bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermo‐mechanical properties of candelilla wax and dotriacontane organogels in safflower oil
Authors: Morales‐Rueda Juan A. , Dibildox‐Alvarado Elena , Charó‐Alonso Miriam A. , Weiss Richard G. , Toro‐Vazquez Jorge F.
Published: January 2009

The thermo‐mechanical properties of organogels developed by a complex mixture of n‐alkanes present in candelilla wax (CW) were investigated and compared with the ones of organogels developed by a pure n‐alkane, dotriacontane (C32). In both cases, the liquid phase used was safflower oil high in triolein (SFO) and the variables studied were two levels of gelator concentration (1 and 3%), cooling rates of 1 and 10 °C/min, and two gel setting temperatures, 5 and 25 °C (Tset). Based on comparisons of the organogels made with C32, the presence of minor molecular components in CW had a profound effect on the crystal habit of the n‐alkanes in CW‐based organogels, and therefore on their physical properties. Thus, independent of the cooling rate and Tset, C32 showed a higher solubility and higher self‐assembly capability in the SFO than CW. Nevertheless, for the same gelator concentration and time‐temperature conditions, C32 organogels had lower G' profiles than CW organogels. Additionally, independent of the type of gelator, more stable organogel structures were developed at Tset = 5 °C and using the lower cooling rate. The rheological behavior of the organogels was explained considering the formation of a rotator phase by the n‐alkanes, its solid‐solid transition, and their dependence as a function of the cooling rate and Tset. The results here obtained showed that it is possible to gelate SFO through organogelation with CW and without the use of trans fats.
A simple and sensitive transient ITP method for on‐chip analysis of PCR samples
Authors: Wang Lihui , Liu Dayu , Chen Hao , Zhou Xiaomian
Published: January 2009

We present a sensitive, simple and robust on‐chip transient ITP (TITP) method for the analysis of polymerase chain reaction (PCR) samples. This TITP analysis was performed on a poly (methyl methacrylate) microchip with cross structure. The PCR sample was injected into a 4 mm free‐solution buffer channel to increase sample loading. When applied separation voltage, the sample ions were stacked by TITP using chloride ions in the sample matrix as the leading ions and HEPES in the background electrolyte as the terminating ions. The stacked sample plug was then separated by zone electrophoresis (ZE) in hydroxypropylmethyl cellulose polymer. The whole operation was carried out in single background electrolyte. Sample injection, preconcentration / separation were performed continuously with the sequential switching of voltage. By injection of the sample into the free‐solution buffer channel, sampling bias was avoided and the injection time was reduced. With this TITP method, the detection sensitivity was improved without loss of resolution, a 20‐fold signal enhancement was achieved and the average limit of detection was estimated to be 0.24 pg/μL (S/N = 3). The TITP method is simple, fast and sensitive, thus is well suited to direct analysis of the highly saline PCR samples.
Manipulation of self‐assembly amyloid peptide nanotubes by dielectrophoresis
Authors: Castillo Jaime , Tanzi Simone , Dimaki Maria , Svendsen Winnie
Published: January 2009

Self‐assembled amyloid peptide nanotubes (SAPNT) were manipulated and immobilized using dielectrophoresis. Micro‐patterned electrodes of Au were fabricated by photolithography and lifted off on a silicon dioxide layer. SAPNT were manipulated by adjusting the amplitude and frequency of the applied voltage. The immobilized SAPNT were evaluated by SEM and atomic force microscopy. The conductivity of the immobilized SAPNT was studied by I–V characterization, for both single SAPNT and bundles. This work illustrates a way to manipulate and integrate biological nanostructures into novel bio‐nanoassemblies with concrete applications, such as field‐effect transistors, microprobes, microarrays, and biosensing devices.
Micropumps actuated negative pressure injection for microchip electrophoresis
Authors: Li Bowei , Jiang Lei , Wang Qi , Qin Jianhua , Lin Bingcheng
Published: January 2009

A simple negative pressure pinched sample injection method was presented. This method combined diaphragm micropumps and a single voltage supply to generate controllable well‐defined sample plug, and led to effective electrophoresis separation. The pinched plug was found to be favorable for obtaining representative and reproducible results that the RSD of the migration time and peak height of sodium fluorescein were 0.5 and 2.1%, respectively (n=25). The established method had been applied in separation of amino acid samples. This method has the advantages of well‐defined plug, free sample bias effect, high reproducibility and convenience of controlling the negative pressure by the integrated pumps on the microchip. In addition, the single high voltage supply and the world‐to‐chip interface simplified the instrumentation, which is of benefit to the minimization and automation. These advantages demonstrate the potential of this method for a wide range of applications.
Microchips for CE: Breakthroughs in real‐world food analysis
Authors: Escarpa Alberto , González María Cristina , López Gil Miguel Angel , Crevillén Agustín G. , Hervás Miriam , García Miguel
Published: January 2009

