bluuebunny/crossref_metadata_2025 huggingface dataset:
Reducing Time to Diagnosis Does Not Improve Outcomes for Women With Symptomatic Ovarian Cancer: A Report From the Australian Ovarian Cancer Study Group
Authors: Nagle Christina M. , Francis Jane E. , Nelson Anne E. , Zorbas Helen , Luxford Karen , de Fazio Anna , Fereday Sian , Bowtell David D. , Green Adèle C. , Webb Penelope M.
Published: May 2011

Purpose

To determine if time to diagnosis is associated with stage of disease at diagnosis or survival among women with symptomatic ovarian cancer.

Methods

A representative sample of Australian women (n = 1,463) with ovarian cancer diagnosed between 2002 and 2005 who participated in a population-based case-control study were interviewed regarding the events leading to their diagnosis and were observed for mortality for 5 years.

Results

Of the 1,318 women (90%) who presented to a medical practitioner with symptoms, 55% presented within 1 month, 70% in less than 2 months, and 92% within 6 months of symptom onset. There were no significant differences in the time from symptom onset to first medical practitioner consultation (P = .19) or symptom onset to diagnosis (P = .64) among women with borderline, early (International Federation of Gynecology and Obstetrics [FIGO] stages I to II) or late (FIGO stages III to IV) disease. There was also no association between time to diagnosis and survival; adjusted hazard ratio for long delay (> 12 months from symptom onset to diagnosis) versus short delay (≤ 1 month) was 0.94 (95% CI, 0.68 to 1.30). Women who had asymptomatic cancers diagnosed incidentally (n = 145) were younger and were more likely to have borderline or stage I disease compared with women who had symptomatic ovarian cancer.

Conclusion

The results of this study suggest that, once ovarian cancer is symptomatic, reducing the time to diagnosis would not greatly alter stage of disease at diagnosis or survival.
Survival Outcomes After Radiation Therapy for Stage III Non–Small-Cell Lung Cancer After Adoption of Computed Tomography–Based Simulation
Authors: Chen Aileen B. , Neville Bridget A. , Sher David J. , Chen Kun , Schrag Deborah
Published: May 2011

Purpose

Technical studies suggest that computed tomography (CT) –based simulation improves the therapeutic ratio for thoracic radiation therapy (TRT), although few studies have evaluated its use or impact on outcomes.

Methods

We used the Surveillance, Epidemiology and End Results (SEER) –Medicare linked data to identify CT-based simulation for TRT among Medicare beneficiaries diagnosed with stage III non–small-cell lung cancer (NSCLC) between 2000 and 2005. Demographic and clinical factors associated with use of CT simulation were identified, and the impact of CT simulation on survival was analyzed by using Cox models and propensity score analysis.

Results

The proportion of patients treated with TRT who had CT simulation increased from 2.4% in 1994 to 34.0% in 2000 to 77.6% in 2005. Of the 5,540 patients treated with TRT from 2000 to 2005, 60.1% had CT simulation. Geographic variation was seen in rates of CT simulation, with lower rates in rural areas and in the South and West compared with those in the Northeast and Midwest. Patients treated with chemotherapy were more likely to have CT simulation (65.2% v 51.2%; adjusted odds ratio, 1.67; 95% CI, 1.48 to 1.88; P < .01), although there was no significant association between use of surgery and CT simulation. Controlling for demographic and clinical characteristics, CT simulation was associated with lower risk of death (adjusted hazard ratio, 0.77; 95% CI, 0.73 to 0.82; P < .01) compared with conventional simulation.

Conclusion

CT-based simulation has been widely, although not uniformly, adopted for the treatment of stage III NSCLC and is associated with higher survival among patients receiving TRT.
Enhancing dewatering of thermo-mechanical pulp (TMP) based papermaking through enzymatic treatment
Authors: Oksanen Antti , Edelmann Kari , Kataja-aho Janne , Suurnäkki Anna
Published: May 2011

The aim of this work was to improve the dewatering characteristics of thermo-mechanical pulp (TMP) through enzymatic treatment without any significant reduction of the quality of the end product. The cellulose and hemicellulose content of TMP was altered by means of enzymatic treatments using different purified cellulases and hemicellulases as well as commercial enzyme preparations, in order to clarify the target carbohydrate components affecting the dewatering of TMP. The effects of enzymatic treatments on the properties of the pulp as well as its forming, pressing and drying were studied by lab scale measurements. An increased dewatering rate of TMP was observed in initial drainage, wet pressing and drying laboratory experiments, as a result of various enzymatic treatments. Interestingly, both cellulose and galactoglucomannan components in TMP were found to affect the dewatering properties of the pulp, and a greatest improvement in dewatering could be obtained with a combined treatment with an endoglucanase type of cellulase and mannanase.
Situationally independent prosodic phrasing
Authors: Speer Shari R. , Warren Paul , Schafer Amy J.
Published: May 2011

A series of speech production and categorization experiments demonstrates that naïve speakers and listeners reliably use correspondences between prosodic phrasing and syntactic constituent structure to resolve standing and temporary ambiguity. Materials obtained from a co-operative gameboard task show that prosodic phrasing effects (e.g., the location of the strongest break in an utterance) are independent of discourse factors that might be expected to influence the impact of syntactic ambiguity, including the availability of visual referents for the meanings of ambiguous utterances and the use of utterances as instructions versus confirmations of instructions. These effects hold across two dialects of English, spoken in the American Midwest, and New Zealand. Results from PP-attachment and verb transitivity ambiguities indicate clearly that the production of prosody-syntax correspondences is not conditional upon situational disambiguation of syntactic structure, but is rather more directly tied to grammatical constraints on the production of prosodic and syntactic form. Differences between our results and those reported elsewhere are best explained in terms of differences in task demands.
Neuromagnetic reflections of harmony and constraint violations in Turkish
Authors: Scharinger Mathias , Idsardi William J. , Poe Samantha
Published: May 2011

