bluuebunny/crossref_metadata_2025 huggingface dataset:
Feedback control of one‐link flexible manipulator with gear train
Authors: Gorinevsky D. M. , Lensky A. V. , Sabitov E. I.
Published: July 2007

This article reports experimental results in control of a one‐link flexible manipulator. A d.c. drive with gear train rotates the link with a tip‐mass in the horizontal plane. A “stiff” hardware servo‐system tracks the commanded drive velocity. We describe the experimental setup and develop a dynamic model for the one‐mode flexible vibration control. We design and experimentally test controllers for active damping of the vibrations and stabilization of the link‐tip position. Results for continuous control implemented with an analog computer and a sampled‐data, digital‐computer control are reported. A high control performance is achieved despite the gear‐train friction influence. In addition, sampled‐data digital controllers for tracking control of the link reference motion are designed and tested.
NASA laboratory telerobotic manipulator control system architecture
Authors: Rowe J. C. , Butler P. L. , Glassell R. L. , Herndon J. N.
Published: July 2007

In support of the National Aeronautics and Space Administration (NASA) goals to increase the utilization of dexterous robotic systems in space, the Oak Ridge National Laboratory (ORNL) has developed the Laboratory Telerobotic Manipulator (LTM) system. It is a dexterous, dual‐arm, force‐reflecting teleoperator system with robotic features for NASA ground‐based research. This article describes the overall control system architecture, including both hardware and software. The control system is a distributed, modular, and hierarchical design with flexible expansion capabilities for future enhancements of both hardware and software.
Intermodulation in multiple fixed beam distributed amplifier phased array antenna systems
Authors: Johannsen K. G. , Hintze J.
Published: July 2007

In the recent development of phased array/distributed amplifier systems for application to mobile satellite or thin route communication systems, the intermodulation (IM) generated by the element amplifiers is spatially dispersed in such a way that some of the IM radiated energy falls outside the intended beam area. In addition, some of the IM falling inside the beam area has frequencies different from the carriers intended for that area.

It is known that for fixed beam systems with frequency reuse, an average IM noise reduction of several dB can be realized. In the specific case under investigation, of four beams, nine frequencies and 12 carriers (1‐33 frequency reuse factor), an IM improvement of about 2‐0 dB is realized. The improvement in carrier‐to‐IM‐noise ratio can be applied to increase system capacity, or for given capacity it can be used to reduce RF power amplifier back‐off, which can be translated into a reduction of spacecraft prime power requirement.

The considerable advantage gained from the multiple beam distributed amplifier approach makes it worthwhile to explore the workings of such a system and other benefits it may offer. One of the benefits is a common RF power pool for all carriers and beams, and the other is the spatial dispersion of intermodulation (IM). A satellite multiple beam pattern and the spatial dispersion of IM products are shown in Figure 1.
Carrier recovery and inter‐burst interference in a symbol‐synchronous tdma system
Authors: Harris R. A. , Yarwood M.
Published: July 2007

ESA is studying future communications satellite systems involving switching and processing on board the satellite. One concept uses a symbol‐synchronous MF‐TDMA system with very short data bursts. This paper investigates QPSK carrier phase estimation for coherent demodulation in such a system. The Viterbi and Viterbi algorithm is used to produce one phase estimate separately for each data burst. The algorithm and its properties are reviewed and computer simulation results are presented to show its performance. It offers excellent performance under the conditions planned for the MF‐TDMA system and is robust against distortions and interference.

One potential problem in such a system, with no interburst guard‐time and possible level differences between adjacent bursts, is interburst interference. It is found that clear‐weather level differences of several dB can be tolerated easily. Atmospheric attenuation of the wanted burst may result in major level differences between adjacent bursts, but the interburst interference itself does not increase with respect to the thermal noise environment and so does not contribute any new problems. Any requirement for power control, for instance, will be determined by considerations of noise rather than interference.

The burst timing accuracy in such a system is set by normal intersymbol interference considerations, rather than by the interburst interference or the needs of the phase estimator.
Error probability of m‐ary fsk with a limiter‐discriminator detector in satellite mobile channels
Authors: Korn I.
Published: July 2007

We derive formulae for the error probability of M‐ary frequency shift keying with a limiter‐discriminator detector in a satellite mobile channel, which includes as special cases the land mobile (Rayleigh) channel and the Gaussian channel. The received signal in this channel is composed of a specular signal, a diffuse signal and white Gaussian noise; hence the composite signal is fading with a Rician envelope. The error probability depends on the signal‐to‐noise ratio, the power ratio of the specular and diffuse components, the frequency deviation, the Doppler frequency, the maximum Doppler frequency, the time delay between diffuse and specular components, the autocorrelation of the diffuse component and the transfer function of the receive filter. Numerical results are presented as functions of the various parameters. Effects of the receive filter on the signal dependent components are neglected.
Global corporate communications with integrated services digital networks
Authors: Chan Conway , Eng Jim M.
Published: July 2007

