bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface and grain-boundary segregation studied by quantitative AES and XPS
Authors: Hofmann Siegfried , Lejček Pavel
Published: September 2009

Applied surface and interface analysis methods such as Auger electron spectroscopy and X-ray photoelectron spectroscopy are particularly well suited to studying intergranular segregation. In the case of internal interfaces such as grain boundaries, they must be transformed into two open surfaces by intergranular fracture. The main task is quantification of the measured spectra. Advantages and disadvantages of different approaches are discussed. It is shown that only for very low segregation levels do the simple and modified ratio methods give acceptable results. With increasing amount of enrichment, the more complicated methods with full description of the contribution of the first few monolayers to the total measured intensity have to be applied in order to obtain reliable concentration values that are useful for the determination of the concentration- and temperature-independent standard enthalpy and entropy of segregation.
Pierre Auger – Lise Meitner: Comparative contributions to the Auger effect
Authors: Hardouin Duparc Olivier
Published: September 2009

It has been claimed by R. Sietmann that the attribution of the discovery of the so-called ‘Auger’ effect to Pierre Auger was a false attribution and that Lise Meitner should have got the credit for that discovery. However Sietmann himself recognised that Meitner's description of this effect was ‘buried in’ two larger papers whose primary concern was nuclear physics. Sietmann only mentioned Auger's 1925 article and did not mention his 1923 article, an omission now found in many places. We examine again L. Meitner's and P. Auger's contributions to the description of the ‘Auger’ effect. Meitner's concern was the exact nature of the (nuclear) beta radiations about which she opposed Ch. D. Ellis, and this had been the subject of an intense Berlin–Cambridge controversy where Ellis' description eventually prevailed. Auger's observations were the central theme of his PhD thesis at the J. Perrin's laboratory on the composed photoelectric effect. We thus believe that while L. Meitner should have shared the Nobel Prize with O. Hahn, the Auger effect has rightly been attributed to Auger.
The effect of electro-thermal fatigue on the structure of power electronic devices. Micro-structural evolution of the metallization layer
Authors: Khong Benjamin , Legros Marc , Dupuy Philippe , Levade Colette , Vanderschaeve Guy
Published: September 2009

The fatigue-induced modifications of the structure of power devices on components that underwent extreme electro-thermal fatigue were investigated, with special attention to the behaviour of the Al metallization layer. Electrical cycling induced a moderate grain growth in the metallization layer, except for the regions located beneath the connection wires. There the wire bonding process is associated with severe plastic deformation, leading to a fragmentation of the initial grains and significant grain growth. Grain-boundary grooving is another example of fatigue-induced structural changes: it reveals an intense stress- and temperature-driven grain boundary diffusion process.
f-Element hydrides: structure and magnetism
Authors: Havela Ladislav , Miliyanchuk Khrystyna , Kolomiets Alexandre
Published: September 2009

Systematic magnetic and specific-heat studies of hydrides of ternary compounds on the basis of rare earths or actinides help to unravel different roles of f-states in these two classes of materials. In rare earths, H absorption tends to suppress magnetism by weakening the exchange interaction mediated by conduction electrons. Light actinides exhibit a 5f band of variable width at the Fermi level and the hydrogenation makes magnetic features typically stronger. 5f band narrowing due to volume expansion is responsible for this net tendency, but the effects of H bonding cannot be neglected.
Structural, magnetic, and transport properties of quantum well GaAs/δ-Mn/GaAs/In
x
Ga1–x
As/GaAs heterostructures
Authors: Chuev Mikhail , Pashaev Elhan , Koval'chuk Mikhail , Kvardakov Vladimir , Subbotin Ilia , Likhachev Igor
Published: September 2009

The results of high-resolution X-ray diffraction and X-ray glancing-incidence mirror reflection studies of structural characteristics of the GaAs/Ga1–x
In
x
As/GaAs diluted magnetic semiconductors, with an Mn δ-layer well separated from the Ga1–x
In
x
As quantum by the GaAs spacer, are presented. A strong correlation between the structural, magnetic, electro-physical and optical properties of the samples gives evidence that the samples consist of a distribution of ferromagnetic and paramagnetic regions. Such a phase separation can be understood by a non-random distribution of the local magnetic moments and fluctuations of the exchange interaction in the samples having semiconductor-type conductivity.
X-ray characterization of magnetic digital alloys
Authors: Pashaev Elhan , Chuev Mikhail , Kvardakov Vladimir , Subbotin Ilia , Golovanov Aleksandr
Published: September 2009

Superlattices of 15 periods of (GaSb/Mn) with bilayer periods of 3 nm and 10 nm were grown on a GaAs(001) substrate by laser ablation and studied by X-ray glancing-incidence reflectometry. Both qualitative analysis and quantitative treatment of the X-ray reflection curves allow us to restore the depth profiles of the core electron density into the samples studied and to estimate the diffusion depth of Mn atoms into adjacent thicker GaSb layers, which appeared to be 3.5 nm thick.
HoZn5Al3: rare-earth magnetism in a new structure type
Authors: Stelmakhovych Olha , Havela Ladislav , Stelmakhovych Bohdan , Kalychak Yaroslav
Published: September 2009