Vowel harmony is a phonotactic principle that requires adjacent vowels to agree in certain vowel features. Phonological theory considers this principle to be represented in one's native grammar, but its abstractness and perceptual consequences remain a matter of debate. In this paper, we are interested in the brain's response to violations of harmony in Turkish. For this purpose, we test two acoustically close and two acoustically distant vowel pairs in Turkish, involving different kinds of harmony violations. Our measure is the Mismatch Negativity (MMN), an automatic change detection response of the brain that has previously been applied for the study of native phoneme representations in a variety of languages. The results of our experiment support the view that vowel harmony is a phonological principle with a language-specific long-term memory representation. Asymmetries in MMN responses support a phonological analysis of the pattern of results, but do not provide evidence for a pure acoustic or a pure probabilistic approach. Phonological analyses are given within Optimality Theory (OT) and within an underspecification account.
In Vitro Knee Wear, Kinematics, and Particle Morphology Among Different Bearing Geometries in a Mobile Bearing Knee System
Authors: Grupp T. M. , Miehlke R. K. , Hintner M. , Schwiesau J. , Kaddick C.
Published: May 2011

Excellent clinical long term results were reported from individual clinical centers for both of the two fundamental design principles—fixed and mobile bearing knee designs. Several pre-clinical studies are dealing with a direct comparison between fixed and mobile bearing knee replacements, but to our knowledge there is no published data comparing the in vitro wear and kinematic behaviour of mobile bearing designs with floating, rotating and posterior stabilized gliding surfaces. The objective of our study was to evaluate the influence of the tibio-femoral bearing type on abrasive wear, tibio-femoral kinematics and particle release for a mobile bearing knee system with three different design alternatives. Wear simulator testing on 12 e.motion® TKA devices (Aesculap, Germany) was performed according to ISO 14243-1. The knee replacements were tested for 5 million cycles on a customized 4 station knee wear simulator (Endolab, Germany) in the bearing configurations floating platform (FP), ultra-concruent rotating platform (UC) and posterior stabilized (PS). The amount of wear in the polyethylene gliding surfaces was estimated to 4.4±0.9 mg/million cycles (FP design) to 2.3±0.1 mg/million cycles (UC) and 5.2±1.0 mg/million cycles (PS). The amplitudes of A/P displacement during 5 million cycles showed a mean value of 3.7±0.33 mm (FP design), 2.3±0.14 mm (UC) and 2.9±0.26 mm (PS). For the I/E rotation angle, the amplitudes of the recorded mean values were 6.3°±0.82° (FP design), 3.7±0.41° (UC) and 4.9°±0.48° (PS). The polyethylene particle release (mean size and morphology) is comparable for the mobile bearing articulations FP, UC, and PS. The present study demonstrates the influence of different mobile bearing types on abrasive wear, tibio-femoral kinematics, and particle release under elimination of bearing material influences.
Field Scale Evaluation of Spray Drift Reduction Technologies from Ground and Aerial Application Systems
Authors: Fritz Bradley K. , Hoffmann W. Clint , Bagley W. E. , Hewitt Andrew
Published: May 2011

The objective of this work is to evaluate a proposed test plan for the validation testing of pesticide spray drift reduction technologies (DRTs) for row and field crops, focusing on the testing of ground and aerial application systems under full-scale field evaluations. The measure of performance for a given DRT tested under field conditions is the downwind deposition as measured on horizontal fallout collectors. Ground and aerial application equipment were evaluated for in-swath and downwind deposition of sprays as applied by both a reference system and a drift reducing technology. For this study, the reference system was defined as a spray boom outfitted with the ASABE Fine/Medium boundary reference nozzles. For the ground system, the drift reducing system tested was a ground sprayer outfitted with an air-induction version of the reference nozzle. The aerial system DRT was a flat fan nozzle specifically designed for aerial application usage. Downwind deposition was measured from the edge of the swath out to 100 m downwind. Additionally, the airborne portion of the spray remaining suspended in the air at 50 m downwind was measured. There were a number of confounding issues with the measured data including poor recovery of deposits and non-ideal wind directions during specific replications. Even with these issues, the drift reduction between the reference and DRT system measured in the field for the aerial trials was similar to that estimated using the agricultural dispersion model. A number of additional improvements and checks are suggested prior to further field evaluations.
Length Effects in Tensile Strength in the Orthogonal Directions of Structural Composite Lumber
Authors: Arwade Sanjay R. , Clouston Peggi L. , Krupka Meghan T.
Published: May 2011

The natural variation of strength properties within brittle materials leads to the phenomenon of size effect which causes the expected strength of a material to decrease as the stressed volume increases. An important implication of size effect is that size adjustment parameters must be incorporated into multi-axial constitutive and failure models used in numerical simulations such as those made using the finite element method. These size adjustments are based on the sizes of the individual elements, rather than the size of the structural member. This experimental study seeks to determine whether such a size effect is present in the orthotropic principal material directions of parallel strand lumber (PSL) and laminated veneer lumber (LVL), and, if the effect is present, to quantify it. Tensile tests were performed on specimens of different test section lengths oriented in the longitudinal, transverse, and through-thickness (PSL only) directions and size effect adjustment parameters were estimated. Statistical results indicate the existence of size effect in LVL and PSL for the longitudinal and transverse directions.
Investigation on the production and isolation of 149,150,151Tb from 12C irradiated natural praseodymium target
Authors: Maiti Moumita , Lahiri Susanta , Tomar B. S.
Published: May 2011

