bluuebunny/crossref_metadata_2025 huggingface dataset:
Active Piezoelectric Vibration Control of Subscale Composite Fan Blades
Authors: Duffy Kirsten P. , Choi Benjamin B. , Provenza Andrew J. , Min James B. , Kray Nicholas
Published: November 2012

As part of the Fundamental Aeronautics program, researchers at NASA Glenn Research Center (GRC) are investigating new technologies supporting the development of lighter, quieter, and more efficient fans for turbomachinery applications. High performance fan blades designed to achieve such goals will be subjected to higher levels of aerodynamic excitations which could lead to more serious and complex vibration problems. Piezoelectric materials have been proposed as a means of decreasing engine blade vibration either through a passive damping scheme, or as part of an active vibration control system. For polymer matrix fiber composite blades, the piezoelectric elements could be embedded within the blade material, protecting the brittle piezoceramic material from the airflow and from debris. To investigate this idea, spin testing was performed on two General Electric Aviation (GE) subscale composite fan blades in the NASA GRC Dynamic Spin Rig Facility. The first bending mode (1B) was targeted for vibration control. Because these subscale blades are very thin, the piezoelectric material was surface-mounted on the blades. Three thin piezoelectric patches were applied to each blade—two actuator patches and one small sensor patch. These flexible macro-fiber-composite patches were placed in a location of high resonant strain for the 1B mode. The blades were tested up to 5000 rpm, with patches used as sensors, as excitation for the blade, and as part of open- and closed-loop vibration control. Results show that with a single actuator patch, active vibration control causes the damping ratio to increase from a baseline of 0.3% critical damping to about 1.0% damping at 0 rpm. As the rotor speed approaches 5000 rpm, the actively controlled blade damping ratio decreases to about 0.5% damping. This occurs primarily because of centrifugal blade stiffening, and can be observed by the decrease in the generalized electromechanical coupling with rotor speed.
Control of inclination angle of glass-like carbon mold by defocus UV exposure on Si-containing photoresist
Authors: Mekaru Harutaka , Okuyama Chieko , Ueno Akihisa
Published: November 2012

The authors fabricated micropatterns with inclined sidewalls in a glass-like carbon (GC) mold to thermal imprint on a glass substrate, and succeeded in controlling its inclination angle. The technology comprised three features: (1) A Si-containing photoresist was used with its etching resistance higher than that of the conventional photoresist; (2) the inclination angle of pattern's sidewalls was controlled by a defocus UV exposure technique; and (3) a GC substrate was etched to form a mold by using a Si-containing photoresist structure with inclined sidewalls as a masking layer; the technique was also used to control the inclination angle of the trench's sidewalls in the GC mold. The authors input different focus offset values to defocus the image in order to control the intensity distribution of UV lights within a film of Si-containing photoresist that was spin-coated on a polished GC wafer. In the next step, GC was etched by a 19:1 mixture of O2 and CHF3 which then created a trench structure with inclined sidewalls according to the variations in local masking thicknesses. By changing the focus offset in the UV exposure system from 0 to −12 μm, the inclination angle of the Si-containing photoresist microstructures was varied from 17° to 40°. With these changes, the range of the angles of GC molds became 6° to 17°. Then by thermal imprinting on Pyrex glass and quartz, these numbers expanded from 10° to 32°.
Optical properties of TaTe2O7 thin films as absorber materials for extreme ultraviolet lithography binary masks
Authors: Young Kang Hee , Peranantham Pazhanisami , Kwon Hwangbo Chang , Seo Hwan-Seok , Kim Seong-Su , Hoon Lee Jang
Published: November 2012

