bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of blood flow velocity in the basal cerebral circulation: Advantages of transcranial color‐coded sonography over conventional transcranial doppler
Authors: Martin P. J. , Evans D. H. , Naylor A. R.
Published: February 2007

Unlike conventional transcranial Doppler (TCD), transcranial color‐coded sonography (TCCS) enables imaging of the basal cerebral arteries using color‐flow ultrasonography and correction for the angle of insonation when determining blood flow velocities. We present hemodynamic data from 20 normal subjects, each studied with TCD and TCCS.

Velocities derived using TCCS with angle correction were significantly greater than those derived using TCD in all vessels (mean velocities [cm/sec; mean with 95% confidence intervals])—anterior cerebral artery: TCD 48 (45–50), TCCS 62 (58–66), p < .0001; middle cerebral artery: TCD 61 (58–64), TCCS 70 (66–74), p < .0001; posterior cerebral artery: TCD 43 (41–46), TCCS 54 (50–57), p < .0001; basilar artery: TCD 40 (34–45), TCCS 45 (38–52), p <.01. Pulsatility index values were significantly greater in all arteries when determined by TCCS, and resistance index values were significantly greater except in the basilar artery. Correcting for the angle of insonation using TCCS may enable estimation of blood flow velocities closer to the “true” values than those derived using conventional TCD. © 1995 John Wiley & Sons, Inc.
A case of extrahepatic portal vein aneurysm accompanying lupoid hepatitis
Authors: Itoh Yuko , Kawasaki Toshihiko , Nishikawa Haruhiro , Ochi Jiro , Miura Kensuke , Moriyasu Fuminori
Published: February 2007

Portal vein aneurysm, especially that of the extrahepatic portal vein, is a very rare entity. We recently observed a case of aneurysm at the junction of the superior mesenteric vein and the splenic vein which accompanied lupoid hepatitis. Abdominal ultrasonography, color Doppler ultrasonography, abdominal computed tomography (CT), magnetic resonance imaging (MRI), and angiography revealed a portal vein aneurysm that increased in size after a period of about 10 months. © 1995 John Wiley & Sons, Inc.
Effect of Fixative on Chromatin Structure and DNA Detection
Authors: Falconi Mirella , Teti Gabriella , Zago Michela , Pelotti Susi , Gobbi Pietro , Breschi Lorenzo , Mazzotti Giovanni
Published: February 2007

In this study, we analyzed the chromatin ultrastructure in interphase cells after different chemical fixations. In light of the fact that there is little information regarding the fixation of biological samples in combination with molecular biology methods (such as DNA extraction and in situ hybridization methods) we analyzed the ultrastructure of chromatin in interphase cells fixed with different fixatives and tested under the same conditions for both DNA extraction and in situ hybridization. The results showed that, among the different combinations and concentrations we analyzed, the solution of 4% paraformaldehyde/0.1% glutaraldehyde was the best compromise in order to achieve a well‐preserved morphology, successful DNA extraction, and specific signaling of in situ hybridization, suggesting a low interference of this fixative with the chromatin organization. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.
Multifunctional Imaging of Endogenous Contrast by Simultaneous Nonlinear and Optical Coherence Microscopy of Thick Tissues
Authors: Yazdanfar Siavash , Chen Yen Yu , So Peter T.C. , Laiho Lily H.
Published: February 2007

A variety of high resolution optical microscopy techniques have been developed in recent years for basic and clinical studies of biological systems. We demonstrate a trimodal microscope combining optical coherence microscopy (OCM) with two forms of nonlinear microscopy, namely two‐photon excited fluorescence (2PF) and second harmonic generation (SHG), for imaging turbid media. OCM combines the advantages of confocal detection and coherence gating for structural imaging in highly scattering tissues. Nonlinear microscopy enables the detection of biochemical species, such as elastin, NAD(P)H, and collagen. While 2PF arises from nonlinear excitation of fluorescent species, SHG is a form of nonlinear scattering observed in materials that lack a center of inversion symmetry, such as type I collagen. Characterization of the microscope showed nearly diffraction‐limited spatial resolution in all modalities. Images were obtained in fish scales and excised human skin samples. The primary endogenous sources of contrast in the dermis were due to elastin autofluorescence and collagen SHG. Multimodal microscopy allows the simultaneous visualization of structural and functional information of biological systems. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.
Neuron‐specific phosphorylation of mitogen‐ and stress‐activated protein kinase‐1 involved in cerebral hypoxic preconditioning of mice
Authors: Huang Ping , Qi Zhifeng , Bu Xiangning , Zhang Nan , Han Song , Fang Li , Li Junfa
Published: February 2007

