bluuebunny/crossref_metadata_2025 huggingface dataset:
Unified approaches to integrated‐service networks–burst and fast packet switching
Authors: Maples Tracy Bradley , Suda Tatsuya
Published: July 2007

The increasing demand for communication services, coupled with recent technological advances in communication media and switching techniques, has resulted in a proliferation of new and expanded services. Currently, networks are needed which can transmit voice, data and video services in an application‐independent fashion. Unified approaches employ a single switching technique across the entire network bandwidth, thus allowing services to be switched in an application‐independent manner. This paper presents a taxonomy of integrated‐service networks, including a look at NISDN, while focusing on unified approaches to integrated‐service networks.

The two most promising unified approaches are burst and fast packet switching. Burst switching is a circuit switching‐based approach which allocates channel bandwidth to a connection only during the transmission of ‘bursts’ of information. Fast packet switching is a packet switching‐based approach which can be characterized by very high transmission rates on network links and simple, hard‐wired protocols which match the rapid channel speed of the network. Both approaches are being proposed as possible implementations for integrated‐service networks. We survey these two approaches, and also examine the key performance issues found in fast packet switching. We then present the results of a simulation study of a fast packet switching network.
Video and image applications on narrowband and broadband isdn
Authors: Dewitt Russ , Ramasastry Jay , Kim Kap , Li Peter
Published: July 2007

Two major ISDN applications which will undoubtedly affect world‐wide telecommunications in the coming decade are discussed. They are: (1) video transmission and (2) image transmission.

Brief reviews of videophone chronicle and the current video coding technologies are presented. The application of videophones using p × 64 (CCITT coding algorithm up to 1·5 Mb/s) and the DCT (discrete cosine transform) algorithm for narrowband ISDN are discussed. Broadcast TV quality DS3‐45 MB/s video codecs are also briefly discussed as a probable videophone system in the broadband ISDN era.

The explosive growth of facsimile services is reviewed, and the progress of image coding technologies and their standards are covered. The prospects of high resolution image transfer systems with ISDN are addressed.
Optimal policies for integrating heterogeneous services on isdn channels
Authors: El dessouki O. , Baraka H. , El sayed S.
Published: July 2007

A technique for the classification and evaluation of hierarchical access integration policies of ISDN channels is proposed. The essence of the basic control decisions based on several parameters of the servers and channel is captured in a single priority‐based‐layered model of multiple queues. We solve for the resulting delay of different policies and investigate the performance in one tractable limit of this model. Using our understanding of the problem parameters and their interaction, we propose a number of heuristic policies for the general model. The results of the general problem complexity investigations suggest the use of simulation models. Problem parameters considered are channel acceptable access delay value, number of servers needed, and flow duration time of a request. Preemptive and non‐pre‐emptive policies on queued traffic are considered. Performance considers average delay, delay variation and channel utilization. Simulation data on these policies suggest that policies that favour shorter services given better overall delay over a wide range of system parameters. Policies that favour longer and broadband services, on the other hand, show better quality and smaller delay variation.
Guidelines for a preliminary dimensioning of a transaction‐oriented vsat network
Authors: Zein Tarif , Maral Gérard , Jabbari Bijan
Published: July 2007

Very small aperture terminal (VSAT) satellite networks have recently emerged as an attractive and cost‐effective alternative to traditional terrestrial circuit or packet switching networks for transaction enquiry‐response data applications. VSAT star networks are particularly well adapted to this kind of application, offering high link reliability, better flexibility, wide service area coverage and several economic and operational advantages. However, one major drawback associated with satellite links is the relatively high propagation delay, which is about 0·27 s for one hop (ground–satellite‐ground). This requires special design and dimensioning optimization in order to keep the response time of the network within acceptable limits.

This paper provides guidelines for the dimensioning of such enquiry‐response star VSAT networks. Dimensioning refers to determining the minimum transmission bit rates required, on the different terrestrial and satellite segments of the network, for a given network configuration and mean delay requirement. The approach presented in this paper allows network designers to determine, in a simple way, the required modem speeds of the network segments.
New formulation and plots for error probability in the pulse position modulation (PPM) photon counting satellite‐to‐earth channel
Authors: Amoroso Frank , Bricker Jacob L.
Published: July 2007

In digital satellite‐to‐earth transmission the entry of substantial undesired solar radiation into the receiver antenna is sometimes unavoidable. When the signal transmission takes the form of incoherent optical pulse position modulation (PPM) the parameters of signal and consequent intense noise can fall outside the range of routinely available classical numerical results on symbol error probability.

This paper presents an alternative system for parametrization of signal and noise in the classical PPM channel, i.e. that characterized by Poisson photon arrival statistics for signal itself, the noise itself, and the signal plus noise.

The resulting formulation for error probability, the scheme for probability calculation, and the simple, compact plots of error probability versus newly conceived parameters cover the entire range of signal and noise intensities, from weakest to strongest.

