bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and signal integrity simulation of high speed digital system
Authors: Wang Yuanqing , Hong Wei , Wang Haiming , Zhang Nianzu , Yang Guangqi , Liu Leilei , Zhang Hui , Chang Jin
Published: November 2006

In this article, the design and implementation of a high‐speed digital system including two daughter boards and a backplane are described, where the emphasis is focused on the systematic analysis of the signal integrity performance using full wave electromagnetic methods combined with circuit simulation. Shielded differential vias is presented for high‐speed digital design. The proposed digital system achieves a data rate exceeding 3 Gbps (bit per second)/pair. Deembed process is presented to improve the accuracy of simulation. The simulated and measured results in time domain are in agreement. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 203–210, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22076
Multiband internal antenna using two layer shorted patches for mobile handsets
Authors: Rhyu Hanphil , Jo Jae‐Hoon , Harackiewicz Frances J. , Lee Byungje
Published: November 2006

A compact multiband internal antenna for mobile handset applications is proposed. Multiband operation is realised by two connected patches in the lower frequency band and wide band characteristics in the higher frequency band. The simulated and measured results show that the proposed antenna can effectively cover GSM, GPS, DCS, PCS, UMTS, Bluetooth/WiFi, and SDMB bands. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 176–179, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22077
Single field‐based equivalent circuit for stripline discontinuities and its applications
Authors: Lu Cheng , Tang Wanchun , Zhou Puke
Published: November 2006

A single field‐based equivalent circuit model for different stripline discontinuities has been constructed and applied to commonly encountered stripline discontinuities, such as: open‐circuit, step, right‐angle bend, and T‐junction. Also, a low‐pass filter and a branch line coupler are analyzed by using this field‐based equivalent circuit. Compared with numerical results, the average errors of S parameters are less than 2%. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 234–237, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22082
Characteristic of narrow‐slot antennas on periodic ground planes
Authors: Lin Shun‐Yun
Published: November 2006

This article presents the experimental results of two narrow slot antennas, a line‐slot antenna, and a square‐slot antenna with microstrip feeding, for wide‐band operation. By selecting certain elements resembled in the slot shape, we implemented two designs with a ground plane of periodical surface, and obtained significant enhancements in the antenna bandwidth for both designs. The impedance bandwidth enhancement was as many as seven times and four times of conventional line‐ and square narrow slot antennas, respectively. Details of the experimental results are presented and discussed. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 138–141, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22087
Safety assessment of breast cancer detection via ultrawideband microwave radar operating in pulsed‐radiation mode
Authors: Zastrow Earl , Davis Shakti K. , Hagness Susan C.
Published: November 2006

We conduct an finite‐difference time‐domain computational electromagnetic analysis of the safety of ultrawideband microwave breast cancer detection techniques. Pulses are transmitted into anatomically realistic MRI‐derived numerical breast phantoms with different levels of tissue heterogeneity as well as foreign entities such as implants and surgical clips, and the specific absorption is computed. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 221–225, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22089
Experimental investigation of the influence of filters on regeneration performance in self‐phase modulation based regenerator
Authors: Yang Yanfu , Lou Caiyun
Published: November 2006

In this paper the influence of optical filters on regeneration performance in self‐phase modulation (SPM) based regenerator is investigated experimentally. The center wavelength offset of the spectral slicing filter is optimized for achieving best performance. The Amplified‐ Spontaneous‐Emission (ASE)‐removing filter is critical for creating clear off‐center spectral region and making signal regeneration feasible. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 192–195, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22093
Hexagonal dielectric resonator antenna for 2.4 GHz WLAN applications
Authors: Hamsakutty V. , Kumar A. V. Praveen , Yohannan Jaimon , Mathew K. T.
Published: November 2006

A dielectric resonator antenna (DRA) with hexagonal geometry for WLAN applications is proposed. The antenna is excited with a simple 50 Ω microstrip transmission line. The proposed antenna produces an impedance bandwidth of 105 MHz from 2.395 to 2.50 GHz, which covers the 2.4 GHz wireless local area networks band (WLAN: 2.4–2.485 GHz). The radiation patterns are measured and are found to be omnidirectional. An average gain of 5.4 dBi is measured in the operating band. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 162–164, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22095
Posterior root–muscle reflexes elicited by transcutaneous stimulation of the human lumbosacral cord
Authors: Minassian Karen , Persy Ilse , Rattay Frank , Dimitrijevic Milan R. , Hofer Christian , Kern Helmut
Published: November 2006

Continuous epidural stimulation of lumbar posterior root afferents can modify the activity of lumbar cord networks and motoneurons, resulting in suppression of spasticity or elicitation of locomotor‐like movements in spinal cord–injured people. The aim of the present study was to demonstrate that posterior root afferents can also be depolarized by transcutaneous stimulation with moderate stimulus intensities. In healthy subjects, single stimuli applied through surface electrodes placed over the T11–T12 vertebrae with a mean intensity of 28.6 V elicited simultaneous, bilateral monosynaptic reflexes in quadriceps, hamstrings, tibialis anterior, and triceps surae by depolarization of lumbosacral posterior root fibers. The nature of these posterior root–muscle reflexes was demonstrated by the duration of the refractory period, and by modifying the responses with vibration and active and passive movements. Stimulation over the L4–L5 vertebrae selectively depolarized posterior root fibers or additionally activated anterior root fibers within the cauda equina depending on stimulus intensity. Transcutaneous posterior root stimulation with single pulses allows neurophysiological studies of state‐ and task‐dependent modulations of monosynaptic reflexes at multiple segmental levels. Continuous transcutaneous posterior root stimulation represents a novel, non‐invasive, neuromodulative approach for individuals with different neurological disorders. Muscle Nerve, 2006
Simple and accurate four‐node axisymmetric element
Authors: Fredriksson Magnus , Ottosen Niels Saabye
Published: November 2006