Short lived α-emitting radionuclides have enormous potential to be used in the targeted therapy. 149Tb (4.118 h) is among the few α-emitting radionuclides which are projected for human clinical use. Therefore, direct production of 149Tb was aimed from the 12C induced reaction on natural praseodymium target of 15 mg∕cm2 thickness at 71.5 MeV incident beam energy. No-carrier-added (nca) 149,150,151Tb radionuclides were produced in the target matrix along with 149Gd, which is also the decay product of 149Tb, with relatively high yield of 149Tb. An efficient radiochemical separation method was developed to separate nca 149–151Tb from bulk praseodymium and coproduced Gd by liquid–liquid extraction (LLX) using aqueous HCl and liquid cation extracting agent di-(2-ethylhexyl)phosphoric acid (HDEHP) dissolved in cyclohexane. Quantitative extraction of nca 149–151Tb was achieved from bulk target with a high separation factor of 4.7×105.
Investigation of the 236U/238U isotope abundance ratio in uranium ores and yellow cake samples
Authors: Srncik M. , Mayer K. , Hrnecek Erich , Wallenius Maria , Varga Z. , Steier P. , Wallner G.
Published: May 2011

Uranium ores and yellow cake samples of known geographic origin were investigated for their n(236U)/n(238U) isotope abundance ratio. Samples from four different uranium mines in Australia, Brazil and Canada were selected. Uranium was separated by UTEVA® Resin and was measured by Accelerator Mass Spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA). The measurement of the isotope abundance ratio n(236U)/n(238U) will be used to investigate possible correlations between the original mineral (uranium ore) and the intermediate product (yellow cake). Such correlations are useful indicators for nuclear forensic or for non-proliferation purposes.
Temperature-dependent neutron diffraction on TiI3
Authors: Angelkort Joachim , Senyshyn Anatoliy , Schönleber Andreas , Smaalen Sander van
Published: May 2011

Crystal structures of TiI3 were determined and refined at selected temperatures between 4 and 340 K against neutron powder diffraction data. On heating, thermal expansion is found to increase abruptly at the phase transition at T
c = 323 K. Most prominently, linear thermal expansion is highly anisotropic and small along c (i.e. along chains of Ti atoms) in the low-temperature phase, while above T
c it is much larger along c. An order parameter is defined by the ratio between the long and the short Ti—Ti distances on the metal chains. The temperature dependence of the order parameter indicates the transition to be of first order.
Syntheses, crystal structures, magnetic properties and vibrational spectra of nitridoborate-halide compounds Sr2[BN2]Br and Eu2[BN2]X(X= Br, I) with isolated [BN2]3–units
Authors: Kokal Ilkin , Aydemir Umut , Prots Yurii , Schnelle Walter , Akselrud Lev , Höhn Peter , Somer Mehmet
Published: May 2011

The title compounds Sr2[BN2]Br (1), Eu2[BN2]Br (2) and Eu2[BN2]I (3) were obtained from reactions of mixtures of Sr3[BN2]2and SrBr2(1) and the binaries EuN, h-BN and EuX2(X= Br, I) (2,3), respectively. The crystal structure of Sr2[BN2]Br was solved from X-ray powder diffraction data and those of the europium compounds from X-ray single crystal data. Sr2[BN2]Br and Eu2[BN2]Br are isotypic crystallizing in the rhombohedral space groupR-3m(No. 166, Pearson code:hR18;Z= 3;a= 4.11692(2) Å,c= 26.4611(2) Å (1);a= 4.0728(3) Å,c= 26.589(3) Å (2)). The crystal structures are built up by layers of condensed edge-sharing [B—N—B]@Eu6and [Br]@Eu6trigonal antiprisms, which are alternately stacked along [001]. Eu2[BN2]I – isotypic to Sr2[BN2]I – crystallizes in the monoclinic space groupP21/m(No. 11, Pearson code:mP24;Z= 4;a= 10.2548(6) Å,b= 4.1587(3) Å,c= 13.1234(9) Å,β= 91.215(4)°). The crystal structure is characterized by slightly puckered layers formed by condensed edge sharing I@Eu6octahedra which are separated by isolated [BN2]3–units. The bond lengths for the strictly linear [BN2]3–anions in(1)and(2)ared(B—N) = 1.351(4) Å and 1.356(8) Å, respectively. In Eu2[BN2]I two crystallograhically distinct [BN2]3–anions are present withd(B1—N) = 1.32(4) Å, 1.37(4) Å andd(B2—N) = 1.30(4) Å, 1.34(4) Å, respectively. Their bond angles vary slightly: ∠(N—B1—N) = 179(3)° and ∠(N—B2—N) = 177(3)°. The magnetic susceptibility data of the europium compounds (2) and (3) indicate that the Eu ions are divalent with 4f7configuration. Vibrational spectra were measured and interpreted based on theD∞hsymmetry of the discrete linear [N—B—N]3–moieties, considering the site symmetry reduction and the presence of two distinct [BN2]3–groups in (3).
Photochemical Properties and Reactions with Biomolecules of 4'-N-Acetyl Derivative of Norfloxacin
Authors: Zhang Peng , Li Haixia , Liu Yancheng , Yao Side , Wang Wenfeng
Published: May 2011