Antiferromagnetic order at TN = 21 K was discovered in the intermetallic compound HoZn5Al3, which crystallizes in its own structure type. A metamagnetic transition can be induced by magnetic fields of 4 T. Enormous values of specific heat below 1 K are attributed to the Ho nuclear specific heat.
The influence of substitutions on the magnetocaloric effect in RCo2 compounds
Authors: Kaštil Jiří , Javorský Pavel
Published: September 2009

We present a study of the magnetocaloric effect in selected substituted RCo2 compounds. The first system was Gd(Rh
x
Co1 – x
)2 with x = 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30. The substitution of Co by Rh leads to a decrease in the critical temperature with increasing rhodium content from Tc = 350 K for x = 0.05 to T
c = 200 K for x = 0.30. The maximum entropy change slowly increases with increasing Rh concentration and reaches about 1 J K– 1 kg– 1 for x = 0.30 and a field change of 1 T. The second studied system was Dy(Fe
x
Co1 – x
)2 with x = 0.00, 0.01, and 0.03. The critical temperature as well as the magnetic entropy change strongly depends on the Fe concentration. The transition temperature increases from 140 K in DyCo2 to 210 K for 3 % Fe but the maximum of the entropy change quickly decreases from 5 to 1.2 J K–1 kg– 1 for field of 1 T.
Thickness shear modes and magnetoelastic waves in a bi-layered structure: magnetic film–non-magnetic substrate
Authors: Gareeva Zukhra , Doroshenko Rurik
Published: September 2009

Thickness modes of magnetoelastic waves in a bi-layered structure magnetic–non-magnetic material have been theoretically investigated. Plots illustrating the dependence of harmonics of resonant frequencies upon the magnetic layer thickness were constructed at various magnetoelastic wave vectors. A dependence of the dimensional resonance frequencies on the wave number of magnetoelastic waves propagating along the saturating field direction is found. Peculiarities of the resonant frequency harmonics behavior with varying magnetic layer thickness and number are analyzed. The multimode character of the thickness magnetoelastic resonances, attributed to the possibility of excitation of magnetoelastic waves with different wave number is discussed.
Effect of co-doping by Pb and La on structural and magnetic properties of Bi2212 superconducting ceramics
Authors: Kaki A. Ait , Benmaamar F. , Mosbah M.-F. , Amira A.
Published: September 2009

Doping the Bi2212 phase by Pb usually results in an enhancement of the pinning properties and the T
c. Using elements other than Bi and/or other sites one may obtain opposite results. In this work we present the effect on structural and magnetic properties of Bi2212 superconducting ceramics when co-doping with La and Pb is used. Bi1.4Pb0.6Sr2Ca1–x
La
x
Cu2O8+δ (0 ≤ x ≤ 0.025) superconducting ceramic samples were prepared using a solid-state reaction method. Structural and magnetic characterizations were made by means of X-ray diffraction, scanning electron microscopy and AC susceptibility measurements. The obtained crystalline structure is mainly tetragonal with a c-axis lattice parameter decreasing with La content. Substitution by La reduces the fraction content of the parasitic phase Bi2201 and the size of the grains. The transition temperature Tc is enhanced quasi linearly with the La content and the superconducting volume fraction has a maximum for x = 0.01.
Magnetic properties of the hydrogenated unconventional superconductor UCoGe–H
Authors: Adamska Anna , Havela Ladislav , Eichinger Karl , Pospíšil Jiří , Miliyanchuk Khrystyna
Published: September 2009

The effect of hydrogenation on magnetic properties of the weakly ferromagnetic superconductor UCoGe was studied. UCoGe hydrides were synthesized at T = 773 K at different pressure of H2 gas (8, 5, 2 bar). The hydrogenation at 8 bar and 5 bar results in a change of the crystal structure from orthorhombic (TiNiSi structure type) to hexagonal (ZrBeSi type) with H concentrations just below 2 H/f. u. For one of such β-hydrides, UCoGeH1.7, the Curie temperature increases from 3 K up to 50 K and the spontaneous magnetic moment from 0.03 μB/f. u. to 0.05 μB/f. u. An α-hydride of UCoGe (ΔV/V = 0.25 %) with a hydrogen concentration 0.1 H/f. u. was obtained at 2 bar. It has the same crystal structure as a pure compound and surprisingly exhibits no magnetic order.
Electrophoresis deposition of metal nanoparticles with reverse micelles onto InP
Authors: Zdansky Karel , Zavadil Jiri , Kacerovsky Pavel , Lorincik Jan , Vanis Jan , Kostka Frantisek , Cernohorsky Ondrej , Fojtik Anton , Reboun Jan , Cermak Jan
Published: September 2009

Nanolayers were deposited onto surfaces of n-type InP single crystal wafers by electrophoresis from reverse micelle colloid solutions containing palladium nanoparticles. Two types of nanolayers were deposited, by applying a positive potential or a negative potential on the InP wafer. Further, wafers with nanolayers were annealed in high vacuum at 400 °C. The nanolayers were studied using capacitance–voltage characteristics on a mercury probe, by atomic force microscopy and by secondary-ion mass spectroscopy. Two types of Schottky-like diodes were prepared on wafers with the two types of nanolayers and studied by current–voltage characteristics. The diodes with nanolayers deposited by applying the positive potential, which contained Pd nanolayers, showed characteristics with better rectifying properties than the other type of diodes. Correlations among measured characterizations were found.
Low-temperature specific heat of selected ceramics
Authors: Svoboda Pavel , Leitner Jindřich , Sedmidubský David
Published: September 2009

