bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical properties of Si and Ge nanocrystals: Parameter‐free calculations
Authors: Ramos L. E. , Weissker H.‐Ch. , Furthmüller J. , Bechstedt F.
Published: November 2005

The cover picture of the current issue refers to the Edi‐tor's Choice article of Ramos et al. [1]. The paper gives an overview of the electronic and optical properties of silicon and germanium nanocrystals determined by state‐of‐the‐art ab initio methods. Nanocrystals have promising applications in opto‐electronic devices, since they can be used to confine electrons and holes and facilitate radiative recombination. Since meas‐urements for single nanoparticles are difficult to make, ab initio theoretical investigations become important to understand the mechanisms of luminescence.

The cover picture shows nanocrystals of four sizes with tetrahedral coordination whose dangling bonds at the surface are passivated with hydrogen. As often observed in experiments, the nanocrystals are not perfectly spherical, but contain facets. Apart from the size of the nanocrystals, which determines the quantum confinement, the way their dangling bonds are passivated is relevant for their electronic and optical properties. For instance, the passivation with hydroxyls reduces the quantum confine‐ment. On the other hand, the oxidation of the silicon nanocrys‐tals increases the quantum confinement and reduces the effect of single surface terminations on the gap. Due to the oscillator strengths of the lowest‐energy optical transitions, Ge nanocrys‐tals are in principle more suitable for opto‐electronic applica‐tions than Si nanocrystals.

The first author, Luis E. Ramos, is a postdoc at the Institute of Solid‐State Physics and Optics (IFTO), Friedrich‐Schiller University Jena, Germany. He investigates electronic and optical properties of semiconductor nanocrystallites and is a member of the European Network of Excellence NANO‐QUANTA and of the European Theoretical Spectroscopy Facility (ETSF).
Ion motion in the rectangular wave quadrupole field and digital operation mode of a quadrupole ion trap mass spectrometer
Authors: Ding L. , Kumashiro S.
Published: November 2005

A quadrupolar electric field driven by a rectangular wave voltage can be used for mass‐selective storage and analysis. The ion motion in such an electric field is derived, and the stability of ions is presented in the a‐q diagram that is commonly used for sinusoidal wave quadrupole mass spectrometry in association with the solution of the Mathieu equation. The pseudo‐potential well is discussed in an approximation that leads to the relation of secular frequency to operating parameters. A scheme for a digital ion trap mass spectrometer is described, based on this theory. An ion optics simulation was performed to check the theory of resonant ejection, and to prove the feasibility of the mass scan method for a practical ion trap of such geometry. Copyright © 2005 John Wiley & Sons, Ltd.
Learning oceanography from a computer simulation compared with direct experience at sea
Authors: Winn William , Stahr Frederick , Sarason Christian , Fruland Ruth , Oppenheimer Peter , Lee Yen‐Ling
Published: November 2005

Considerable research has compared how students learn science from computer simulations with how they learn from “traditional” classes. Little research has compared how students learn science from computer simulations with how they learn from direct experience in the real environment on which the simulations are based. This study compared two college classes studying introductory oceanography. One class learned using an interactive computer simulation based on a dynamic, three‐dimensional model of physical oceanography. The other class learned by spending a day on a research ship using scientific tools and instruments to measure physical properties of the ocean directly. In classes preceding and following the simulation or field experience, students performed the same exercises regarding currents and salinity, had the same instructor presentations, and did the same homework. The study found that the field experience helped contextualize learning for students with little prior experience of the ocean while the simulation made it easier for students to connect what they learned from it to other content they learned in class. These and other findings shed light on what computer simulations can and cannot help students learn, and what concepts are best learned in the real environment. © 2005 Wiley Periodicals, Inc. J Res Sci Teach 43: 25–42, 2006
Fetoscopic and ultrasound‐guided decompression of the fetal trachea in a human fetus with Fraser syndrome and congenital high airway obstruction syndrome (CHAOS) from laryngeal atresia
Authors: Kohl T. , Hering R. , Bauriedel G. , Van de Vondel P. , Heep A. , Keiner S. , Müller A. , Franz A. , Bartmann P. , Gembruch U.
Published: November 2005

Congenital high airway obstruction syndrome (CHAOS) from laryngeal atresia bears a poor prognosis for hydropic fetuses owing to cardiac failure. We attempted percutaneous fetoscopic and ultrasound‐guided tracheal decompression in a hydropic human fetus with CHAOS associated with Fraser syndrome.

Percutaneous fetoscopic and ultrasound‐guided tracheal decompression was performed using three trocars under general materno‐fetal anesthesia at 19 + 5 weeks of gestation. Abnormal fetoplacental blood flow normalized within hours as a result of the intervention. Furthermore, a normalization of lung : heart size and lung echogenicity was observed within days. Resolution of hydrops was complete within 3 weeks. Premature rupture of membranes and premature contractions prompted emergency delivery of the fetus by ex‐utero intrapartum treatment (EXIT) at 28 + 2 weeks of gestation. Following delivery, the lungs could be ventilated at low pressures and ambient oxygen concentration. Weaning from ventilation was achieved at 18 days of postnatal life.