Studies have demonstrated the involvement of mitogen‐activated protein kinase (MAPK) cascade pathways in the development of cerebral ischemic/hypoxic preconditioning (I/HPC). However, the role of mitogen‐ and stress‐activated protein kinase 1 (MSK1), an important downstream kinase of MAPK signaling pathways, in cerebral I/HPC is unclear. By using Western blot and immunostaining methods, we applied our unique “autohypoxia”‐induced I/HPC mouse model to investigate the effects of repetitive hypoxic exposure (H0–H6, n = 6 for each group) on phosphorylation and protein expression levels of MSK1 in the brain of mice. We found that the levels of phosphorylation on threonine 645 (Thr645) and serine 375 (Ser375) of MSK1, but not the protein expression, increased significantly both in hippocampus and in cortex of mice from H1–H6 groups (P < 0.05) over that of the normoxic group (H0, n = 6). Similarly, enhanced phosphorylations on Thr645 and Ser375 of MSK1 were also observed by immunostaining in both the cortex and the hippocampus of mice following three series of hypoxic exposures (H3). In addition, we found by using double‐immunofluorescence labeling that phosphorylated Thr645‐MSK1 colocalized with a neuron‐specific protein, neurogranin, in both cortex and hippocampus of I/HPC mice (H3). These results suggest that the increased neuron‐specific phosphorylation of MSK1 on Thr645 and Ser375, not protein expression, might be involved in the development of cerebral I/HPC in mice. © 2007 Wiley‐Liss, Inc.
Different Methods of Creatinine Measurement Significantly Affect MELD Scores
Authors: Cholongitas Evangelos , Marelli Laura , Kerry Andrew , Senzolo Marco , Goodier David W. , Nair Devaki , Thomas Michael , Patch David , Burroughs Andrew K.
Published: February 2007

Bilirubin (Bil) interferes with creatinine (Cr) measurement. Different laboratory methods are used to overcome this problem. Model for end-stage liver disease (MELD) scoring incorporates Cr and is used to prioritize patients for liver transplantation. Thus, MELD scores may vary with different Cr measurements influencing patients' priority. Our aim was to evaluate 4 different Cr assays (O'Leary modified Jaffe [mJCr], compensated [rate blanked] kinetic Jaffe [cJCr], enzymatic [ECr], and standard kinetic Jaffe [JCr]) in patients with abnormal liver function tests and assess changes in MELD score. A total of 403 consecutive samples from 158 patients' Cr assays were evaluated. Bland-Altman plots and MELD scores were also evaluated for each assay. Agreement was found to be poor among all Cr assays. Increased variability in Cr occurred with increasing Bil concentrations: Bil <100 μmol/L ≤3-point MELD variation - 3-point difference in 2%; Bil ≥400μmol/L ≤7-point MELD variation - ≥3-point difference in 78%. When MELD was ≥25 (mJCr as reference; mean, 30.5 points), MELD variation was greatest: mean, 28 (MELD cJCr), 27.5 (MELD ECr), and 28.4 (MELD JCr) (P < 0.001). In conclusion, there is poor agreement among different assays for Cr. As Bil concentration rises, there is greater variability in each creatinine measurements and thus greater variability in MELD scores that, this affect prioritization for liver transplantation. Liver Transpl, 2006. © 2006 AASLD.
Reconstructive potential of the lateral arm flap after tumor resection
Authors: Haas Franz , Ensat Florian , Windhager Reinhard , Stammberger Heinz , Koch Horst , Scharnagl Erwin
Published: February 2007

The reconstruction of extended tumor‐related defects in different anatomic regions requires a versatile and reliable flap. For many surgeons, the lateral arm flap has become the technique of choice in the reconstruction of small‐ to medium‐sized defects. The aim of this study was to analyze the reconstructive potential of the lateral arm flap after cancer ablation in various indications. Between 1998 and 2006, 14 patients underwent reconstruction with differently composed and designed lateral arm flaps at our institution. Complete coverage of all defects was achieved with a single surgical procedure. With a flap survival rate of 100% in our series, excellent long term results and high patient satisfaction combined with low donor site morbidity, we can recommend the use of the lateral arm flap in tumor patients. © 2007 Wiley‐Liss, Inc. Microsurgery, 2007.
On the uniform decay for the Korteweg–de Vries equation with weak damping
Authors: Massarolo C. P. , Menzala G. P. , Pazoto A. F.
Published: February 2007

The aim of this work is to consider the Korteweg–de Vries equation in a finite interval with a very weak localized dissipation namely the H−1‐norm. Our main result says that the total energy decays locally uniform at an exponential rate. Our analysis improves earlier works on the subject (Q. Appl. Math. 2002; LX(1):111–129; ESAIM Control Optim. Calculus Variations 2005; 11(3):473–486) and gives a satisfactory answer to a problem suggested in (Q. Appl. Math. 2002; LX(1):111–129). Copyright © 2007 John Wiley & Sons, Ltd.
Characterization of the variation in the imidazole alkaloid profile of Pilocarpus microphyllus in different seasons and parts of the plant by electrospray ionization mass spectrometry fingerprinting and identification of novel alkaloids by tandem mass spectrometry
Authors: Abreu IIka N. , Mazzafera Paulo , Eberlin Marcos N. , Zullo Marco António T. , Sawaya Alexandra C. H. F.
Published: February 2007