The photochemical properties of 4'-N-acetyl derivative of norfloxacin (ANFX) were investigated in different solutions. Both UV-Vis absorption and the quantum yields of excited states are pH-dependent, and pK
a value of ground state for the protonation of 3-carboxylic group was determined to be 6.5 ± 0.2. Pulse radiolysis and laser flash photolysis experiments were carried out to characterize transient species of ANFX and to investigate reactions with tryptophan (TrpH) and 2'-seoxyguanosine-5'-monophosphoric acid disodium salt (dGMP). The ANFX undergoes the photoejection of electron by a mixed mechanism of one-photon and two-photon processes. Under moderate laser energy conditions, two-photon process is predominantly. The ANFX radical dianion (ANFX(–H)·2−) formed in reaction with eaq
− is characterized by the absorption around 370 nm, and the rate constant was determined to be 1.2 × 1010 dm3 mol−1 s−1. The 3ANFX(–H)−∗ is able to oxidize TrpH and dGMP with bimolecular rate constants of 5.4 × 108 and 9.5 × 106 dm3 mol−1 s−1, respectively. The ANFX(–H)·2− and the oxidized radicals of TrpH and dGMP were observed directly. Under aerobic conditions, the photo-oxidations involve both type I and type II mechanisms.
Direct Access to the Dipole-Forbidden n
π
∗
T
1 State of p-Benzoquinone by Photodetachment Photoelectron Spectroscopy
Authors: Siegert S. , Vogeler F. , Weinkauf R.
Published: May 2011

In this work we show that photodetachment photoelectron (PD-PE) spectroscopy on radical anions allows direct access to dark states, such as dipole-forbidden n
π
∗ triplet and singlet states. p-benzoquinone (BQ) was chosen as model molecule because it is experimentally and theoretically well investigated and its lowest electronic states are electric dipole-forbidden n
π
∗ triplet and singlet states. Because of the high density of electronic states we observe a dense structure with many transitions in our PD-PE spectrum. We identify the first peak at 2.3 eV above the S
0 onset as the T
1 state origin, in good agreement with previous data. We are not able to resolve the splitting between the states T
1 (13
B
1g
) and T
2 (13
A

u
) as well as the corresponding S
1 (11
A

u
) and S
2 (11
B
1g
) states, but perform a tentative assignment of the singlet-triplet splitting on the basis of literature data. The fact that the spectral features in our PD-PE spectrum cover a broad energy range is taken as a strong experimental evidence for the presence of the T
3
π
π
∗ state, which has been predicted to lie in this energy range. Our investigations on BQ show that in principle, by starting spectroscopy in radical anions most of the selection rules, valid in neutral BQ molecules, can be circumvented and n
π
∗ states, triplet states and other dipole-forbidden states become directly accessible with bright intensity. Much higher electron energy resolution is required to allow unambiguous assignments and make PD-PES of radical anions a valuable method for the spectroscopy dark states of neutral closed-shell molecules.
Individual Extraction Constants of Some Univalent Organic Cations in the Two-Phase Water–Phenyltrifluoromethyl Sulfone System
Authors: Makrlík Emanuel , Selucký P. , Vanura P.
Published: May 2011

From extraction experiments and γ-activity measurements, the extraction constants corresponding to the general equilibrium C+(aq) + I−(aq) ⇔ C+(org) + I−(org) taking place in the two-phase water–phenyltrifluoromethyl sulfone (abbrev. FS 13) system (C+ = organic cation; aq = aqueous phase, org = FS 13 phase) were evaluated. Furthermore, the individual extraction constants of 8 univalent organic cations in the mentioned two-phase system were calculated.
Human Security and Development in the Lao PDR
Authors: Howe Brendan , Sims Kearrin
Published: May 2011

Development in Laos has occurred slowly, with uneven distribution and significant negative effects. This article challenges the simplistic assumption of human development and human security as mutually reinforcing processes. It suggests a holistic approach addressing simultaneously competing demands from the perspective of the most vulnerable sectors of society.
Creating Flexibility in Pediatric Resident Education
Authors: Hobson Wendy L. , Bruse Jaime , Bale James F.
Published: May 2011

INTRODUCTION:

Pediatric residency programs must meet the challenge of producing graduates who are prepared to enter primary care, subspecialty fellowships or another career path. Meeting this challenge requires flexibility, which can be difficult to achieve. A program with 2 half days of continuity clinic that offers an option for residents to use 1 half day for advocacy or research projects may offer such flexibility.

OBJECTIVE:

To describe 1 residency program's experience with an alternative half- day continuity clinic program.

METHODS:

We conducted a retrospective review of resident participation, project types, scholarly products, and test scores associated with alternative half day program participation.

RESULTS:

Second- and third-year resident participation increased from 21% (7/33) in 2005 to 2006 to 41% (17/42) in 2008 to 2009. Forty-six residents undertook projects: 80% were research and 20% advocacy. The number of residents who presented abstracts at national meetings increased to 5 from a baseline of 4 per year. Four residents received advocacy grants. Three residents won national or regional research awards. The average score on the American Board of Pediatrics certifying examination was lower for residents in the alternative half day group, but pass rates remained high. All participants met the requirements for continuity clinic days and patient numbers.