Our experience indicated that percutaneous fetoscopic and ultrasound‐guided decompression of the fetal trachea is feasible and may permit normalization of hemodynamics in hydropic human fetuses with CHAOS from laryngeal atresia. The procedure may also result in normalization of heart : lung size and provide the time needed to regain the function of the overstretched diaphragm in this grave fetal condition. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Fetal lung development in pregnancies of diabetic women assessed by quantitative ultrasonic tissue characterization
Authors: Tekesin I. , Anderer G. , Hellmeyer L. , Köhler S. , Kühnert M. , Schmidt S.
Published: November 2005

Objectives

This study was performed to compare quantitative ultrasonic tissue characterization of the fetal lung at different gestational ages in uncontrolled diabetic patients with that in normal uncomplicated pregnancies.

Methods

A total of 44 women at 24–37 weeks' gestation with the diagnosis of diabetes in pregnancy were enrolled. Data were compared to those of the control group, which consisted of 140 women with uncomplicated pregnancies of the same gestational age. Longitudinal and transverse sections of the fetal thorax and upper abdomen were examined. A region of interest of constant size was defined and the tissue‐specific gray scale was determined by using interactive software.

Results

Compared with normal pregnancies, fetal lungs of diabetic pregnancies have a higher echogenicity between 28 and 37 weeks of gestation. The lung mean gray values (MGV) only differed significantly between 30 and 31 weeks of gestation in the group with diabetes (P = 0.033) compared to the control group. The MGV of the liver in diabetic and normal pregnancies is similar during pregnancy, significant differences being found only at 30–31 weeks of gestation (P = 0.038). The lung‐to‐liver ratio in the control group showed a significant increase from 24 to 31 weeks and a slight non‐significant decrease after 31 weeks. The ratio in the group with diabetes increased slightly up to week 33 and decreased slightly afterwards.

Conclusion

Fetal lung MGV in uncontrolled diabetic pregnancies compared to that in uncomplicated pregnancies differs significantly only between 30 and 31 weeks of gestation. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Cervical length at 18–22 weeks of gestation for prediction of spontaneous preterm delivery in Hong Kong Chinese women
Authors: Leung T. N. , Pang M. W. , Leung T. Y. , Poon C. F. , Wong S. M. , Lau T. K.
Published: November 2005

Objective

To assess the value of a single cervical length measurement by transvaginal sonography (TVS) at the time of mid‐trimester anomaly scan for predicting spontaneous preterm delivery (SPD) among Chinese women.

Methods

A prospective observational study was carried out involving 2880 subjects with singleton pregnancies and confirmed gestational age. Cervical length was measured at 18–22 weeks of gestation.

Results

The incidence of SPD < 34 weeks and < 37 weeks were 0.7% and 3.7%, respectively. Women with SPD < 34 weeks and SPD < 37 weeks had shorter median cervical lengths (32.6 mm and 36.2 mm, respectively) than those with term deliveries (37.6 mm) (P = 0.006 and 0.025, respectively). The predictive performance of cervical length was better for SPD < 34 weeks compared with < 37 weeks. A cervical length ≤ 27 mm, which corresponded to the 4th centile, occurred in 36.8%, 62.5% and 100% of those with SPD < 34, < 30 and < 26 weeks, respectively. The positive likelihood ratio (LR) of a cervical length ≤ 27 mm in predicting SPD < 34 weeks was 9.8. Using logistic regression, both short cervix and funneling were independent predictors for SPD < 34 weeks of gestation. The coexistence of funneling and a cervical length ≤ 27 mm gave a positive predictive value (PPV) and LR of SPD < 34 weeks of 14.7% and 26.0, respectively.

Conclusions

Mid‐trimester cervical length is predictive of SPD in Chinese women. However, given the low PPV of a short cervical length, its clinical utility is still limited in low‐risk populations. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Assessing clinical performance of gynecology residents: sonographic evaluation of adnexal masses based on morphological scoring systems
Authors: Lee T. S. , Kim J. W. , Park N. H. , Song Y. S. , Kang S. B. , Lee H. P.
Published: November 2005

Objective

To assess the performance of inexperienced gynecology residents in the evaluation of adnexal masses using sonographic scoring systems.

Methods

From April 2003 to October 2004, transvaginal sonography was performed preoperatively by junior gynecology residents on 1‐month shifts on 123 patients suspected of having adnexal masses. A total of 137 adnexal masses were found and evaluated using two different morphological scoring systems (those of DePriest and Lerner). The diagnostic performance of the sonographic scoring systems was assessed using the McNemar test and receiver–operating characteristics (ROC) curve analysis was used for lesion characterization. The diagnostic accuracy when the results of both scoring systems satisfied malignancy cut‐off values was also investigated.

Results

Histopathological analysis revealed that, of the 137 lesions, 109 were benign, 23 were malignant and five were borderline. Best clinical cut‐off levels were ≥ 5 on the DePriest and ≥ 3 on the Lerner scores. Both systems achieved good performance for characterizing malignancy. No significant difference was found in terms of the accuracy of the two systems as determined by mean areas under the ROC curves (0.816 and 0.783, P = 0.562). The combined approach using both scoring systems resulted in higher specificity (77.1%, P < 0.05) and positive predictive value without a significant decrease in sensitivity (82.1%) compared with either system alone. Of the 43 histologically confirmed false‐positive cases, mature cystic teratoma was most common, with 13/22 (59%) cases being misinterpreted as malignancies.