The well‐known complexity of food matrices is approached using CE microchips with different strategies to improve the selectivity and sensitivity of the analysis by avoiding and/or making the sample preparation as simple as possible: (i) enhancing the peak capacity in order to perform direct injection, (ii) using the microchip platform to measure one target analyte/group of analytes with or without separating other related interferences, (iii) integrating sample preparation steps on the microchip platform, and (iv) integrating new analytical tools from nanotechnology in the detection stage. New analyte separations of food significance involving DNA probes, biogenic amines, vanilla flavors, and dyes have been reported as successfully breaking new barriers in areas of high impact in the market, such as transgenic food analysis, as well as the detection of frauds and toxins. Simple microchip layouts are still the most common designs used, though sophisticated new ones are emerging. In contrast to other application areas, electrochemical detection continues to be the most common detection route, followed by LIF, though non‐conventional detection routes are also emerging, such as chemiluminescence or UV. In terms of analytical performance, the integration of calibration and quality control on a microchip platform, and remarkable accuracy and precision are being obtained using creative analytical methodologies that enhance the analytical potency of microfluidic chips for their future commercialization. This review critically states the most important advances derived from work done in the field over the past 2–3 years.
A nanochannel‐based concentrator utilizing the concentration polarization effect
Authors: Huang Kuan‐Da , Yang Ruey‐Jen
Published: January 2009

This study develops a microfluidic device comprising two microchannels connected by a nanochannel in which the sample is concentrated via an ionic depletion effect. Using Rhodamine 6G dye for visualization purposes, it is shown that through an appropriate manipulation of the external potentials applied to the reservoirs of the device, an ionic depletion region with an electrical conductivity around 50 times lower than that of the buffer solution can be induced on the anodic side of the nanochannel. Furthermore, via an appropriate time‐based switching of the external electrical potentials, the sample species can be concentrated close to the conductivity ratio within an interval of 1 min. Finally, it is shown that by varying the configuration of the electrical potentials applied to the device reservoirs, the concentrated sample can be delivered either to a single outlet reservoir or to multiple reservoirs.
A novel, environmentally friendly sodium lauryl ether sulfate‐, cocamidopropyl betaine‐, cocamide monoethanolamine‐containing buffer for MEKC on microfluidic devices
Authors: Hoeman Kurt W. , Culbertson Christopher T.
Published: January 2009

A new buffer has been developed for fast, high‐efficiency separations of amino acids by MEKC. This buffer was more environmentally friendly than the most commonly used surfactant‐containing buffers for MEKC separations. It used a commercially available dishwashing soap by Seventh Generation™ (Burlington, VT, USA), which contained three micelle‐forming agents. The mixed micelles were composed of sodium lauryl ether sulfate (anionic), cocamidopropyl betaine (zwitterionic), and cocamide monoethanolamine (non‐ionic). The optimized buffer contained 5.0% w/w Seventh Generation™ Free & Clear™ dishwashing soap, 10 mM sodium borate, and was completely void of organics. The lack of organics and the biodegradability of the surfactant molecules made this buffer more environmentally friendly than typical SDS‐containing buffers. This new buffer also had a different selectivity and provided faster separations with higher separation efficiencies than SDS‐based buffers. Fast separations of BODIPY FL labeled amino acids yielded peaks with separation efficiencies greater than 100 000 in less than 20 s.
Light at work: The use of optical forces for particle manipulation, sorting, and analysis
Authors: Jonáš Alexandr , Zemánek Pavel
Published: January 2009

We review the combinations of optical micro‐manipulation with other techniques and their classical and emerging applications to non‐contact optical separation and sorting of micro‐ and nanoparticle suspensions, compositional and structural analysis of specimens, and quantification of force interactions at the microscopic scale. The review aims at inspiring researchers, especially those working outside the optical micro‐manipulation field, to find new and interesting applications of these methods.
Microfluidic device for integrated restriction digestion reaction and resulting DNA fragment analysis
Authors: Xie Hua , Li Bowei , Zhong Runtao , Qin Jianhua , Zhu Yisheng , Lin Bingcheng
Published: January 2009

A microfluidic system combining temperature‐controlled reactor, analyte delivery, chip electrophoresis (CE) separation, and fluorescence detection was developed, in which the heaters, resistance temperature detectors, enzymatic reactors, CE channels, and pneumatic valves/pumps were integrated onto a single glass–PDMS chip. The microdevice was used to perform the digestion reaction, followed by on‐line electrophoresis separation and detection of the resulting fragments with endonuclease BamHI and FokI as models. Pneumatic valves/pumps served not only for isolating the reaction region from the separation medium to prevent contamination, but also for delivering and quantitatively diluting the fluid from the reaction chamber to the CE section. Thus enzymatic reaction and electrophoresis separation could be insulated and connected as needed. A dynamic coating procedure with the use of PVP and mannitol was firstly adopted for glass–PDMS hybrid chip‐based DNA separations, leading to an improved separation efficiency with reproducible migration time and theoretical plates. The expected 263‐ and 287‐bp digestion products of BamHI and FokI were definitely verified by the size‐based electrophoretic separation and detection. The whole integrated reaction‐CE system can be manipulated in a simple manner with good reproducibility, which is expected to be applied in other on‐line analysis of various biochemical reactions.
Das Licht läuft auf zwei Beinen
Authors: Wegener Martin , Linden Stefan
Published: January 2009

Nanoklein und künstlich hergestellt: Metamaterialien bieten Forschern ungeahnte Möglichkeiten. Maßgeschneiderte „photonische Atome”︁ verhelfen ihnen zu neuen optischen Eigenschaften und inspirieren sie zu innovativen Anwendungen
Expansion und Exzellenz
Authors: Streier Eva‐Maria
Published: January 2009