CONCLUSIONS:

This unique 2 half day continuity clinic program not only enhances the education of residents entering primary care but also allows opportunities for residents anticipating careers in research or advocacy. This approach allows programmatic flexibility without creating a track system.
Symptomatic Liver Involvement in Neonatal Hereditary Hemorrhagic Telangiectasia
Authors: Al-Saleh Suhail , John Philip R. , Letarte Michelle , Faughnan Marie E. , Belik Jaques , Ratjen Felix
Published: May 2011

High-flow hepatic vascular anomalies with arteriovenous shunting commonly manifest during the neonatal period with signs and symptoms of congestive heart failure, but to our knowledge, they have never been described in patients with hereditary hemorrhagic telangiectasia (HHT). We report here our experience with 3 patients with hepatic arteriovenous malformations (AVMs) who presented with symptoms of high-output congestive heart failure during the neonatal period and were subsequently diagnosed with HHT. Imaging showed large hypervascular lesions and multiple hepatic arteriovenous shunts that differentiated these lesions from liver hemangiomas. Transcatheter embolization was performed in all cases. One infant died of sepsis shortly after embolization; follow-up at the age of 2.5 years of the surviving infants revealed involution of the vascular lesions and no evidence of symptom recurrence. We conclude that severe symptoms related to hepatic AVMs in HHT can occur in the neonatal period and that HHT should therefore be included in the differential diagnosis of symptomatic neonatal hepatic vascular malformations. Imaging plays a key role in differentiating hepatic AVMs from hemangiomas, because the latter require additional pharmacologic treatments. Early transcatheter embolization seems to be effective, but long-term outcomes still need to be assessed.
Reproducibility of Acute Mountain Sickness in Children and Adults: A Prospective Study
Authors: Rexhaj Emrush , Garcin Sophie , Rimoldi Stefano F. , Duplain Hervé , Stuber Thomas , Allemann Yves , Sartori Claudio , Scherrer Urs
Published: May 2011

OBJECTIVE:

Although a history of previous acute mountain sickness (AMS) is commonly used for providing advice and recommending its prophylaxis during subsequent exposure, the intraindividual reproducibility of AMS during repeated high-altitude exposure has never been examined in a prospective controlled study.

METHODS:

In 27 nonacclimatized children and 29 adults, AMS was assessed during the first 48 hours after rapid ascent to 3450 m on 2 consecutive occasions 9 to 12 months apart.

RESULTS:

During the first exposure, 18 adults (62%) and 6 children (22%) suffered from AMS; during the second exposure, 14 adults (48%) and 4 children (15%) suffered from this problem (adults versus children, P ≤ .01). Most importantly, the intraindividual reproducibility of AMS was very different (P < .001) between children and adults. None of the 6 children having suffered from AMS during the first exposure suffered from AMS during the second exposure, but 4 children with no AMS during the first exposure did experience this problem during the second exposure. In contrast, 14 of the 18 adults who suffered from AMS on the first occasion also presented with this problem during the second exposure, and no new case developed in those who had not experienced AMS on the first occasion.

CONCLUSIONS:

In adults, a history of AMS is highly predictable of the disease on subsequent exposure, whereas in children it has no predictive value. A history of AMS should not prompt practitioners to advise against reexposure to high altitude or to prescribe drugs for its prophylaxis in children.
End-Grafted Semiconducting Polymer—Candidate for Molecular Wire
Authors: Furukawa Kazuaki , Ebata Keisuke , Fujiki Michiya
Published: May 2011

We report on polysilane, a synthetically accessible μ-conjugated silicon-catenated polymer with such semiconducting properties as photoconductivity, high hole drift mobility, and electroluminescence, as a candidate for molecular wire. We apply the “end-graft” technique, which we developed for fixing individual polymer chains on a substrate surface, to a semiflexible polysilane. The end-grafted semiflexible polysilane extended more than 500 nm across the Si(111) surface, and was clearly observed by means of atomic force microscopy (AFM).
Transport Measurements of Individual Bi Nanowires
Authors: Cronin Stephen B. , Lin Yu Ming , Koga Takaaki , Ying Jackie Y. , Dresselhaus Mildred S.
Published: May 2011

Transport properties are reported for Bi nanowires, prepared by the filling of an alumina template with molten Bi. The temperature dependence of the resistance is presented for such arrays of Bi nanowires with diameters in the 40 to 200nm range. The data are understood qualitatively on the basis of a model for a quantum-confined system. Finally, a 4-point measurement is performed on an individual Bi nanowire prepared by using an electron beam lithography technique. Techniques for handling the practical issues of non-ohmic contacts and wire burn-out are given. The physical significance of the final results of the measurements are discussed in light of various scattering mechanisms in the nanowire.
Nanoscale Patterns of Metal Nanoparticles Chemically-Assembled on Biomolecular Scaffolds: Assembly, Stability and Electron Transport Properties
Authors: Hutchison James E. , Brown Leif O. , Mooster Jana L. , Reed Scott M. , Schmidt Mary E. , Clarke Laura I. , Wybourne Martin N.
Published: May 2011

A wet chemical approach to preparing one- and two-dimensional arrays of gold nanoparticles assembled onto a polypeptide (poly-L-lysine) scaffold layer is reported. The electrical properties of biopolymer templated and nontemplated gold nanoparticle samples are compared. The electrical response of nontemplated samples is unstable, likely due to nanoparticle mobility. Biopolymer templating provides a simple, chemical method to immobilize the particles and is found to stabilize the electrical response (Coulomb blockade) of the array. A striking feature of the electrical properties is that the electron transport properties are dominated by transport through one-dimensional chains within the sample. Structural studies by AFM and XPS support the transport findings and provide evidence for the formation of one-dimensional assemblies within the arrays.
Unimolecular Electrical Rectification Down to 105 K, and Spectroscopy of Hexadecylquinolinium Tricyanoquinodimethanide
Authors: Metzger R. M.
Published: May 2011

A Langmuir-Blodgett monolayer of γ-(n-hexadecyl)quinolinum tricyanoquinodimethanide, C16H33Q-3CNQ (1), sandwiched between Al electrodes, shows asymmetric DC electrical conductivity between 370 K and 105 K. The enhanced forward current is attributable to rectification of electrical current by a single molecule, and is explained by an electronic transition from a high-moment zwitterionic ground state to a low-moment undissociated first excited state.
Room Temperature Single Electron Charging in Gold Nanoparticle Networks Formed on Biopolymer Templates
Authors: Wybourne M.N. , Clarke L. , Berven C.A. , Hutchison J.E. , Brown L.O. , Mooster J.L.
Published: May 2011