Of course, when properly interpreted the new results agree entirely with classically available numerical results within the parametric range of the former.
A review of Ka and Ku band propagation measurements on satellite paths made at the bt laboratories in the U.K.
Authors: Howell Robert , Thompson Paul
Published: July 2007

Measurements of slant‐path attenuation and crosspolar discrimination, obtained from four satellite measurement programmes carried out at the BT Laboratories, Martlesham Heath, England, are described. The measurements covered frequencies in the range 11.3 GHz to 30 GHz, path elevations ranging from 8.3° to 29.9°, and were made using both circularly and linearly polarized signals. Cumulative distributions, derived from the measured data, are extrapolated to frequencies of 12.5, 14.3, 19.8 and 29.7 GHz and then combined to give statistics for a database of more than 20 years.
Performance of A prioritized non‐blocking switch under hotspot traffic conditions with head of line resolution
Authors: Bohm Stephan , Elhakeem A. K. , Murthy K. M. S.
Published: July 2007

In this paper, we pursue a performance analysis under hotspot traffic conditions of a four‐level prioritized non‐blocking baseband switch for use on board a switching multibeam satellite. Both finite input and output buffering as well as speed‐up are employed to reduce the loss which is critical in a satellite application. In addition, in order to improve the performance of the two lowest priority users a head of line resolution (HLR) technique is implemented. It is shown that with HLR and the proper adjustment of the switch speed‐up and the input and output buffers the loss can be substantially reduced. It is also shown that the dependence on the switch size which is characteristic of the unbuffered discard case is substantially reduced, even in a prioritized environment, allowing larger switches to be implemented.
A future satellite communications system using millimetre‐wave bands and an on‐board processor
Authors: Endo Minoru , Kumagai Takeo , Yamamoto Tetsuo , Otsu Yuichi , Kikuchi Takaaki , Komiyama Norio
Published: July 2007

This paper proposes the system concept of a personal satellite communications system that will be available in the first decade of the 21st century. Technologies of millimetre‐wave bands and an onboard processor with baseband switching promise to meet the requirements of a personal communications system: portability, low‐cost, and large capacity. Based on the prospects of these technologies, the most likely parameters for the future personal satellite communications system and the configuration of a suitable on‐board processor are proposed. A trial model of such an on‐board processor has been made. In this paper, details of the trial model on‐board processor and its future developments are described.
Architectures for the INTELSAT NISDN‐compatible satellite communications network
Authors: Chitre D. M. , Oei W. S.
Published: July 2007

This paper presents a conceptual description of a number of possible satellite network architectures for integration into and between the emerging narrowband 64 kb/s based integrated services digital networks (ISDNs). The discussion, which focuses on functional and architectural aspects of network‐integrated satellite systems, is based on two underlying themes. First, the satellite system, as a strict digital transmission system in international ISDN networks, must be virtually ISDN service transparent (i.e. it must not cause any unintended degradation to the transported signals and communication protocols). Secondly, the inherent features of satellite systems are exploited to offer additional functional network support to the ISDN network capabilities for select ISDN services.
250 MHz SAW FILTERS FOR SS/FDMA SYSTEM EMPLOYING ST‐CUT QUARTZ SUBSTRATES
Authors: Shinonaga Hideyuki , Ito Yasuhiko
Published: July 2007

Surface acoustic wave (SAW) filters are key devices in developing the bandwidth‐variable filter matrix for the subchannel switched frequency division multiple access (SS/FDMA) system. This paper addresses the design and fabrication of two 250 MHz SAW filters employing temperature‐stable ST‐cut quartz substrates. The specafications for these filters are decided with due consideration of practical use by INTELSAT‐type satellites. Measured electrical responses of the individual and combined channels show satisfactory performance. Computer simulations are performed using the measured responses to assess the effects of the SAW filters on digital carriers. Finally, the effects of the temperature and ageing stability characteristics are discussed based on the measured and calculated responses.
Personal communications by satellite
Authors: Golding L. S. , Palmer L. C.
Published: July 2007

Personal communications (PC) refers to two‐way voice (and possibly data) communications to a small hand‐held unit, capable of being carried by a person and used in various locations. PC via satellite refers to the case where this hand‐held unit communicates directly with a satellite to provide the duplex voice (or data) service. Both geosynchronous earth orbit (GEO) and low earth orbit (LEO) satellites have been considered to provide this service. GEO and LEO satellite systems must compete with existing mobile cellular radio systems both in meeting performance requirements and service costs, if they are to be a significant supplier of PC services. GEO and LEO systems each have unique advantages and disadvantages when used to provide a PC service. While these general characteristics are identified in Section 1 of the paper, a more quantitative comparison is needed. This quantitative comparison is made by comparing a GEO PC satellite system, operating at EHF (Ka‐band) frequencies with a LEO system operating at UHF (L‐band) frequencies, including service costs for both systems. The two systems used in the comparison are examples of realistic GEO and LEO system designs for PC service, and although it is not exhaustive, the comparison points out some of the key differences between GEO and LEO systems that affect service performance and cost.
Multiple‐access phased array antenna simulator for A digital beam‐forming system investigation
Authors: Kerczewski Robert J. , Yu John , Walton Joanne C. , Perl Thomas D. , Andro Monty , Alexovich Robert E.
Published: July 2007