This paper presents proposals and justification for standards governing the implementation of integrated service digital networks (ISDN). Using several programming protocols in a layered architecture provides continuing service during system evolution. The authors use a corporate communications environment for examples as the most probable initial implementation of the networks described. Some ISDN sites are operating, although not yet on a global scale, and present the building blocks for more advanced services in the near future. The authors present arguments supporting a concerted effort be started now to establish global standards for ISDN, so that design and development can comply in the most time‐effective manner.
Pereormance analysis of slotted ALOHA for land mobile satellite networks
Authors: Tan Harry H. , Hung Santiago V.
Published: July 2007

The ALOHA protocol has been proposed for accessing reservation channels in demand‐assigned channel access protocols for land mobile satellite communications networks. This paper provides a rigorous performance analysis of both the slotted ALOHA protocol and two‐packet replication ALOHA protocol taking into account the effects of the fading multipath communications environment. Throughput, delay and stability of these two protocols are determined using a Gilbert channel error model with memory. Comparison of slotted ALOHA and two‐packet replication ALOHA shows that a smaller average delay can be achieved by replication. Moreover average throughput is improved in some cases. However replication reduces stability.
A rural messaging network using spread ALOHA access with VSAT satellite terminals
Authors: Goel M. K. , Chandra Vinod
Published: July 2007

This paper underlines the characteristics of a proposed mesh network for messaging applications in C‐band using spread ALOHA protocol. A simulation program has been developed for studying the behaviour of large networks employing ALOHA access or its variants. It is a simulation for a large population network consisting of thin traffic small messaging terminals (SMTs), and models an infinite user population which employs fixed length data packets. The program is general and allows for the study of either the mesh or the star connected networks. Certain variations of the classical ALOHA schemes, such as slotted ALOHA (with user selectable slot length) and spread ALOHA, have been studied for network operation. In the case of spread ALOHA access, the program can be run with Barker, pseudorandom, Ping Fai Li or any other spreading sequence. The results of the simulation have confirmed the utility of spread ALOHA as an access protocol for MESCOMNET. It has identified an operating point on the throughput‐traffic curve at which spread advantage is available for power reduction of SMTs.
Land mobile satellite communication channel model for simultaneous transmission from A land mobile terminal via two separate satellites
Authors: Robet P. P. , Evans B. G. , Ekman A.
Published: July 2007

There are certain data services that could use transmit‐only land‐mobile satellite communication terminals. Such terminals would not be able to receive acknowledged messages and transmit them onward. Thus it is of interest to study alternative means of improving the system reliability. In this paper we propose the use of transmission to two satellites separated in azimuth and elevation in order to improve the reliability of throughput.

We have investigated the improvements by building upon the model proposed by Lutz for land mobile satellite communications via one satellite, and extended this using measurements of the shadowing coefficient in different areas (suburban, countryside and city) to two separated satellites. The measured data is used to produce an empirical model of the equivalent shadowing coefficient variations with the separation angle variation between two satellites.

The results show good agreement with the shadowing coefficients produced by the Lutz model for a single satellite. The degree of improvement produced by using two separated satellites in the different environments, in terms of bit rate and probability of the received power is given.
Transmission of group 3 facsimile over inmarsat maritime digital satellite mobile channels
Authors: Dimolitsas Spiros , Rieser Jack , Davis Earl , Ragland Rod , Feldman Howard
Published: July 2007

The importance of facsimile communication over public telephone networks is evidenced by the rapid growth in the number of Group 3 facsimile end‐user terminals. In this paper the main characteristics of a real‐time bit‐rate reducing approach are described whereby facsimile signals are demodulated and their associated protocols converted by a facsimile interface unit (FIU) to a format suitable for transmission over Inmarsat‐B maritime digital satellite channels. The FIU concept was developed to allow ‘off‐the‐shelf’ facsimile terminals to be interconnected via the PSTN through Inmarsat's satellite networks and to permit the provision of enhanced user services by converting Group 3 facsimile protocols to broadcast operation. In addition, the FIU concept is designed to compensate for the longer access and transport link delays encountered in mobile satellite systems, and to permit facsimile call recovery procedures to be successfully concatenated with satellite channel error detection mechanisms.
Burst error characterization of FEC coded digital channels
Authors: Kennedy D. J. , Nakhla M. B.
Published: July 2007

This paper reports on laboratory measurements to determine the characteristics of error bursts encountered on INTELSAT IDR and IBS links for data rates between 64 and 44,736 kb/s. In addition to burst length distributions, several other burst statistics are presented: number of errors per burst, average BER within bursts, and the distribution of error‐free block lengths. These results are intended for use in system design and evaluation of video/speech/data codec performance which are employed on such links.
Improving concatenated coding communications by employing signal editing techniques
Authors: Ng W. H. , Ungar J. L.
Published: July 2007

Signal editing (SE) is a technique used to locate and erase unreliable data before error correction decoding. Consider a concatenated coding (CC) communication system in which the inner code employs convolutional encoding with Viterbi decoding (CEVD) and the outer code could employ either a convolutional or a Reed‐Solomon code. In this study, we show that useful information can be derived from the inner Viterbi decoding process to perform two special operations: (i) to locate and erase unreliable decoded data and (ii) to estimate the input channel noise level. As a result, the number of errors input to the outer decoder is reduced and the overall CC system performance is improved.
Standardization of VSAT communication systems in the CCIR
Authors: Ito Yasuhiko , Amadesi Paolo
Published: July 2007