Here we present an analysis of the low-temperature specific heat of selected nitrides (Cr3GaN, GaN, and InN) and niobates (CaNb2O6, Ca2Nb2O7, and Sr2Nb2O7). The low-temperature specific heat is considered as a sum of electronic and phonon contributions, where the electronic part is almost negligible. The phonon specific heat is then described using an additive combination of the Debye and Einstein approaches for acoustic and optical phonons, respectively, together with the correction for the anharmonicity of the phonon spectrum.
Charge transport in photosensitive nanocrystalline PbTe(In) films in an alternating electric field
Authors: Dobrovolsky A. , Komissarova T. , Akimov B. , Dashevsky Z. , Kasiyan V. , Khokhlov D. , Ryabova L.
Published: September 2009

Frequency and temperature dependences of the impedance components have been investigated in darkness and under illumination for PbTe(In) nanocrystalline films. Synthesis of the films was performed using evaporation of a target source to a cooled glass substrate. The films have a column-like structure with a mean grain size varying from about 60 nm to 170 nm depending on the deposition temperature. Analysis of the data obtained revealed that the conductivity of the films is determined by two mechanisms: charge transport along the inversion channels at the grain surface and activation through barriers at the grain boundary. Persistent photoconductivity appears in the films below T = 150 K. The frequency dependence of the relative photoresponse has a pronounced maximum. The photoresponse in the ac mode may be higher by two orders of magnitude than in the dc measurements.
Emerging Arboviral Diseases
Authors: Hussain Sultana M , Ahmed Iftikhar , Ekram ARM Saifuddin , Rahman M Fazlur
Published: September 2009

doi: 10.3329/taj.v17i2.3448TAJ December 2004; Volume 17 Number 2
Preliminary Report of Encephalitis Surveillance Study in Rajshahi Medical College Hospital
Authors: Hussain Sultana M , Hossain MJ , Ekram ARMS , Gurley ES , Alam MM , Montgomery SP , Azad MAK , Breiman RF , Luby SP , Ahmed I , Rahman MF , Siddiqui AB
Published: September 2009

More than 100 different viruses, bacteria, toxins and drugs can cause acute encephalitis. A prospective, hospital-based study to define the causes of encephalitis in Bangladesh began in June 2003. At Rajshahi Medical College Hospital in one year 105 out of 391 suspected encephalitis patients were enrolled. The specimens were collected from these patients and were tested for a variety of pathogens at twelve laboratories at the Centers for Disease Control and Prevention (CDC) in Atlanta and Ft. Collins, USA. Among the first 105 patients enrolled, the median age of the patient was 18 years; 55% were male. Twenty-four percent (n-25) died in hospital or before completing the follow-up. Thirteen out of 105 (12.38%) patients had Japanese encephalitis; three of the encephalitis patients had a positive test result of having recent infection with dengue virus and one had encephalitis due to alpha virus, another patient had encephalitis due to echovirus. Three (2.8%) were polymerase chain reaction (PCR) or culture positive for Streptococcus pneumoniae, and 4 for Mycoplasma pneumoniae. No Nipah virus infection was identified among the first 105 serum samples tested. These data suggest that Japanese encephalitis virus is an emerging cause of encephalitis in northern part of Bangladesh. doi: 10.3329/taj.v17i2.3449 TAJ 2004; 17(2): 75-79
A Clinical Study of 100 Cases of Eclampsia In Rajshahi Medical College Hospital
Authors: Khanum Marina , Ashraf Fatema , Sahrin Humaira
Published: September 2009

Eclampsia is the occurrence of one or more convulsion in association with the syndrome of pre eclampsia. It is relatively uncommon in developed countries where it complicates about one in every 200 deliveries. Eclampsia can be 20 times more common in developing countries and it probably accounts for more than 50,000 maternal deaths worldwide each year. Which anticonvulsant for women with eclampsia Evidence from the collaborative Eclampsia Trial lancet 1995, 345, 1445-63. The main objective of this study was to observe the clinical profile of antepartum eclampsia cases. The study was carried out with 100 cases that were selected randomly during year 2004. 58% of the patients were primigravida; among them 25% patients were in age group 15-14 years. About 95% patients were illiterate, low socio economic group, and in 53% patients' convulsion occurred in 32-37 weeks of pregnancy.Among 100 patients, 71 patients had normal vaginal delivery and 25% patients needed Caesarean section. Maternal mortality rate was 2%, perinatal mortality was 38%. Perinatal mortality was higher in vaginal group (12%) than LSCS group (7%). doi: 10.3329/taj.v17i2.3450 TAJ 2004; 17(2): 80-83
Study of Abdominal Injury: An Analysis of 50 Cases
Authors: Siddique MAB , Rahman MK , Hannan ABMA
Published: September 2009