Based on the assumed strain method, a simple four‐node axisymmetric solid element is introduced. The assumed strain field is carefully selected to preserve the correct rank of the element stiffness matrix and to achieve high accuracy. The strain field is developed in conjunction with orthogonal projections and no matrix inversions are needed. The coarse mesh accuracy in bending and in typical axisymmetric load cases is excellent even for nearly incompressible materials. The strain‐driven format obtained is well suited for materials with non‐linear stress–strain relations. Several numerical examples are presented where the excellent performance of the proposed simple element is verified. Copyright © 2006 John Wiley & Sons, Ltd.
OCT4: biological functions and clinical applications as a marker of germ cell neoplasia
Authors: Cheng L , Sung M‐T , Cossu‐Rocca P , Jones TD , MacLennan GT , De Jong J , Lopez‐Beltran A , Montironi R , Looijenga LHJ
Published: November 2006

Germ cell tumours (GCTs) are a heterogeneous group of neoplasms, which develop in the gonads as well as in extragonadal sites, that share morphological patterns and an overall good prognosis, owing to their responsiveness to current surgical, chemotherapeutic, and radiotherapeutic measures. GCTs demonstrate extremely interesting biological features because of their close relationships with normal embryonal development as demonstrated by the pluripotentiality of some undifferentiated GCT variants. The similarities between GCTs and normal germ cell development have made it possible to identify possible pathogenetic pathways in neoplastic transformation and progression of GCTs. Genotypic and immunophenotypic profiles of these tumours are also useful in establishing and narrowing the differential diagnosis in cases of suspected GCTs. Recently, OCT4 (also known as OCT3 or POU5F1), a transcription factor that has been recognized as fundamental in the maintenance of pluripotency in embryonic stem cells and primordial germ cells, has been proposed as a useful marker for GCTs that exhibit features of pluripotentiality, specifically seminoma/dysgerminoma/germinoma and embryonal carcinoma. The development of commercially available OCT4‐specific antibodies suitable for immunohistochemistry on paraffin‐embedded specimens has generated increasing numbers of reports of OCT4 expression in a wide variety of gonadal and extragonadal GCTs. OCT4 immunostaining has been shown to be a sensitive and specific marker for seminomatous/(dys)germinomatous tumours and in embryonal carcinoma variants of non‐seminomatous GCTs, whether in primary gonadal or extragonadal sites or in metastatic lesions. Therefore, OCT4 immunohistochemistry is an additional helpful marker both in the differential diagnosis of specific histological subtypes of GCTs and in establishing a germ cell origin for some metastatic tumours of uncertain primary. OCT4 expression has also been reported in pre‐invasive conditions such as intratubular germ cell neoplasia, unclassified (IGCNU) and the germ cell component of gonadoblastoma. Additionally, OCT4 immunostaining shows promise as a useful tool in managing patients known to be at high risk for the development of invasive GCTs. Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Psychological distress and concerns of elderly patients treated with palliative radiotherapy for lung cancer
Authors: Turner N. J. , Muers M. F. , Haward R. A. , Mulley G. P.
Published: November 2006

We conducted a prospective observational cohort study of 83 elderly patients (aged 75 and above) being treated with palliative radiotherapy for lung cancer, with a comparison group of 49 younger patients (aged 65 and under). Psychological distress and concerns were measured before and after treatment using the Hospital Anxiety and Depression Scale (HADS) and a Concerns Checklist.

Psychosocial morbidity was common, however, prevalence was similar in both age groups. There was a trend towards worsening of both anxiety and depression scores after treatment, but this did not reach statistical significance. Younger patients reported more concerns than the older group (median 12 vs 10) but this too was not statistically significant. Concerns about the illness and symptoms were more likely to have been addressed by the care team than were concerns about psychosocial issues such as the family and the future.

People of all ages have similar concerns and levels of anxiety and depression whilst receiving palliative radiotherapy for lung cancer. Further research is needed to explore the use of screening tools, like those used in this study, to identify patients' difficulties and target interventions to improve their quality of life. Copyright © 2006 John Wiley & Sons, Ltd.
Nitrite‐assisted peptide iodination and conjugation
Authors: Deng Haiteng
Published: November 2006

In this study, a simple method for selective iodination of peptides and proteins is established. Using angiotensin II as the model system, we demonstrate that nitrite catalyzed the selective iodination of the peptide at the N‐terminus in an acidic solution. The N‐terminal‐iodinated peptides alkylated thiol‐containing molecules such as N‐acetylcysteine and glutathione to form peptide conjugates in a basic solution. Reactive species formed by increasing the pH of the reaction mixture of sodium nitrite and sodium iodide from 4 to 8 selectively iodinated peptides and proteins at tyrosine and histidine residues. These results show that nitrite is a useful catalyst for peptide and protein ligation. Copyright © 2006 European Peptide Society and John Wiley & Sons, Ltd.
Soft Coulomb hole method applied to molecules
Authors: Ortega‐Castro J. , Alfonso‐Méndez L. , Otto P. , Hernández‐Laguna A.
Published: November 2006