This paper presents an overview of the CCIR Recommendations on VSAT systems. The first part presents the activities of the CCIR Task Group 4/2 which was created in 1990 and issued five Recommendations for VSAT earth‐stations. These Recommendations specify the RF characteristics of the VSAT earth‐stations and their maintenance functions. The TG 4/2 finished its task in 1991. The second part of this paper presents the activities of the CCIR Task Group 4/3 which was created in 1991 for the preparation of Recommendations on the connection of VSAT networks with the public switched networks. The activities of the TG 4/3 are still going on, and the Draft Recommendations will be formalized in two more meetings. The subjects of dicussion and the expected outcomes will be briefly presented.
The development of VSAT performance standards in the United States of America
Authors: Mitchell Michael W. , Hedinger Robert A.
Published: July 2007

During the 1980s, when satellite communication systems and applications experienced significant growth, the Federal Communications Commission (FCC) in the U.S. recognized that special regulations were required for the licensing and operation of VSAT systems in order to maintain efficient use of the radio spectrum and geostationary orbit (GSO) and to expedite the authorization of VSAT networks featuring large numbers of earth‐stations. The FSS allocated frequency bands, which are used extensively by domestic satellite communication systems in the U.S. and throughout Region 2, are in the 4–6 GHz and 12–14 GHz bands. In order to satisfy the heavy demand in the U.S. for fixed satellite services in these bands, the FCC devised an orbit plan of two degrees spacing between satellites in the relevant portion of the GSO. In a co‐coverage environment, the two most important technical factors for controlling interference between neighbouring satellite systems are (1) earth‐station antenna discrimination and (2) cross‐polarization. Since VSAT systems, by definition, use very small aperture terminals with relatively low levels of antenna discrimination, it was necessary to establish limits for transmit power flux densities and the minimum size of antennas. These limits, based on compatible operation at two‐degree satellite orbit separations, evolved into VSAT standards for the U.S. domestic satellite industry. To expedite the licensing of large numbers of VSAT terminals, conforming systems were given ‘blanket authorizations’ for all VSATs in a network. This paper traces the history of the development of VSAT standards in the U.S. and discusses the technical considerations which were used in these developments. A brief review of receive‐only (RO) terminals is also provided.
VSAT networks in India—specifications and applications
Authors: Ghose A. K.
Published: July 2007

This paper describes briefly the evolution of VSATs in India, including the existing and proposed networks and their applications. The salient specifications of the various types of VSATs are described. Some of the VSATs under advanced stages of development as well as those to be used in proposed networks due for implementation soon are also covered.
VSAT networks in the intelsat system
Authors: Albuquerque J. , Buchsbaum L. , Meulman C. , Rieger F. , Zhu X.
Published: July 2007

This paper describes how VSAT networks currently operate in the INTELSAT system. Four classes of VSAT networks (data transaction; circuit‐switched; data distribution; microterminals) are identified, and it is verified that all of them can operate with INTELSAT satellites. Most VSAT networks in operation on INTELSAT today operate in fractional transponder leases. Fractional transponder capacity estimates are presented for a wide range of scenarios and different INTELSAT satellite series. These estimates clearly show increasing bandwidth utilization efficiencies for newer generations of INTELSAT satellites. Provided that VSAT and hub sizes are appropriately selected, efficiencies are already significant with existing satellites.

Two possible ways of increasing the utilization of satellite resources are examined in the paper: demand assignment multiple access (DAMA) and multiple channel‐per‐carrier (MCPC) techniques. The impact of using DAMA in circuit‐switched VSAT networks is quantified.
Analysis of basic system parameters of communication networks based on low earth orbit satellites
Authors: Böttcher A. , Jahn A. , Lutz E. , Werner M.
Published: July 2007

Currently many efforts are undertaken to develop and install communication networks based on low earth orbit (LEO) and intermediate circular orbit (ICO) satellites. However, many problems are to be solved until the final operation of such networks. This paper deals with basic design problems of LEO/ICO‐based networks. In the first part, estimates for the necessary number of satellites, orbits and number of communication channels per satellite are derived. Since the latter is a crucial quantity, the number of communication links and channels per link are derived with a more elaborate model in the second part of the paper. This includes the radio links from the satellites to mobile users and to gateways, as well as intersatellite links and terrestrial lines. We introduce a formal model for LEO/ICO‐based networks and propose a method for the evaluation of link capacities, given the network topology and the traffic requirements. As an example, two constellations are investigated in detail. One of these constellations is the IRIDIUM system proposed by Motorola.
Precision waveform shaping and precompensation for high data rate space communications systems
Authors: Tague John A. , Shimoda Lisa M.
Published: July 2007

This paper studies a memory‐based pulse shaping and travelling wave tube precompensation technique applied to high data rate satellite communications. Baseband I and Q waveforms are synthesized from data stored in a distributed arithmetic architecture. The waveforms are adjusted to minimize intersymbol interference, spectral bandwidth and travelling wave tube distortion. We evaluate its performance in a simulated BPSK link. The results show that memory‐based precompensation has great potential to improve link performance.
On the performance and complexity of A generalized minimum distance reed–solomon decoding algorithm
Authors: Peile R. E.
Published: July 2007