Conclusion

Junior residents, inexperienced at sonography, performed fairly in terms of evaluating adnexal masses with the help of morphological scoring systems. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Accuracy of fetal lung volume assessed by three‐dimensional sonography
Authors: Ruano R. , Martinovic J. , Dommergues M. , Aubry M.‐C. , Dumez Y. , Benachi A.
Published: November 2005

Objective

To determine the accuracy and precision of prenatal three‐dimensional (3D) ultrasound in estimating fetal lung volume using the rotational multiplanar technique (VOCAL™) by comparing it to postmortem volume measurements.

Methods

Fetal lung volume was measured during 3D ultrasound examination using a rotational multiplanar technique in eight cases of congenital diaphragmatic hernia (CDH) (six left and two right‐sided) and in 25 controls without pulmonary malformation, immediately before termination. Prenatal 3D sonographic estimates of fetal lung volume were compared with postmortem measurement of fetal lung volume achieved by water displacement.

Results

The intraclass correlation coefficient of fetal lung volume estimated by 3D ultrasound and measured at postmortem examination was 0.95 in CDH cases and 0.99 in controls. Based on Bland–Altman analysis, the bias, precision and limits of agreement were, respectively, 0.35 cm3, 1.46 cm3 and between −2.51 and + 3.21 cm3 in cases with CDH and 0.08 cm3, 2.80 cm3 and between −5.41 and + 5.57 cm3 in controls. The mean relative error of 3D ultrasound fetal lung volume measurement was −7.19% (from −42.70% to + 18.11%) in CDH cases and −0.72% (from −30.25% to + 19.22%) in controls, while the mean absolute error of 3D ultrasound fetal lung volume measurement was 1.40 (range, 0.71–2.52) cm3 and 2.12 (range, 0.05–4.98) cm3, respectively. Accuracy of 3D ultrasound for measuring fetal lung volumes was 84.86 (range, 57.30–99.48)% in cases with CDH and 91.38 (range, 69.75–99.45)% in controls. The mean intraobserver variability for lung volume estimated by 3D ultrasound was 0.28 cm3 in controls and 0.17 cm3 in CDH cases.

Conclusion

Prenatal 3D ultrasound can estimate accurately fetal lung volume using the rotational multiplanar technique for volume measurements (VOCAL), even in fetuses with very small lungs, such as cases with isolated CDH. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Giant omphaloceles with a small abdominal defect: prenatal diagnosis and neonatal management
Authors: Pelizzo G. , Maso G. , Dell'Oste C. , D'Ottavio G. , Bussani R. , Uxa F. , Conoscenti G. , Schleef J.
Published: November 2005

A giant omphalocele is a liver‐containing protrusion through an abdominal defect wider than 5 cm in diameter. The giant form with a small abdominal wall defect is a rare condition which, to our knowledge, has not been described previously. We describe three cases with the typical features of elongated vascular liver pedicle and angiomatosis of the hepatic portal system. The abnormal liver organogenesis, due to extra‐abdominal development, represented a significant risk factor for hepatic thrombosis after visceral reduction and liver rotation. All the neonates underwent surgery on the first day of postnatal life. One died because of a postoperative liver infarction, and the survivors needed prolonged respiratory support. Prenatal sonographic features, timing, delivery, type of surgical repair, and postnatal outcome are reviewed. A prenatal sonographic diagnosis could be useful to evaluate the abdominal ring and serial ultrasound examinations are recommended to detect promptly ominous signs of hepatic and bowel damage. Color Doppler may be useful to assess the anatomy of the abdominal vessels and their relationships with the herniated organs, although it was not used in any of the cases reported here. This congenital malformation might be considered as a pathological entity separate from giant omphalocele with large abdominal defect, with a severe prognosis due possibly to its different embryological development. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Evaluation and validation of a new risk score (CLEOPATRA score) to predict the probability of premature delivery for patients with threatened preterm labor
Authors: Tekesin I. , Eberhart L. H. J. , Schaefer V. , Wallwiener D. , Schmidt S.
Published: November 2005

Objective

To develop a clinically useful tool to predict the probability of preterm delivery in patients with threatened preterm labor.

Methods

One hundred and seventy patients with preterm labor between 24 and 34 weeks of gestation were included. Preterm delivery < 37 weeks of gestation was the main endpoint of the study. The data were randomized and split into an evaluation set (n = 85) and a validation set (n = 85). The evaluation set was subjected to stepwise backward logistic regression analysis to quantify the relative impact of four potential risk factors, including individual patient factors, results of a rapid fetal fibronectin assay, and sonographic measurement of cervical length. Using the constant of the logistic regression analysis and the beta‐coefficients for the identified risk factors the individual probability of preterm delivery for each woman of the validation dataset was calculated. The area under a receiver–operating characteristics curve (AUC) was used to evaluate the discriminating power of the score.