Das Forschungsland Indien vor großen Herausforderungen
Abgeschaut von der Natur
Authors: Weigand Bernhard , Neumann Sven Olaf , Steinbrück Helga , Zehner Sebastian
Published: January 2009

Wovon Ingenieure träumen: Die Eisformations‐Methode optimiert umströmte Körper – und erleichtert so das Design neuer Maschinenbauteile
Who knows more about future currency volatility?
Authors: Charoenwong Charlie , Jenwittayaroje Nattawut , Low Buen Sin
Published: January 2009

We use four currency pairs from October 1, 2001 to September 29, 2006 to compare the predictive power of the implied volatility derived from currency option prices that are traded on the Philadelphia Stock Exchange (PHLX), Chicago Mercantile Exchange (CME), and over‐the‐counter market (OTC). Among the competing implied volatility forecasts, OTC‐implied volatility subsumes the information content of PHLX‐ and CME‐implied volatility. Consistent with extant studies our result also shows that the implied volatility provides more information about future volatility–regardless of whether it is from the OTC, PHLX, or CME markets–than time series based volatility. © 2009 Wiley Periodicals, Inc. Jrl Fut Mark 29:270–295, 2009
Persistent mispricing in a recently opened emerging index futures market: Arbitrageurs invited
Authors: McMillan David G. , Ülkü Numan
Published: January 2009

The purpose of this study is to analyze the persistent, typically negative, mispricing in the new stock index futures market in Turkey, which has amounted to 5–8%, several multiples of transaction costs. The observations suggest that it is the outcome of a combination of practical difficulties of shorting in the spot stock market, behavioral effects, and insufficient arbitrage. The magnitude of the mispricing and the absence of arbitrage make behavioral effects more visible and provide a unique opportunity to examine extant behavioral hypotheses. Results confirm effects such as disposition and/or conservatism with the mispricing negatively related to past returns, but unrelated to future returns. Finally, an orderly weakening of the negative relation to past returns and behavioral effects is observed, suggesting that such effects will diminish as the market matures. © 2009 Wiley Periodicals, Inc. Jrl Fut Mark 29:218–243, 2009
Estimating error in measuring thermal conductivity using a T‐type nanosensor
Authors: Ito Yohei , Takahashi Koji , Fujii Motoo , Zhang Xing
Published: January 2009

We discuss the measurement error caused by fabrication and measurement of a T‐type nanosensor with a suspended sub‐micrometer Pt hot film that was developed to measure the thermal properties of individual nanowire materials. Comparison of numerical simulation and one‐dimensional analysis revealed that the thermal conductivity of nanowire material such as a carbon nanotube is calculated to be 17% lower. As an example, the thermal conductivity measurement result for a SiC nanowire is reported. The error caused by contact thermal resistance is found to depend on the contact length and can be as great as 20%. It can be said that future measuring can have higher reliability by correcting the estimated measurement error. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20228
A lubricious formulation exhibiting reduced thrombogenicity, cell proliferation, and protein adsorption
Authors: Vicario Pasquale P. , Lu Zichun J. , Grigorian Irina A. , Schottman Tom
Published: January 2009

The adhesion of human platelets, erythrocytes, and leukocytes, the adsorption of protein, and the proliferation of human umbilical vein endothelial cells (HUVEC) on the surface of electropolished stainless steel and the lumen of polyurethane tubing coated with Hydromer's lubricious Duality™ T8B formulation was evaluated. Following exposure to a platelet‐enriched suspension from citrated human whole blood, stainless steel coated with this formulation exhibited significantly reduced adhesion of platelets, erythrocytes, and granulocytes. This reduction in adhesion was confirmed using an immunohistochemical method utilizing antibodies to CD41, CD235, and CD15, respectively. The proliferation of HUVEC cells were significantly reduced when cultured on coated stainless steel. This formulation was also able to significantly reduce the adsorption of plasma proteins and the major protein in tear fluid (lysozyme) to the surface of stainless steel. The nonthrombogenic properties of Duality™ T8B after application to the lumen of polyurethane tubing were also examined. Following a short‐term (3 h) static exposure to citrated human whole blood, microscopic examination revealed that the adhesion of platelets and erythrocytes was reduced significantly, a finding confirmed using anti‐CD41 and anti‐CD235 antibodies in the immunohistochemical method. A long‐term (12 day) study yielded essentially identical results indicating a significant reduction in the adhesion of blood components on the luminal surface of coated polyurethane tubing. In summary, these data indicate that the application of Duality™ T8B onto surfaces of medical devices, such as catheters, extracorporeal circuitry, and coronary stents, could aid in reducing or preventing not only thrombus formation but also the process of restenosis. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009
Stem cell sources to treat diabetes
Authors: Furth Mark E. , Atala Anthony
Published: January 2009