The article reports on the characteristics of an algorithm that implements generalized minimum distance (GMD) decoding of Reed‐Solomon codes. The algorithm uses the novel Welch‐Berlekamp (WB) algorithm, as modified by Tze‐Hua, in order to minimize the complexity of the decoder. Both the WB algorithm and the GMD extension of the WB algorithm are described in outline. The performance of the GMD algorithm was simulated on AWGN channels and fading channels. Results are presented both for RS and concatenated RS codes. The gains over conventional decoding are larger for fading channels than for AWGN conditions but seem useful in all cases. The complexities of the GMD algorithm and the WB algorithm are analysed and compared to that of conventional RS decoding algorithms.
GPS synchronized power system phase angle measurements
Authors: Wilson Robert E. , Sterlina Patrick S.
Published: July 2007

Before a major new 500 kV transmission line was placed in service between Oregon and the San Francisco, California area, a series of high‐voltage short circuit tests were performed on the transmission system. The short circuit faults produced a brief ‘delta function’ shock to the regional power system. This paper discusses the use of Global Positioning System (GPS) synchronized equipment for the measurement and analysis of key power system quantities.

Before the testing, the authors installed two GPS synchronized phasor measurement units (PMUs). The PMUs use GPS to globally synchronize the measurement of the state vector of the power system, the complex voltages of substation busses. Complex voltage means the magnitude and the relative phase angles of substation voltages. GPS provides the global time reference marker for phase angle measurement. One electrical degree of the 60 Hz waveform equals about 46 μs. Across short transmission lines (less than 50 km), measurements may need to be made to 0.1 electrical degree, which translates to clock synchronizations of roughly 5 μs.

The PMUs recorded the dynamic response of the power system phase angles when the northern California power grid was excited by the artificial short circuits. Power system planning engineers perform detailed computer generated simulations of the dynamic response of the power system to naturally occurring short circuits, e.g. faults caused by lightning. The computer simulations use models of transmission lines, transformers, circuit breakers, and other high voltage components. This work will compare computer simulations of the same event with field measurements.
The role of vsat systems in broadband networks and intelligent networks
Authors: Ananasso Fulvio , Verde Giorgio Lo
Published: July 2007

The scope of this paper is to present the status and the preliminary results of the research activities that Telespazio is carrying out with the aim at identifying the role of the VSAT systems in the advanced telecommunications services, which will be dominant in the second half of nineties and beyond. The first part of the paper is devoted to an overview of the evolution trend of the terrestrial networks. The main body of the paper presents the results of our investigations on the application of VSAT systems in two fields: broadband networks and intelligent networks. Background information has been intentionally added for the easier comprehension of the topics presented in the paper. A list of acronyms appears as an Appendix.
The italsat satellite system
Authors: Carducci F. , Francesi M.
Published: July 2007

In 1995 the second flight unit of ITALSAT telecommunication satellite will be ary orbit, making operative the ITALSAT telecommunication system after the experimental and preoperational phase performed by ITALSAT F1, which was launched in January 1991 by the Italian Space Agency.

A general view of the ITALSAT system is presented with emphasis on the satellite design, the telecommunication mission, the new technologies and the prospects.
Performance of cofdm for satellite digital audio broadcasting
Authors: Franchi A. , Colzi E. , Elia C. , Harris R. A.
Published: July 2007

This paper analyses the performance of a coded orthogonal frequency division multiplexing (COFDM) based system for digital audio broadcasting using a highly inclined orbit satellite constellation. The sources of performance degradation considered are non‐linear amplification in the satellite transponder and multipath propagation for mobile reception. Despite its strong peak‐to‐mean amplitude variation, COFDM has been found to be very robust against non‐linear amplification. In the multipath channel, practical cases demonstrate low performance losses even in highly populated areas when highly inclined elliptical orbits (HEO) are used.
Substrate Wetting and Topographically Induced Ordering of Amorphous PI‐b‐PFS Block‐Copolymer Domains
Authors: Roerdink Monique , Hempenius Mark A. , Gunst Ullrich , Arlinghaus Heinrich F. , Vancso G. Julius
Published: July 2007

The substrate wetting of an amorphous, low‐glass‐transition‐temperature spherical poly(isoprene‐block‐ferrocenylsilane) (PI‐b‐PFS) block copolymer and the alignment of the microdomains in grooves of various geometry are studied. Compositional analysis by time‐of‐flight secondary ion mass spectrometry depth profiling (TOF‐SIMS) indicates the presence of both PI and PFS directly at the film–substrate interface on silicon and silica substrates. The TOF‐SIMS depth‐profiling study indicates a transition in the packing of the domains between the two‐dimensional (2D) monolayer and 3D, thicker layers. In a monolayer of domains, a hexagonal packing is adopted. In films of two or three layers, the hexagonal packing reorganizes towards a body‐centered cubic (bcc) packing by the extension of the copolymer chains in the direction normal to the substrate, as indicated by an increase in spacing between PFS layers and an increase in domain size. For thicker layers, a bcc morphology with the (110) plane parallel to the substrate is found to extend from the free surface downwards. Films of one monolayer of domains of the copolymer exhibit long‐range lateral ordering on the micrometer scale on flat substrates without high‐temperature annealing. On topographically patterned silicon substrates the position of the domains of the minority PFS phase directly near the side walls is fixed by the neutral wetting condition. Successful positioning of the block‐copolymer spheres in linear and hexagonal grooves is achieved in grooves up to 1.3 μm wide, whereby the hexagonal grooves demonstrate complete 2D alignment. In circular pits, this graphoepitaxial effect is absent.
Some additional notes on the kinetics and theory of fatty oil hydrogenation
Authors: Bailey A. E.
Published: July 2007