The soft Coulomb hole method introduces a perturbation operator, defined by −e/r12to take into account electron correlation effects, where ω represents the width of the Coulomb hole. A new parametrization for the soft Coulomb hole operator is presented with the purpose of obtaining better molecular geometries than those resulting from Hartree–Fock calculations, as well as correlation energies. The 12 parameters included in ω were determined for a reference set of 12 molecules and applied to a large set of molecules (38 homo‐ and heteronuclear diatomic molecules, and 37 small and medium‐size molecules). For these systems, the optimized geometries were compared with experimental values; correlation energies were compared with results of the MP2, B3LYP, and Gaussian 3 approach. On average, molecular geometries are better than the Hartree–Fock values, and correlation energies yield results halfway between MP2 and B3LYP. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Density functional theory study of the interaction between formamide and uracil
Authors: Duan Chunsheng , Wu Qunyan , Ma Hongkun , Zhou Xinming , Zhou Zhengyu
Published: November 2006

The hydrogen bonding of complexes formed between the formamide and uracil molecule has been fully investigated in the present study using the density functional theory (DFT) method at varied basis set levels from 6‐31G to 6‐311++G(d,p). Eight stable cyclic structures with two hydrogen bonds involved in the interaction are found on the potential energy surface (PES). The four structures are seven‐membered rings; the others are eight‐membered rings. The eight‐membered ring is preferred over the seven‐membered one by analyzing the hydrogen bond lengths and the interaction energies. The infrared (IR) spectrum frequencies, IR intensities, and the vibrational frequency shifts are reported. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Robust and efficient quantization and coding for control of multidimensional linear systems under data rate constraints
Authors: Li K. , Baillieul J.
Published: November 2006

Recently, we reported results on coding strategies for scalar feedback systems with data‐rate‐limited feedback channels in which the data‐rate constraints are time varying. Such rate‐varying channels are typically encountered in communication networks in which links between nodes are subject to noise, congestion, and intermittent disruption.

The present paper describes results of extending this research into the multidimensional domain. An important consideration is that for systems of dimension greater than one, many classical feedback designs cannot be realized for operation near the theoretical minimum possible data rate. A novel control coding scheme will be presented, and in terms of this, it will be shown that the advantages of coarse signal quantization that had been reported earlier for scalar systems remain in the multidimensional case. The key is to allocate the communication bandwidth efficiently among faster and slower modes. We discuss various strategies that allocate bandwidth by scheduling the time slots assigned to each mode. In particular, we propose a ‘robust attention varying’ technique, whose merit will be discussed in terms of its robustness with respect to time‐varying communication channel capacity and also in terms of how well it operates when the feedback channel capacity is near the theoretical minimum data rate. Copyright © 2006 John Wiley & Sons, Ltd.
Adaptive sensorless robust control of AC drives based on sliding mode control theory
Authors: Barambones O. , Garrido A. J.
Published: November 2006

This paper focuses in the design of a new adaptive sensorless robust control to improve the trajectory tracking performance of induction motors. The proposed design employs the so‐called vector (or field oriented) control theory for the induction motor drives, being the designed control law based on an integral sliding‐mode algorithm that overcomes the system uncertainties. This sliding‐mode control law incorporates an adaptive switching gain in order to avoid the need of calculating an upper limit for the system uncertainties. The proposed design also includes a new method in order to estimate the rotor speed. In this method, the rotor speed estimation error is presented as a first‐order simple function based on the difference between the real stator currents and the estimated stator currents.

The stability analysis of the proposed controller under parameter uncertainties and load disturbances is provided using the Lyapunov stability theory. The simulated results show, on the one hand that the proposed controller with the proposed rotor speed estimator provides high‐performance dynamic characteristics, and on the other hand that this scheme is robust with respect to plant parameter variations and external load disturbances. Finally, experimental results show the performance of the proposed control scheme. Copyright © 2006 John Wiley & Sons, Ltd.
Estimation of attributable number of deaths and standard errors from simple and complex sampled cohorts
Authors: Graubard Barry I. , Flegal Katherine M. , Williamson David F. , Gail Mitchell H.
Published: November 2006

Estimates of the attributable number of deaths (AD) from all causes can be obtained by first estimating population attributable risk (AR) adjusted for confounding covariates, and then multiplying the AR by the number of deaths determined from vital mortality statistics that occurred in the population for a specific time period. Proportional hazard regression estimates of adjusted relative hazards obtained from mortality follow‐up data from a cohort is combined with a joint distribution of risk factor and confounders to compute an adjusted AR. Two estimators of adjusted AR are examined. These estimators differ according to which reference population is used to obtain the joint distribution of risk factor and confounders. Two types of reference populations were considered: (i) the population represented by the baseline cohort and (ii) a population that is external to the cohort. Methods used in survey sampling are applied to obtain estimates of the variance of the AD estimator. These variances can be applied to data that range from simple random samples to multistage stratified cluster samples, which are used in national household surveys. The variance estimation of AD is illustrated in an analysis of excess deaths due to having a non‐ideal body mass index using the second National Health and Examination Survey (NHANES) Mortality Study and the 1999–2002 NHANES. These methods can also be used to estimate the attributable number of cause‐specific deaths and their standard errors when the time period for the accrual of deaths is short. Published in 2006 by John Wiley & Sons, Ltd.
Confidence intervals for the standardized effect arising in the comparison of two normal populations
Authors: Kulinskaya Elena , Staudte Robert G.
Published: November 2006