Results

The overall rate of preterm delivery was 27.1%. The logistic regression analysis was performed for the potential predictors of spontaneous preterm delivery, identified by univariate analysis. These were positive fetal fibronectin, cervical length, previous preterm delivery and maternal age. Two risk factors were independent predictors of preterm delivery and were included in the CLEOPATRA I (clinical evaluation of preterm delivery and theoretical risk assessment) score: cervical length measurement and previous preterm delivery were associated with a higher risk of preterm delivery (odds ratio, 7.65 and 6.74, respectively). Since fetal fibronectin assay is not available at all institutions worldwide, it was excluded from the initial model. In the CLEOPATRA II model the risk factors fetal fibronectin and previous preterm delivery were associated with higher risk of preterm delivery, with odds ratios of 17.9 and 4.56, respectively. The discrimination power (AUC) obtained from the models were: CLEOPATRA I, 0.69 (95% CI, 0.56–0.82); CLEOPATRA II, 0.81 (95% CI, 0.69–0.93).

Conclusion

In symptomatic women the risk for preterm delivery can be predicted best with the CLEOPATRA II score based on fetal fibronectin and previous preterm delivery. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Diagnostic accuracy of varying discriminatory zones for the prediction of ectopic pregnancy in women with a pregnancy of unknown location
Authors: Condous G. , Kirk E. , Lu C. , Van Huffel S. , Gevaert O. , De Moor B. , De Smet F. , Timmerman D. , Bourne T.
Published: November 2005

Objectives

Various serum human chorionic gonadotropin (hCG) discriminatory zones are currently used for evaluating the likelihood of an ectopic pregnancy in women classified as having a pregnancy of unknown location (PUL) following a transvaginal ultrasound examination. We evaluated the diagnostic accuracy of discriminatory zones for serum hCG levels of > 1000 IU/L, 1500 IU/L and 2000 IU/L for the detection of ectopic pregnancy in such women.

Methods

This was a prospective observational study of women who were assessed in a specialized transvaginal scanning unit. All women with a PUL had serum hCG measured at presentation. Expectant management of PULs was adopted. These women were followed up with transvaginal ultrasound, monitoring of serum hormone levels and laparoscopy until a final diagnosis was established: a failing PUL, an intrauterine pregnancy (IUP), an ectopic pregnancy or a persisting PUL. The persisting PULs probably represented ectopic pregnancies which had been missed on ultrasound and these were incorporated into the ectopic pregnancy group. Three different discriminatory zones (1000 IU/L, 1500 IU/L and 2000 IU/L) were evaluated for predicting ectopic pregnancy in this PUL population.

Results

A total of 5544 consecutive women presented to the early pregnancy unit between 25 June 2001 and 14 April 2003. Of these, 569 (10.3%) women were classified as having a PUL, 42 of which were lost to follow up. Of the 527 (9.5%) cases with PUL analyzed, there were 300 (56.9%) failing PULs, 181 (34.3%) IUPs and 46 (8.7%) ectopic pregnancies. Overall, 74.6% were symptomatic and 25.4% were asymptomatic (P = 8.825E–07). The sensitivity and specificity of an hCG level of > 1000 IU/L to detect ectopic pregnancy were 21.7% (10/46) and 87.3% (420/481), respectively; for an hCG level of > 1500 IU/L these values were 15.2% (7/46) and 93.4% (449/481), respectively, and for an hCG level of > 2000 IU/L they were 10.9% (5/46) and 95.2% (458/481), respectively.

Conclusions

Varying the discriminatory zone does not significantly improve the detection of ectopic pregnancy in a PUL population. A single measurement of serum hCG is not only potentially falsely reassuring but also unhelpful in excluding the presence of an ectopic pregnancy. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Analysis of Z‐score distribution for the quality control of fetal ultrasound measurements at 20–24 weeks
Authors: Salomon L. J. , Bernard J. P. , Ville Y.
Published: November 2005

Objectives

To develop and evaluate the feasibility of Z‐score distribution‐based quality assessment for fetal biometry at 20–24 gestational weeks.

Methods

Four sonographers measured fetal biparietal diameter, head circumference, abdominal circumference and femur length in unselected pregnancies undergoing routine sonography at 20–24 weeks in our center between June 2001 and January 2004. All measurements were transformed into Z‐scores. Distributions of Z‐scores were compared with the expected standard normal distribution based on mean, SD and the Kolmogorov–Smirnov test. Modelling was performed to assess the sensitivity, specificity and Youden's index (sensitivity + specificity − 1) of each sonographer, reflecting their ability to detect fetuses with abnormal biometry in our population.

Results

A total of 5241 ultrasound examinations were included. None of the Z‐score distributions could be considered similar to the standard normal distribution: means of Z‐scores ranged from −0.604 to 0.73 and the SD ranged from 0.726 to 0.896. Sensitivity and specificity ranged from 25.31% to 68.67% and 93.44% to 100%, respectively; Youden's index ranged from 0.25 to 0.69.

Conclusion

Analysis of Z‐score distribution can be used to assess the quality of fetal measurements. Several indices can be extracted from this analysis in order to improve quality assessment of fetal biometry measured by ultrasound. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Three‐dimensional sonographic description of abnormal metopic suture in second‐ and third‐trimester fetuses
Authors: Chaoui R. , Levaillant J. M. , Benoit B. , Faro C. , Wegrzyn P. , Nicolaides K. H.
Published: November 2005

Objective

To describe patterns of abnormal development of the metopic suture in association with fetal malformations during the second and third trimesters of pregnancy.

Methods

This was a cross‐sectional study of the frontal bones and metopic suture in 11 fetuses at 17–32 weeks of gestation. Cases were selected because there were obvious abnormalities in the metopic sutures. In each case, a malformation was detected by two‐dimensional (2D) ultrasound and the abnormality of the metopic suture was detected and evaluated on three‐dimensional (3D) ultrasound, using transparent maximum mode.