Abdominal injury is an important aspect of trauma because of difficulty in diagnosis and its lethal potential if not properly treated. Fifty cases of abdominal injury admitted in the surgical wards of Rajshahi Medical College Hospital over 2 years have been studied here. All the patients underwent laparotomy for their management. The age range of the patient was 14 to 70 years and most commonly involved age group was 21 to 30 years. Male to female ratio was 15.6:1. The incidence of penetrating injury predominated (64%) over non-penetrating injury and majority had stab injuries. Road traffic accident predominated in blunt injury. Small gut injury outnumbered all other injuries in both groups. Abdominal pain was the most frequent symptom. Most of the patient arrived in the hospital within 24 hours. Considering clinical presentations and results of investigations, decision for laparotomy was taken with prior resuscitation.   doi: 10.3329/taj.v17i2.3452 TAJ 2004; 17(2): 84-88
Birth Weight Status of the New Born Babies Born at Dhaka Medical College Hospital
Authors: Mahmood AR , Haque GM Sharful , Parvin Tahera , Karim SR , Osman K , Ferdousi SK
Published: September 2009

A cross-sectional study was carried out to determine the birth weight status of the newborn babies born at Dhaka Medical College Hospital as well as to find out the prevalence of low birth weight among them. All the new born babies (202) born at the labour room of Dhaka Medical College Hospital during the specified period were included in the study. Maximum newborn babies (78.71%) had birth weight 2.5Kg or more and 21.29% had low birth weight (<2.5 Kg). It was found that mean weight of newborn babies was 2.73 Kg and standard deviation was ± 0.52 Kg. Among them 93.56% were full term babies. In a developing country like ours, occurrence of low birth weight is still very alarming, although it is preventable. Emphasis on health education to inform all the women during antenatal visit about the consequences of low birth weight and significance of delivering the babies with normal birth weight is recommended.   doi: 10.3329/taj.v17i2.3454   TAJ 2004; 17(2): 95-98
Kala-azar in Children: A Retrospective Study
Authors: Bari MI , Talukdar MQK , Nazir FH , Siddiqui AB , Haidary MH
Published: September 2009

Fifty children with Kala-azar {27 male (54%) and 23 female (46%)} aged between 2-12 yrs, were studied retrospectively in the pediatric unit of Rajshahi Medical College Hospital to find out the optimal treatment of Kala-azar in children. Sodium stibogluconate was given intravenously at a dose of 10 mg/kbw/day for 20 days in one group (Group-A), 15 mg/kbw/day for 20 days in another group (Group-B), 10 mg/kbw/day B.D. for 20 days in another group (Group-C), and 20 mg/kg of body wt/day for 40 days is last group (Group-D). The apparent cure rates of all regimens were 100%. Side effects of sodium stibogluconate were mild, however, myocarditis developed on 37th day of treatment in one patient which reversed to normal after discontinuation of the drug. 27 patients (54%) could be followed up to six months after discharge from hospital. Two patients in group-A relapsed and none relapsed from group B, C or D. Follow-up of patients in group B, C and D showed improvement in general condition, increase in body weight, Hb% and regression of the size of the liver and spleen and ultimate rate of cure in B, C, D regimens were 100%. But ultimate cure rate in-group A was 71.4% and the significance of difference between A and other regimens (P<0.10) were statistically significant. Sodium stibogluconate 15mg/kg body weight once daily for 20 days (Group-B) had the best of cure rate with low toxicity and may be recommended for routine treatment of childhood Kala-azar in this country.   doi: 10.3329/taj.v17i2.3455   TAJ 2004; 17(2): 99-103
Smear Positive Tuberculosis Cases in Rajshahi District A Comparison Between Rural and Urban Areas
Authors: Hussain W Wasim , Haque M Azizul , Sharmin Laila Shamima , Ekram ARM Saifuddin , Rahman M Fazlur
Published: September 2009

This study was designed to know the case finding of sputum smear positive tuberculosis in Rajshahi district and also to see whether case finding was different in urban and rural settings. Our study reveals that case finding rate of smear positive tuberculosis cases in the city corporation area and rural areas of Rajshahi district are 52% and 28% respectively. Case detection rate of total Rajshahi district was 33%. Stronger efforts are needed to reach the national target of detecting 70% new smear positive TB cases by the end of 2005.   doi: 10.3329/taj.v17i2.3456   TAJ 2004; 17(2): 104-105
Porokeratosis mibelli- A Case Report
Authors: Siddiqui MA , Kabir MR , Badruddoza SM , Amin AA
Published: September 2009

A twelve years old girl of class VII reported at skin & VD out patient department of Rajshahi Medical college Hospital in November 2003 with multiple small pink to violeceous non pruritic patches extending from medial aspect of left ankle joint to the medial aspect of left thigh in a linear fashion. The individual lesions are small-circumscribed patches having hyperkeratotic margin and central atrophy. The raised hyperkeratotic margin contains on its top a furrow along the course of the wall. The surface was verrucous and many of the lesions have serpiginous border. Near the ankle joint and below the ankle joint individual lesion forms zosteriform groups. On the thigh the lesions are linear. Some small satellite lesions are also present. All the lesions are hairless and anhidrotic. The onset of the individual lesions was at the age of six years, near the ankle joint. Lesions enlarge slowly and progressed to upward direction in a linear fashion. Skin biopsy for histopathology revealed the picture of porokeratosis. doi: 10.3329/taj.v17i2.3457 TAJ 2004; 17(2):  106-107
Tension-Type, the Forgotten Headache A Common but under Treated Condition
Authors: Kundu Narayan Chandra , Ahmad Quamruddin
Published: September 2009