We report the current-voltage characteristics of gold nanoparticle – biopolymer networks at room temperature. Above a threshold voltage the current-voltage relationship is almost linear. From the current-voltage scaling above threshold we argue that one-dimensional regions of the network dominate the transport. Periodic features in the conductance are found in many samples. Both the threshold voltage and the conductance features occur at voltages much greater than expected for the capacitance of the nanoparticles. Possible explanations for the structure are considered.
Room Temperature Negative Differential Resistance in Nanoscale Molecular
Authors: Chen J. , Wang W. , Reed M. A. , Rawlett A. M. , Price D. W. , Tour J. M.
Published: May 2011

Molecular devices utilizing active self-assembled monolayer (SAM) (containing nitroamine (2′-amino-4-ethynylphenyl-4′-ethynylphenyl-5′-nitro-1-benzenethiolate) and nitro (4-ethynylphenyl-4′-ethynylphenyl-2′-nitro-1-benzenethiolate) redox center) as the active component are reported. Current-voltage measurements of the devices exhibited negative differential resistance at room temperature and an on-off peak-to-valley ratio in excess of 1000:1 at low temperature.
Molecular Scale Electronics
Authors: Rawlett A. M. , Mickelson E. T. , Reinerth W. A. , Jones L. , Kozaki M. , Burgin T. P. , Tour J. M. , Chen J. , Zhou C.-W. , Muller C. J. , Deshpande M. R. , Reed M. A. , Bumm L. A. , Cygan M. T. , Dunbar T. D. , Weiss P. S. , Allara D. L.
Published: May 2011

This paper reports on some of the recent advances in the development and testing of molecular-scale electronic devices, devices that may ultimately be the basis of a molecular-based computer. These advances include: the synthesis of molecules which will perform specific electronic functions, self-assembled monolayer formation of rigid-rod conjugated oligomers, novel methodologies for the design and testing of molecular electronic devices, and the observance of negative differential resistance (NDR) through a molecule.
Influence of Structural Organization On Optical and Transport Properties in Organic Materials
Authors: Cornil J. , Calbert J.Ph. , Beljonne D. , Dos Santos D.A. , Bredas J.L.
Published: May 2011

Correlated quantum-chemical calculations performed on supermolecular structures, i.e., on clusters made of several oligomer chains in interaction, provide insight into structure-property relationships in well-organized molecular films. This supermolecular approach is applied to crystalline phases of two prototypical conjugated oligomers and shows that variations in chain packing can lead to dramatically different optical (Davydov) splittings and carrier mobilities. Optimal chain organizations for various types of devices are discussed.
Nanoscale Control of Layer Thickness for EL Devices by Mass-controlled Layer-by-layer Sequential Adsorption Process
Authors: Shiratori Seimei , Yamada Masayoshi , Ito Takahiro , Wang Tom.C. , Rubner Michael F.
Published: May 2011

A mass controlled layer-by-layer sequenitial adsorption process for polyelectlrolytes was newly developed for the fabrication of functional devices using ultra-thin organic film formed by various polymers of different polarity of charge. In this study hydrophobic Ruthenium complex monomer • tris(bipyridyl) ruthenium(II) hexafluorophosphate • was micelle-wrapped with an anionic surfactant, sodium dodecylbenzenesulfonate, and was assembled with PAH (poly (allylamine hydrochloride)), which has the opposite charge, on ITO substrates. With this method, we succeeded in fabricating ultra-thin organic films even when the adsorption material is not polymer but monomer. Moreover it was found that the film thickness of the self-assembled Ru micelle/PAH had a linear relationship with the number of bilayers. By using this process, an EL device was fabricated by depositing the thin film of micelle-wrapping ruthenium complex monomer on ITO and metal electrode on top of the film. Light emission was observed by applying voltage to this device.
Epitaxial Thin Film Structures of Electroluminescent Materials
Authors: Koch Norbert , Hosoi Yoshinobu , Ishii Hisao , Vollmer Antje , Leising Günther , Seki Kazuhiko
Published: May 2011

Despite the fast-paced new developments and improvements of applications incorporating conjugated organic materials, rather little effort is made to obtain well-defined structures and thin films of these in order to exploit the highly anisotropic properties (e.g. conductivity, polarized light emission) of most conjugated organic materials. It has been shown that oligomers, which can easily be evaporated under ultrahigh vacuum conditions, exhibit heteroepitaxial growth on various substrates. Depending on the nature of the interaction of the organic molecules with the substrate different orientations can be obtained, as well as by simply changing the conditions of evaporation. Therefore, by going from amorphous or polycrystalline structures to highly textured or single crystalline ones new insights into the physical properties of the materials can be expected, and also new applications. We studied the formation of well-defined films of the electroluminescent oligomer p -sexiphenyl on various metal and semiconductor surfaces and determined the orientation of the molecules by means of low energy electron diffraction (LEED), infrared reflection absorption spectroscopy (IRRAS) and atomic force microscopy (AFM). Depending on the substrate material we found that the molecules are oriented either parallel or perpendicular to the substrate surface. In addition to that, highly oriented 6P films were doped with potassium, and the change in the molecular vibrational signature was investigated with IR-RAS.
Light Emitting Vacuum Evaporated Devices Based on Triaryldiamine Materials and 8-Hydroxyquinoline Complexes of Al(III) and Zn(II)
Authors: Giro Gabriele , Cocchi Massimo , Marco Piergiulio Di , Fattori Valeria , Dembech Pasquale , Fabbri Gaia , Ghedini Mauro
Published: May 2011