Equations are given for estimating from the composition of oil samples the relative reaction rates of the different unsaturated fatty acids in an oil subjected to catalytic hydrogenation.

Application of the equations to data from the hydrogenation of cottonseed oil reveals that the ratio of reaction rates, linoleic acid to oleic acid, varies from about 4 to 1 in very non‐selective to about 50 to 1 in very selective hydrogenation. Re‐examination of analytical data on two series of linseed oils hydrogenated selectively and non‐selectively showed the following relative reaction rates for oleic, isolinoleic (9: 10, 15: 16 octadecadienoic), linoleic, and linolenic acids, respectively: non‐selective, 1, 2.5, 7.5, 12.5; selective, 1, 3.85, 31, 77. In the non‐selective hydrogenation of the oil, 24% of the linolenic acid reacting went to linoleic acid, 65% to isolinoleic acid, and 11% directly to oleic acid. In the selective reaction the corresponding figures were none to linoleic acid, 54% to isolinoleic acid, and 46% to oleic acid. The behavior of soybean oil hydrogenated selectively was quite similar to that of linseed oil.

The results are discussed in relation to the theory of catalytic hydrogenation. They indicate that the solution of hydrogen in the oil and the adsorption of unsaturated oil on the catalyst are the two steps which are controlling with respect to the reaction rate. It is suggested that the hydrogen pressure, the degree of hydrogen dispersion through the oil, the catalyst concentration, and the temperature all affect the selectivity of the reaction through their influence on the concentration of hydrogen in the reaction zone, with selectivity being favored by a low concentration.
Polymerization of styrene with ethyl linoleate
Authors: Dyer Elizabeth , Maxwell Jane L.
Published: July 2007

The emulsion polymerization at 40°C. of mixtures of oxidized ethyl linoleate and styrene with potassium persulfate as catalyst yielded copolymers containing a maximum of one mole of ester per thirteen moles of styrene. A product of similar composition was obtained by bulk polymerization at 80°C.

When the amount of ester in the monomer mixture was increased to 50 per cent in the emulsion polymerization, the ester content of the polymer was increased and the molecular weight and yield were decreased.
Fatty acid distillation—Comparison of two column types
Authors: Williams F. C. , Osburn J. O.
Published: July 2007

Conclusions

Vapor‐liquid equilibrium data are presented for the systems lauric acid‐myristic acid, myristic acid‐palmitic acid, and palmitic acid‐stearic acid at four mm. pressure. Deviations from Raoult's law are observed.

The performance of a small glass column packed with fibrous glass was studied. The H.E.T.P. was 30 to 35 inches and showed no consistent variation with composition. Above a vapor velocity of about seven feet per second, the H.E.T.P. increased.

The performance of a small bubble‐cap column was studied. The overall plate efficiency was about 35%. The allowable vapor velocity was between four and five feet per second.

For the distillation of fatty acids at four mm. of Hg pressure the bubble‐cap column was more satisfactory than the packed column containing fibrous glass since the pressure drop per theoretical plate was about one‐fifth as great at comparable capacities. The comparison should be even more favorable to the bubble‐cap column with larger sizes.
Determination of free gossypol in cottonseed materials
Authors: Pons Walter A. , Guthrie John D.
Published: July 2007

A method for the determination of free gossypol in cottonseed materials is described. The method consists of extraction of gossypol with a measured volume of 70% aqueous acetone on a shaker for one hour, filtration, and colorimetric analysis for gossypol in an aliquot of the filtrate by means of the reaction between gossypol andp‐anisidine.

The conditions for complete extraction of gossypol from various types of cottonseed materials have been investigated, the stability of gossypol in aqueous acetone has been demonstrated, and data are presented on recovery of gossypol added to cottonseed materials. The method has been compared with the method of Smith (2).
Naturally occurring epoxy oils1
Authors: Krewson C. F.
Published: July 2007

Fatty acids containing oxirane functional groups have unexpectedly been found in wide distribution in seed oils, usually present as longchain glycerides. Four such acids have been discovered:cis‐ andtrans‐9,10‐epoxystearic acid; vernolic (cis‐12,13‐epoxyoleic) acid; coronaric acid, isomeric with vernolic acid but with the oxirane and double‐bond functions in the reverse positions; andcis‐15,16‐epoxylinoleic acid. No single analytical tool has been universally successful in measuring the oxirance content of epoxides. This appears to be caused by the way in which the chemical reactivity of the three‐membered cyclic ether is modified by molecular structure and by the presence of nearby substituents.