Confidence intervals for a standardized effect are derived after stabilizing the variance of the Welch t‐statistic. Simulation studies demonstrate the viability of the resulting intervals for a wide range of parameter values and sample sizes as small as five. The methodology is extended to the combination of results from several studies, so as to obtain a confidence interval for a representative standardized effect for all the studies. The methods are illustrated on a recent meta‐analytic study of systolic blood pressure reduction during a weight reducing regime, as well as the classical Mumford data on psychological intervention and hospital length of stay. Copyright © 2006 John Wiley & Sons, Ltd.
Role of cyclic GMP signaling in the melanocyte response to hypergravity
Authors: Ivanova Krassimira , Block Ingrid , Das Pranab K. , Gerzer Rupert
Published: November 2006

The human skin acts as a first barrier of defense to protect the internal organs from various chemical and physical environmental stress factors like solar ultraviolet radiation (UV) and mechanical stimuli. Human melanocytes (located strategically in the basal layer of the skin epidermis) represent a crucial protective barrier against UV irradiation and oxidative stress by generating the radical‐scavenging pigment melanin. However, melanin is also known to act as a photosensitizer that generates active oxygen species upon UV irradiation, which may initiate pigmentary disorders like vitiligo due to loss of melanocytes as well as oncogenic melanocyte transformation. Melanocytes may further act as a protective immune barrier at the dermo‐epidermal junction and thus participate in immune surveillance. For melanocytes it is known that the second messenger cyclic guanosine‐3′,5′‐monophosphate (cGMP) plays a key role in UVB‐induced melanogenesis involving nitric oxide (NO) signaling. Moreover, cGMP is involved in NO‐induced perturbation of melanocyte‐extracellular matrix interactions that may lead to loss of melanocytes and support melanoma metastasis. In the frame of the current space exploration, investigations on the influence of altered gravity on melanocyte physiology are of special interest. As cGMP appears to play an important signaling role in melanocyte physiology, a brief overview is presented on the role of the guanylyl cyclase‐cGMP signaling, with a focus on the melanocyte response to hypergravity. An estimation of the gravity impact on melanocyte function may be of importance to asses the risk of astronauts to develop pigmentary disorders, particularly melanoma and other relevant skin cancers, during long‐term spaceflights.
Signal transduction in gravisensing of flagellates
Authors: Häder Donat‐P. , Richter Peter , Lebert Michael
Published: November 2006

Many photosynthetic or heterotrophic flagellates, from various taxa, show positive, negative and, in some cases, transversal gravitaxis. Most flagellates are unicellular; however, they can form aggregates or colonies. Two species have been studied in more detail, Chlamydomonas and Euglena, which can serve as model systems. Earlier theories suggested that gravitaxis is caused by a buoy effect: The cell is tail‐heavy, and the propelling flagellum (flagella), inserting at the anterior end, pulls the organism upwards. Recent investigations, however, falsify these hypotheses and indicate the presence of an active, physiological graviperception mechanism, in some cases supported by a passive mechanism. In the photosynthetic Euglena, the cell body is heavier (1.04 g/mL) than the surrounding medium (water) and is assumed to exert pressure onto the lower membrane. The resulting force is believed to trigger mechano‐sensitive calcium‐specific ion channels. The molecular sensory transduction chain starts with the Ca influx which causes a depolarization of the membrane potential. The calcium is believed to bind to calmodulin which in turn activates an adenylyl cyclase. The produced cAMP is a secondary messenger and finally activates the flagellum reorientation. In Chlamydomonas, a mutant with defective mechano‐sensitive channels was found which is agravitactic, indicating that also in this flagellate gravitaxis is mediated by an active physiological receptor.
Topographical organization of GABAergic neurons within the ventral tegmental area of the rat
Authors: Olson Valerie G. , Nestler Eric J.
Published: November 2006

The ventral tegmental area (VTA), the origin of dopaminergic cell bodies that comprise the mesocorticolimibic DA system, is widely implicated in drug and natural reward, cognition, and several psychiatric disorders. In addition to dopaminergic neurons, this region is populated by GABAergic neurons, which both regulate the firing of their dopaminergic counterparts and send projections throughout the brain. Although the dopaminergic neurons of the VTA have been extensively characterized neuroanatomically, much less is known about the GABAergic neurons in this region. Recent data suggest that the rostro‐caudal topographic organization of these GABAergic neurons may correspond to their ability to regulate drug reward. In the present study, we used immunohistochemical techniques to examine the frequency and topography of GABAergic neurons throughout the rostro‐caudal axis of the VTA and the extent to which they coexpress other proteins, including tyrosine hydroxylase (a marker of DA neurons), cholecystokinin, parvalbumin, calretinin, and calbindin d 28k. Synapse 61:87–95, 2007. © 2006 Wiley‐Liss, Inc.
In vivo and in vitro measurement of brain phosphodiesterase 4 in rats after antidepressant administration
Authors: Fujita Masahiro , Imaizumi Masao , D'Sa Carrol , Zoghbi Sami S. , Crescenzo Matthew S. , Hong Jinsoo , Musachio John L. , Gee Antony D. , Seidel Jurgen , Green Michael V. , Pike Victor W. , Duman Ronald S. , Innis Robert B.
Published: November 2006