Vapor deposited double-layer (DL) organic light emitting diodes (OLEDs) based on the combination of materials belonging to the triaryldiamine family as hole transporting materials (HTM) and metal complexes of 8-hydroxyquinoline as electron transporting materials (ETM) have been characterized. As HTM N,N'-bis(diphenyl-4-yl)-N,N'-diphenyl-benzidine (NBDB), N,N'-(naphthalen-1-yl)-N,N'-diphenyl-benzidine (NPB) or N,N'-diphenyl-N,N'-(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine (TPD) were used. As ETM tris-(8-hydroxyquinolinate)-Al(III) (Alq3) or bis-(8-hydroxyquinolinate)-Zn(II) (Znq2) were used. The typical cell configuration was: ITO/HTM/ETM/Ca,Ag. A comparison of the electrical and light emitting features between devices constructed with the new molecule NBDB and NPB or TPD was made, with the aim of improving their efficiency and stability.
Hexa-Alkoxytriphenylenes As Hole Transporting Materials Inc Stable Oleds Using ALQ3 As Emitting Layer
Authors: Emerich Markus , Tasch S. , Resel R. , Leising G. , Freudenmann R. , Hanack M. , Shaheen S. E. , Jabbour G. E. , Peyghambarian N.
Published: May 2011

Devices consisting of hexa-alkoxythriphenylene derivatives as hole transport materials and 8-hydroxyquinoline aluminium (Alq3) as emitting layer with ITO as anode and magnesium as cathode are presented. Moreover X-ray diffraction studies of evaporated triphenylene films were performed leading to a better understanding of crystal structure, morphology and the alignment of the triphenylene molecules on the surface of the substrate.
Exciplex Formation in Light Emitting Molecularly Doped Polymer Diodes Based on Polycarbonate:TPD:PBD Blends
Authors: Giro Gabriele , Cocchi Massimo , Marco Piergiulio Di , Fattori Valeria
Published: May 2011

Observation of electroluminescence (EL) in single layer of molecularly doped polymer (MDP) films is reported. The EL diodes constructed by spin coating technique contain Bisphenol-A-polycarbonate (PC), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) and 2-(4-biphenyl)-5-(4-terbutylphenyl)1,3,4-oxadiazole (PBD) with the configuration: ITO/PC(20%):TPD(40%):PBD(40%)/Ca, Ag. The EL emission ranges in the green-yellow part of the spectrum and is red shifted respect to the photolu minescence (PL) both of PC:TPD and of PC:PBD. It can be assigned to emission from an exciplex state resulting from the interaction between TPD and PBD, as confirmed by stationary and pulsed fluorescence spectroscopy, and also from other states (triplets, traps or ‘electoplexes’) emitting at lower energies.
Substrate Mediated Ordering in PmPV Thin Films
Authors: McCarthy B. , Czerw R. , Strevens A. , Davey A. P. , Carroll D. L. , Blau W. J.
Published: May 2011

Monolayer films of poly(m-phenylenevinylene-co-2,5-dioctoxy-p-phenylenevinylene) (PmPV) supported on highly orientated pyrolytic graphite (HOPG) have been investigated using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). While there are areas of the surface covered with a featureless polymer layer, we also observe large regions with surprisingly long range order. Structural models of the polymer, as well as tunneling spectra, suggest that this ordering is derived from substrate-polymer epitaxy.
Low Voltage Operation of Polymer Light-Emitting Device with Conducting Polymer Distributed Bragg Reflector
Authors: Kawase Takeo , Ho Peter K. H. , Friend Richard H. , Shimoda Tatsuya
Published: May 2011

Polymer light-emitting devices with a conducting polymer distributed Bragg reflector (DBR) are reported. Polymer DBRs were formed from alternate spin-coating of poly (3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulphonate) (PSS) as the low-index layer and a hole-transporting polyfluorene derivative as the high-index layer onto ITO deposited glass substrates. The polymer DBR with 5 periods showed reflectivity of 40% at the wavelength of 560nm. Onto this polymer DBR, a green-light-emitting polyfluorene was spin-coated to give the emissive layer and Ca/Al was deposited to form the cathode served another reflector. These LEDs operated successfully at low voltages and emitted light having a narrower spectrum (FWHM=47nm) than structures without the DBR (FWHM=102nm). The peak wavelengths varied corresponding to the thickness of the emissive layer, that is, the cavity length as expected from calculations. The luminance turn-on voltage of the LED with the polymer DBR is 2V, which is the same as LEDs without a DBR. The current was found to be limited by injection in the low field region and limited by space charge density at high fields. The current does not depend on the number of layers in the DBR in the low field region, and this implies that there are no effective energy barriers in the polymer DBR.
Synthesis and Characterization of New Star-Shaped Metal-Containing Polymers for Optical Applications
Authors: Bader Mamoun M. , Pham Phuong-Truc T. , Moser Justin D.
Published: May 2011

We report here on our continued investigations of the synthesis and characterization of new metal-containing polymers incorporating 8-hydroxyquinoline. We reported earlier on three types of linear metal-containing polymers with ether, ester and amide functionalities in the chain's backbone. In this report, we extended our previous studies by targeting star-shaped metal-containing polymers. Again, these polymers still have the favorable structural characteristics, which would allow for a large degree of control over their physio-chemical properties.
Versatile Syntheses of Various Homo- and Copolymers of Poly(1,4-Arylene Vinylene)S
Authors: Martin R. E. , Chuah B. S. , Riehn R. H. , Geneste F. , Cacialli F. , Friend R. H. , Holmes A. B. , Morgado J.
Published: May 2011