Results

There were essentially four patterns of abnormality in the metopic suture: firstly, delayed development with a V‐ or Y‐shaped open suture, which is found in normal fetuses at 12–16 weeks; secondly, a U‐shaped open suture, presumably due to upward growth of the frontal bones with delayed closure; thirdly, premature closure of the suture, which is normally observed after 32 weeks; fourthly, the presence of additional bone between the frontal bones. Premature closure of the suture or additional bone between the frontal bones was observed in fetuses with holoprosencephaly and abnormalities of the corpus callosum, whereas the V‐, Y‐ and U‐shaped metopic sutures were observed in fetuses with facial defects involving the orbits, nasal bones, lip, palate and mandible, in the absence of holoprosencephaly and abnormal corpus callosum.

Conclusions

This preliminary study describes the pattern of possible abnormalities of the metopic suture and should stimulate further investigation to establish the prevalence and evolution of abnormal sutures as well as the incidence and pattern of other associated defects. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Assessment of lung area in normal fetuses at 12–32 weeks
Authors: Peralta C. F. A. , Cavoretto P. , Csapo B. , Vandecruys H. , Nicolaides K. H.
Published: November 2005

Objective

To establish reference intervals with gestation for the right and left lung areas and lung area to head circumference ratio (LHR).

Methods

This was a cross‐sectional study of 650 normal singleton pregnancies at 12–32 weeks of gestation. We measured the left and right lung areas on the cross‐sectional plane of the thorax, used for examination of the four‐chamber view of the heart, by three different techniques: firstly, manual tracing of the limits of the lungs; secondly, multiplication of the longest diameter of the lung by its longest perpendicular diameter; thirdly, multiplication of the anteroposterior diameter of the lung at the mid‐clavicular line by the perpendicular diameter at the midpoint of the anteroposterior diameter.

Results

The respective mean left and right lung areas (manual tracing) increased with gestational age, from 36 and 58 mm2 at 12 weeks to 220 and 325 mm2 at 20 weeks and 594 and 885 mm2 at 32 weeks. This 16‐fold increase in lung area was accompanied by a four‐fold increase in head circumference. Consequently, the left and right LHR increased with gestational age. The most reproducible way of measuring the lung area was by manual tracing of the limits of the lungs and the least reproducible was by multiplying the longest diameter of the lungs by their longest perpendicular diameter. Furthermore, the method employing the longest diameter, compared with the tracing method, overestimated both the left and the right lung areas by about 45% and the method employing the anteroposterior diameter overestimated the area of the right lung by about 35%, but not that of the left lung.

Conclusions

In the antenatal prediction of pulmonary hypoplasia by the assessment of lung area it is important to take gestational age into account. Dividing the lung area by the head circumference does not correct for the gestation‐related increase in lung area. Reproducible measurement of the lung area is provided by manual tracing of the limits of the lungs, rather than by multiplication of lung diameters. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Performance evaluation of wireless cellular networks under more realistic assumptions
Authors: Fang Yuguang
Published: November 2005

In wireless cellular networks, performance evaluation is an important part in modeling and designing effective schemes to utilize the limited resource. In the past, performance evaluation was carried out either under restricted assumption on some time variables such as exponential assumption or via simulations. In this paper, we present a survey on a new analytical approach we have developed in the last few years to evaluate the performance of wireless cellular networks under more realistic assumptions. In particular, we apply this approach to the analysis of call connection performance and mobility management under assumptions that many time variables such as call holding time, cell residence time, channel holding time, registration area (RA) residence time, and inter‐service time are assumed to be generally distributed and show how we can obtain more general analytical results. Copyright © 2005 John Wiley & Sons, Ltd.
QoS‐aware mobility support architecture for next generation mobile networks
Authors: Jamalipour Abbas , Mirchandani Vinod , Kibria M. Rubaiyat
Published: November 2005

Provision of quality of service (QoS) support with mobility has received impetus from the evolution that has occurred in mobile communication technologies. This is especially the main driver behind 4G/B3G networks that will enable a user to access any type of services anytime, anywhere, and anyhow. In this paper, we first review some of the state‐of‐the‐art techniques in the area of QoS and resource management based mobility. We then propose an augmented 4G/B3G architecture that addresses key limitations in the salient 4G architectures examined in the literature. Our proposed novel augmentations in mobility, QoS, and resource management schemes consolidate operation of the 4G architecture. The other defining attributes of our proposed 4G architecture are that it is open, hierarchical, layered, and modular with cross‐layer coordination and distributed network functionalities. Well‐defined message interfaces enable the layers/levels within the architecture to support cross‐layer coordination under dynamic network conditions. A signaling network that operates independent of the heterogeneous access networks in the architecture is incorporated to carry out wireless system discovery and paging. This facilitates to conserve mobile terminal's battery power. Copyright © 2005 John Wiley & Sons, Ltd.
NCTUns network simulation and emulation for wireless resource management
Authors: Wang Shie‐Yuan , Lin Yi‐Bing
Published: November 2005