We review progress towards the goal of utilizing stem cells as a source of engineered pancreatic β‐cells for therapy of diabetes. Protocols for the in vitro differentiation of embryonic stem (ES) cells based on normal developmental cues have generated β‐like cells that produce high levels of insulin, albeit at low efficiency and without full responsiveness to extracellular levels of glucose. Induced pluripotent stem (iPS) cells also can yield insulin‐producing cells following similar approaches. An important recent report shows that when transplanted into mice, human ES‐derived cells with a phenotype corresponding to pancreatic endoderm matured to yield cells capable of maintaining near‐normal regulation of blood sugar [Kroon et al., 2008]. Major hurdles that must be overcome to enable the broad clinical translation of these advances include teratoma formation by ES and iPS cells, and the need for immunosuppressive drugs. Classes of stem cells that can be expanded extensively in culture but do not form teratomas, such as amniotic fluid‐derived stem cells and hepatic stem cells, offer possible alternatives for the production of β‐like cells, but further evidence is required to document this potential. Generation of autologous iPS cells should prevent transplant rejection, but may prove prohibitively expensive. Banking strategies to identify small numbers of stem cell lines homozygous for major histocompatibility loci have been proposed to enable beneficial genetic matching that would decrease the need for immunosuppression. J. Cell. Biochem. 106: 507–511, 2009. © 2009 Wiley‐Liss, Inc.
High expression of apolipoprotein E impairs lipid storage and promotes cell proliferation in human adipocytes
Authors: Carmel Jean‐François , Tarnus Evelyne , Cohn Jeffrey S. , Bourdon Emmanuel , Davignon Jean , Bernier Lise
Published: January 2009

Apolipoprotein E (apoE), a key regulator of lipid metabolism, is highly produced by adipose tissue and adipocytes. However, there is little information about its role on adipocyte functions. Because apoE‐deficiency in adipocytes was shown to impair adipocyte differentiation, we investigated the consequences of apoE high expression on differentiation and proliferation of a human adipocytic cell line (SW872). SW872 cells were transfected with human apoE to induce a fivefold increase in apoE production and secretion. Adipocyte differentiation and proliferation were assayed by measuring lipid content, adipogenic gene expression, cell number, cell resistance to serum deprivation, and cell division kinetics. Cultured apoE‐transfected cells accumulated less triglycerides and less cholesterol than control cells. This decrease in lipid accumulation was associated with a strong downregulation of peroxisome proliferator‐activated receptors γ1 and γ2 and stearoyl‐CoA desaturase 1. The decrease in lipid accumulation was not dependent on the presence of lipids, lipoproteins, or PPAR‐γ agonists in the culture medium, nor was it observed with exogenously added apoE. Moreover, we observed that apoE‐transfected cells were more resistant to death induced by serum deprivation, and that these cells underwent more cell divisions than control cells. These results bring new evidence of apoE‐involvement in metabolic disorders at the adipocyte level. J. Cell. Biochem. 106: 608–617, 2009. © 2009 Wiley‐Liss, Inc.
A new iterative linear integral isoconversional method for the determination of the activation energy varying with the conversion degree
Authors: Cai Junmeng , Chen Siyu
Published: January 2009

The conventional linear integral isoconversional methods may lead to important errors in the determination of the activation energy when the significant variation of the activation energy with the conversion degree occurs. Vyazovkin proposed an advanced nonlinear isoconversional method, which allows the activation energy to be accurately determined [Vyazovkin, J Comput Chem 2001, 22, 178]. However, the use of the Vyazovkin method raises the problem of the time‐consuming minimization without derivatives. A new iterative linear integral isoconversional method for the determination of the activation energy as a function of the conversion degree has been proposed, which is capable of providing valid values of the activation energy even if the latter strongly varies with the conversion degree. Also, the new method leads to the correct values of the activation energy in much less time than the Vyazovkin method. The application of the new method is illustrated by processing of theoretically simulated data of a strongly varying activation energy process. © 2009 Wiley Periodicals, Inc. J Comput Chem 2009
Optimization of bimetallic Cu–Au and Ag–Au clusters by using a modified adaptive immune optimization algorithm
Authors: Wu Xia , Cai Wensheng , Shao Xueguang
Published: January 2009

A modified adaptive immune optimization algorithm (AIOA) is designed for optimization of Cu–Au and Ag–Au bimetallic clusters with Gupta potential. Compared with homoatom clusters, there are homotopic isomers in bimetallic cluster, so atom exchange operation is presented in the modified AIOA. The efficiency of the algorithm is tested by optimization of CunAu38‐n (0 ≤ n ≤ 38). Results show that all the structures with the putative global minimal energies are successfully located. In the optimization of AgnAu55‐n (0 ≤ n ≤ 55) bimetallic clusters, all the structures with the reported minimal energies are obtained, and 36 structures with even lower potential energies are found. On the other hand, with the optimized structures of CunAu55‐n, it is shown that all 55‐atom Cu–Au bimetallic clusters are Mackay icosahedra except for Au55, which is a face‐centered cubic (fcc)‐like structure; Cu55, Cu12Au43, and Cu1Au54 have two‐shell Mackay icosahedral geometries with Ih point group symmetry. © 2009 Wiley Periodicals, Inc. J Comput Chem 2009
Haptic quantum chemistry
Authors: Marti Konrad H. , Reiher Markus
Published: January 2009