Future versions of data relay satellite systems are currently being planned by NASA. Being given consideration for implementation are on‐board digital beam‐forming techniques which will allow multiple users to simultaneously access a single S‐band phased array antenna system. To investigate the potential performance of such a system, a laboratory simulator has been developed at NASA's Lewis Research Center. This paper describes the system simulator, and in particular, the requirements, design and performance of a key subsystem, the phased array antenna simulator, which provides realistic inputs to the digital processor including multiple signals, noise and non‐linearities.
Static and dynamic retransmission control for slotted aloha in transmission channels with erasure and capture
Authors: Böttcher Axel , Meier‐Hedde Christoph
Published: July 2007

Slotted Aloha can be an attractive multiple access scheme for mobile radio applications, mainly for mobile satellite services. This is especially so when capture‐effects occur, i.e. when one out of several colliding data packets can capture the common receiver. Mostly this is due to varying signal levels of the transmitters. It is well‐known that a slotted Aloha channel can become unstable. It performs acceptably only if a good retransmission control policy is applied. In this paper, static and dynamic stabilization methods for slotted Aloha in transmission channels with capture and erasure are compared. They are analysed by analytical methods as well as by simulation. It turns out that a dynamic control procedure is more flexible and outperforms a static retransmission policy also in mobile radio channels.
Orbital performance of communication satellite microwave power amplifiers (MPAs)
Authors: Strauss R.
Published: July 2007

This paper presents background data on the performance of microwave power amplifiers (MPAs) used as transmitters in currently operating commercial communication satellites. Specifically, aspects of two competing MPA types are discussed. These are the well known TWTA (travelling wave tube amplifier) and the SSPA (solid state power amplifier). Extensive in‐orbit data has been collected from over 2000 MPAs in 1991 and 1993. The study in 1991 involved 75 S/C (spacecraft) covering 463 S/C years. The 1993 ‘second look’ study encompassed a slightly different population of 72 S/C with 497 S/C years of operation. A surprising result of both studies was that SSPAs, although quite reliable, did not achieve the reliability of TWTAs. TWTAs were one‐third more reliable in the 1993 study. This was atC‐band with comparable power amplifiers, e.g. 6‐16W of RF output power and similar gains. Data atKu‐band is for TWTAs only since there are no SSPAs in the current S/C inventory. The other complementary result was that the projected failure rates used as S/C payload design guidelines were, on average, somewhat higher for TWTAs than the actual failure rates uncovered by this study. SSPA rates were as projected.
A co‐designed coding, modulation and equalization scheme for the transmission of 155‐52 Mbit/s data over a 72 MHz intelsat transponder. Part 1: Coding and modulation performance
Authors: Peile R. E.
Published: July 2007

This paper reports on the application of co‐designed coding, modulation and equalization techniques to an INTELSAT requirement for transmitting 155‐52 Mbit/s data over a 72 MHz satellite channel. A specific solution as regards coding, modulation and equalization is proposed and analysed that differs from ‘standard’ concatenation in that the inner decoder integrates equalization, modulation and coding. In Part 1 results of extensive computer simulations are presented, examining the effect of adjacent channel interference, co‐channel interference, non‐linear distortion in representative ground and space TWTAs, multiplexers and filter distortion. In Part 2 a novel technique for integrating decision feedback equalization into the inner decoder is described. The gains in integrating the coding and equalization are shown to be significant for channels that need equalizing.
Performance analysis of A dynamic channel allocation technique for satellite mobile cellular networks
Authors: Re Enrico Del , Fantacci Romano , Giambene Giovanni
Published: July 2007

This paper deals with an efficient dynamic channel allocation (DCA) technique suitable for applications in mobile satellite cellular networks. A cost function is defined to allow an optimum selection of channels to be allocated on demand. A mobility model suitable for low earth orbit (LEO) satellite systems is presented. The performance of the novel DCA technique in terms of call blocking probability has been derived by simulations. The obtained results are compared with those achieved by a fixed channel allocation (FCA) technique to show a better behaviour.
Network and common channel signalling aspects of dynamic satellite constellations
Authors: Cullen C. , Benedicto X. , Tafazolli R. , Evans B.
Published: July 2007

This paper discusses networking issues associated with the provision of L/S‐band personal satellite communications. Both the UMTS and IMT‐2000 third generation mobile communication concepts have identified the need for a satellite component as part of their overall structure. The work is mostly based on the ESA‐developed medium altitude global satellite system (MAGSS‐14).1 It is, therefore, mainly relevant to MEO (medium earth orbit) constellations but most ideas can also be extended to LEO (low earth orbit) constellations. After examining user and service requirements the specific networking issues associated with personal satellite communications are reviewed. A network architecture is then proposed which takes these restrictions into account. Based on this network architecture, network signalling requirements, more specifically those relevant to network common control channels, are estimated.
Analysis of A movable boundary access technique for A multiservice multibeam satellite system
Authors: Bohm S. , Elhakeem A. K. , Murthy K. M. S. , Hachicha M. , Kadoch M.
Published: July 2007