Headache is a universal problem. Of all the types of headache, the commonest is Tension-type Headache. The word 'tension' implies that this type of headache can be attributed entirely to tension or stress, which may make people with this type of headache reluctant to consult a physician. Physicians misperceptions that tension-type headache are mild, benign, self-treatable and occur solely due to stress may further trivialize the problem. Thus this disease is often under-diagnosed and not treated properly. This article describes the disease and its management and is being published to increases awareness of the disease amongst the physicians.   doi: 10.3329/taj.v17i2.3462   TAJ 2004; 17(2): 121-128
Stefan Problem through Extended Finite Elements: Review and Further Investigations
Authors: Salvatori Luca , Tosi Niccolò
Published: September 2009

A general review of the extended finite element method and its application to the simulation of first-order phase transitions is provided. Detailed numerical investigations are then performed by focusing on the one-dimensional case and studying: (i) spatial and temporal discretisations, (ii) different numerical techniques for the interface-condition enforcement, and (iii) different treatments for the blending elements. An embeddeddiscontinuity finite element approach is also developed and compared with the extended finite element method, so that a clearer insight of the latter can be given. Numerical examples for melting/solidification in planar, cylindrical, and spherical symmetry are presented and the results are compared with analytical solutions.
Liquid Crystals in Tribology
Authors: Carrión Francisco-José , Martínez-Nicolás Ginés , Iglesias Patricia , Sanes José , Bermúdez María-Dolores
Published: September 2009

Two decades ago, the literature dealing with the possible applications of low molar mass liquid crystals, also called monomer liquid crystals (MLCs), only included about 50 references. Today, thousands of papers, conference reports, books or book chapters and patents refer to the study and applications of MLCs as lubricants and lubricant additives and efforts are made to develop new commercial applications. The development of more efficient lubricants is of paramount technological and economic relevance as it is estimated that half the energy consumption is dissipated as friction. MLCs have shown their ability to form ordered boundary layers with good load-carrying capacity and to lower the friction coefficients, wear rates and contact temperature of sliding surfaces, thus contributing to increase the components service life and to save energy. This review includes the use of MLCs in lubrication, and dispersions of MLCs in conventional polymers (PDMLCs). Finally, new lubricating system composed of MLC blends with surfactants, ionic liquids or nanophases are considered.
5-Chloro-4-iodo-1,3-dimethyl-1H-pyrazole
Authors: Vilkauskaitė Gytė , Eller Gernot , Šačkus Algirdas , Holzer Wolfgang
Published: September 2009

Reaction of 5-chloro-1,3-dimethyl-1H-pyrazole with I2/HIO3 in refluxing acetic acid gives the title compound in good yield. Detailed spectroscopic data (1H NMR, 13C NMR, 15N NMR, IR, MS) are presented.
Increased Biocompatibility and Bioactivity after Energetic PVD Surface Treatments
Authors: Mändl Stephan
Published: September 2009

Ion implantation, a common technology in semiconductor processing, has been applied to biomaterials since the 1960s. Using energetic ion bombardment, a general term which includes conventional ion implantation plasma immersion ion implantation (PIII) and ion beam assisted thin film deposition, functionalization of surfaces is possible. By varying and adjusting the process parameters, several surface properties can be attuned simultaneously. Extensive research details improvements in the biocompatibility, mainly by reducing corrosion rates and increasing wear resistance after surface modification. Recently, enhanced bioactivity strongly correlated with the surface topography and less with the surface chemistry has been reported, with an increased roughness on the nanometer scale induced by self-organisation processes during ion bombardment leading to faster cellular adhesion processes.
Synthesis of Novel Asymmetric Zinc (II) Phthalocyanines Bearing Octadecyloxyl and Glucosyl Groups
Authors: Zhang Pei , Zhang Shufen , Han Gang
Published: September 2009

A novel asymmetric zinc (II) phthalocyanine substituted by one lipophilic octadecyloxyl group and three hydrophilic glucosyl groups was synthesized. Using Q-TOF MS, the major byproducts formed during the deprotection processes were identified. An improved procedure was worked out to convert these byproducts to the desired product in quantitative yield.
A New Cytotoxic 19-Nor-cardenolide from the Latex of Antiaris toxicaria
Authors: Dai Hao-Fu , Gan Yu-Juan , Que Dong-Mei , Wu Jiao , Wen Zhen-Chang , Mei Wen-Li
Published: September 2009

A new nor-cardenolide, named toxicarioside H (1), was isolated from the latex of Antiaris toxicaria (Pers.) Lesch (Moraceae). Its structure was elucidated on the basis of HRFAB-MS and spectroscopic techniques (IR, UV, 1D and 2D NMR). Compound 1 showed significant cytotoxicity against K562, SGC-7901, SMMC-7721, and HeLa cell lines in vitro by MTT method.
Neuro-Genetic Optimization of the Diffuser Elements for Applications in a Valveless Diaphragm Micropumps System
Authors: Lee Hing Wah , Azid Ishak H. Abdul
Published: September 2009