Based largely on in vitro measurements, the mechanism of several antidepressant treatments is thought to involve upregulation of 3′‐5′‐cyclic adenosine monophosphate (cAMP) signal transduction cascade and a corresponding increase in phosphodiesterase (PDE) 4, the enzyme that metabolizes cAMP. To assess the in vivo status of PDE4, rats were chronically treated with imipramine and then studied with: (1) in vivo positron emission tomography (PET) measurement of (R)‐[11C]rolipram binding, (2) in vitro measurement of [3H]rolipram binding in brain homogenates, and (3) Western blotting for protein levels of PDE4 isoforms. Imipramine administration caused no significant change in Bmax/Kd, for both in vivo measurements with (R)‐[11C]rolipram and in vitro measurements with [3H]rolipram in frontal cortex, hippocampus, and diencephalon. None of 10 isoforms of PDE4A, B, and D measured with immunoblots of frontal cortex and hippocampus showed a significant change. In summary, using relatively large brain regions for both in vivo imaging and in vitro measures of radiolabeled ligand binding and protein levels, chronic imipramine treatment via continuous mini‐pump administration caused no significant change in PDE4 levels. Most, but not all, prior in vitro studies have found increased PDE4 levels after antidepressant administration. The current results raise questions about the in vivo effects of antidepressant treatment on PDE4 and on other potentially important experimental factors (e.g., continuous infusion vs. intermittent injection of antidepressant) in large brain areas. However, the results do not deny possibility of changes in discrete areas, which were not studied in the current study applying PET. Synapse 61:78–86, 2007. Published 2006 Wiley‐Liss, Inc.
Effect of a P‐glycoprotein inhibitor, cyclosporin A, on the disposition in rodent brain and blood of the 5‐HT1A receptor radioligand, [11C](R)‐(––)‐RWAY
Authors: Liow Jeih‐San , Lu Shuiyu , McCarron Julie A. , Hong Jinsoo , Musachio John L. , Pike Victor W. , Innis Robert B. , Zoghbi Sami S.
Published: November 2006

Limited brain uptake of radioligands with otherwise optimal properties for imaging brain receptors can be improved by blocking the effect of P‐glycoprotein (P‐gp), an efflux pump at the blood‐brain barrier. Using small animal positron emission tomography (PET), we investigated how P‐gp and its blockade with Cyclosporin A (CsA) affect rodent brain uptake of [11C](R)‐(−)‐RWAY, a radioligand for brain 5‐HT1A receptors.

 Brain uptake of radioactivity was compared in control and CsA‐treated rats as well as P‐gp knockout and wild type mice. Parent radioligand and radiometabolite in plasma and brain samples were determined at 30 min after injection of radioligand. PET binding potential (BP) was calculated with a reference tissue model.

 P‐gp knockout mice had 2.5‐ and 2.8‐fold greater brain uptake of [11C](R)‐(−)‐RWAY than wild type ones, measured by in vivo PET and ex vivo tissue sampling, respectively. Similarly, CsA increased rat brain uptake 4.9‐ and 5.3‐fold, in vivo and ex vivo. In addition, CsA increased the plasma free fraction of [11C](R)‐(−)‐RWAY in rats by 2.7‐fold. Although CsA increased brain uptake in wild type mice by 2.5‐fold, it had no effect on plasma free fraction in knockout animals. Three radiometabolites of [11C](R)‐(−)‐RWAY were uniformly distributed in rat brain, suggesting they were inactive. CsA treatment increased brain uptake of [11C](R)‐(−)‐RWAY and only one of its radiometabolites. Regional rat brain BP increased 27–70% in the CsA‐treated rats and the P‐gp knockout mice.

 [11C](R)‐(−)‐RWAY is a P‐gp substrate in rat and mouse. The effects of CsA in rats are mediated by both P‐gp blockade and displacement of the radiotracer from plasma proteins. Studies with wild type and knockout mice showed that CsA affected only P‐gp in this species. Synapse 61:96–105, 2007. © 2006 Wiley‐Liss, Inc.
Sugar fatty acid ester surfactants: Structure and ultimate aerobic biodegradability
Authors: Baker Irene J. A. , Matthews Barry , Suares Hector , Krodkiewska Irena , Furlong D. Neil , Grieser Franz , Drummond Calum I.
Published: November 2006