We present an implementation designed to physically experience quantum mechanical forces between reactants in chemical reactions. This allows one to screen the profile of potential energy surfaces for the study of reaction mechanisms. For this, we have developed a interface between the user and a virtual laboratory by means of a force‐feedback haptic device. Potential energy surfaces of chemical reactions can be explored efficiently by rendering in the haptic device the gradients calculated with first‐principles methods. The underlying potential energy surface is accurately fitted on the fly by the interpolating moving least‐squares (IMLS) scheme to a grid of quantum chemical electronic energies (and geometric gradients). In addition, we introduce a new IMLS‐based method to locate minimum‐energy paths between two points on a potential energy surface. © 2009 Wiley Periodicals, Inc. J Comput Chem 2009
Femtosecond electron diffraction: Direct probe of ultrafast structural dynamics in metal films
Authors: Nie Shouhua , Wang Xuan , Li Junjie , Clinite Richard , Cao Jianming
Published: January 2009

Femtosecond electron diffraction is a rapidly advancing technique that holds a great promise for studying ultrafast structural dynamics in phase transitions, chemical reactions, and function of biological molecules at the atomic time and length scales. In this paper, we summarize our development of a tabletop femtosecond electron diffractometer. Using a delicate instrument design and careful experimental configurations, we demonstrate the unprecedented capability of detecting submilli‐ångström lattice spacing change on a subpicosecond timescale with this new technique. We have conducted an in‐depth investigation of ultrafast coherent phonon dynamics induced by an impulsive optical excitation in thin‐film metals. By probing both coherent acoustic and random thermal lattice motions simultaneously in real time, we have provided the first and unambiguous experimental evidence that the pressure of hot electrons contributes significantly to the generation of coherent acoustic phonons under nonequilibrium conditions when electrons and phonons are not thermalized. Based on these observations, we also propose an innovative approach to measure the electronic Grüneisen parameter in magnetic materials at and above room temperature, which provides a way to gain new insights into electronic thermal expansion in ferromagnetic transition metals. Microsc. Res. Tech. 2009. © 2009 Wiley‐Liss, Inc.
Kinetic measurements from in situ TEM observations
Authors: Sharma Renu
Published: January 2009

Environmental transmission or scanning transmission electron microscope is ideally suited to observe gas solid interactions at nanoscale. It is shown that the time and temperature resolved data, obtained from in situ observations, can be used to obtain reaction rates and understand the kinetics of the processes. Low or high magnification images provide the change in length, area or volume with time at constant temperature and pressure conditions during nitridation of Cu–Cr thin films, deposition of Au particles, growth of Si nanowire and carbon nanotubes. Effect of electron beam is estimated by making observations with and without constant electron beam exposure. Quantitative electron energy loss spectroscopy is employed to measure the reduction rate of Ce+4 in pure ceria, mixed oxides (ceria‐zirconia) and catalyst (Rh‐ceria‐zirconia) powders. Microsc. Res. Tech. 2009. © 2009 Wiley‐Liss, Inc.
In situ TEM of radiation effects in complex ceramics
Authors: Lian Jie , Wang L.M. , Sun Kai , Ewing Rodney C.
Published: January 2009

In situ transmission electron microscopy (TEM) has been extensively applied to study radiation effects in a wide variety of materials, such as metals, ceramics and semiconductors and is an indispensable tool in obtaining a fundamental understanding of energetic beam‐matter interactions, damage events, and materials' behavior under intense radiation environments. In this article, in situ TEM observations of radiation effects in complex ceramics (e.g., oxides, silicates, and phosphates) subjected to energetic ion and electron irradiations have been summarized with a focus on irradiation‐induced microstructural evolution, changes in microchemistry, and the formation of nanostructures. New results for in situ TEM observation of radiation effects in pyrochlore, A2B2O7, and zircon, ZrSiO4, subjected to multiple beam irradiations are presented, and the effects of simultaneous irradiations of α‐decay and β‐decay on the microstructural evolution of potential nuclear waste forms are discussed. Furthermore, in situ TEM results of radiation effects in a sodium borosilicate glass subjected to electron‐beam exposure are introduced to highlight the important applications of advanced analytical TEM techniques, including Z‐contrast imaging, energy filtered TEM (EFTEM), and electron energy loss spectroscopy (EELS), in studying radiation effects in materials microstructural evolution and microchemical changes. By combining ex situ TEM and advanced analytical TEM techniques with in situ TEM observations under energetic beam irradiations, one can obtain invaluable information on the phase stability and response behaviors of materials under a wide range of irradiation conditions. Microsc. Res. Tech., 2009. © 2009 Wiley‐Liss, Inc.
Oxygen isotope analysis of phosphate: improved precision using TC/EA CF‐IRMS
Authors: LaPorte D. F. , Holmden C. , Patterson W. P. , Prokopiuk T. , Eglington B. M.
Published: January 2009

