at the base of the bearing, the discrepancies becoming marked in regions where the approximations of the theory are inherently inadequate.
Luminescence During Intermittent Electron Bombardment
Authors: Nelson R. B. , Johnson R. P. , Nottingham W. B.
Published: January 2005

The dynamic luminescence characteristics of five samples of commercial phosphors excited intermittently by electron bombardment have been studied. The decay of artificial willemite follows closely a simple exponential law, except for a rapid fall during the first three milliseconds after bombardment, the prominence of this component increasing with the current density. An attempt is made to correlate the observed dependence of build-up rate on current density with the phenomenon of current-saturation under continuous bombardment. A sample of calcium tungstate follows changes in the intensity of excitation within 100 microseconds, the resolving time of the apparatus. Two samples of ZnS·Ag and one sample of ZnS·CdS·Ag decay more rapidly the higher the intensity of excitation. The initial rate for ZnS·Ag is greater than would be predicted for a simple bimolecular reaction, and cannot plausibly be explained by non-uniformity in the initial distribution of reactants in a bimolecular reaction. The ZnS·CdS·Ag decays initially according to a simple bimolecular law.
Dielectric Resonators
Authors: Richtmyer R. D.
Published: January 2005

We show that suitably shaped objects made of a dielectric material can function as electrical resonators for high frequency oscillations. We develop the theory of such resonators very briefly and compute their resonant frequencies and losses in some very simple cases. The paper concludes with an observation on the behavior of dielectric wave guides.
Ionic Mobility in Solid Dielectrics
Authors: Gemant Andrew
Published: January 2005

1. It is assumed that ionic mobility in solid dielectrics is controlled by a combined resistance of viscosity, elasticity and solid friction.

2. Under this assumption ionic mobility under alternating electric stress is calculated. It appears from the formulae that there is a finite contribution due to ions toward both the dielectric constant and loss factor. In the range of technical and acoustical frequencies both are in first approximation independent of frequency. The loss factor, controlled by the solid friction, is equivalent to an a.c. conductivity several orders higher than the d.c. conductivity, as known from observation.

3. Applying the same conception to ionic mobility in a constant field of high intensity, it appears that ions cover only part of their travel by a viscous flow, a small fraction being due to elastic displacements. This latter increases with the field strength. The energy stored during this displacement is finally converted into vibratory kinetic energy of the ion, thus enabling it to accumulate energy and finally ionize. The theory shows that this process becomes appreciable at a field strength between 104 and 105 v/cm in agreement with observations on the increase with field strength of the conductivity.
Electron Diffraction Study of Copper Oxides
Authors: Dunholter H. , Kersten H.
Published: January 2005

This paper describes an electron diffraction study of copper oxides formed from evaporated copper by exposing it in an oxygen atmosphere at various temperatures for various lengths of time. It also discusses several of the orientations which were observed in the evaporated copper.
An X-Ray Investigation of Crystallinity in Rubber
Authors: Gehman S. D. , Field J. E.
Published: January 2005

X-ray diffraction evidence has shown that a crystalline structure can be produced in rubber by stretching or by freezing. In the former case, a fiber diagram is generally secured, in the latter, Debye-Scherrer rings. When raw rubber was stretched to moderate elongations and frozen an intense fiber diagram was found, showing that the crystallization proceeded from nuclei set up by the stretching. A series of diffraction patterns illustrating the effect are reproduced. The geometrical conditions of stretching under which ``higher orientation'' occurs in stretched rubber were studied by photometric measurements of the relative densities of the first two equatorial spots. Graphs are included demonstrating the effect of variations in gauge, width, length and elongation of the specimens. Higher orientation occurs when the percent contraction in gauge exceeds the percent contraction in width. The different physical structures of vulcanized pure gum stocks became apparent in the ``higher orientation'' characteristics, although the same diffraction pattern was secured. A correlation of the results with current views on the micellar or secondary structure of rubber and the crystallization of supercooled liquids is attempted.
The Thermal Distribution and Temperature Gradient in the Arc Welding of Oil Well Casing
Authors: Bruce W. A.
Published: January 2005