This paper describes NCTUns, an innovative network simulator and emulator for wireless and mobile networks. Effects of various radio resource management and quality of service (QoS) schemes on higher‐layer protocols and real‐world applications can be easily studied using NCTUns. In this paper, we elaborate on NCTUns simulation methodology, architecture, design, functionalities, performance, and applications. NCTUns simulation for wireless ad hoc, sensor, inter‐vehicle communication networks, GPRS cellular networks, and wireless mesh networks are also illustrated. More details about this tool can be found in http://NSL.csie.nctu.edu.tw/nctuns.html. Copyright © 2005 John Wiley & Sons, Ltd.
Performance analysis of Bluetooth piconets with finite baseband buffers
Authors: Mišić Jelena , Mišić Vojislav B.
Published: November 2005

We analyze the performance of Bluetooth piconets under bursty traffic and finite buffer sizes. We model the joint probability distributions of uplink and downlink queues using theM[x]/G/1/Kmodel with vacations and derive buffer blocking probabilities at slaves and at the master. The results, which are confirmed through simulations, provide some practical guidelines as to the sizing of device buffers. Copyright © 2005 John Wiley & Sons, Ltd.
On greedy construction of connected dominating sets in wireless networks
Authors: Li Yingshu , Thai My T. , Wang Feng , Yi Chih‐Wei , Wan Peng‐Jun , Du Ding‐Zhu
Published: November 2005

Since no fixed infrastructure and no centralized management present in wireless networks, a connected dominating set (CDS) of the graph representing the network is widely used as a virtual backbone. Constructing a minimum CDS is NP‐hard. In this paper, we propose a new greedy algorithm, called S‐MIS, with the help of Steiner tree that can construct a CDS within a factor of 4.8 + ln5 from the optimal solution. We also introduce the distributed version of this algorithm. We prove that the proposed algorithm is better than the current best performance ratio which is 6.8. A simulation is conducted to compare S‐MIS with its variation which is rS‐MIS. The simulation shows that the sizes of the CDSs generated by S‐MIS and rS‐MIS are almost the same. Copyright © 2005 John Wiley & Sons, Ltd.
Interference‐aware routing and bandwidth allocation for QoS provisioning in multihop wireless networks
Authors: Tang Jian , Xue Guoliang , Chandler Christopher
Published: November 2005

In this paper, we study the bandwidth guaranteed routing and timeslot allocation (BANDRA) in TDMA‐based multihop wireless networks with dynamic traffic. We formally model BANDRA as an optimization problem and present an integer linear programming (ILP) formulation to provide optimal solutions. This problem turns out to be a hard problem because of the impact of interference. Therefore, we propose a two‐step scheme, i.e., seeking a path for routing first and then allocating bandwidth along the found path. We present two routing algorithms to compute interference‐optimal cost‐bounded paths. In addition, we present an optimal bandwidth allocation algorithm to allocate timeslots along the found paths for connection requests with unit bandwidth requirements. For the general case where the bandwidth requirement is larger than one, we present an effective heuristic algorithm. Our simulation results show that the average difference between solutions given by our efficient scheme and optimal ones in terms of call‐blocking ratio is only 7%. Compared with the shortest path routing, our interference‐aware routing algorithms combined with our bandwidth allocation algorithm always reduce call‐blocking ratios. Copyright © 2005 John Wiley & Sons, Ltd.
Saturation throughput analysis of error‐prone 802.11 wireless networks
Authors: Ni Qiang , Li Tianji , Turletti Thierry , Xiao Yang
Published: November 2005

It is well known that the medium access control (MAC) layer is the main bottleneck for the IEEE 802.11 wireless LANs. Much work has been done on performance analysis of the 802.11 MAC. However, most of them assume that the wireless channel is error free. In this paper, we investigate the saturation throughput performance achieved at the MAC layer, in both congested and error‐prone channels. We provide a simple and accurate analytical model to calculate the MAC throughput. The model is validated through extensive simulation results. Our results show that channel errors have a significant impact on the system performance. Copyright © 2005 John Wiley & Sons, Ltd.
QoS provisioning in wireless networks
Authors: Wu Dapeng
Published: November 2005

The next‐generation wireless networks such as the fourth generation (4G) cellular systems are targeted at supporting various applications such as voice, data, and multimedia over packet‐switched networks. Providing quality of service (QoS) guarantees for these applications is an important objective in the design of the next‐generation wireless networks. In this paper, we overview the issues and techniques in QoS provisioning for wireless networks, and present some of our recent results in this area. Specifically, we survey the results in five sub‐areas, namely, network services models, traffic specification, packet scheduling for wireless transmission, call admission control in wireless networks, and wireless channel characterization. For each sub‐area, we address the particular issues, review major approaches and mechanisms, and discuss the trade‐offs of the approaches. Copyright © 2005 John Wiley & Sons, Ltd.
Resource management and QoS control in multiple traffic wireless and mobile Internet systems
Authors: Xu Yong , Liu Huazhou , Zeng Qing‐An
Published: November 2005