In this study, a hybridized neuro-genetic optimization methodology realized by embedding numerical simulations trained artificial neural networks (ANN) into a genetic algorithm (GA) is used to optimize the flow rectification efficiency of the diffuser element for a valveless diaphragm micropump application. A higher efficiency ratio of the diffuser element consequently yields a higher flow rate for the micropump. For that purpose, optimization of the diffuser element is essential to determine the maximum pumping rate that the micropump is able to generate. Numerical simulations are initially carried out using CoventorWare® to analyze the effects of varying parameters such as diffuser angle, Reynolds number and aspect ratio on the volumetric flow rate of the micropump. A limited range of simulation results will then be used to train the neural network via back-propagation algorithm and optimization process commence subsequently by embedding the trained ANN results as a fitness function into GA. The objective of the optimization is to maximize the efficiency ratio of the diffuser element for the range of parameters investigated. The optimized efficiency ratio obtained from the neuro-genetic optimization is 1.38, which is higher than any of the maximum efficiency ratio attained from the overall parametric studies, establishing the superiority of the optimization method.
Platform for a Hydrocarbon Exhaust Gas Sensor Utilizing a Pumping Cell and a Conductometric Sensor
Authors: Biskupski Diana , Geupel Andrea , Wiesner Kerstin , Fleischer Maximilian , Moos Ralf
Published: September 2009

Very often, high-temperature operated gas sensors are cross-sensitive to oxygen and/or they cannot be operated in oxygen-deficient (rich) atmospheres. For instance, some metal oxides like Ga2O3 or doped SrTiO3 are excellent materials for conductometric hydrocarbon detection in the rough atmosphere of automotive exhausts, but have to be operated preferably at a constant oxygen concentration. We propose a modular sensor platform that combines a conductometric two-sensor-setup with an electrochemical pumping cell made of YSZ to establish a constant oxygen concentration in the ambient of the conductometric sensor film. In this paper, the platform is introduced, the two-sensor-setup is integrated into this new design, and sensing performance is characterized. Such a platform can be used for other sensor principles as well.
Exploring and Contextualizing Public Opposition to Renewable Electricity in the United States
Authors: Sovacool Benjamin K.
Published: September 2009

This article explores public opposition to renewable power technologies in the United States. It begins by discussing the genesis of environmental ethics, or how some Americans have come to place importance on the protection of the environment and preservation of species, ecosystems, and the biosphere. As result, renewable power systems have become challenged on ethical and environmental grounds and are occasionally opposed by local communities and environmentalists. The article finds that, however, such concern may be misplaced. Renewable electricity resources have many environmental benefits compared to power stations fueled by coal, oil, natural gas, and uranium. Opposition towards renewable resources can at times obscure the true costs and risks associated with electricity use and entrench potential racial and class-based inequalities within the current energy system.
Nuclei, Primes and the Random Matrix Connection
Authors: Firk Frank W. K. , Miller Steven J.
Published: September 2009

In this article, we discuss the remarkable connection between two very different fields, number theory and nuclear physics. We describe the essential aspects of these fields, the quantities studied, and how insights in one have been fruitfully applied in the other. The exciting branch of modern mathematics – random matrix theory – provides the connection between the two fields. We assume no detailed knowledge of number theory, nuclear physics, or random matrix theory; all that is required is some familiarity with linear algebra and probability theory, as well as some results from complex analysis. Our goal is to provide the inquisitive reader with a sound overview of the subjects, placing them in their historical context in a way that is not traditionally given in the popular and technical surveys.
Spatial mapping of submerged cave systems by means of airborne electromagnetics: an emerging technology to support protection of endangered karst aquifers
Authors: Supper Robert , Motschka Klaus , Ahl Andreas , Bauer‐Gottwein Peter , Gondwe Bibi , Alonso Gonzalo Merediz , Römer Alexander , Ottowitz David , Kinzelbach Wolfgang
Published: September 2009

Karst aquifers represent important but very vulnerable sources for water supply to a significant part of the Earth’s population. For sustainable use of these resources, development of integrated management tools based on numerical groundwater models is required. In principle karst aquifers are characterized by the presence of two distinct flow domains: the limestone matrix fractures and the conduits. A flow model of karst aquifers requires detailed, spatially distributed information on the hydrologic characteristics of the aquifer and flow paths. Geophysical methods determining the distribution of the electrical resistivities within the subsurface could provide such information. An international scientific research project was initiated to explore the potential of airborne electromagnetic mapping for providing such innovative information for improving groundwater modelling of karst aquifers. The project study area is located in the Sian Ka’an Biosphere Reserve located in Yucatán, Mexico, a coastal wetland of international importance. As a first step ground geoelectric and ground electromagnetic measurements were performed in March 2006 to determine the electrical properties of the Sian Ka’an Biosphere Reserve subsurface environment. These results were used for 3D forward modelling to calculate the expected airborne electromagnetic response. Based on these promising results, an airborne pilot survey was performed in 2007 to evaluate the applicability of airborne electromagnetic methodology. This survey covers an area of 40 square kilometres above the well‐mapped Ox Bel Ha cave system. The results showed that the signature of the cave system could be clearly detected. The pilot survey offered as well the chance to define the limits of current state‐of‐the‐art airborne data acquisition and inversion. The study helped to define the needs for further developments and improvements to establish the frequency domain electromagnetic method as a practical karst exploration method.
Effective medium theories for modelling the relationships between electromagnetic properties and hydrological variables in geomaterials: a review
Authors: Cosenza P. , Ghorbani A. , Camerlynck C. , Rejiba F. , Guérin R. , Tabbagh A.
Published: September 2009