In this paper, the performance of a new movable boundary accessing (MBA) technique for future integrated services multibeam satellite systems is studied. The multiservice environment considered includes both asynchronous and isochronous traffic consisting of video, voice, file transfer and interactive data. The movable boundary access technique proposed here will maximize the utilization of the uplink frame capacity. It is shown that the potential user population is substantially increased with the use of a moving boundary policy with minimal overhead.
The BMLA/LS technique and its application in A mobile satellite communication channel
Authors: Liu Yi‐Song
Published: July 2007

The burst mode link analyser with least squares algorithm (BMLA/LS) is a real‐time impulse or frequency response extraction (IRE/FRE) technique of a satellite communication channel, originated and explored by the author. This paper summarizes some key technical points of the BMLA/LS and presents its novel simulation results and applications in a land‐mobile DBPSK/DQPSK satellite channel at Ka‐band, including the channel additive white Gaussian noise (AWGN) effect on IRE/FRE by BMLA/LS, and the instantaneous IRE/FRE in a Rician channel with multi‐path reflection, in a shadowed channel by trees and in a combinational fading channel, and their comparisons and conclusions.
Space flight tests of attitude determination using GPS
Authors: Cohen Clark E. , Lightsey E. Glenn , Parkinson Bradford W. , Feess William A.
Published: July 2007

Preliminary space flight results of attitude determination using GPS are presented from a spacecraft in low Earth orbit. Relative position measurements accurate to the sub‐centimetre level are made among multiple GPS antennas mounted on the space vehicle. A Trimble Navigation TANS Quadrex (a GPS receiver specially adapted for attitude determination by Stanford University) is used as a differential carrier phase sensor for the flight.

Four GPS antennas are mounted on the zenith face of RADCAL, a polar orbiting, gravity‐gradient‐stabilized Air Force Space Test Program Satellite, built by Defense Systems, Inc. The four antennas are equally spaced about the perimeter of the 30 inch diameter cylindrical spacecraft bus.

The Quadrex receiver measures the phase of the L‐band GPS carrier (1575 MHz) at each of up to four antennas for up to six GPS satellites simultaneously. From these measurements, an initial assessment of attitude determination in space is performed in post‐processing. For RADCAL, the attitude solution is greatly overdetermined. In a preliminary evaluation of system performance, the system accuracy is determined through measurement self‐consistency. Analysis of the attitude motion in the context of a gravity gradient dynamic model yields further insight into the system performance.
The intelsat VIII/VIIIA generation of global communication satellites
Authors: Cornelius D. J. , Herridge A. J. , Silk R. , Thompson P. T.
Published: July 2007

Developed originally to meet increased demand forecast for C‐band capacity in the Pacific Ocean Region (POR), this latest generation of INTELSAT satellites is planned to be operated in a number of traditional and new roles. To date INTELSAT has bought four INTELSAT VIII spacecraft for Pacific, Indian and Atlantic Ocean regions and two modified VIII‐A to meet the specific Landmass requirements for the rapidly expanding Asia‐Pacific and pan‐American market. The VIII spacecraft, using Martin Marietta Astro Space's GS7000 bus has sufficient power and payload carrying capability that it can accommodate a wide variety of services. A new feature for INTELSAT is the inclusion of arcjet propulsion which has the potential for long lifetime while needing only half of the fuel requirement of conventional thrusters. This new high power satellite will form a key part of the INTELSAT global network through to the year 2010 and complement the INTELSAT VII and VIIA series.
Modelling of the rainfall rate cumulative distribution for the design of satellite and terrestrial communication systems
Authors: Moupfouma F. , Martin L.
Published: July 2007

The design of line of sight (L.O.S.) or satellite links requires annual point rainfall rate statistics for several percentages of time in the locations where the radiocommunication links are planned. Rain rate data within an average year, indeed, allow the estimation of the time percentage during which attenuation due to rain is significant, and consequently the future link margin.

To meet ITU Radiocommunication Sector's Recommendations, we propose a probability law model allowing the prediction of the rainfall rate cumulative distribution in temperate and tropical climates.

This model, which can be easily used, may serve as a very useful and accurate enough tool for radiocommunication engineers and scientists.
Interference considerations in frequency sharing between low earth orbit satellites and the geostationary fixed satellite and terrestrial service
Authors: James Michel C.
Published: July 2007

Recently many companies and consortia have considered launching LEO satellites for such projects as remote sensing, transportation and mining operations. When the multiple low Earth orbit (LEO) satellites are transmitting they can interfere with existing terrestrial microwave and satellite earth‐stations in the fixed and mobile service. The interference problem is related to the number of proposed LEOs and the altitude and consequently the time to orbit the earth. These systems usually consist of many small satellites, and each satellite stays in the beam of a terrestrial station for up to 72 seconds in each 222 minute orbit. Earth coverage could be obtained by 48 (LEO) satellites 1500 km above the earth in polar orbit, and hence at least one LEO would always be interfering with terrestrial networks. A technical evaluation would then be required to determine the resultant BER (bit error rate) effecting existing terrestrial services. A determination can then be made to support such a LEO system or object via official channels such as the ITU.
Planning aspects of satellite and terrestrial digital sound broadcasting
Authors: Sauvet‐Goichon Daniel
Published: July 2007

DAB is one of the most promising sound broadcasting techniques for the future. It will soon start terrestrial operations, and later on will be used for satellite broadcasting.