The problem studied here is the thermal distribution due to a number of moving heat sources. It is assumed that the pipe is a circular cylinder and that the welders move on a circle of the cylinder. The Kelvin method for determining the thermal distribution about a stationary source of heat is extended to a case in which the source of heat is moving with a constant velocity. By integration of the effect of stationary sources the general effect of a moving welder is obtained. It is shown that an infinite plate with an infinite number of sources on a line and w cm apart is equivalent to an infinite cylindrical shell with n = c/w sources spaced w cm apart around the cylinder (c = circumference). With the aid of this and Kelvin's solution it is possible to build a complete general solution of the problem. This method of constructing the solution of a heat problem has many practical applications—such as the determination of thermal distributions in the welding of plates, seamed pipe and other bounded objects.
Convection and Conduction of Heat in Gases
Authors: Brody I. , Kőrösy F.
Published: January 2005

The diameter of the ``Langmuir film'' (b) around warm filaments in gases was at first determined by Langmuir's own method in A, Kr and N2. The calculated film thickness beside a plane surface is 3.3 mm, 1.4 mm and 4.3 mm, respectively. The said diameter was then redefined as the distance of thermal interaction between two similar, warm filaments; temperature measurements revealed that this conventional definition corresponds to the 90°C isothermals. b is a linear function of the temperature; bt = b1000[1+(t−1000) ·0,000255] and b1000 decreases with increasing molecular weight of the gases. b decreases with increasing gas pressure: b/b1= (p1/p)0.42 and it increases somewhat slower with the diameter of the filament (a) than would correspond to the equation of Langmuir: 2B = b · ln b/a. The detailed temperature field around warm filaments was determined under varied conditions. Evidence was gathered, that although 90 percent of the wattage lost can be accounted for by assuming pure conduction, the gas is definitely moving upwards within the film as well as outside of it.
Beam Tubes as Ultra-High Frequency Generators
Authors: King Ronold
Published: January 2005

The operation of beam power tubes in regenerative ultra-high frequency oscillators is investigated experimentally. Wave-length characteristics of oscillating 6Y6-G and 6V6-G tubes are displayed and compared with a corresponding curve for a type 56 triode. Wave-lengths as low as 150 cm were obtained. Current and wave-length characteristics of the oscillating 6Y6-G are given as functions of plate, screen and control grid voltages. The efficiency of the generator is investigated near its lowest wave-length limit. Means for preventing oscillation in amplifier circuits using beam tubes are suggested.
Some Properties of the Hydrogen Arc
Authors: Suits C. G.
Published: January 2005

The gradient E, total voltage e, and current density I in the one-atmosphere hydrogen arc between pure carbon electrodes in the 0–10-ampere range are measured by an oscillographic method. An abrupt change in e takes place at 2 and 0.6 ampere, and in E at 2 amperes, leading to the identification of three states of the hydrogen discharge in this current range and pressure. Rapid motion pictures of this arc at pressures above atmospheric show violent arc movements originating from convection forces. The exponent of the E-i relation is found to be 0.70 for the normal arc state at p = 1 atmos.
The Magnetostrictive Oscillation of Quartz Plates
Authors: Colwell R. C. , Hill L. R.
Published: January 2005

Small quartz plates were vibrated by mechanical impact from magnetostrictive rods cut to the proper lengths. Sand scattered on the plates gathered at the nodal lines and produced figures similar to those on Chladni plates. The quartz plates were then vibrated in an electrical field produced by the same vacuum tube circuit which was used to vibrate the magnetostrictive rods. Electrical and mechanical vibrations gave exactly similar patterns on each crystal provided the frequencies were identical.
Electrical and Luminescent Properties of Willemite Under Electron Bombardment
Authors: Nottingham W. B.
Published: January 2005

An insulated surface uniformly bombarded with electrons of a given energy attains a potential relative to other elements in a high vacuum tube such that exactly as many electrons leave the surface by secondary emission as there are primary electrons arriving. A tube and circuit have been constructed for determining accurately this potential for willemite surfaces while being bombarded by electrons of energy range up to 10,000 volts. It was found that the surface potential was only slightly negative with respect to the most positive anode of the tube over the lower range of energy but finally reached an upper limit of potential relative to the cathode usually between 6000 and 7000 volts. The resistance between wires covered by the willemite was found to be independent of the bombarding current and voltage except in so far as this bombardment changed the temperature of the material. A special potassium phototube is described which was used to determine the light output from the bombarded surface as a function of the current density and the electron energy. The light was found to be accurately proportional to the current for densities below 2.5×10−6 amp. per sq. cm but above this a saturation effect set in quite gradually so that with a current of 20×10−6 amp. per sq. cm the light output was only 65 percent of the value which it would have been had the light intensity per unit current density remained constant. The light output for a constant current was found to increase with (V – V0)2 where V0 is the ``dead voltage'' when the bombarding energy was less than that required to penetrate through the individual grains of the willemite. An experimental nine-inch cathode-ray tube was also studied for screen potential and light output as a function of current density and anode voltage. The difference in potential between the screen and the anode was again small for the lower range in voltage but with anode voltages above 7000 volts, the apparent screen potential depended on the current density so that a change of potential of the screen of as much as 1500 volts was observed as the current density was increased from one to ten milliamperes per sq. cm. The light output increased with the square of the bombarding potential up to 1500 volts but above this it increased with the 1.2 power of the voltage. The light output per unit current density observed at 10−2 amp. per sq. cm was only two percent of that observed at 10−6 amp. per sq. cm on account of the severe ``saturation'' effect found at high current densities.
Some Physical and Radiographic Properties of Metallic Intensifying Screens
Authors: Seemann Herman E.
Published: January 2005