The paper reviews the effective medium theories used for modelling the relationships between electromagnetic properties (low‐frequency conductivity and high‐frequency permittivity) and hydrological variables (water content, salinity, suction, permeability) in soils and rocks. It aims a) to provide a simple presentation of these theoretical approaches, b) to present their theoretical and practical limitations and c) to establish some connections with empirical equations usually used in hydrogeophysics (i.e., Archie relationships, Topp equation and complex refractive index model). This review demonstrates that two groups of effective medium theories can be clearly identified. The first group constituted by the Maxwell‐Wagner and Symmetric‐Bruggeman rules is characterized by easy‐to‐use models. When the volumetric water content and the texture are known, they allow to obtain fast estimates of effective electromagnetic properties. In the second group, the differential effective medium schemes that are more complex from a mathematical point of view are preferred when frequency‐dependent properties are studied. In particular, differential effective medium schemes are used for providing some insights into the physical basis of spectral induced polarization measurements in hydrogeophysical applications.
Simultaneous inversion of magnetic resonance sounding in terms of water content, resistivity and decay times
Authors: Braun Martina , Kamm Jochen , Yaramanci Ugur
Published: September 2009

Magnetic resonance sounding (MRS) or surface nuclear magnetic resonance (SNMR) is used for direct groundwater exploration and for an improved aquifer characterization. Currently, it is the only geophysical method that is capable of directly determining the free water content and estimating the pore sizes of the aquifer in the subsurface. However, MRS is basically an electromagnetic method. Therefore, it is sensitive to the resistivity of the subsurface. The water content is the main target of investigation, therefore first inversion routines focused on the water content. Later on, inversion routines determining water content and decay times became available. Very recently, MRS inversion for water content and resistivity has been realized.

We present here a simultaneous inversion of MRS in terms of determining the three inversion parameters – water content, resistivity and decay time – within one single inversion routine. Within the iterative inversion scheme, the extrapolated initial values are determined on the basis of the physical effective decay times in the subsurface, which are estimated within the inversion scheme.

Due to an instrumental dead time, the initial values for amplitude and phase, which are related to water content and resistivity, cannot be measured directly. Therefore, the initial amplitude must be extrapolated using the decay time of the signal. The standard approach is a mono‐exponential decay curve; implicitly, the phase is assumed to be time‐invariant. However, multi‐exponential signals are natural when considering relaxation behaviour in the underground. It originates from multi‐modal pore size distributions or simply a number of differently relaxing signal contributions from the various lithological units.
Characterization of a coastal aquifer using seismic and geoelectric borehole methods
Authors: Maurer Hansraedi , Friedel Sven , Jaeggi David
Published: September 2009

To characterize a coastal aquifer in southern Mallorca (Spain), we have acquired geoelectric and seismic data. The area of investigation lies within a Miocene reefal carbonate platform consisting of lagoon sediments, reef cores and talus sediments. Since the groundwater table was at about 40 m depth , the delineation of small‐scale structural features (1–2 m) within the aquifer required the use of borehole methods. Geoelectric single‐hole tomography was performed in six deep boreholes. This fast and inexpensive technique provided horizontal resolution well beyond the limits of traditional logging techniques. Furthermore, the tomographic inversion results remained virtually unaffected by the insertion of slotted PVC casing tubes and comparisons with electromagnetic induction logs showed an excellent match of resistivities in regions near to the boreholes. In addition to the single‐hole measurements, geoelectric and seismic cross‐hole data were acquired. Combined analyses of all data sets showed the reef core to be particularly susceptible to karstification and recrystallization. These two processes have caused substantial variations in the porosity. Comparison of fluid logs and electrical resistivity versus depth and seismic velocity versus depth functions along all boreholes revealed a surprisingly high correspondence. This unexpected correlation of electrical resistivity (governed by the fluid salinity) and seismic velocities can be explained by geochemical processes occurring in the saltwater‐freshwater mixing zone and/or near the groundwater table. Such processes need to be considered for establishing reliable ground‐water flow models.
Ultra‐shallow imaging using 3D seismic‐reflection methods
Authors: Sloan Steven D. , Steeples Don W. , Tsoflias Georgios P.
Published: September 2009