The Eureka 147 DAB system is based on a set of well‐demonstrated techniques, in particular the MUSICAM coding, adopted by MPEG, and OFDM modulation. It allows great spectrum efficiency, profiting from the single frequency network concept, one of the most interesting characteristics of the system.

However, frequency problems remain a difficulty, as DAB must either examine the possibility of entering existing heavily used frequency bands or wait until the new frequency bands allocated by WARC 92 become fully available.

For terrestrial broadcasting, most interested operators, broadcasters and manufacturers are convinced that appropriate solutions will be found and that DAB will start operational services from about 1996. In Europe, a CEPT planning conference will address the matter in 1995.

Satellite broadcasting may come later. Short wave broadcasters examine possibilities to replace short waves, the quality of which is so poor, by digital satellite broadcasting. From the frequency spectrum point of view, this raises the difficulty of sharing frequency allocations with terrestrial applications.
In‐orbit test of the first Hughes United States direct broadcast satellite
Authors: Egly Keith , Leacock Rick , Riginos Vasilis
Published: July 2007

This paper describes the in‐orbit test of the first United States direct broadcasting satellite (DBS‐1) developed by Hughes Space and Communications (HSC) for Hughes Communications Galaxy, Inc. and DIRECTV Inc. This satellite provides direct broadcast of digitally compressed television channels across the United States for service providers DIRECTV™ and United States Satellite Broadcasting (USSB).

Following a brief description of the communication system of the spacecraft, the in‐orbit test set‐up and the measurements that were performed are described. Measurements which have not been described elsewhere (antenna contour verification, modulated e.i.r.p., e.i.r.p. with wide band energy dispersal function (EDF), auto saturation, etc.) are covered in some detail.

Finally, the results of the in‐orbit test of DBS‐1 which was performed in January 1994 are presented.
Two‐station in‐orbit testing using swept techniques
Authors: Cradock Robert
Published: July 2007

This paper describes the system, consisting of hardware and software, and two of the two‐station in‐orbit test (IOT) measurements that were developed for INTELSAT as part of their IOTE (in‐orbit test equipment) project. Three systems have been designed and manufactured by SED Systems, and installed in Beijing, Clarksburg and Fucino. The system is capable of two types of synchronized sweeps: sweeps in power and sweeps in frequency; gain transfer and frequency response, respectively, are given as examples. Two‐station measurements are used on complex satellites that contain transmit and receive beams (such as spot beams) that cannot both be seen at the same earth‐station. This paper briefly describes how the measurements are done and discusses some of the more important performance issues.
Open loop testing of communication satellites from two in‐orbit test (IOT) stations
Authors: De Vincenti P. , Kasstan B. , Paris D. , Riginos V. , Shen P. , Absolonne F. A. , Stjernevic J.
Published: July 2007

The implementation of the IOT for the EUTELSAT II‐F6 (HOT BIRD 1) spacecraft is based on the new concept of an ’open loop measurements‘ architecture connecting two IOT stations geographically separated. This architecture was implemented because the EUTELSAT test facilities in Rambouillet near Paris could not transmit in the 13 GHz band required by the HOT BIRD 1 up‐link. The up‐link carriers were thus provided by the ex‐Olympus IOT antenna situated at the ESA facilities in Redu, Belgium, whereas all the down‐link measurements and the test management were performed by the EUTELSAT test facility in Rambouillet. The two IOT stations were mutually connected by a dedicated data transmission line.

The paper describes the changes that were made to the existing EUTELSAT and ESA facilities and the implementation of the new measurement software and of specific networking equipment, such as the remote server that was installed at Redu to control the up‐link signals from the Rambouillet site.

The paper also discusses the implementation of new satellite test procedures for remote measurements and in particular how the spacecraft channel group delay is measured from two independent stations in open loop mode.
Choice of λ‐Margin and dependency of non‐inferiority trials
Authors: Tsong Yi , Levenson Mark , Zhang Joanne , Zhong Jinglin
Published: July 2007

For a two‐arm active control clinical trial designed to test for non‐inferiority of the test treatment compared with the active control standard treatment, data of historical studies are often utilized. For example, with a cross‐trial comparison approach (also called synthetic approach or λ‐margin approach), the trial is conducted to test the hypothesis that the mean difference or the ratio between the current test product and the active control is no larger than a certain portion of the mean difference or the ratio of the active control and placebo obtained in
the historical data when the positive response indicates treatment effectiveness. The regulatory agency usually requires that the clinical trials of two different test treatments are independent in most regular cases. It also requires, in general, two independent trials of the same test treatment in order to provide confirmatory evidence of the efficacy of the test product. In this article, we derived the relationship between the correlation of the test statistics of two trials with the choice of λ (the percentage to preserve), the sample sizes and variances under the normality assumption. We showed that the smaller a λ, the higher the correlation between the two non‐inferiority tests. It is further shown that when an 80 per cent or larger λ is used, the correlation can be controlled to be less than 10 per cent if the variances of the response variables in the current trial are not much smaller than those of the historical studies. Published in 2007 by John Wiley & Sons, Ltd.
Flavor reversion in soybean oil. V. Isolation and identification of reversion compounds in hydrogenated soybean oil
Authors: Schepartz A. I. , Daubert B. F.
Published: July 2007

A reinvestigation of the deodorization condensates obtained from reverted, hydrogenated soybean oil has been made. The flavor materials were further concentrated by vacuum distillation at room temperature and by separation into neutral and acid fractions.