End‐to‐end quality of service (QoS) control for multiple traffic in wired networks is carried out through Differentiated services (DiffServ). Edge routers in DiffServ domain classify incoming flows into different per‐hop behavior (PHB) groups and give a policy‐based QoS guarantee to these behavior aggregates. As Internet extends into the wireless and mobile section, different traffic flows should be treated differently not only in wired core network, but also in wireless resource allocations. In this paper, we propose a preemptive priority handoff and adaptive resource allocation scheme. DiffServ PHB groups are mapped into different wireless and mobile QoS classes. Traffic flows are categorized into these classes in order to allow the system to allocate different bandwidth and make resource reservation according to their priorities. Higher priority traffic flows are permitted to preempt lower priority flows in service. Lower ones, on the contrary, can expand their bandwidth into areas reserved for higher priority traffic flows for better resource utilization. We use both analytical model and simulation to evaluate the system performance in terms of blocking probabilities, forced termination probabilities, and delay. The forced termination probability of high priority traffic flows can be decreased significantly by introducing the preemptive priority scheme. Therefore, this scheme can be used in wireless part of the system along with DiffServ to give further guarantee for low delay, low jitter, and low loss services to high priority services. Copyright © 2005 John Wiley & Sons, Ltd.
A channel‐aware adaptive control to the MAC protocol in rate adaptive wireless LANs
Authors: Zhu Yanfeng , Niu Zhisheng
Published: November 2005

Due to the low efficiency of legacy IEEE 802.11 MAC protocol, it has been the main bottleneck of wireless local area networks (WLANs). In this paper, we focus on multi‐rate WLANs and propose an adaptive transmission control scheme, which adapts the transmission probability according to the number of active stations, transmission rates, and channel conditions. At first, an analytical model is built in terms of the proposed scheme to explore the throughput of the network. Then, by means of the characteristics of practical system, a heuristic algorithm is developed to approach the maximum throughput on‐line. Extensive numerical calculations and simulations based on NS‐2 are implemented to evaluate the performance of the proposed algorithm and the impact of inaccurate estimation of parameters. The results show that our algorithm outperforms the existing adaptive algorithms in imperfect channel, and insensitive to inaccurate estimation of parameters. Copyright © 2005 John Wiley & Sons, Ltd.
The association between the phytoplankton, Rhopalosolen species (Chlorophyta; Chlorophyceae), and Anophelesgambiae sensu lato (Diptera: Culicidae) larval abundance in western Kenya
Authors: Tuno Nobuko , Githeko Andrew K. , Nakayama Takeshi , Minakawa Noboru , Takagi Masahiro , Yan Guiyun
Published: November 2005

Algae are important food resources of the larvae of the African malaria vectors, Anopheles gambiae Giles and Anopheles arabiensis Patton (Anopheles gambiae sensu lato), and other zooplankton, but empirical evidence remains meager about the agal flora in ephemeral water bodies. The animals present in natural aquatic habitats in western Kenya were sampled from July to November 2002 to study abiotic and biotic environmental factors determining A. gambiae sl larval abundance. The five highest concentrations of third and fourth instars and pupae (hereafter referred to as old‐stage larvae) were sampled in conjunction with the unicellular epizoic green algae, Rhopalosolen species (Chlorophyta; Chlorophyceae). Canonical correspondence analysis revealed that the presence of Rhopalosolen species was the most important determinant of the animal assemblage. The density of old‐stage A. gambiae sl larvae was positively correlated with the presence of Rhopalosolen species, but the density of first and second instars of A. gambiae sl was not. The water bodies with Rhopalosolen sp. yielded larger mosquitoes in spite of the higher density of larvae. We demonstrated that the productivity of water bodies in terms of the larvae of malaria vectors can differ in magnitude depending on the agal flora. We discuss phytoplankton as a regulator of mosquito larval populations.
Haplotype association analysis of human disease traits using genotype data of unrelated individuals
Authors: TAN QIHUA , CHRISTIANSEN LENE , CHRISTENSEN KAARE , BATHUM LISE , LI SHUXIA , ZHAO JING HUA , KRUSE TORBEN A.
Published: November 2005

Haplotype inference has become an important part of human genetic data analysis due to its functional and statistical advantages over the single-locus approach in linkage disequilibrium mapping. Different statistical methods have been proposed for detecting haplotype – disease associations using unphased multi-locus genotype data, ranging from the early approach by the simple gene-counting method to the recent work using the generalized linear model. However, these methods are either confined to case – control design or unable to yield unbiased point and interval estimates of haplotype effects. Based on the popular logistic regression model, we present a new approach for haplotype association analysis of human disease traits. Using haplotype-based parameterization, our model infers the effects of specific haplotypes (point estimation) and constructs confidence interval for the risks of haplotypes (interval estimation). Based on the estimated parameters, the model calculates haplotype frequency conditional on the trait value for both discrete and continuous traits. Moreover, our model provides an overall significance level for the association between the disease trait and a group or all of the haplotypes. Featured by the direct maximization in haplotype estimation, our method also facilitates a computer simulation approach for correcting the significance level of individual haplotype to adjust for multiple testing. We show, by applying the model to an empirical data set, that our method based on the well-known logistic regression model is a useful tool for haplotype association analysis of human disease traits.
Quantitative genetics of larval life-history traits in Rana temporaria in different environmental conditions
Authors: LAUGEN ANE T. , KRUUK LOESKE E. B. , LAURILA ANSSI , RÄSÄNEN KATJA , STONE JONATHAN , MERILÄ JUHA
Published: November 2005