A survey of the published methods for the determination of oxirane functions, including mention of the nature of interfering substances, is given. Techniques used to overcome some of these difficulties are discussed. These procedures include the use of chromatographic and spectrophotometric procedures to solve some of the analytical problems which are encountered. Special consideration is given to vernolic acid and its glycerides since this is the most widely distributed and abundant epoxy acid found in seed oils to date.
The domestic tung industry today
Authors: Potter George F.
Published: July 2007

The tung tree (Aleurites fordii) requires a moderately acid soil, an annual rainfall of 45 to 70 in., and a long hot summer, yet it must have a period of cold weather in winter. These factors limit its culture in North America to a narrow belt along the Gulf of Mexico from Florida to Texas. The majority of the orchards presently consist of miscellaneous seedlings that are about 30 years of age. By replacing these with orchards of new varieties, on suitable soil, and by following recommended practices, growers can produce oil at lower costs than previously. However, crop loss from frost is still a serious problem. Machine harvesting is now a reality. During World War II the government requisitioned the entire domestic production of tung oil for military purposes, and regular customers had to turn to other products. This market has not yet been fully won back, and growers look to utilization research to improve the market.
Chronic lung inflammation in aging mice
Authors: Aoshiba Kazutetsu , Nagai Atsushi
Published: July 2007

To determine whether aging is associated with a pro‐inflammatory shift in the lung, inflammation and inflammation‐related gene expression in the lungs of 12‐week‐old and 24‐month‐old Balb/c mice were studied. cDNA microarray and quantitative reverse transcription‐polymerase chain reaction analyses showed that eight inflammation‐related genes, including CD20, Burkitt lymphoma receptor 1, CXCR‐3, provirus integration site for Moloney murine leukemia virus‐2, CD72, IL‐8RB, C‐Fgr, and CD8β, were upregulated in the aged mice. Immunohistochemistry showed that the lungs of the aged mice contained increased numbers of CD4 cells, CD8 cells, B cells and macrophages. These results suggest that a pro‐inflammatory shift occurs in the lungs of mice with aging.
Pregnancy and perinatal health in Inner Mongolia, China, 1996–1999
Authors: Liu Z. , Lobdell D.T. , Myers S.L. , He L. , Yang M. , Kwok R.K. , Mumford J.L. , Mendola P.
Published: July 2007

Objective

To obtain descriptive measures of maternal and perinatal health in the Ba Men Region of Inner Mongolia, China.

Methods

Data collected from the Examination Chart for Pregnant Women for approximately 22,000 pregnancies in a three‐county area of Inner Mongolia, China from December 1, 1996 through December 31, 1999 were analyzed for maternal, perinatal, and neonatal outcomes.

Results

Compared to selected developing countries, a higher percentage of women (99%) in this region received at least one prenatal care visit. This region was also characterized by a low percentage of low birthweight (< 2.5 kg) infants (1%) and neonatal mortality rate (5 deaths per 1000 live births).

Conclusions

Maternal and neonatal health outcomes in this region of Inner Mongolia were better than those in selected developing countries.
Understanding and attitudes towards patient safety concepts in obstetrics
Authors: Nabhan A. , Ahmed‐Tawfik M.S.
Published: July 2007

Objectives: To measure attitudes of health personnel towards patient safety, and to determine how the concept of patient safety varies between maternal health centers and types of health care personnel. Methods: A cross‐sectional descriptive study included 35 primary heath centers in three governorates in Egypt. The subjects comprised all managers, physicians, nurses, pharmacists, and technicians. Results: The overall mean for all questions and respondents was 3.89 ± 0.59 (scale 1–5). The safety climate mean was 3.64 ± 0.67. The percentage of respondents viewing the safety climate as positive was 36%. Only 7% of respondents had received feedback after referral of a case of severe pre‐eclampsia. Conclusion: The concept of patient safety in the centers studied is not as strong as desirable for the provision of reliable health care. The culture is one of a penalizing nature with suppressed error reporting, lack of proper communication, and feedback failure.
Vertebrate burrows in late pleistocene paleosols at Korean Palaeolithic sites and their significance as a stratigraphic marker
Authors: Lim Hyoun Soo , Lee Yong Il , Yi Seonbok , Kim Cheong-Bin , Chung Chull-Hwan , Lee Heon-Jong , Choi Jeong Heon
Published: July 2007

A vertebrate burrow-bearing layer of late Pleistocene age is commonly found at many Paleolithic archaeological sites in Korea. The burrows are straight to slightly curved in horizontal (plan) view and gently inclined in lateral (sectional) view. They are interpreted as having been produced by rodent-like mammals based on their size and architecture. The significance of such burrow-bearing layers as a characteristic stratigraphic marker unit is demonstrated by high burrow abundance, consistent stratigraphic position, lack of stratigraphic recurrence at these sites, and widespread geographic extent. Three dating methods, tephrochronology, radiocarbon, and OSL dating, were used to infer the age of these burrow-bearing layers. The dating results indicate that they were formed between ca. 40,000 and 25,000 yr (MIS 3−2), and this suggests that this layer can be used as a stratigraphic time-marker in late Pleistocene paleosol sequences for this region.
INTRODUCING IMPROVED CULTIVARS: UNDERSTANDING FARMERS' SEED DRYING AND STORAGE PRACTICES IN CENTRAL GHANA
Authors: BAM R. K. , CRAUFURD P. Q. , DORWARD P. T. , ASIEDU E. A. , KUMAGA F. K. , OFORI K.
Published: July 2007