Oxygen isotope values of biogenic apatite have long demonstrated considerable promise for paleothermometry potential because of the abundance of material in the fossil record and greater resistance of apatite to diagenesis compared to carbonate. Unfortunately, this promise has not been fully realized because of relatively poor precision of isotopic measurements, and exceedingly small size of some substrates for analysis. Building on previous work, we demonstrate that it is possible to improve precision of δ18OPO4 measurements using a ‘reverse‐plumbed’ thermal conversion elemental analyzer (TC/EA) coupled to a continuous flow isotope ratio mass spectrometer (CF‐IRMS) via a helium stream [Correction made here after initial online publication]. This modification to the flow of helium through the TC/EA, and careful location of the packing of glassy carbon fragments relative to the hot spot in the reactor, leads to narrower, more symmetrically distributed CO elution peaks with diminished tailing. In addition, we describe our apatite purification chemistry that uses nitric acid and cation exchange resin. Purification chemistry is optimized for processing small samples, minimizing isotopic fractionation of PO4−3 and permitting Ca, Sr and Nd to be eluted and purified further for the measurement of δ44Ca and 87Sr/86Sr in modern biogenic apatite and 143Nd/144Nd in fossil apatite. Our methodology yields an external precision of ± 0.15‰ (1σ) for δ18OPO4. The uncertainty is related to the preparation of the Ag3PO4 salt, conversion to CO gas in a reversed‐plumbed TC/EA, analysis of oxygen isotopes using a CF‐IRMS, and uncertainty in constructing calibration lines that convert raw δ18O data to the VSMOW scale. Matrix matching of samples and standards for the purpose of calibration to the VSMOW scale was determined to be unnecessary. Our method requires only slightly modified equipment that is widely available. This fact, and the demonstrated improvement in precision, should help to make apatite paleothermometry far more accessible to paleoclimate researchers. Copyright © 2009 John Wiley & Sons, Ltd.
A spectroscopic approach to assess trace–heavy metal contents in contaminated floodplain soils via spectrally active soil components
Authors: Vohland Michael , Bossung Christian , Fründ Heinz‐Christian
Published: January 2009

Soil samples from grassland plots in the Hase floodplain near Osnabrück (NW Germany) were analyzed using visible and near‐infrared laboratory spectroscopy (VNIRS) by means of an ASD FieldSpec II Pro FR‐ spectroradiometer (spectral range 0.4–2.5 µm), paralleled by atomic‐absorption spectrometry (AAS), automated combustion for Corg quantification, and texture analysis. By AAS, contents of Cu, Zn, and Pb were found to be clearly elevated which is due to industrial effluents into the river in the 19th and 20th century. As these heavy metals (HMs) cannot be assessed directly by VNIRS, it was one major task to clarify whether they can be quantified indirectly using intercorrelations with spectrally active soil components. A second goal was to identify the specific spectroscopic predictive mechanism which may also be applicable to assess trace‐HM contents of other soil samples similar to those investigated here. For the latter, Corg was found to be most indicative, whereas the binding of the metals to other constituents (Fe oxides, clay) was not utilizable in the spectroscopic approach. The measured spectra were subjected to a multiplicative scatter correction and afterwards used to establish partial least‐squares regression (PLSR) models to estimate the contents of the different soil constituents. For Corg, very reliable estimates were obtained for both calibration and validation samples (in the validation, r² amounted to 0.90 and the percentage root mean square error [RMSE] was equal to 30.6%). Estimation accuracies obtained by PLSR for the trace HMs were considerably lower (r² between 0.56 and 0.71, percentage RMSE > 50%), which can be traced back to moderate correlations with Corg as main spectral determinant. According to these results, VNIRS can be applied as rapid and precise screening method for Corg to complement traditional analytical methods and to be used efficiently for a large number of samples. The method of VNIRS may also be applied for an indirect estimation of Corg‐associated metals to address their spatial variability, for example. This issue appears to be of high importance for digital soil mapping by imaging spectroscopy on a local to medium spatial scale.
Determination of soil texture: Comparison of the sedimentation method and the laser‐diffraction analysis
Authors: Taubner Heidi , Roth Birgit , Tippkötter Rolf
Published: January 2009

Laser‐diffraction analysis (LDA) is a rapid automated method achieving highly resolved frequency distributions of particle sizes. Recently, LDA has come into use in environmental sciences. However, in the size range of silt and clay deviations from the particle‐size analysis with the standard pipette method, which is regarded as the reference method for soil‐texture classification, have been reported. Therefore, this study concentrates (1) on the verification of systematic relations between both methods using a series of soils of Lower Saxony (Germany) and (2) on the general applicability of the laser‐diffraction method to soil‐texture classification as well as (3) texture‐based estimates of air capacity, available field capacity, and permanent wilting point.

The comparison of LDA with the pipette method demonstrated highly significant linear correlations in each of the particle‐size fractions from clay to coarse silt. The slope of regressions ranged from 0.4 with fine silt to 3.1 with clay. If the clay content derived from LDA was applied to texture classification, the resulting textural classes differed from the standard textural classes, except for purely sandy samples with a clay content of <5%. However, the linear‐regression model enabled an approach of the LDA‐based clay content to values produced with the standard pipette method. Using this transformation, a texture classification became practicable in many cases, but, despite of a high significance level between LDA and pipette method, still led to wrong textural classes in several cases. A comparison with regression models from other regions in Europe showed both similarities and discrepancies, even for similar substrates. Hence, the laser‐diffraction analysis cannot be used for the texture classification of soil samples without verification by the standard pipette method.
Laser Micro Manufacturing
Authors: Gillner Arnold
Published: January 2009