The degree to which genetic variation in a given trait varies among different populations of the same species and across different environments has seldom been quantified in wild vertebrate species. We investigated the expression of genetic variability and maternal effects in three larval life-history traits of the amphibian Rana temporaria. In a factorial laboratory experiment, five widely separated populations (max. 1600 km) were subjected to two different environmental treatments. Animal model analyses revealed that all traits were heritable (h2≈0·20) in all populations and under most treatment combinations. Although the cross-food treatment genetic correlations were close to unity, heritabilities under a restricted food regime tended to be lower than those under an ad libitum food regime. Likewise, maternal effects (m2≈0·05) were detected in most traits, and they tended to be most pronounced under restricted food conditions. We detected several cross-temperature genetic and maternal effects correlations that were lower than unity, suggesting that genotype–environment interactions and maternal effect–environment interactions are a significant source of phenotypic variation. The results reinforce the perspective that although the expression of genetic and maternal effects may be relatively homogeneous across different populations of the same species, local variation in environmental conditions can lead to significant variation in phenotypic expression of quantitative traits through genotype–environment and maternal effect–environment interactions.
Clustering expressed genes on the basis of their association with a quantitative phenotype
Authors: JIA ZHENYU , XU SHIZHONG
Published: November 2005

Cluster analyses of gene expression data are usually conducted based on their associations with the phenotype of a particular disease. Many disease traits have a clearly defined binary phenotype (presence or absence), so that genes can be clustered based on the differences of expression levels between the two contrasting phenotypic groups. For example, cluster analysis based on binary phenotype has been successfully used in tumour research. Some complex diseases have phenotypes that vary in a continuous manner and the method developed for a binary trait is not immediately applicable to a continuous trait. However, understanding the role of gene expression in these complex traits is of fundamental importance. Therefore, it is necessary to develop a new statistical method to cluster expressed genes based on their association with a quantitative trait phenotype. We developed a model-based clustering method to classify genes based on their association with a continuous phenotype. We used a linear model to describe the relationship between gene expression and the phenotypic value. The model effects of the linear model (linear regression coefficients) represent the strength of the association. We assumed that the model effects of each gene follow a mixture of several multivariate Gaussian distributions. Parameter estimation and cluster assignment were accomplished via an Expectation-Maximization (EM) algorithm. The method was verified by analysing two simulated datasets, and further demonstrated using real data generated in a microarray experiment for the study of gene expression associated with Alzheimer's disease.
Pulsatile tinnitus
Authors: Liyanage S H , Singh A , Savundra P , Kalan A
Published: November 2005

Pulsatile tinnitus is an uncommon otological symptom. Objective pulsatile tinnitus has numerous causes, including benign intracranial hypertension, glomus tumours and atherosclerotic carotid artery disease. History and physical examination can give important information as to the underlying diagnosis. Radiographic evaluation is essential in all patients with pulsatile tinnitus. Many patients have a treatable underlying aetiology. Early diagnosis and appropriate intervention may save patients from unnecessary morbidity.
Outcomes in the use of intra-tympanic gentamicin in the treatment of Ménière's disease
Authors: Flanagan Sean , Mukherjee Payal , Tonkin John
Published: November 2005

The pathogenesis of Ménière's disease is associated with a disorder of ionic homeostasis, with the pathologic correlate being endolymphatic hydrops. Despite uncertainty as to its particular mode of action, it is accepted wisdom that intra-tympanic gentamicin has a definite therapeutic role in the control of symptoms in patients who fail to respond to medical therapy. This study reports an evaluation of the efficacy of intra-tympanic gentamicin in the treatment of Ménière's disease and also presents a simple, reliable, safe method of administering gentamicin for this purpose.

A retrospective review of 56 patients undergoing intra-tympanic gentamicin treatment for Ménière's disease was conducted. Response to treatment was analysed using a patient survey and examination of pure-tone averages. An overall significant improvement in vertigo symptoms of 81.3 per cent was found. There was a 21.4 per cent rate of significant hearing loss, defined as greater than 10 dB, with an average loss in this group of 18.5 dB. A single dose of gentamicin applied directly to the round window resulted in a high rate of control of vertigo, with acceptably low rates of hearing loss.
Follow-up results in tuberculous cervical lymphadenitis
Authors: Oktay Mehmet F , Topcu Ismail , Senyigit Abdurrahman , Bilici Aslan , Arslan Adem , Cureoglu Sebahattin , Yildirim Muzeyyen
Published: November 2005

Objective: To investigate the efficacy of medical antituberculous treatment in patients with tuberculous cervical lymphadenitis (TCL).

Methods: In the period 1996–2002, 73 TCL patients were reviewed and the results of clinical and laboratory testing were documented. The efficacy of a four-drug chemotherapy regimen was investigated.

Results: Purified protein derivatives (PPD) skin test results were positive in 58 (79 per cent) patients. Chest X-rays revealed changes consistent with tuberculosis in nine (12.3 per cent) patients. The mean duration of medical treatment was 10.04 months. In follow-up evaluation, 14 (20 per cent) patients were considered suspicious for resistant TCL and total excision of all nodes was performed. Histopathology confirmed TB in only 10 of these cases.

Conclusion: The high incidence of residual disease in our study indicates that medical treatment (at least nine months of four combined antituberculous drugs) did not seem to be effective. If lymphadenopathy persists, total surgical excision of lymph nodes should be the treatment of choice.