In this study, the authors propose tantalum-tellurium oxide (TaTe2O7) as a new mask material for extreme ultraviolet lithography (EUVL). TaTe2O7 films were deposited by using the RF magnetron sputtering method. The optical constants of the TaTe2O7 film were calculated as n = 0.9529 and k = 0.05548 at a wavelength of 13.5 nm by using an indirect optical method. The reflectance spectra for the deposited TaTe2O7 film on a (Mo/Si) multilayer mirror were measured in the EUV region and also simulated by using the optical constants. The simulated reflectance spectra show that the minimum reflectance of 0.2% required for a EUVL mask absorber material is attained at 44.14 nm thickness for the TaTe2O7 film and 37.05 nm for the bulk TaTe2O7. The measured reflectance for the TaTe2O7 films of various thicknesses (4.88, 13.12, 22.5, 41.18, and 54.47 nm) agreed relatively well with the simulated results.
Long nanoscale gaps on III–V substrates by electron beam lithography
Authors: Thoms Stephen , Macintyre Douglas S.
Published: November 2012

Deep submicron gaps between metal pads of around 100 μm in size are difficult to fabricate on III-V substrates using electron beam lithography, polymethyl methacrylate (PMMA) resist, and metal lift-off. In device fabrication, gold is commonly used to form metal contacts. However, gold etch methods are not well suited to high resolution patterning and lift-off methods are frequently employed. In this paper, the authors investigate a number of different methods for realizing long 100 nm scale gaps for structures fabricated on III–V substrates. Initially, they explain why the fabrication of long narrow gaps between metal pads using PMMA resist and metal lift-off is difficult. The authors show that 15 nm gaps can be fabricated using a double patterning method and discuss the limitations of this technique. They show that good undercut profiles for metal lift-off can be realized by the controlled etching of a sacrificial polymer layer placed beneath the resist. The authors demonstrate that reliable 100 nm scale gaps can be fabricated between 100 μm square metal pads using these methods.
Probe current distribution characterization technique for focused ion beam
Authors: Tan Shida , Livengood Richard , Greenzweig Yuval , Drezner Yariv , Shima Darryl
Published: November 2012

Focused ion beam technology continues to scale into the nano regime to keep pace with the scaling of semiconductor processes and biological science research. As the requirements for higher image resolution and machining precision increase, the necessity for comprehensive analysis and fine tuning of the ion beam profile is becoming increasingly important and more challenging. Older techniques such as edge resolution analysis or ion beam spot burns provide only a limited understanding of the ion beam probe current distribution. In this paper, the authors discuss a quantitative ion beam probe current distribution measurement technique. The principle of the approach will be discussed; modeling and empirical results of a gallium beam profile are presented in this paper.
Mechanical properties of polymeric nanostructures fabricated through directed self-assembly of symmetric diblock and triblock copolymers
Authors: Delcambre Sean P. , Ji Shengxiang , Nealey Paul F.
Published: November 2012

Grating arrays of polystyrenic nanostructures were fabricated by directed assembly of lamellae-forming poly(styrene-b-methyl methacrylate) diblock and poly(methyl methacrylate-b-styrene-b-methyl methacrylate) triblock copolymer films on chemical patterns and subsequent removal of polyacrylic regions by soft x-ray blanket exposure and fluid development. The collapse of gratings induced by capillary forces in a fluid rinse was observed when the aspect ratio of gratings was above a critical value or the critical aspect ratio of collapse (CARC). In stark contrast to the performance of traditional polymer photoresists, the CARC of gratings fabricated from block copolymers decreased monotonically with increasing LS. For a given pattern period (LS), the CARC of polystyrenic gratings fabricated from diblock copolymers was larger than that of gratings fabricated from an analogous triblock copolymer. The apparent elastic moduli of gratings that were calculated from CARC data using an elastic cantilever beam bending model decreased monotonically with increasing LS/L0 ratio, where L0 is the natural domain period of the block copolymer. This result is discussed in terms of possible LS-dependent changes in chain conformation, line width roughness, and domain shape of nanostructures fabricated from self-assembled block copolymer films.
Improved single ion implantation with scanning probe alignment
Authors: Ilg Michael , Weis Christoph D. , Schwartz Julian , Persaud Arun , Ji Qing , Chi Lo Cheuk , Bokor Jeffrey , Hegyi Alex , Guliyev Elshad , Rangelow Ivo W. , Schenkel Thomas
Published: November 2012