Ultimate aerobic biodegradabilities of an array of sugar ester surfactants were determined by International Standards Organisation method 7827, “Water Quality—Evaluation in an Aqueous Medium of the Aerobic Biodegradability of Organic Compounds, Method by Dissolved Organic Carbon” (1984). The surfactants were nonionic sugar esters with different‐sized sugar head groups (formed from glucose, sucrose, or raffinose) and different lengths and numbers of alkyl chains [formed from lauric (C12) or palmitic (C16) acid]. Analogous anionic sugar ester surfactants, formed by attaching an α‐sulfonyl group adjacent to the ester bond, and sugar esters with α‐alkyl substituents were also studied. It was found that variations in sugar head group size or in alkyl chain length and number do not significantly affect biodegradability. In contrast, the biodegradation rate of sugar esters with α‐sulfonyl or α‐alkyl groups, although sufficient for them to be classified as readily biodegradable, was dramatically reduced compared to that of the unsubstituted sugar esters. An understanding of the relationship between structure and biodegradability provided by the results of this study will aid the targeted design of readily biodegradable sugar ester surfactants for use in consumer products.
Sugar fatty acid ester surfactants: Biodegradation pathways
Authors: Baker Irene J. A. , Willing R. Ian , Furlong D. Neil , Grieser Franz , Drummond Calum J.
Published: November 2006

In previous work, we found that the presence of a sulfonyl or alkyl group adjacent to the ester bond of sugar ester surfactants is associated with a dramatic reduction in the rate of biodegradation relative to that of unsubstituted esters. In this study, we investigated the pathways followed during the biodegradation of sucrose laurate, sucrose α‐sulfonyl laurate, and sucrose α‐ethyl laurate to determine the reasons for their different biodegradation rates. Through the use of high‐performance liquid chromatography and proton nuclear magnetic resonance spectroscopy, the nature of the intermediates formed during the biodegradation of these three key sugar esters was determined. It was found that sucrose laurate biodegradation occurs via initial ester hydrolysis. In contrast, sucrose α‐sulfonyl laurate degrades by initial alkyl chain oxidation. This indicates that the ester hydrolysis pathway is blocked by the sulfonyl group adjacent to the ester bond so that biodegradation is forced to proceed via the slower alkyl chain oxidation pathway. Sucrose α‐ethyl laurate was degraded at least in part by alkyl chain oxidation, indicating that ester hydrolysis was also inhibited by the presence of an ethyl group. It is therefore concluded that previously observed relationships between structure and biodegradability arise because of the influence that different structural elements have on the pathways followed during biodegradation.
Multivariate quantitative structure‐activity relationships for the aquatic toxicity of technical nonionic surfactants
Authors: Uppgård Lise‐Lott , Lindgren Åsa , Sjöström Michael , Wold Svante
Published: November 2006

The aquatic toxicity of 36 technical nonionic surfactants (ethoxylated fatty alcohols) was examined toward two freshwater animal species, the fairy shrimp Thamnocephalus playtyurus and the rotifer Brachionus calyciflorus. Responses of the two species to the surfactants were generally similar. A multivariate‐quantitative structure‐activity relationship (M‐QSAR) model was developed from the data. The M‐QSAR model consisted of a partial least squares model with three components and explained 92.4% of the response variance and had a predictive capability of 89.1%. The most important physicochemical variables for the M‐QSAR model were the number of carbon atoms in the longest chain of the surfactant hydrophobe (redC), the molecular hydrophobicity (log P), the number of carbon atoms in the hydrophobe (C), the hydrophilic‐lipophilic balance according to Davis (Davis), the critical packing parameter with respect to whether the hydrophobe was branched or not (redCPP), and the critical micelle concentration. Surfactant toxicity tended to increase with increasing alkyl chain lengths.
Removal of cadmium or lead from polluted water by biological amphiphiles
Authors: Pekdemir Turgay , Tokunaga Shuzo , Ishigami Yutaka , Hong Kyung‐Jin
Published: November 2006

Biological amphiphiles were examined for the removal of Cd2+ or Pb2+ from polluted water within a pH range from 2.5 to 7.5 at a fixed ratio of amphiphilic concentration to heavy metal concentration (CA/CM) on a molar basis of approximately 11. Tannic acid, among eight amphiphiles, was selected for Cd2+ or Pb2+ removal because it exerted noticeable improvement within limited pH ranges. In the presence of tannic acid, the removal of Cd2+ or Pb2+ was investigated as a function of pH ranging from 2.5 to 13 at CA/CM ratios from 1.2 to 11. The removal capacity (mass of metal/mass of tannic acid) increased with decreasing CA/CM for both Cd2+ and Pb2+. Removal capacities were 0.084 and 0.154 g/g‐tannic acid for Cd2+ and Pb2+ at pH 6.9 and 4.4, respectively. The maximal removals for Cd2+ and Pb2+ were 99 and 96%, respectively.
Prediction of critical micelle concentration of some anionic surfactants using multiple regression techniques: A quantitative structure‐activity relationship study
Authors: Jalali‐Heravi M. , Konouz E.
Published: November 2006

Computer‐assisted methods were employed to develop a statistical relationship between molecular‐based structural parameters and log critical micelle concentration (CMC) of some anionic surfactants. The CMC of 31 alkyl sulfates and alkanesulfonates were used for model generation. Among different models, two equations were selected as the best, and their specifications are given. The statistics of these models together with cross‐validation results indicate the capability of both models to predict the CMC of anionic surfactants. Three descriptors of Wiener number, reciprocal of the dipole moment, and reciprocal of the Randic index appear in the models. Results indicate that topological characteristics, such as compactness and branching of anionic surfactants, play major roles in micelle formation. Polarity of the molecules is also important, but its effect is less than that of topology of the surfactants.
On the measurement of critical micelle concentrations of pure and technical‐grade nonionic surfactants
Authors: Patist A. , Bhagwat S. S. , Penfield K. W. , Aikens P. , Shah D. O.
Published: November 2006