The photographic intensifying action of metal screens has been known for a number of years but it is only with the advent of high voltages and thick materials of industrial radiography that their use has become especially advantageous. Lead is the material now commonly employed. The present work is an attempt to extend our quantitative knowledge of this subject by studying the various phenomena separately. The higher atomic number elements are shown to be the most suitable for intensifying screens and of these lead provides the best combination of properties. The front screen is more effective in its intensification than the back screen. This is explained on the basis of present-day knowledge of electron emission under x-ray excitation. Most of the intensifying action seems to be due to the electrons emitted and only a small part to characteristic and scattered x-rays. The intensification factor increases with kilovoltage and filtration between 160 and 200 kv and from 0.6 to 2.5 cm of steel, but apparently with sufficient decrease in x-ray wave-length, the intensification of lead foil decreases, because it is much less in gamma-ray radiography. The effect on intensification of variation in thickness of lead screens is very slight but, for practical reasons, it is desirable to have the back screen fairly thick. The thickness of the front screen is determined largely by its reduction of secondary radiation and a value from 0.010 to 0.015 cm is satisfactory. The experiments indicate that, in the reduction of secondary radiation by lead screens, differential intensification of the primary and secondary radiation is of major importance. Differential absorption by the front screen is also a factor. Lead screens are of advantage in welding and casting inspection but one of their most striking properties is shown in the radiography of small objects that normally require masking in which masking may often be eliminated because of the characteristics of the lead screens. The screens should be kept clean, since light materials absorb the intensifying radiation considerably. Visually, definition with the lead screen is just as good as it is with a nonscreen exposure but intimate contact in the cassette is essential. There seems to be little hope of making important improvements in the radiographic properties of lead screen, as e.g., by the addition of a fluorescing surface layer.
The Effect of Pressure on the Modulus of Rigidity of Several Metals and Glasses
Authors: Birch Francis
Published: January 2005

The effect of pressure on the modulus of rigidity has been determined for five metals and two glasses, to 4000 kg/cm2, by a dynamical method. The corrections due to the viscous motion of the pressure medium are computed approximately and shown to be negligible. Absolute values of the dynamical Young's modulus and modulus of rigidity are also given, and the derived compressibilities compared with directly measured compressibilities.
Plastic Behavior of Metals in the Strain-Hardening Range. Part I
Authors: Nadai A.
Published: January 2005

The stress-strain relations for the cold working of the ductile metals are described for a group of cases assuming that the stresses under which they yield plastically depend only on the permanent parts of the strains, leaving out of the consideration the influence of the elasticity and of the speed of the plastic deformation. The behavior of the metals in the strain-hardening range is expressed by means of a strain-hardening function which connects the octahedral shearing stress with the octahedral unit shear. These variables are defined for strains of finite magnitude.
Dielectric Loss Measurements Parallel to Laminations
Authors: Albert Gerard A.
Published: January 2005

Laminated material is often used as insulation in an electrical device in such a way that a large component of the dielectric field passes through it parallel to its laminations. In present test methods dielectric loss measurements are made on such material with the dielectric field passing through it perpendicular to its lamination. It is evident that the two conditions are different and the dielectric losses as measured by test are not the same as exist when in use. This paper presents a test method by which power factor, dielectric constant and dielectric loss factor of laminated insulating materials can be measured with the dielectric field parallel to the laminations. Results of measurements made with the dielectric field parallel to laminations of both unconditioned and conditioned specimens are compared, respectively, with results obtained with the field perpendicular to laminations.
Transformations Useful in Certain Antenna Calculations
Authors: Hansen William W.
Published: January 2005

Transformation formulas are derived which greatly simplify computations relative to an antenna above a plane earth when the antenna is of a form easily specifiable in polar coordinates but not in cylindricals.