Single dopant atoms can affect transport properties in scaled semiconductor devices and coherent control of spin and charge degrees of freedom of single dopant atoms promises to enable quantum computing. The authors report on an improved technique for deterministic placement of single dopant atoms by single ion implantation with scanning probe alignment. Ions are generated in a microwave driven ion source, mass analyzed in a Wien filter, and impinge on spin readout devices after alignment of the ion beam to regions of interest with a noncontact scanning force microscope.
Fabrication of on-chip fluidic channels incorporating nanopores using self-aligned double layer resist processing technique
Authors: Kim Bongho , Kwon Jihun , Kim Daehong , Chun Sungwoo , Lee Hyungyu , Lee Seung-Beck
Published: November 2012

The authors report on the development of a self-aligned double layer resist processing technique that allows incorporation of ion channel nanopores into on-chip microfluidic channels. The patterned positive/negative electron-beam resist double layer acts as a sacrificial template for the fabrication of on-chip fluidic channels and the nanopores. By controlling the resist dimensions, it was possible to tailor the shape of the on-chip fluidic channel and the nanopore dimensions. Using this technique, the authors demonstrated the fabrication of sub-10 nm nanopore arrays on 2 μm wide and 800 nm high on-chip fluidic channels. With further developments, it will be possible to have controllable on-chip nanopores with integrated nanofluidics.
Simulation of electron scattering in a scanning electron microscope for subsurface metrology
Authors: Okai Nobuhiro , Sohda Yasunari
Published: November 2012

Electron scattering on a flat sample with a subsurface structure was simulated to investigate the signal profile and critical dimension (CD) measured by scanning electron microscope (SEM). The authors modified an electron-scattering simulator, monsel, which was developed by the National Institute of Standards and Technology for applications to line-width metrology using CD-SEM, to simulate a flat tungsten (W) and silicon (Si) pattern under a nanometer-order-thick amorphous carbon (a-C) film and to classify the emitted electrons from the sample according to their generation processes. The simulation result shows that the material contrast between W and Si regions for measuring backscattered electrons (BSEs) is larger than that for measuring secondary electrons (SEs), though the yield of BSEs is lower than that of SEs. The low contrast given by the SE profile is attributed to the contribution of SEs generated from the a-C film by the incident electrons, which becomes an offset component. In contrast, the offset component in the BSE profile (which is also attributed to the a-C film) is much smaller than that in the SE profile. It is therefore concluded that BSE detection is suitable for CD measurement of a subsurface pattern even under a several-nanometer-thick layer. The simulation result also shows that both CD bias (between the top width of the pattern and measured CD) and material contrast increase with increasing irradiation energy for a tapered pattern. This tradeoff relationship (i.e., where both factors increase) indicates that control of the irradiation energy is necessary to obtain an accurate CD measurement of a flat sample with a tapered subsurface pattern. Moreover, in a similar manner to the simulation result, the experimentally measured SE contrast shows a similar dependence on a-C film thickness and irradiation energy.
Sub-30 nm pitch line-space patterning of semiconductor and dielectric materials using directed self-assembly
Authors: Tsai Hsin-Yu , Miyazoe Hiroyuki , Engelmann Sebastian , To Bang , Sikorski Ed , Bucchignano Jim , Klaus Dave , Liu Chi-Chun , Cheng Joy , Sanders Dan , Fuller Nicholas , Guillorn Michael
Published: November 2012

The authors demonstrate pattern transfer of 29-nm-pitch self-assembled line-space polystyrene-poly(methyl methacrylate) patterns generated by graphoepitaxy into three important materials for semiconductor device integration: silicon, silicon nitride, and silicon oxide. High fidelity plasma etch transfer with production-style reactors was achieved through co-optimization of multilayer masking film stacks and reactor conditions. The authors present a systematic study of the line edge roughness (LER) and line width roughness evolution during pattern transfer. Application of a postetch annealing process shows reduction of the LER of silicon features from around ∼3 nm to less than 1.5 nm. These results further demonstrate that directed self-assembly-based patterning may be a suitable technique for semiconductor device manufacturing.
Sensing properties of infrared nanostructured plasmonic crystals fabricated by electron beam lithography and argon ion milling
Authors: Quan Baogang , Liu Zhe , Li Lin , Sun Weijie , Xu Xinlong , Xia Xiaoxiang , Yang Haifang , Li Junjie , Gu Changzhi
Published: November 2012