Qualitative tests indicated that the flavor components were mainly α,β‐unsaturated carbonyls.

Hydrogenation of the fractions possessing flavors destroyed the α,β‐unsaturated carbonyls as well as the flavors. Oxidation of the carbonyls to the corresponding acids gave similar results.

Three compounds were isolated as the 2,4‐dinitrophenylhydrazones. They were identified as maleic dialdehyde, di‐n‐propyl ketone, and 2‐heptenal by the use of physical as well as chemical data.

A possible mechanism for the formation of two of these compounds from fatty acid precursors has been indicated.
Studies on surface activity of linear alkylbenzene sulfonates II: Effect of water hardness
Authors: Kumar Raj , Bhat S. G. T.
Published: July 2007

Adsorption behavior of a mixture of homologs and isomers of sodium linear alkylbenzene sulfonates from their aqueous solutions in hard water at the solution/air interface has been investigated. Increasing the concentration of surfactant in hard water results in the precipitation of the surfactant, which starts redissolving in the solution with further increases in surfactant concentration beyond a certain value characteristic of the surfactant, and finally results in a clear solution. Surface tension versus the logarithm of concentration curves shows an unusual behavior of multiple breaks. Attempts have been made to explain the results in terms of the equilibrium existing among the different forms of the surfactant, namely monomer, precipitate and the micelle.
The effect of a non‐ionic detergent on the detergency of alkylaryl sulfonates and soap in hard water
Authors: Barker G. E.
Published: July 2007

A non‐ionic detergent, Renex, has been shown to improve markedly the detergency of alkylaryl sulfonates in the washing of synthetically soiled cotton. This improvement was found to exist also when the alkylaryl sulfonates were built with CMC, salts, and alkalies.

A combination of tallow soap with the non‐ionic detergent, Renex, has been shown to have greater effectiveness than tallow soap alone in hard water. Sodium laurate‐Renex combinations show less improvement over straight sodium laurate. When Renex replaces half the tallow soap in a formula containing CMC, sodium carbonate, and tetrasodium pyrophosphate as builders, it improves the detergency in hard water. When Renex replaces half the sodium laurate in a formula containing CMC, sodium carbonate, and tetrasodium pyrophosphate as builders, it improves the detergency.
The determination of potassium in soap and mixed caustic lye
Authors: Miller W. J. , Andrews J. T. R.
Published: July 2007

The method of determining potassium as KIO4, as suggested by Willard and Boyle, has been modified and applied to the analysis of soap and caustic lye. The precipitated periodate is completely reduced, and the liberated iodine is titrated with standard thiosulfate. The determination is sensitive to 0.1 mg. of potassium and the analysis of large numbers of samples may be carried out simultaneously in a relatively short time. This, along with the low cost of the reagents, makes the method applicable to industrial control work. An extensive literature search was made and the complete list of references is included.
Binary mixtures of fatty acid derivatives. I. Dihydrazides of dicarboxylic acids‐glutaric to sebacic
Authors: Paschke R. F. , Wheeler D. H.
Published: July 2007

A simple preparation of the dihydrazides is given. The recrystallized dihydrazides of glutaric, adipic, pimelic, suberic, azelaic, and sebacic acids melted at 176, 182, 185, 187, and 188°C., respectively.

The melting point curves are reported for binary mixtures of a) the dihydrazides of adjacent members of the homologous series of dicarboxylic acids from glutaric to sebacic, b) suberic and sebacic dihydrazide, and c) sebacic dihydrazide and stearic hydrazide.

The binary mixtures of the dihydrazides show formation of a eutectic containing 52–53 weight per cent of the lower component.

The binary mixture of stearic hydrazide and sebacic dihydrazide shows no eutectic by the method used.
Effect of temperature on the content of pigments of stored cottonseed
Authors: Castillon L. E. , Hall C. M. , O'Connor R. T. , Miller C. B.
Published: July 2007

Three pure‐bred varieties of cottonseed,G. hirsutum, which were planted and grown under similar environmental conditions were stored at 38°, 77°, and 85°F. After determining the initial contents of lipids, nitrogen, moisture, gossypol, and gossypurpurin each lot of seed was stored at the different temperatures and analyzed periodically with respect to changes in pigmentation.

The content of gossypurpurin was found to increase during storage in all of the samples. Its increase was proportional to the temperature and length of storage. On the other hand, gossypol decreased during storage of all samples.

The antimony trichloride test for gossypol was found to be applicable only to extracts prepared from fresh cottonseed. During storage of the seed another yellow‐colored pigment(s) developed which could be separated from gossypol by alkaline extraction of the original chloroform extract of the stored seed. The alkali extractable portion of the chloroform extract gave a red‐colored antimony trichloride reaction product characteristic of gossypol.