The synthesis of poly(1,4-phenylene vinylene)s (PPVs) containing a 2,3-dialkoxy substitution pattern has been developed. Poly[2,3-bis(2-ethylhexyloxy)-1,4-phenylene vinylene)] (BEH-PPV, 4) was prepared and its optical properties compared with the recently discussed poly(2,3-dibutoxy-1,4-phenylene vinylene) (DB-PPV, 1), which showed in contrast to classical 2,5-substituted PPV derivatives a notable blue-shift of the longest-wavelength absorption (λmax) and a considerable increase of the solid-state photoluminescence (PL) efficiency. The two statistical PPV copolymers 5 and 6 comprising 2,3-dibutoxy and dimethyloctylsilyl- or 2,5-bis(dimethyloctylsilyl) side-chains, respectively, were synthesized via the Gilch dehydrohalogenation route. Double-layer light-emitting devices (LEDs) were demonstrated to combine high electroluminescence efficiencies with low turn-on voltages.
Synthesis of a Water Dispersible Inter-Polymer Complex of Polyaniline
Authors: Mccarthy Patrick A. , Yang Sze C.
Published: May 2011

The conductive polymer, polyaniline, has been proposed as a material for applications such as flexible batteries, anti-static coatings and anti-corrosion paints. Polyaniline (PAN), however, is an intractable solid. Its rigid backbone and high cohesive energy lead to insoluble polymers. Dispersing polyaniline in solution has been a problem for industrial scale applications.
Recoverable Photodegradation of Light-Emitting Polymers
Authors: Zhang X. H. , Chua S. J. , Wang H. , Huang W.
Published: May 2011

The photodegradation of light-emitting polymers was studied by measuring the decay of the photoluminescence with exposure time to He-Cd laser beam at room temperature. It was found that the photoluminescence intensity decreases very fast initially, and then tends to saturate on the order of several tens of minutes. More interestingly, it was found that the degradation induced by laser beam can be self-healed. By stopping the exposure of the sample to the laser beam, the photoluminescence intensity recovers gradually without any treatment.
Redox Control of Stilbylvinylpyridine Chormophore Pairwise Orientations: Towards Solid State Materials for Molecular Electronics
Authors: Zahn Steffen , Canary James W.
Published: May 2011

Tripodal ligand complexes of copper salts are described that display redoxdependent exciton coupled circular dichroism spectra. Significant spectral amplitude is observed at 400 nm in both solution and microcrystalline films. The synthesis and characterization of two new ligands and the preliminary characterization of the circular dichroism properties of their copper complexes is reported. The results constitute a significant step toward the development of molecules that can be used as on/off molecular switches.
Photoinduced Charge Transfer Between Tetracyano-Anthraquino-Dimethane Derivatives and Conjugated Polymers
Authors: Zerza G. , Scharber M. , Segura J. L. , Gomez R. , Martin N. , Sariciftci N. S.
Published: May 2011

The photo-induced charge transfer between tetracyano-anthraquino-dimethane (TCAQ) derivatives and poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene vinylene) MDMO-PPV was studied by means of photoinduced absorption (PIA) spectroscopy in the VIS and IR spectral region and lightinduced electron spin resonance (LESR) spectroscopy. Three different TCAQ derivatives with alkyl-side chains for increased solubility compared to TCAQ and one of them attached to a C60 molecule serve as strong electron acceptors. The photoinduced absorption in the VIS near-IR range shows a broad plateau around 1.8 eV followed by two peaks at 1.35 and 1.24eV for all three acceptors. All PIA features have a power law excitation intensity dependence with an exponent close to 0.5 as expected for bimolecular kinetics. The modulation frequency dependent excited state absorption decreases with a power law. LESR studies of all donor-acceptor combinations show one radical line at a g = 2.0028 with.H = 3.5 Gauss, originating from TCAQ anion and the polymer cation.
Quenching of the Magnetic Field Effect on the Photocurrent and Photocurrent Detected Magnetic Resonance in Conjugated Polymer-Fullerene Diodes
Authors: Scharber M. C. , Brabec C. J. , Padinger F. , Sariciftci N. S.
Published: May 2011

We have studied the effect of a magnetic field on the photocurrent of MDMO-PPV (poly(2-methoxy,5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene) and MDMOPPV/fullerene diodes (plastic solar cells) and performed photocurrent detected magnetic resonance (PCDMR) experiments on these devices consisting of an active layer sandwiched between a low and a high workfunction metal electrode. Results clearly show that the magnetic field effect (MFE) on the photocuttent as well as PCDMR signals are quenched in conjugated polymer/fullerene composite devices in contrast to large signals observed in the pristine conjugated polymer devices. Photoinduced electron transfer from conjugated polymers onto fullerene is proposed to be responsible for this quenching.
Effects of Conformational Diversity and Structural Dynamics on the Optical Properties of Diazoluminomelanin
Authors: Ferris Kim F. , Risser Steven M. , Wagner-Brown Katrina B. , Kiel Johnathan L. , Albanese Richard A.
Published: May 2011

Diazoluminomelanin (DALM) is a luminescent polymer belonging to the broader class of conjugated polyphenylene materials, which has shown significant optical activity in response to perturbing fields. In this paper we use semiempirical electronic structure calculations and molecular dynamics simulations to investigate the molecular structure and absorption characteristics of model phenolic oligomers. Molecular dynamics simulations show the polymer backbone can be extremely flexible depending upon the ionization state of the phenolic hydroxyl groups. The interring torsion angle is a critical variable as it relates charge localization effects and electronic excitation energies. Comparison with experimental data demonstrates the need for a multistate basis to describe the absorption properties of this system.