Laser processes have been used for specific manufacturing processes already since decades in applications, where conventional could not meet the demands on accuracy and flexibility. However, the share of micro applications within the whole laser market was always a minor one and laser cutting and welding are still dominating the laser application sector. Due to the increasing trend to miniaturization and higher integration of consumer products laser processes become more and more important and laser micro manufacturing is showing the highest market increase. This development is not only fostered by a strong market pull but also due to the availability of very high quality lasers, which allow the specific energy deposition on a micrometer scale at high processing speeds. Lower laser costs, easy installation and low maintenance costs have made lasers to a versatile tool for industrial micro manufacturing processes.
Power Is (Not) Everything
Authors: Mayerhofer Roland
Published: January 2009

The variety of different laser sources, either a brand new product or a derivate of already existing concepts is growing almost every day. Even an experienced application guy like me struggles more and more to find the appropriate laser for a specific application in the first shot. It is out of question, that it is more difficult for our customers who have not been so close to the evolution process of lasers, penetrating more and more areas of industrial production. Thus, this article is intended to give a broad overview on the fundamentals of laser material processing in order to help finding suitable laser properties for your application quickly. The influence of the most important parameter in laser material interaction, the amount of laser power, necessary for specific industrial applications is outlined.
The Midas Touch: Surface Processing With the UV Excimer Laser
Authors: Delmdahl Ralph , Paetzel Rainer
Published: January 2009

Very much like the ancient king Midas who as the legend tells was able to transform ordinary material into gold by the touch of his hand, today's excimer lasers are capable of transforming an unspecificmaterial layer into a high value, functional surface by their unique beam properties.

Representing today's most cost‐effective and dependable pulsed, ultraviolet (UV) laser technology, excimer lasers enable disruptive innovation in various growth industries as diverse as the markets for flat panel displays, automobiles, biomedical devices and alternative energies.

It is the combination of two fundamental aspects, namely wavelength and output power, which determines the excimer laser's unique value adding potential in high tech industries which more than ever have to balance product size‐efficiency and performance demands with process speed and production costs. This article will try to provide an insight into some key applications of the excimer laser.
High Speed Processing for Microelectronics and Photovoltaics
Authors: Kauf Michael , Patel Raj , Bovatsek Jim
Published: January 2009

Q‐switched infrared, green, UV and DUV lasers are being used routinely for various microelectronics and photovoltaic manufacturing applications, such as ablation and cutting of dielectric materials, LED scribe and cleave processes in microelectronics, and scribing thin film solar cells.

To create functional good results when micromachining any material, the laser energy density needs to be set higher than the material removal threshold and a reasonable laser beam spot overlap is required. The maximum scribing speed achieved using a system with a pulsed laser source therefore is usually limited by the laser repetition rate and the energy per pulse available at that repetition rate. For a given repetition rate, as processing speed increases the beam spot overlap decreases and at certain critical processing speed laser beam spots gets separated in space and continuous scribing of material is not possible. This fundamental limitation has to be solved in order to achieve faster processing speeds, higher throughput, and lower cost per part.

To overcome this limitation in next generation laser processing systems, SpectraPhysics has developed and evaluated high repetition rate mode‐locked lasers as an alternative to Q‐switched lasers. Using a high average power mode‐locked laser operating at 80 MHz, we have been able to demonstrate processing speeds that are an order of magnitude higher in thin layers of select materials than that with current Q‐switched technology. The following article reviews results obtained for micromachining dielectrics, scribing and cleaving blue LEDs, and scribing different solar cell materials.
Innovative Laser Materials Processing for Photovoltaics
Authors: Homburg Oliver , Harten Paul
Published: January 2009

There are several laser‐based processes which are currently used in solar cell manufacturing or show a high potential for being implemented in series production in the future. Among these are laser edge isolation, laser fired contacts, metal/emitter wrap through, laser doping as well as P1, P2 and P3 structuring of thin film solar cells. Currently, all these direct‐patterning processes are mostly performed by single‐mode lasers with Gaussian intensity distributions. In contrast, top hat profiles offer larger process stability as well as cost savings. Another process that is still in the research and development stage is the crystallization of amorphous Si into polycrystalline Si. Here an increase of the electron mobility results in a better separation of the charge carriers in the cell and finally increased cell efficiency. A novel diode laser line scanning system and first processing results are presented in this article.
Preparation of a Novel Polymer‐Modified Si Surface for DNA Immobilization
Authors: Demirel Gökçen Birlik , Coşkun Samet , Kalkan Meryem , Çaykara Tuncer
Published: January 2009

The design of a novel polymer‐modified overlayer composed of PPAPE and GPMS on a silicon wafer for immobilization of DNA molecules is described. After hydroxylation of Si(100) surfaces, GPMS molecules were self‐assembled onto these surfaces. PPAPE molecules were then covalently attached to the epoxy‐terminated surfaces. The incubation time and concentration of PPAPE was found to effect both layer thickness and water CA. The type of organic solvent and the pH were found to change the nature of the PPAPE‐modified surface for DNA immobilization. It is concluded that PPAPE‐modified surfaces show advantages for DNA immobilization by electrostatic interactions between DNA molecules and positively charged free amino groups of the PPAPE‐modified surfaces at the appropriate pH values.