It is postulated that at least a fraction of the non‐acidic pigment(s) in the crude chloroform extracts obtained from stored cottonseed is diaminogossypol.
Cellular organelles and lipids
Authors: Wolken Jerome J.
Published: July 2007

These structural and biochemical studies indicate that the internal structure of the cell is a complex system of macromolecules which are organized into organelles for function. These organelles consist of complicated internal membranes, the structure of which in molecular dimensions is best represented by a double layer of lipid and protein, referred to as the unit membrane (Fig. 3b, 3d, 4d, 5d). Such a structure provides large surface areas for the orientation of pigment molecules as in the photoreceptors (Fig. 8) and sites for enzymatic reactions. Since these membranes contain high concentrations of lipids, their synthesis and molecular organization become important.

Such ordered organelle structures behave like liquid crystals for they undergo phase transitions from ordered to disordered states which depend upon temperature and concentration. The determining of the kinds and distribution of the fatty acids in a variety of cells may be an approach for developing phylogenetic relationships as well as biochemical patterns in the evolution of the plant → animal. For a deeper understanding of the biological mechanism however, newer tools need to be developed to study the subtleties in the chemistry of the cell and its organelles in the living state.
The fatty acid composition of edible marine fish oils
Authors: Khalid Qamar , Mirza Ahmed Saeed , Hameed Khan A.
Published: July 2007

The body oils of 13 species of marine edible fishes found around the Karachi‐Makran coast were studied by gas‐liquid chromatography (GLC) for their fatty acid composition. The analyses showed the presence of fatty acids with chain lengths from 10 to 24 carbon atoms and with zero to six double bonds. The oils were found to be rich in polyunsaturated acids, particularly the penta‐ and hexaenoic. Certain major fatty acids were found to vary widely among the species: myristic acid 2.3 to 13.7%; palmitic 11.6 to 41.2%; stearich 7.2 to 23.2%; oleic 6.9 to 29.6%; eicosapentaenoic 1.4 to 19.0%; docosapentaenoic zero to 10.2%; and docosahexaenoic zero to 36.4%. The linoleic and linolenic acids were present in small amounts in some of the fish oils, and arachidonic acid was present in all of them.
Tung oil research and development at the southern regional laboratory
Authors: Kopacz B. M.
Published: July 2007

This paper reviews utilization research on tung oil conducted at the Southern Regional Research Laboratory in New Orleans. The tung oil program began with the inception of the Laboratory in 1940. Utilization research on tung oil has been concerned with exploratory chemical reactions to develop new or improved industrial products and with the development of improved paint formulations. The emphasis of the domestic and foreign extra‐mural program supervised by this Laboratory has been aimed at the practical applications of tung oil in plastics and the effects of heat on tung oil. Accomplishments over the past few years in these areas are described, and some projection for future research needs are proposed.
Random median sampling to enhance the precision of population estimates
Authors: Yamamura Kohji , Wada Takashi , Urano Satoru
Published: July 2007

We describe the characteristics of a sampling procedure called random median sampling that was proposed to enhance the precision of population estimates. In performing random median sampling, we first select a sampling item at random from the sampling area. We roughly compare the abundance of individuals in the selected item with that of the adjacent two items in order to identify the item that has median abundance, i.e., the item that has the second largest abundance among the three items. We count the number of individuals of the item having the median abundance. This procedure is repeated n times in the sampling area (i = 1, 2, …, n). Let mi be the ith median abundance. The estimates of the mean abundance per sampling item and the variance of estimates are given by Σmi/n and Σ(mi –Σmi/n)2/n(n – 1), respectively. This method is a local application of the median ranked set sampling that was proposed by Muttlak (J Appl Stat Sci 6:245–255, 1997). Random median sampling is effective when the correlation coefficient between adjacent items is small. If the correlation coefficient is close to zero, random median sampling reduces the variance of estimates to 45 or 32% of that in simple random sampling when the distribution follows a normal distribution or a Laplace distribution, respectively. The sample size required to achieve a given precision of estimate decreases accordingly. The effectiveness of random median sampling, however, is small if the correlation coefficient is large. The condition in which random median sampling is superior to simple random sampling is also discussed.
Fractionation and characterization of proteins from Gevuina avellana and Rosa rubiginosa seeds
Authors: Moure Andrés , Rúa María Luisa , Sineiro Jorge , Domíguez Herminia
Published: July 2007