The critical micelle concentrations (CMC) of nine commercial nonionic surfactants (Tween 20, 22, 40, 60, and 80; Triton X‐100; Brij 35, 58, and 78) and two pure nonionics [C12(EO)5 and C12(EO)8] were determined by surface tension and dye micellization methods. Commercially available nonionic surfactants (technical grade) usually contain impurities and have a broad molecular weight distribution owing to the degree of ethoxylation. It was shown that the surface tension method (Wilhelmy plate) is very sensitive to the presence of impurities. Much lower CMC values were obtained with the surface tension method than with the dye micellization method (up to 6.5 times for Tween 22). In the presence of highly surfaceactive impurities, the air/liquid interface is already saturated at concentrations well below the true CMC, leading to a wrong interpretation of the break in the curve of surface tension (γ) vs. concentration of nonionic surfactant (log C). The actual onset of micellization happens at higher concentrations, as measured by the dye micellization method. Furthermore, it was shown that when a commercial surfactant sample (Tween 20) is subjected to foam fractionation, thereby removing species with higher surface activity, the sample yields almost the same CMC values as measured by surface tension and dye micellization methods. It was found that for monodisperse pure nonionic surfactants, both CMC determination methods yield the same results. Therefore, this study indicates that precaution should be taken when determining the CMC of commercial nonionic surfactants by the surface tension method, as it indicates the surface concentration of all surface‐active species at the surface only, whereas the dye method indicates the presence of micelles in the bulk solution.
Synthesis and surface properties of chemodegradable anionic surfactants: Diastereomeric (2‐n‐alkyl‐1,3‐dioxan‐5‐yl) sulfates with monovalent counter‐ions
Authors: Piasecki Andrzej , Mayhew Alexandra
Published: November 2006

Sodium, potassium and ammonium cis‐ and trans‐(2‐n‐alkyl‐1,3‐dioxan‐5‐yl) sulfates 6–8 (alkyl: n‐C9H19, 6a–8a, and n‐C11H23, 6b–8b) were synthesized in a reaction of aliphatic aldehydes 1a,b with glycerol 2 followed by separation in high yields of individual geometric isomers of cis‐and trans‐2‐n‐alkyl‐5‐hydroxy‐1,3‐dioxanes, cis‐3a,b and trans‐3a,b, followed by sulfation with sulfur trioxide‐pyridine complex, and finally neutralization with NaOH, KOH, and NH4OH, respectively. Physical data of the compounds and some surface properties of 2‐n‐nonyl derivatives, such as critical micelle concentration (CMC), effectiveness of aqueous surface tension reduction (ΠCMC), surface excess concentration ΓCMC, and the surface area demand per molecule (ACMC), were determined. It was shown that the surface activity of these compounds is influenced both by their geometric structure and by the monovalent counter‐ion.
Comparison of analyses of surfactants in cosmetics using high‐performance liquid chromatography and high‐performance capillary electrophoresis
Authors: Lin Wen‐Chung , Lin Shaw‐Tao , Shu Shwu‐Ling
Published: November 2006

Separation of anionic, cationic, and amphoteric surfactants containing n‐dodecyl groups and hydrophilic moieties was done by high‐performance liquid chromatography (HPLC) and high‐performance capillary electrophoresis (HPCE), and an ultraviolet‐visible detector. Quantitation of surfactants in commercial cosmetic and toiletry products was also done using similar methods. Conditions used to separate mixtures of surfactants by HPLC are as follows: stationary phase: ODS 2; mobile phase: MeOH/H2O (80∶20, vol/vol) containing 1.0M NH4Cl, 0.003 M tetrabutylammonium hydrogen sulfate, and 0.005 M diammonium phosphate buffer solution at pH=6.0. Conditions for HPCE are as follows: an uncoated capillary (100 μm i.d., 110 cm in length, effective length of 75 cm) with 25 kV of applied voltage, and an aqueous buffer containing 80 mM sodium borate/20 mM NaOH at pH=9.2. Surfactants were eluted within 15 min. The accuracy of both techniques was evaluated by analyzing the recovery ratio of surfactants in the mixture.
Cleavable surfactants
Authors: Hellberg Per‐Erik , Bergström Karin , Holmberg Krister
Published: November 2006

Cleavable surfactants are of interest for several reasons. Above all, the development of surfactants with weak bonds deliberately built into the structure is driven by the need for improved biodegradability of amphiphiles. The breakdown may be catalyzed by enzymes, and biodegradation would be the normal mechanism in sewage plants. Alternatively, the surfactant may degrade by chemical means, e.g., induced by acid, alkali, ultraviolet (UV) light, heat, or ozone. Acid‐ and alkali‐labile surfactants have attracted particular attention, and there is often a compromise between required stability at one stage and ease of breakdown at a subsequent stage. The paper reviews the main routes used to prepare cleavable surfactants and points out advantages and disadvantages of the different approaches. Emphasis is placed on the development during recent years. Cyclic and acyclic acetals, ketals, and ortho esters are the most important types of bonds for the preparation of acid‐labile surfactants, whereas alkali‐labile amphiphiles usually are based on ester bonds. The ester bond approach has been particularly important for cationic surfactants, and so‐called ester quats have rapidly taken a large share of the traditional market for quats. Betaine esters constitute a special class of ester with very pronounced pH dependence. UV‐labile surfactants based, for instance, on an azo bond, offer promise for the future.
Impact of molecular structure on the performance of methyl ester ethoxylates
Authors: Cox Michael F. , Weerasooriya Upali
Published: November 2006