Pilocarpus microphyllus (Rutaceae), popularly known as jaborandi, is the only commercial source of an imidazole alkaloid named pilocarpine. In the present study, the variation in the profile of imidazole alkaloids in different seasons and in different parts of the P. microphyllus plant during the summer was analyzed by electrospray ionization mass spectrometry in the positive ion mode [ESI(+)‐MS]. The fingerprints of these extracts repeatedly presented similar ions which were mass‐selected and studied by tandem mass spectrometry (ESI‐MS/MS and ESI‐MS/MS/MS) and high‐resolution mass spectrometry, resulting in the characterization of eight imidazole alkaloids. The data from the ESI(+)‐MS fingerprints were analyzed by principal component analysis (PCA), showing that pilocarpine was present mainly in the summer, whereas in the autumn mainly pilosine and winter anhydropilosine were found. Three alkaloids, reported for the first time in extracts of P. microphyllus, were found. Analysis of the distribution of alkaloids in different parts of the plant during the summer showed that, although pilocarpine was present throughout the plant, 13‐nor‐8(11)‐dihydropilocarpine was found mainly in the stem, pilosine and anhydropilosine were present mainly in the intermediary leaves, and the three new alkaloids were mainly found in the leaflets and petioles. Based on the dissociation patterns of these alkaloids, we observed that there were three structurally related groups of alkaloids differing in their distribution in the plant tissues and responding differently to seasonal variations. These results also indicate that these three groups of alkaloids could belong to intermediate, parallel or competitive pathways for pilocarpine formation biosynthesis. Copyright © 2007 John Wiley & Sons, Ltd.
Determination of indican, isatin, indirubin and indigotin in Isatis indigotica by liquid chromatography/electrospray ionization tandem mass spectrometry
Authors: Zou Peng , Koh Hwee Ling
Published: February 2007

The roots and leaves of Isatis indigotica, named ‘Ban‐Lan‐Gen’ and ‘Da‐Qing‐Ye’, respectively, are widely used for the treatment of influenza, viral pneumonia, mumps, pharyngitis, and hepatitis. The indoxyl derivatives detected in the roots and leaves of I. indigotica have been reported to be biologically active. In the present study, a liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI‐MS/MS) method was developed to determine indican, isatin, indirubin and indigotin in the roots and leaves of I. indigotica. The method has been validated for linearity, precision and accuracy. Using multiple reaction monitoring (MRM), the limits of detection (LODs) were determined as 0.004 ng for indican, 0.01 ng for isatin, 0.01 ng for indrubin and 0.03 ng for indigotin, while the limits of quantitation (LOQs) were 0.015 ng for indican, 0.04 ng for isatin, 0.04 ng for indirubin and 0.1 ng for indigotin. Compared with previously reported methods, the current method is more rapid, selective and sensitive. This is the first report of the LC/MS/MS determination of indican, isatin, indirubin and indigotin. Copyright © 2007 John Wiley & Sons, Ltd.
Clinical and molecular survey in 124 Chinese patients with Leigh or Leigh‐like syndrome
Authors: Zhang Y. , Yang Y. L. , Sun F. , Cai X. , Qian N. , Yuan Y. , Wang Z. X. , Qi Y. , Xiao J. X. , Wang X. Y. , Zhang Y. H. , Jiang Y. W. , Qin J. , Wu X. R.
Published: February 2007

Leigh syndrome is the most common mitochondrial disorder in children characterized by necrotic lesions in the central nervous system. Both mitochondrial DNA (mtDNA) and nuclear DNA defects in the mitochondrial respiratory chain can lead to this disease. To characterize the clinical and genetic traits of Leigh or Leigh‐like syndrome patients in China, 124 unrelated cases were collected between 1992 and 2005. Seventy‐seven cases (62.1%) met the typical criteria of Leigh syndrome, including symmetrical bilateral abnormal signals in the basal ganglia, thalamus and brain stem, etc. Other cases (37.9%) belonged to Leigh‐like syndrome with atypical clinical or radiological manifestations. Late‐onset patients accounted for 20.2%, which is more than previously reported. Movement disorder was the most common symptoms in our patients. Thirty‐two patients (25.8%) were confirmed to carry mutant genes. Among them, six cases (4.8%) have been demonstrated to have point mutations in mitochondrial DNA. Two separate patients were detected to have mutations on A8344G and A3243G. The T8993G point mutation was identified in one patient and T8993C in one other patient. SURF1 mutations associated with cytochrome‐c oxidase deficiency were identified in 25 patients (20.2%). Four unreported variations have been identified in SURF1 gene from three patients. G604C was found in 22 patients. Only one patient had C214T mutation in the pyruvate dehydrogenase E1α subunit gene. In the remaining 92 patients (74.2%), a specific molecular dysfunction or underlying metabolic abnormality could not be identified.
Clinical pictures of 75 patients with neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD)
Authors: Ohura T. , Kobayashi K. , Tazawa Y. , Abukawa D. , Sakamoto O. , Tsuchiya S. , Saheki T.
Published: February 2007

We clarified the clinical features of NICCD (neonatal intrahepatic cholestasis caused by citrin deficiency) by retrospective review of symptoms, management and long‐term outcome of 75 patients. The data were generated from questionnaires to paediatricians in charge of the patients. Thirty of the patients were referred to hospitals before 1 month of age because of positive results in newborn screening (hypergalactosaemia, hypermethioninaemia, and hyperphenylalaninaemia). The other 45, the screen‐negative patients, were referred to hospitals with suspected neonatal hepatitis or biliary atresia because of jaundice or discoloured stool. Most of the screen‐negative patients presented before 4 months of age, and 11 had failure to thrive. Laboratory data showed elevated serum bile acid concentrations, hypoproteinaemia, low levels of vitamin K‐dependent coagulation factors and hypergalactosaemia. Hypoglycaemia was detected in 18 patients. Serum amino acid analyses showed significant elevation of citrulline and methionine concentrations. Most of the patients were given a lactose‐free and/or medium‐chain triglyceride‐enriched formula and fat‐soluble vitamins. Symptoms resolved in all but two of the patients by 12 months of age. The two patients with unresolved symptoms suffered from progressive liver failure and underwent liver transplantation before their first birthday. Another patient developed citrullinaemia type II (CTLN2) at age 16 years. It is important to recognize that NICCD is not always a benign condition.
Cross pinning of supracondylar fractures from a lateral approach. Stabilization achieved with safety
Authors: Eberhardt Oliver , Fernandez Francisco , Ilchmann Thomas , Parsch Klaus
Published: February 2007