Gevuina avellana and Rosa rubiginosa proteins were evaluated for their potential food use. The proteins were sequentially separated into five fractions according to their solubilities in deionized water, 0.5 M NaCl, 70% (vol/vol) isopropyl alcohol, 50% (vol/vol) glacial acetic acid, and 0.1 M NaOH. The five fractionated protein groups were then characterized by SDS‐PAGE and gel filtration chromatography to determine their M.W. profiles. Ninety‐six percent of G. avellana total protein was solubilized in three extraction stages, and 88% of R. rubiginosa total protein was solubilized in one extraction stage. Albumins were the major protein fraction in G. avellana and glutelins‐1 the most abundant in R. rubiginosa. The protein solubility profile determined over the pH range 1–12 showed minimal solubilities at pH 3–5 and pH 3–7 for G. avellana and R. rubiginosa, respectively. Electrophoretic studies revealed the existence of proteins composed of two major kinds of polypeptides linked together via disulfide bonds and with molecular masses ranging from 13 to 119 kDa. Gel filtration chromatography profiles of globulins and albumins were studied for both seeds. Isoelectric focusing showed an isoelectric point in the ranges of 4.5–6 and 3–6.5 for G. avellana and R. rubiginosa proteins, respectively.
Enzymatic Interesterification of Extra Virgin Olive Oil with a Fully Hydrogenated Fat: Characterization of the Reaction and Its Products
Authors: Criado Manuel , Hernández‐Martín Estela , López‐Hernández Arnoldo , Otero Cristina
Published: July 2007

The lipase‐catalyzed interesterification of extra virgin olive oil (EVOO) and fully hydrogenated palm oil (FHPO) was studied in a batch reactor operating at 75 °C. The compositions of the semi‐solid fat products depend on the reaction conditions and the initial ratio of EVOO to FHPO. The dependence of the quasi‐equilibrium product TAG profile on the reaction time was determined for initial weight ratios of EVOO to FHPO from 80:20 to 20:80. Lipozyme TL IM, Lipozyme RM IM and Novozym 435 were employed as biocatalysts. The interesterification reaction was optimized with respect to the type and loading of biocatalyst. Equilibrium was approached in the shortest time with Novozym 435 (80% conversion in 4 h). The chemical, physical, and functional properties of the products were characterized. Appropriate choices of the reaction conditions and the initial ratio of EVOO to FHPO lead to TAG with melting profiles and solid fat contents similar to those of commercial products. Differences were observed in the solid fat contents, melting profiles, and oxidative stabilities of the various interesterified products and also between the indicated properties of each category of product and the corresponding physical blend of the precursor reagents.
Changing patterns of emergency obstetric care at a Nigerian University hospital
Authors: Oladapo O.T. , Ariba A.J. , Odusoga O.L.
Published: July 2007

Objective: To analyze the changing patterns of critical obstetric care over two consecutive 3‐year periods and identify the factors responsible for the trend through combined audits of near miss and maternal mortality at a Nigerian University hospital. Methods: Retrospective audit and comparison of “near misses” and maternal deaths recorded in 1999–2001 and 2002–2004 at a tertiary care center in southwest Nigeria. The definition of near miss morbidity was based on validated disease‐specific criteria. For each near miss and maternal death, the local audit committee compared the actual management with local treatment protocols and explored avoidable factors. Case fatality rate was calculated for “critically ill obstetric patients” (CIOP‐CFR) for both periods. The cause‐specific case fatality rate (CFR) was used to assess the trend in standards of care for life‐threatening obstetric conditions. Data were compared using the χ2 or Fisher's exact test. P < 0.05 was considered statistically significant. Results: There were 175 near misses and 27 maternal deaths in 1999–2001 and 211 near misses and 44 maternal deaths in 2002–2004. The CIOP‐CFRs for the two periods showed a declining (but non‐significant) trend in the standard of emergency obstetric care for life‐threatening conditions (13.4% to 17.3%, P = 0.250). The CIOP‐CFR for postpartum hemorrhage significantly increased from 3.1% to 21.1% in the 2nd period (P = 0.033), reflecting a decline in the standard of care. Lack of blood for transfusion became a more significant administrative problem in the 2nd period occurring in 17.8% of all critically ill patients managed in 2002–2004. There was a notable though statistically insignificant increase in the non‐adherence to treatment protocol among cases of maternal death in 2002–2004 compared with 1999–2001. Conclusions: The standard of critical obstetric care in this center is suboptimal with no evident improvement over the 6‐year period. This audit supports the feasibility of including near miss reviews in maternal death audits to provide insights into the trend in the quality of emergency services for severe maternal complications while highlighting factors associated with deficiency or improvement in care for specific maternal conditions.
Bacteraemia in 66 cats and antimicrobial susceptibility of the isolates (1995–2004)
Authors: Greiner Martina , Wolf Georg , Hartmann Katrin
Published: July 2007

Bacterial blood culture results of 292 privately owned cats presented to the Clinic for Small Animal Medicine, Ludwig Maximilian University Munich with signs of sepsis were evaluated retrospectively. Of the blood cultures, 23% were positive. In 88%, a single bacterial species was isolated. Of all bacterial isolates, 45% were Gram-positive, 43% were Gram-negative, and 12% were obligate anaerobes. The most frequently isolated bacteria were Enterobacteriaceae, obligate anaerobic species, Staphylococcus species and Streptococcus species. Of the cats with positive blood cultures, 32% were pretreated with antibiotics. Of all bacterial isolates, 77% were susceptible to enrofloxacin, 69% to chloramphenicol, 67% to gentamicin, and 64% to amoxycillin clavulanic acid. Only enrofloxacin reached an in vitro efficacy of more than 70% against Gram-positive and more than 74% against Gram-negative bacteria.