Methyl ester ethoxylates are a new class of ethylene oxide (EO)‐derived surfactants. Little is known about the impact of structural variations on their performance properties. The effects of carbon chain length, EO content, the degree of unsaturation of the methyl ester feedstock, and feedstock purity were examined for their impact on both physical properties and surfactant performance properties. Physical properties examined included surface properties (surface tension, critical micelle concentration, surface excess adsorption), melting point, water solubility, viscosity, foam stability, color, clarity, and odor. The impact of molecular structure on performance was examined for various applications, including laundry detergents, dishwashing detergents, and hard‐surface cleaners.
Synthesis, physicochemical properties, and detergency of disodium 2‐alkyl‐1,3‐propanediyl bissulfates
Authors: Kooreman P. A. , Engberts J. B. F. N. , van Os N. M.
Published: November 2006

In this paper we describe the synthesis and the physicochemical properties of a series of highly calcium‐tolerant anionic surfactants. Detergency tests for one of the surfactants, disodium 2‐n‐hexadecyl‐1,3‐propanediyl bissulfate 3d, in formulations with and without builder are reported. These tests were performed using a robot‐Terg‐O‐tometer. The results of these tests are compared to the results of detergency tests of standard surfactants: LAS 113, a linear alkylbenzenesulfonate, PAS 45, a linear alkylsulfate, and PAES 23‐2S, an alkylethersulfate, representing standard commercial anionic surfactants of which the last is calcium‐tolerant, i.e., it does not precipitate from its aqueous solution in the presence of calcium ions. The detergency performance of bissulfate 3d was similar to that of PAES 23‐2S, with and without builder.
New coupling method without heavy metals for the synthesis of a new class of fatty acid methyl ester oligoglycoside ethers
Authors: Bogaert P. M. P. , Bakker F. K. G. , Slaghek T. M. , de Wit D. , Van der Meeren P.
Published: November 2006

A new method, using poly‐O‐acetyl‐β‐d‐glycopyranosylbromide, methyl 9‐or methyl 12‐hydroxyoctadecanoate and triethylamine as catalyst, is described for the synthesis of a new class of nonionic surfactants. Chemical structures were identified using 1H and 13C nuclear magnetic resonance spectroscopy including two‐dimensional techniques and Fourier transforming infrared. Critical micelle concentrations and surface tension profiles of these O‐alkyl‐β‐d‐glycosides in water were determined.
Applications of protecting groups in the synthesis of surfactants, lipids, and related compounds
Authors: Urata Kouichi , Takaishi Naotake
Published: November 2006

Several types of alkyl ether lipids were prepared in high yield and high purity using protecting groups such as 1,3‐dioxolane compounds or allyl ethers. We also succeeded in the industrial production of alkyl glyceryl ethers using the reaction of alkyl glycidyl ethers with acetone to give 1,3‐dioxolane compounds, from which the desired alkyl glyceryl ethers were obtained in high quantities. 1,3‐Dioxolane (ketal) compounds based on acetone were used in the enzymatic preparation of monoglyceride on an industrial scale. On the basis of these protecting groups, we extended our studies concerning both the preparations and properties of novel polyol ether compounds, beginning with alkyl glycidyl ethers. Another typical property of surfactants containing 1,3‐dioxolane units and acetal is degradability under acidic conditions. Several types of destructible/cleavable surfactants based on polyols, such as carbohydrates and polyethyleneglycol, were prepared. As for natural products containing polyol skeletons, much attention has been paid to their molecular design, in which protecting groups such as 1,3‐dioxolane compounds or allyl ether have contributed to synthetic strategies.
Regioselective synthesis of dimeric (gemini) and trimeric sugar‐based surfactants
Authors: Gao Chunli , Millqvist‐Fureby Anna , Whitcombe Michael J. , Vulfson Evgeny N.
Published: November 2006

A simple and flexible chemoenzymatic route for the preparation of a wide range of dimeric (gemini) and trimeric mono‐ and disaccharide‐based surfactants was developed. The synthesis relies on the use of enzymes for regioselective introduction of fatty acids into carbohydrate moieties. Several structures were prepared containing xylose, glucose, galactose, and lactose, connected via different hydroxyl groups in the sugar molecules or, alternatively, via the OH group of 2‐hydroxytet‐radecanoic acid used as a hydrophobic moiety for the surfactant.
Interfacial mass transfer vs. Formulation in multiple phase anionic surfactant‐oil‐water systems
Authors: Fillous Lauriane , Cardenas Antonio , Rouivere Jacques , Salager Jean‐Louis
Published: November 2006

Mass transfer through a liquid membrane was studied in a macroscopic setup that allowed an estimate of the resistance to interface crossing. It was found that the interfacial transfer was associated with the phase behavior and physicochemical formulation of the surfactant‐oil‐water system. The resistance to interfacial mass transfer closely followed the variation of interfacial tension, i.e., it was minimal at the optimal formulation of the so‐called Winsor III phase behavior systems.