Purpose

Various pin configurations are possible to stabilize a supracondylar fracture. While cross pinning gives the best stabilty the disadvantage is the risk of iatrogenic ulnar nerve injury. We combine a cross pin fixation with a lateral approach. The aim of the study was to prove our method retrospectively to show the advantage of lateral cross-pinning achieving stabilty and avoiding ulnar nerve injury.

Method

Between 1 January 2001 and 31 December 2002, 84 supracondylar fractures were treated with invasive surgical procedure. The intention was a primary closed reduction. Following closed reduction under general anaesthesia, two K-wires were introduced from the lateral side, one ascending and the other descending. If it was not possible to perform a closed reduction, an open reduction was performed by medial–lateral crossed K-wire fixation. After either an open or closed reduction, the pins were buried under the skin. The results were evaluated using Flynn's score. The mean time of follow-up was 18.9 months.

Results

Seventy-seven percent of the patients were treated with a closed reduction, while 23% needed an open reduction. A clinical follow-up examination was done at an average of 18.9 months following the trauma. Of those treated with a closed reduction alone, 93% had an excellent or good functional result. Of those requiring an open reduction, 88% had excellent or good result. None of our patients exhibited secondary dislocation or iatrogenic ulnar palsies.

Conclusion

Closed reduction and lateral crossed pin fixation with ascending and descending K-wires buried under the skin is an effective method to treat type II and III supracondylar fractures in children. The method gives stability and avoids iatrogenic ulnar nerve injuries.
Nasal septal perforations: Our surgical technique
Authors: Presutti Livio , Ciufelli Matteo Alicandri , Marchioni Daniele , Villari Domenico , Marchetti Alessio , Mattioli Francesco
Published: February 2007

Objective

The aim of this paper was to describe our surgical technique for the treatment of nasal septal perforations.

Study and Design

We studied 31 patients with nasal septal perforation treated with an endoscope‐assisted technique, based on a bilateral dissection of monopedicled mucosal flaps from the nasal fossa floor, sutured at the edge of the perforation previously unstuck, without any graft interposed between the two mucosal layers.

Results

In our experience with 31 patients, the use of this technique led to the persistent closing (with follow‐up for at least one year) of 96.3% of the perforations smaller than 3 cm.

Conclusions

Our technique has the advantage of an endonasal approach, without any external incision, and the use of monopedicled flaps from the nasal fossa floor without any graft interposition, avoiding any other surgical procedure and morbidity in the donor site of the graft. The use of nasal endoscopy permits superior precision in all surgical steps.

Significance

The high success rate in perforations smaller than 3 cm seems to confirm the effectiveness of this technique.
Radiation effects on shock propagation in Al target relevant to
equation of state measurements
Authors: DESAI T. , DEZULIAN R. , BATANI D.
Published: February 2007

We present one-dimensional simulations performed using the multi group
radiation hydro code MULTI with the goal of analyzing the target
preheating effect under conditions similar to those of recent experiments
aimed at studying the Equation of State (EOS) of various materials. In
such experiments, aluminum is often used as reference material; therefore
its behavior under strong shock compression and high-intensity laser
irradiation (1013–1014 W/cm2)
should be studied in detail. Our results reveal that at high laser
irradiance, the laser energy available to induce shock pressure is reduced
due to high X-rays generation. Simultaneously X-rays preheat the bulk of
the reference material causing significant heating prior to shock
propagation. Such effects induce deviations in shock propagation with
respect to cold aluminum.
Application of pulsed laser deposition and laser-induced ion
implantation for formation of semiconductor nano-crystallites
Authors: WOŁOWSKI J. , BADZIAK J. , CZARNECKA A. , PARYS P. , PISAREK M. , ROSIŃSKI M. , TURAN R. , YERCI S.
Published: February 2007

This work describes the application of laser ion source (LIS) for
fabrication of semiconductor nanostructures, as well as relevant equipment
completed and tested in the IPPLM for the EU STREP “SEMINANO”
project and the obtained experimental results. A repetitive pulse laser
system of parameters: energy of ∼0.8 J in a 3.5 ns-pulse, wavelength
of 1.06 μm, repetition rate of up to 10 Hz and intensity on the target
of up to 1011 W/cm2, has been employed to
produce Ge ions intended for ion implantation into SiO2
substrate. Simultaneously, laser-ablated material (atoms clusters debris)
was deposited on the substrate surface. The parameters of the Ge ion
streams (energy and angular distributions, charge states, and ion current
densities) were measured with the use of several ion collectors and an
electrostatic ion energy analyzer. The SiO2 films of thickness
from 20–400 nm prepared on substrates of a single Si crystal were
deposited and implanted with the use of laser-produced germanium of
different properties. The modified SiO2 layers and sample
surface properties were characterized with the use of different methods:
X-ray photoelectron and Auger electron spectroscopy (XPS+AES), Raman
scattering spectroscopy (RSS) and scanning electron microscopy (SEM). The
production of the Ge nano-crystallites has been demonstrated for annealed
samples prepared in different experimental conditions.
Editorial from the Editor in Chief: The Start of a New Year
Authors: HOFFMANN DIETER H.H.
Published: February 2007