Three‐dimensional ultra‐shallow seismic reflection methods were used to image multiple reflectors less than 20 m deep, including the top of saturated zone, a paleo‐channel feature and the top of bedrock at a field site located near Lawrence, Kansas. A small 3D demonstration survey was designed and acquired using source and receiver intervals of 0.5 m and source line and receiver line intervals of 2 m. The survey had a nominal fold of 48 and covered an area of ~15.5 m × 35.5 m. Large variations in velocity were present, ranging from ~300–600 m/s laterally in the shallowest layer and ~300–1600 m/s vertically, a degree of variability that is not uncommon in the ultra‐shallow subsurface. Normal moveout corrections cannot account for intersecting reflection hyperbolae such as those caused by large vertical velocity gradients, so a novel processing scheme was applied by extracting offset‐dependent subsets based on the optimum window for each reflection. The subsets were normal moveout corrected independently and then stacked together using conventional 3D processing techniques. Despite the large lateral and vertical velocity variations, we were successful in imaging the top of the saturated zone, paleo‐channel features and the overburden‐bedrock interface located at depths of ~5 m, 8 m and 14 m, respectively. Results of the 3D survey are in agreement with previous studies conducted at the site. The methods presented here could be applied to situations where 3D imaging of the ultra‐shallow subsurface is necessary and may help to identify possible contaminant sinks or flowpaths.
Photometric flowmeter for measuring slow vertical water flow in wells
Authors: Urík J. , Mareš S. , Kobr M. , Lukeš J. , Řezanina S.
Published: September 2009

New construction of a high resolution borehole flowmeter is presented. The logging tool is equipped with an injector enabling to create in the streaming water a colour mark using the food dye Brilliant Blue (E133) as a tracer. A pair of photometric sensors is located in the vertical distance 0.05 m and 0.1 m above and below the special outlet nozzle of the injector. The probe is capable of measuring vertical flow velocities in the range 10−4–10−2 m/s or vertical flow rates in the range 0.001– 0.1 l/s. The proper function and the reliability of the logging tool were checked in the model of the well under laboratory conditions and in two boreholes with different flow rate patterns, one with a very low flow rate upwards and the other with a very low flow rate downwards.
Characterizing lakebed seepage and geologic heterogeneity using resistivity imaging and temperature measurements
Authors: Nyquist Jonathan E. , Heaney Matthew J. , Toran Laura
Published: September 2009

The contribution of groundwater‐surface water exchange to lake budgets is poorly understood and depends in part on lakebed heterogeneities. These heterogeneities are difficult to characterize using traditional point sampling methods. The goal of this project was to use electrical resistivity to identify potential zones of groundwater discharge and recharge, providing focus for point measurements. Multiple resistivity surveys were conducted at Lake Lacawac, a small, glacially‐formed lake in northeastern Pennsylvania. Two types of resistivity surveys were conducted. In a continuous resistivity profile, a multi‐electrode cable was towed parallel to shore to look for spatial variability in resistivity around the lake. Two parallel to shore surveys were conducted, an inner and outer loop, to help characterize the lateral extent of sediment types. The results of these surveys suggested lithology changes both along the shoreline and with distance from shore. Follow‐up resistivity data were collected using cables laid along the lake bottom perpendicular to the shoreline to look for finer scale zonation that affects seepage as a function of distance from shore.

Follow‐up seepage measurements showed that seepage rates are very low, which is consistent with the resistivity data from which we concluded that most of Lake Lacawac is lined with glacial clay and that the lake is essentially perched above the groundwater flow system, with just minor amounts of seepage in a few locations where fingers of sandy sediments extend a short distance from the shore. Discontinuities in these patches of transmissive sediments can result in reversals in the direction of seepage at nearby locations.

We conclude that towed resistivity is useful as a rapid reconnaissance tool for mapping geologic heterogeneity. The results can be used to guide the more time‐consuming but higher‐resolution, lake bottom resistivity measurements, which in turn can guide the placement of seepage meters.
Embankment dam seepage evaluation from resistivity monitoring data
Authors: Sjödahl P. , Dahlin T. , Johansson S.
Published: September 2009

Methods for monitoring seepage are important for the safety of embankment dams. Increased seepage may be associated with internal erosion in the dam and internal erosion is one of the main reasons for dam failures. Internal erosion progresses inside the dam and is difficult to detect by conventional methods. Therefore there is a need for new or improved methods. The resistivity method is a nondestructive method that may accomplish this task. It has been tried in an on‐going research programme in Sweden. Daily resistivity measurements are carried out on permanent installations on two Swedish embankment dams. In this paper the installations on the Sädva embankment dam are described and selected parts of the results are presented. In addition, a method for evaluating the seepage from resistivity monitoring data is theoretically described and tested for four selected areas in the foundation of the Sädva dam. Seasonal resistivity variations are apparent in the reservoir as well as inside the dam. Most parts of the dam have a homogeneous resistivity distribution with consistent variations. The overall status of the dam is satisfactory. However part of the foundation demonstrates a slightly different behaviour pattern with regard to the seasonal variation. The four selected areas represent localities with low, intermediate and high variations in seasonal resistivity. The areas are compared qualitatively and thereby permeable zones within the dam may be identified. Quantitative assessment of the seepage flow is also carried out as an initial test of the described method. It is concluded that the experiences from the Sädva dam are valuable with regard to the use of the resistivity method on embankment dams. Resistivity monitoring data may be used to qualitatively assess the seepage through the dam. For quantitative assessment, the method is promising and the data from the Sädva dam constitute an interesting initial approach. However, many assumptions and simplifications are made and more work on refining the method is needed.