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Nickel‐Ion‐Mediated Control of the Stoichiometry of His‐Tagged Protein/Nanoparticle Interactions
Authors: De Mrinmoy , Rana Subinoy , Rotello Vincent M.
Published: January 2009

The interaction between synthetic materials and biomolecules plays an important role in biomedical and pathological sciences. An important issue in these interactions is control of stoichiometry. The interaction between NTA ligands and proteins with six consecutive His residues has been widely used for protein purification. Control of stoichiometry is an important issue in applying this recognition strategy to the creation of defined nanoparticle‐protein conjugates. In this communication we report the direct control of particle‐protein stoichiometry through variation of nickel chloride concentration, as demonstrated through fluorescence and gel electrophoresis.

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A New Concept for More Biocompliant Bone Cements for Vertebroplasty and Kyphoplasty
Authors: Hu Xianbo , Zhai Xiaowen , Hirt Thomas
Published: January 2009

A series of more biocompliant bone cements with mechanical properties that match those of different vertebral trabecular or cancellous bones for vertebroplasty and kyphoplasty applications, have been developed. The elastic modulus and strength of the bone cements are in a range of 5 to 400 MPa, and 5 to 75 MPa, respectively. The bone cement shows excellent thermal and dimensional stability in simulated body fluid of Ringer's solution at both 37 and 70 °C. The elastic modulus, strength, ultimate strain are constant over time at both temperatures and did not alter dimensions. The bone cement has a much lower exothermic temperature during polymerization compared with commercially available poly(methyl methacrylate) bone cements, and has high cohesiveness in liquid environments. It is able to be delivered through an 18 gauge needle ranging from 4 to 6 inches in length and reaches final mechanical properties within 30 min post delivery.

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Photopolymerization without Photoinitiator of Bismaleimide‐Containing Oligo(oxypropylene)s: Effect of Oligoethers Chain Length
Authors: Vázquez Cuauhtémoc Pozos , Joly‐Duhamel Christine , Boutevin Bernard
Published: January 2009

This article describes the synthesis and characterization of a series of poly(propylene glycol bismaleimide) (PPGM) with molecular weights ($\overline M _{{\rm ws}}$) in the range of 390–2 600 g · mol−1. Their photopolymerization rates without photoiniator were similar to that of an acrylate resin in the presence of a photoinitiator. The reactivities and degrees of conversion of these PPGM oligomers, thermal and mechanical properties of the resulting materials were studied as a function of $\overline M _{\rm w}$. Rigid materials were obtained except for that containing the longest PPGM, which exhibited mechanical properties of a rubber. The glass transition temperature values and the thermal stability were found to decrease when $\overline M _{\rm w}$ of used oligomers was increased. Crosslinking density was the parameter that controlled both mechanical and thermal properties.

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Thin Film Instabilities in Blends under Cylindrical Confinement
Authors: Chen Dian , Chen Jiun‐Tai , Glogowski Elizabeth , Emrick Todd , Russell Thomas P.
Published: January 2009

Rayleigh instabilities in bilayers of poly(methyl methacrylate) (PMMA) and polystyrene (PS) confined within the cylindrical nanoporous anodic aluminum oxide (AAO) membranes were investigated. The bilayered nanotubes were thermally annealed to induce phase separation and instabilities in the confined films. For short annealing times, the nanotubes were transformed into nanorods with periodic encapsulated air pockets. With longer annealing times, the air‐pockets coalesced to form columns of air. Small air inclusions encased in periodic domains of PS were, in turn, incorporated within PMMA nanorods. Selectively removing the PMMA by exposure to UV radiation and washing with acetic acid, left PS nanospheres with an air inclusion. Gold nanoparticles having PS ligands were also incorporated within the PS phase, generating novel composite morphologies.

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Brain temperature and pH measured by 1H chemical shift imaging of a thulium agent
Authors: Coman Daniel , Trubel Hubert K. , Rycyna Robert E. , Hyder Fahmeed
Published: January 2009

Temperature and pH are two of the most important physiological parameters and are believed to be tightly regulated because they are intricately related to energy metabolism in living organisms. Temperature and/or pH data in mammalian brain are scarce, however, mainly because of lack of precise and non‐invasive methods. At 11.7 T, we demonstrate that a thulium‐based macrocyclic complex infused through the bloodstream can be used to obtain temperature and pH maps of rat brain in vivo by 1H chemical shift imaging (CSI) of the sensor itself in conjunction with a multi‐parametric model that depends on several proton resonances of the sensor. Accuracies of temperature and pH determination with the thulium sensor – which has a predominantly extracellular presence – depend on stable signals during the course of the CSI experiment as well as redundancy for temperature and pH sensitivities contained within the observed signals. The thulium‐based method compared well with other methods for temperature (1H MRS of N‐acetylaspartate and water; copper–constantan thermocouple wire) and pH (31P MRS of inorganic phosphate and phosphocreatine) assessment, as established by in vitro and in vivo studies. In vitro studies in phantoms with two compartments of different pH value observed under different ambient temperature conditions generated precise temperature and pH distribution maps. In vivo studies in α‐chloralose‐anesthetized and renal‐ligated rats revealed temperature (33–34°C) and pH (7.3–7.4) distributions in the cerebral cortex that are in agreement with observations by other methods. These results show that the thulium sensor can be used to measure temperature and pH distributions in rat brain in vivo simultaneously and accurately with using biosensor imaging of redundant. Copyright © 2008 John Wiley & Sons, Ltd.