The start of a new issue in a new year is always an opportunity to
look back and to say thank you to the members of the editorial board and
the editorial staff who made it possible that we were able to publish four
interesting issues in Volume 24 last year. First of all, I want to thank
the scientific community for submitting a large number of excellent
original research papers to Laser and Particle Beams. In 2006, we
were able to publish 71 articles plus editorial material and corrections.
The average article in the journal is now 8–9 printed pages, and we
have thus achieved the editorial goal to offer the community a place to
publish their results without general space restrictions. Authors have
accepted this opportunity to present their material with the necessary
details. This seems to be very important to readers and authors as well,
and we see that for a second consecutive year many articles in Laser
and Particle Beams are referenced already during the first year,
which is remarkable for a small journal with only four issues per
year.
Aerial dispersal of springtails on the Antarctic Peninsula: implications for local distribution and demography
Authors: Hawes T.C. , Worland M.R. , Convey P. , Bale J.S.
Published: February 2007

Aerial dispersal has been frequently proposed as a potential mechanism by which polar terrestrial arthropods are transported to, and settle the ice free habitats of Antarctica, but to date there has been little substantive evidence in support of this hypothesis. Using water traps we investigated aerial deposition of arthropods on Lagoon Island, Ryder Bay, on the Antarctic Peninsula. Over a period of five weeks, trapping at three different altitudes, we captured a total of nine springtails, Cryptopygus antarcticus, all alive. This is the first study to demonstrate conclusively the survival of wind-borne native arthropods within Antarctica. By scaling the modest trapping area and success against island surface area, it is clear that hundreds, if not thousands, of springtails are regularly relocated by winds between the terrestrial habitats of Marguerite Bay. We use known desiccation rates of C. antarcticus and wind speeds to predict the likelihood of successful dispersal between the principal terrestrial habitats of the larger Marguerite Bay. Implications for local and long-range dispersal are discussed in relation to C. antarcticus and other polar arthropods.
Electrochemical Quartz Crystal Impedance and Fluorescence Quenching Studies on the Binding of Carbon Nanotubes (CNTs)‐Adsorbed and Solution Rutin with Hemoglobin
Authors: Su Yuhua , Xie Qingji , Yang Qin , Tu Xinman , Cao Zhijun , Jia Xue'en , Su Zhaohong , Zhang Youyu , Meng Wenhua , Yao Shouzhuo
Published: February 2007

Electrochemical quartz crystal impedance (QCI) technique was utilized to monitor in situ the adsorption of rutin (RT) onto a carbon nanotubes (CNTs)‐modified gold electrode and to study the binding process of solution hemoglobin (Hb) to RT immobilized on the electrode. Time courses of the QCI parameters including crystal resonant frequency were simultaneously obtained during the RT adsorption and Hb‐RT binding. In contrast to the negligible RT adsorption at a bare gold electrode, the modification by CNTs notably enhanced the amount of adsorption, and almost all of the adsorbed RT molecules were found to be electroactive. On the basis of the frequency response from the binding of adsorbed RT to solution Hb and the diminished electroactivity of adsorbed RT after the formation of the electrochemically inactive RT‐Hb adduct, the average binding molar ratio of adsorbed RT to Hb was estimated to be 23.9:1, and the association constant (Ka) for the binding was estimated to be 2.87 × 106 (frequency) and 3.92 × 106 (charge) L mol−1, respectively. Comparable results were obtained from fluorescence quenching measurements in mixed solutions containing RT of fixed concentration and Hb of varying concentrations, demonstrating that the interfacial RT here behaved equivalently in the RT‐Hb binding activity compared to that in solution. This work may have presented a new and general protocol involving CNTs to study many other electroactive natural antioxidants or drugs that are at the interface or in solution, their binding with proteins or other biomolecules, and changes of their antioxidant activity after the binding.
A test of the Hapke photometric model
Authors: Shepard Michael K. , Helfenstein Paul
Published: February 2007

We conducted a test of the Hapke (1981, 1984, 1986, 2002) photometric model to determine what physical parameters could be confidently linked to a surface's photometric behavior. The first author selected and measured the bidirectional reflectance distribution functions of 14 different samples in up to three different wavelengths using the Bloomsburg University Goniometer Laboratory. A total of 29 data files were obtained, each file containing more than 700 measurements from different viewing geometries; phase angles varied from 3° to 130°. The 29 files were initially sent “in‐the‐blind” to the second author, who was charged with inverting the data files and extracting best fit model parameters. Our baseline model used the most recent Hapke (2002) formulation with a two‐term Henyey‐Greenstein particle phase function and shadow‐hiding backscatter opposition effect (SHOE) model. We also inverted the data with three other variations that included three‐term Henyey‐Greenstein phase functions and both SHOE and the coherent backscatter opposition effect (CBOE) models. Our results were compared with the known physical properties of our samples. We found no compelling evidence that individual photometric parameters could be uniquely interpreted to reveal the physical state of our samples, either in an absolute or relative sense. Rather, combinations of physical properties such as albedo, roughness, and porosity were convolved within each retrieved photometric parameter. On the basis of our empirical evidence, we speculate that the fault lies with the inability of radiative transfer models to adequately account for discrete media and the effects of porosity, and its deficient assumption that individual particles are the primary scattering units.
Consequences of the evolution of C4photosynthesis for surface energy and water exchange
Authors: Cowling S. A. , Jones C. D. , Cox P. M.
Published: February 2007