Improved upland rice cultivars introduced in Volta Region, Ghana, have been perceived to store poorly compared to farmers' traditional cultivars. A survey was conducted in 2003 in the Hohoe district of this region, where a Participatory Varietal Selection programme had started in 1997, to gain insight into farmers' seed production and storage practices that are likely to affect seed quality in storage. Farmers rated keeping quality (p < 0.001), tolerance to storage pests (p < 0.001), seed quality (p < 0.001) and establishment of their local cultivars Kawomo, Viono and Wuwulili as much better than the improved cultivar IDSA 85. Initial seed moisture content ranged from 12.8 to 18% and germination from 0 to 82%. There was a significant relationship between seed moisture content and duration of drying prior to storage (p < 0.001) and storage method (p = 0.015). Germination loss in storage was rapid at high moisture content and slow at low moisture content. Between 60 and 80% of seeds germinated after six months storage at 12.8% moisture content. The viability equation predicted accurately germination of farmer-saved seed stored under ambient temperature in Ghana. Except for the japonica rice cultivar WAB 126-18-HB, the traditional cultivars Kawomo, Viono and Wuwulili survived better in storage than improved cultivars. There is a need to improve seed quality of improved cultivars if farmers are to benefit from their higher yields and grain quality and to improve storage practices.
A turbulent jet in crossflow analysed with proper orthogonal decomposition
Authors: MEYER KNUD ERIK , PEDERSEN JAKOB M. , ÖZCAN OKTAY
Published: July 2007

Detailed instantaneous velocity fields of a jet in crossflow have been measured with stereoscopic particle image velocimetry (PIV). The jet originated from a fully developed turbulent pipe flow and entered a crossflow with a turbulent boundary layer. The Reynolds number based on crossflow velocity and pipe diameter was 2400 and the jet to crossflow velocity ratios wereR=3.3 andR=1.3. The experimental data have been analysed by proper orthogonal decomposition (POD). ForR=3.3, the results in several different planes indicate that the wake vortices are the dominant dynamic flow structures and that they interact strongly with the jet core. The analysis identifies jet shear-layer vortices and finds that these vortical structures are more local and thus less dominant. ForR=1.3, on the other hand, jet shear-layer vortices are the most dominant, while the wake vortices are much less important. For both cases, the analysis finds that the shear-layer vortices are not coupled to the dynamics of the wake vortices. Finally, the hanging vortices are identified and their contribution to the counter-rotating vortex pair (CVP) and interaction with the newly created wake vortices are described.
Mechanizing metatheory in a logical framework
Authors: HARPER ROBERT , LICATA DANIEL R.
Published: July 2007

The LF logical framework codifies a methodology for representing deductive systems, such as programming languages and logics, within a dependently typed λ-calculus. In this methodology, the syntactic and deductive apparatus of a system is encoded as the canonical forms of associated LF types; an encoding is correct (adequate) if and only if it defines acompositional bijectionbetween the apparatus of the deductive system and the associated canonical forms. Given an adequate encoding, one may establish metatheoretic properties of a deductive system by reasoning about the associated LF representation. The Twelf implementation of the LF logical framework is a convenient and powerful tool for putting this methodology into practice. Twelf supports both the representation of a deductive system and the mechanical verification of proofs of metatheorems about it. The purpose of this article is to provide an up-to-date overview of the LF λ-calculus, the LF methodology for adequate representation, and the Twelf methodology for mechanizing metatheory. We begin by defining a variant of the original LF language, calledCanonical LF, in which only canonical forms (long βη-normal forms) are permitted. This variant is parameterized by asubordination relation, which enables modular reasoning about LF representations. We then give an adequate representation of a simply typed λ-calculus in Canonical LF, both to illustrate adequacy and to serve as an object of analysis. Using this representation, we formalize and verify the proofs of some metatheoretic results, including preservation, determinacy, and strengthening. Each example illustrates a significant aspect of using LF and Twelf for formalized metatheory.
Genetic diversity analysis of yam cultivars (Dioscorea rotundata Poir.) in Benin using simple sequence repeat (SSR) markers
Authors: Tostain Serge , Agbangla Clément , Scarcelli Nora , Mariac Cédric , Daïnou Ogoubi , Berthaud Julien , Pham Jean-Louis
Published: July 2007

Guinea yam (Dioscorea rotundataPoir.) is a dioecious vegetatively propagated tuber crop. It is widely cultivated by traditional techniques in West Africa, its area of origin. The genetic diversity of 146 accessions from Benin was analysed using 10 polymorphic simple sequence repeat (SSR) nuclear markers and agromorphological traits. An average of 8.4 alleles per locus was detected. The mean heterozygosity was 0.57 and the mean polymorphism information content (PIC) for polymorphic markers was 0.51. Some cultivars (23%) were found to have an identical genotype for the 10 markers. The structure of the genetic diversity observed in Benin is the result of farmers' crop management practices and their know-how. The cultivar diversity had a geographical component. We also noted major differentiation between early and late cultivars, with higher diversity in the early ones. Cultivars from northern Benin and early cultivars had the greatest allelic richness. SSR markers proved to be powerful tools for fingerprinting each cultivar and analysing their genetic relationships. The results of this study could be useful for defining a strategy for the conservation of genetic diversity in yams.
Klinische Jugendpsychologie
Authors: Petermann Franz
Published: July 2007