Although comprising less than 4% of all terrestrial plant species, C4plants are an essential component of low‐latitude ecosystems, and in recent modeling simulations have been shown to strongly influence the stable carbon isotope ratio of the atmosphere. We used a fully coupled Earth system model (HadCM3LC) to evaluate the contribution of C4plants to the exchange of energy and water between the biosphere and atmosphere. Our simulations indicate that the presence or absence of C4plants is important for understanding regional climate, specifically with respect to seasonal climate patterns. When C4plants are absent from simulated tropical ecosystems, the percentage of bare soil increases regionally, Amazonia becomes warmer during the dry season, South Africa becomes drier during the dry season, the African Sahara‐Sahel boundary becomes hotter during the dry season, and yet temperatures cool in central Australia during the Austral winter. Our modeling study provides the first insights into the potential climate feedbacks of late‐Miocene C4‐C3ecosystems on surface energy and water exchange.
A tropical storm: Self‐organization and complexity
Authors: Luo Zhexian , Liu Chongjian
Published: February 2007

This paper is aimed at investigating the interaction between a tropical storm (TS) and its adjacent mesoscale convective vortices (MCVs) using a barotropic primitive equation model. The results show that the interaction may result in vortex self‐organization. Compared with the case without MCVs, the quasi‐final state vortex becomes stronger with the increased kinetic energy and lower value of height at the vortex centre owing to the extra vorticity supplied by the MCVs. The intensity of the initial TS controls the complexity of the self‐organization process and determines whether the vorticity of MCVs is either fully or partially absorbed. The quasi‐final state vortex will either keep the intensity the initial TS has or decay dependently on the intensity or number of the MCVs, exhibiting the complexity of the characteristics of the organized quasi‐final state vortex.
Observational constraints on the kinetics of the ClO‐BrO and ClO‐ClO ozone loss cycles in the Arctic winter stratosphere
Authors: Butz A. , Bösch H. , Camy‐Peyret C. , Dorf M. , Engel A. , Payan S. , Pfeilsticker K.
Published: February 2007

Observations of the balloon‐borne LPMA/DOAS remote sensing instruments performed in the Arctic stratosphere in February 1999 are used to constrain a photochemical model. Measurements of all relevant nitrogen, chlorine, and bromine species indicate that moderate heterogeneous chlorine activation occurred in a filament of the Arctic vortex. Model‐measurement comparisons for OClO serve as an indicator of how well various scenarios of the involved reaction kinetics, in particular of the ClO‐BrO and the ClO‐ClO cycles, reproduce the observations. Recent suggestions for the photolysis rate of the ClO dimer, the equilibrium constant between ClO dimer and monomer, the rate of the ClO‐ClO association reaction, and the branching ratio of the ClO‐BrO reaction are consistent with the observations. Formation of an unstable isomer of ClONO2 cannot be reconciled with the observations. Modeled odd oxygen loss rates can be larger by 10% to 20% for the updated reaction kinetics compared to standard recommendations.
Transient channel incision along Bolinas Ridge, California: Evidence for differential rock uplift adjacent to the San Andreas fault
Authors: Kirby Eric , Johnson Courtney , Furlong Kevin , Heimsath Arjun
Published: February 2007

The rates and spatial distribution of active deformation provide critical constraints on the geodynamics of deforming lithosphere, yet such data are often difficult to acquire in eroding landscapes where poor preservation of geomorphic or stratigraphic markers hinders strain reconstruction. Recent advances in understanding of the relationship between bedrock channel profile form and erosion rate have led to their use as an index of rock uplift rate in steady state landscapes. Here we extend this analysis to landscapes experiencing a transient increase in erosion rate using an example from the Marin County region of northern California. We characterize channel and hillslope gradients in a series of small watersheds along a monolithologic portion of the Franciscan terrane in Marin County. Channel steepness indices vary strongly from north to south along the ridge and correspond with the progressive development of relief on threshold hillslopes along valley walls. These patterns argue that recent channel incision has engendered a transient adjustment of hillslope gradient, as incision outpaces soil production rates. These differences in landscape form and inferred incision rate are explained by differential rock uplift within the region east of the San Andreas fault. Relationships between channel gradient and incision rate suggest a threefold to fivefold difference in incision rate across the region and place a minimum bound on differential rock uplift rates. Our study highlights how landscape analysis can place bounds on the distribution of Earth deformation in both space and time and thus lends insight into the processes driving that deformation.
Direct and indirect causes of Fermi level pinning at the SiO∕GaAs interface
Authors: Winn Darby L. , Hale Michael J. , Grassman Tyler J. , Kummel Andrew C. , Droopad Ravi , Passlack Matthias
Published: February 2007