Zusammenfassung: Klinische Jugendpsychologie beschäftigt sich mit auffälligen Entwicklungsverläufen im Übergang zum Erwachsenenalter. Problematische Entwicklungen stellen Rauchen und Alkoholgebrauch/-missbrauch dar. Besondere Anforderungen und Belastungen ergeben sich aus körperlich-chronischen Erkrankungen. Psychische Reaktionen auf Anforderungen und Belastungen äußern sich vielfach geschlechtsspezifisch.
Jugendliche, die frühzeitig rauchen und trinken - eine Risikogruppe?
Authors: Hohm Erika , Blomeyer Dorothea , Schmidt Martin H. , Esser Günter , Laucht Manfred
Published: July 2007

Zusammenfassung: Epidemiologische Studien berichten über einen hohen Konsum legaler Drogen bei Jugendlichen in Deutschland. Ziel der vorliegenden Studie ist es, Kennwerte und Muster des Konsums von Tabak und Alkohol bei Erstkonsumenten zu beschreiben und Determinanten riskanter Konsummuster zu ermitteln. In einer prospektiven Längsschnittstudie an einer Geburtskohorte von 384 Risikokindern wurden im Alter von 15 Jahren der Substanzkonsum sowie mögliche individuelle und soziale Einflussfaktoren untersucht. Jugendliche, die aktuell (in den letzten vier Wochen) sowohl Tabak als auch Alkohol konsumierten, zeichneten sich durch einen exzessiveren und impulsiveren Konsum aus und wiesen eine deutlich höhere Rate von Cannabisgebrauch auf als Jugendliche, die in diesem Zeitraum nur rauchten oder nur tranken. Spezifische, den Doppelkonsum determinierende Faktoren konnten nicht gefunden werden. Jugendliche, die frühzeitig rauchen und trinken, stellen eine mögliche Risikogruppe für einen erhöhten Substanzgebrauch dar und sollten in Präventionsprogrammen gezielt angesprochen werden.
Selbstverletzendes Verhalten bei weiblichen Jugendlichen
Authors: Salbach-Andrae Harriet , Lenz Klaus , Klinkowski Nora , Pfeiffer Ernst , Lehmkuhl Ulrike
Published: July 2007

Zusammenfassung: Ziel der vorliegenden Studie war die Untersuchung der Frage, welche Faktoren bei Patientinnen einer jugendpsychiatrischen Inanspruchnahmepopulation selbstverletzendes Verhalten (SVV) prognostizieren. Insgesamt wurden retrospektiv die Beurteilungen über 957 Patientinnen im Alter von 12 bis 18 Jahren mittels des “Frankfurter Kinder- und Jugendpsychiatrischen Dokumentationssystems” herangezogen. 18.8 % der untersuchten Patientinnen zeigten SVV. Die logistischen Regressionen ergaben, dass lediglich die Variablen “Diagnose” und “Komorbidität” relevante prognostische Faktoren für SVV darstellen. Zusätzlich wurden ROC-Analysen durchgeführt, die vor allem für den Faktor “Diagnose” eine gute Vorhersageeffektivität belegten. Im jugendpsychiatrischen Bereich stellen psychiatrische Störungen einen wichtigen Faktor für SVV dar, wobei vor allem bei Persönlichkeitsstörungen, affektiven Störungen, expansiven Störungen, bulimischer Anorexie und Bulimie eine enge Verknüpfung mit SVV besteht.
Antarctic coastal polynya response to climate change
Authors: Marsland S. J. , Church J. A. , Bindoff N. L. , Williams G. D.
Published: July 2007

Sensitivity of sea ice formation and dense shelf water production to perturbations of air temperature, precipitation, and wind stress in an important Antarctic coastal polynya system is investigated. Shelf water formation in the Mertz Glacier Polynya is a major source of Adélie Land Bottom Water. Coupled ocean and sea ice model simulations for 1996–1999 span a transitional period of the system: The 1996–1997 strong polynya state is characterized by high sea ice growth and export, ocean to atmosphere heat flux, shelf water density, and rate of dense water export; in the 1998–1999 weak polynya state all these quantities are greatly reduced. The 1990s interannual variability in air temperature and precipitation is of similar magnitude to future increases as projected for the Southern Ocean by the IPCC assessment. We model the polynya with perturbed climate change forcing and find that the system shows a reduction in shelf water export in both the strong/weak modes. Overall, the dense water export is reduced by 40% for a 2°C surface warming, and by 33% for a 20 cm a−1 precipitation increase. In the weak polynya state that is more likely in future climate, shelf water export is reduced by 81% for the warming and by 65% for the freshening. The reduction in dense shelf water export implies a corresponding reduction in Antarctic Bottom Water formation.