The correlation between atomic bonding sites and the electronic structure of SiO on GaAs(001)-c(2×8)∕(2×4) was investigated using scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and density functional theory (DFT). At low coverage, STM images reveal that SiO molecules bond Si end down; this is consistent with Si being undercoordinated and O being fully coordinated in molecular SiO. At ∼5% ML (monolayer) coverage, multiple bonding geometries were observed. To confirm the site assignments from STM images, DFT calculations were used to estimate the total adsorption energies of the different bonding geometries as a function of SiO coverage. STS measurements indicated that SiO pins the Fermi level midgap at ∼5% ML coverage. DFT calculations reveal that the direct causes of Fermi level pinning at the SiO GaAs(001)-(2×4) interface are a result of either local charge buildups or the generation of partially filled dangling bonds on Si atoms.
HfTiAlO dielectric as an alternative high-k gate dielectric for the next generation of complementary metal-oxide-semiconductor devices
Authors: Lu N. , Li H.-J. , Peterson J. J. , Kwong D. L.
Published: February 2007

In this letter, the authors report on the material and electrical characterizations of high dielectric constant (k) oxide HfTiAlO for the next generation of complementary metal-oxide semiconductors. Crystallization temperature has been improved to 800–900°C versus that of HfO2. The substitution of Ti and Al in the HfO2 cubic structure results in an increased dielectric constant and an acceptable barrier height. The extracted dielectric constant is 36, and the band offset relative to the Si conduction band is 1.3eV. An equivalent oxide thickness of 11Å and low leakage have been achieved with good interfacial properties.
IF impedance and mixer gain of NbN hot electron bolometers
Authors: Kooi J. W. , Baselmans J. J. A. , Hajenius M. , Gao J. R. , Klapwijk T. M. , Dieleman P. , Baryshev A. , de Lange G.
Published: February 2007

The intermediate frequency (IF) characteristics, the frequency dependent IF impedance, and the mixer conversion gain of a small area hot electron bolometer (HEB) have been measured and modeled. The device used is a twin slot antenna coupled NbN HEB mixer with a bridge area of 1×0.15μm2, and a critical temperature of 8.3K. In the experiment the local oscillator frequency was 1.300THz, and the (IF) 0.05–10GHz. We find that the measured data can be described in a self-consistent manner with a thin film model presented by Nebosis et al. [Proceedings of the Seventh International Symposium on Space Terahertz Technology, Charlottesville, VA, 1996 (unpublished), pp. 601–613], that is based on the two temperature electron-phonon heat balance equations of Perrin-Vanneste [J. Phys. (Paris) 48, 1311 (1987)]. From these results the thermal time constant, governing the gain bandwidth of HEB mixers, is observed to be a function of the electron-phonon scattering time, phonon escape time, and the electron temperature. From the developed theory the maximum predicted gain bandwidth for a NbN HEB is found to be 5.5–6GHz. In contrast, the gain bandwidth of the device under discussion was measured to be ∼2.3GHz which, consistent with the outlined theory, is attributed to a somewhat low critical temperature and nonoptimal film thickness (6nm).
Dealloying of liquid CuAu nanoclusters during rotary motion: A molecular dynamics study
Authors: Neubauer H. , Mayr S. G.
Published: February 2007

Dealloying effects caused by centrifugal forces in rotating multicomponent liquid clusters are investigated with the help of classical molecular dynamics computer simulations. The model system, CuAu, is chosen to investigate the phenomenon as a function of composition and cluster size. In addition to well-established surface energy related effects, we find an enrichment of Au on the surface due to centrifugal forces, which forms a bulge surrounding the rotating cluster. Fluctuations occurring during rotation are found to counteract the dealloying effects by mixing the constituents, leading to a stationary state in the system.
Systematic study of disorder induced by neutron irradiation in MgB2 thin films
Authors: Ferrando V. , Pallecchi I. , Tarantini C. , Marré D. , Putti M. , Ferdeghini C. , Gatti F. , Aebersold H. U. , Lehmann E. , Haanappel E. , Sheikin I. , Orgiani P. , Xi X. X.
Published: February 2007

The effects of neutron irradiation on normal state and superconducting properties of epitaxial magnesium diboride thin films are studied up to fluences of 1020cm−2. All the properties of the films change systematically upon irradiation. Critical temperature is suppressed and, at the highest fluence, no superconducting transition is observed down to 1.8K. Residual resistivity progressively increases from 1to190μΩcm; c axis expands and then saturates at the highest damage level. We discuss the mechanism of damage through the comparison with other damage procedures. The normal state magnetoresistivity of selected samples measured up to high fields (28 and 45T) allows to determine unambiguously the scattering rates in each band; the crossover between the clean and dirty limit in each sample can be monitored. This set of samples, with controlled amount of disorder, is suitable to study the puzzling problem of critical field in magnesium diboride thin films. The measured critical field values are extremely high (of the order of 50T in the parallel direction at low fluences) and turns out to be rather independent of the experimental resistivity, at least at low fluences. A simple model to explain this phenomenology is presented.
Ion acoustic cnoidal waves and associated nonlinear ion flux in a warm ion plasma
Authors: Tiwari R. S. , Jain S. L. , Chawla J. K.
Published: February 2007

Using periodic boundary conditions in the reductive perturbation method for ion acoustic cnoidal waves in a collisionless, unmagnetized plasma consisting of warm ions and hot isothermal electrons, evolution equations for the first order and second order potential are derived. Determining the nonsecular solution of these coupled equations, expressions for wave phase velocity and averaged nonlinear ion flux are obtained. Variations of wave phase velocity and averaged nonlinear ion flux are examined for different values of wave frequency and ion to electron temperature ratio (Ti∕Te). It is found that wave phase velocity increases with an increase in wave amplitude for a given value of frequency and temperature ratio. But for a given wave amplitude, the wave phase velocity increases as the temperature ratio increases or wave frequency decreases. The averaged nonlinear ion flux associated with the propagation of large amplitude cnoidal waves in plasma is found to be negative, which corresponds to back flow of ions. The magnitude of the ion flux increases with increase in wave amplitude as temperature ratio or wave frequency increases.
Electrical properties and near band edge emission of Bi-doped ZnO nanowires
Authors: Xu Congkang , Chun Junghwan , Kim Dong Eon , Kim Ju-Jin , Chon Bonghwan , Joo Taiha
Published: February 2007

Electrical transport of Bi–ZnO nanowires shows n-type semiconducting behavior with a carrier concentration of ∼3.5×108cm−1 (2.7×1019cm−3) and an electron mobility of 1.5cm2∕Vs. The carrier concentration is one order of magnitude larger than that of undoped ZnO nanowires, indicating that Bi acts as donor rather than the usual acceptor in ZnO films. The low mobility may be in association with electron scatterings at the boundaries from small size effect of nanowires. Near band edge emission in photoluminescence spectrum of Bi–ZnO nanowires is redshifted relative to undoped ZnO nanorods as a result of enhanced carrier concentration. The donor-acceptor pair transition associated with Bi was also observed at 3.241eV.
A coarse grain model for DNA
Authors: Knotts Thomas A. , Rathore Nitin , Schwartz David C. , de Pablo Juan J.
Published: February 2007

Understanding the behavior of DNA at the molecular level is of considerable fundamental and engineering importance. While adequate representations of DNA exist at the atomic and continuum level, there is a relative lack of models capable of describing the behavior of DNA at mesoscopic length scales. We present a mesoscale model of DNA that reduces the complexity of a nucleotide to three interactions sites, one each for the phosphate, sugar, and base, thereby rendering the investigation of DNA up to a few microns in length computationally tractable. The charges on these sites are considered explicitly. The model is parametrized using thermal denaturation experimental data at a fixed salt concentration. The validity of the model is established by its ability to predict several aspects of DNA behavior, including salt-dependent melting, bubble formation and rehybridization, and the mechanical properties of the molecule as a function of salt concentration.
Numerical study on xenon positive column discharges of mercury-free lamp
Authors: Ouyang Jiting , He Feng , Miao Jinsong , Wang Jianqi , Hu Wenbo
Published: February 2007

In this paper, the numerical study has been performed on the xenon positive column discharges of mercury-free fluorescent lamp. The plasma discharge characteristics are analyzed by numerical simulation based on two-dimensional fluid model. The effects of cell geometry, such as the dielectric layer, the electrode width, the electrode gap, and the cell height, and the filling gas including the pressure and the xenon percentage are investigated in terms of discharge current and discharge efficiency. The results show that a long transient positive column will form in the xenon lamp when applying ac sinusoidal power and the lamp can operate in a large range of voltage and frequency. The front dielectric layer of the cell plays an important role in the xenon lamp while the back layer has little effect. The ratio of electrode gap to cell height should be large to achieve a long positive column xenon lamp and higher efficiency. Increase of pressure or xenon concentration results in an increase of discharge efficiency and voltage. The discussions will be helpful for the design of commercial xenon lamp cells.
Prediction of stochastic behavior in differential charging of nanopatterned dielectric surfaces during plasma processing
Authors: Kenney Jason A. , Hwang Gyeong S.
Published: February 2007

We investigate differential charging of high aspect ratio dielectric trenches under plasma exposure using a two-dimensional computational model. Rather than considering average fluxes, we track individual ion and electron trajectories within the electric field arising from surface charges on the trench, updating the potentials within the computational domain after each particle. Our results show that, as the trench width shrinks to 100nm and below, the potentials within the trench oscillate over an ever-wider range. The stochastic charging behavior in turn leads to noticeable changes in the flux and energies of ions passing through the trench.
Spectroscopy of silica layers containing Si nanocrystals: Experimental evidence of optical birefringence
Authors: Khriachtchev Leonid , Navarro-Urrios Daniel , Pavesi Lorenzo , Oton Claudio J. , Capuj Nestor E. , Novikov Sergei
Published: February 2007

We report an unusual case of spectral filtering by a silica waveguide containing Si nanocrystals (Si-nc’s) deposited on a silica plate. For a number of Si-rich silica (SiOx) slab waveguides annealed at 1100°C, the TE and TM waveguide mode cutoff positions are found in the inversed order with respect to the classical waveguide theory for an isotropic material. Using the cutoff and m-line spectra, this unusual behavior was explained assuming an optical birefringence of the material. For the highest Si content (x∼1.5), we estimated a maximal positive birefringence of ∼8%. The cutoff spectrum simulated with the optical parameters extracted from the m-line measurements corresponds well to the cutoff spectrum directly obtained by measuring waveguided luminescence. This agreement shows that the spectral filtering effect of silica layers containing Si-nc can be described within the quantitative model of delocalized waveguide modes. The possible origin for the observed birefringence is discussed.