In this paper, the authors report on the fabrication, theory simulation, and optical characterization of X-shaped nanoscale plasmonic crystals (PCs) and their application in biosensors. X-shaped PCs with 30 nm feature line-widths and different intersection angles were fabricated by a combination of electron beam lithography and argon ion beam milling techniques. Both experimental measurement and finite-difference time-domain simulations were employed to study the transmission properties of PCs under two different incident light polarizations. With the reduction of the symmetry of the X-shaped PCs, the transmission spectra of PCs show a new peak at ∼900 nm in the near-infrared region, and the optical experimental results were consistent with the simulated results. Plasmonic crystal-based biosensors were then prepared by self-assembly of octadecanethiol to the PCs followed by biotinylation and immobilization of streptavidin to the biosensor. The sensing properties of the PC-based biosensors with a 30° intersection angle, which is enhanced by a localized surface plasmon resonance with the asymmetry of the PC, are superior to those with a larger intersection angle in biosensor application. The robust fabrication technique and the strategy for enhancing the sensitivity of the biosensor endow X-shaped PCs with a great competitive advantage over other candidates.
Multiaxis and multibeam technology for high throughput maskless E-beam lithography
Authors: Yasuda Hiroshi , Haraguchi Takeshi , Yabara Hidebumi , Takahata Kouji , Murata Hidekazu , Rokuta Eiji , Shimoyama Hiroshi
Published: November 2012

The authors have devised a new maskless E-beam lithography method which can achieve a throughput of 10 wph which the authors are calling a “multiaxis programmable shaped beam” (multiaxis PSB). It is a kind of massive parallel electron beam lithography wherein more than 250 000 beams write a wafer and the total beam current reaches a hundred microamperes. It may be difficult to write a pattern finer than 10 nm with more than 1 μA beam current at 50 kV with a single column because of blurring from Coulomb interaction, so the multiaxis PSB system divides all the beams into 87 groups where each group has 2500–10 000 beams formed by a small column arrayed in a 26 × 33 mm2 lattice. The small column is called a column element (CE) and each CE has an emitter, apertures, deflectors, and small lenses. The key technologies of the multiaxis system are a lens, emitter, and blankers for individual beamlets. The authors have proposed new ideas for these issues and made fundamental experiments.
Piezoelectrically transduced silicon carbide MEMS double-clamped beam resonators
Authors: Sviličić Boris , Mastropaolo Enrico , Chen Tao , Cheung Rebecca
Published: November 2012

Silicon carbide (SiC) double-clamped beam (bridge) microelectromechanical system flexural vertical resonant devices actuated piezoelectrically and sensed piezoelectrically have been fabricated and tested. Lead zirconium titanate has been used as active material to implement the piezoelectric actuator and sensor. The transmission frequency response measurements have shown that the devices with the SiC beam length between 100 μm and 200 μm resonate in the frequency range of 0.8–1.9 MHz. The tuning of the resonant frequency has been demonstrated by applying DC bias voltage in the range of 0–5 V and frequency tuning range of 2500 ppm has been achieved. The resonant frequency tuning range has been shown to increase when the lengths of the actuating electrode and the beam are increased. The untuned devices have been shown to possess good linear behavior, while the presence of a tuning DC bias voltage can exceed the maximum power handling capabilities of a device.
New types of dose distributions for vertical sidewall minimizing total dose in 3-D electron-beam proximity effect correction of nanoscale features
Authors: Dai Qing , Lee Soo-Young , Lee Sang-Hee , Kim Byung-Gook , Cho Han-Ku
Published: November 2012

The spatial dose distribution across a feature, derived by a conventional 2-D proximity effect correction scheme, is a “V-shape,” i.e., higher dose closer to edges. With such a dose distribution, it is extremely difficult to realize a vertical sidewall in the resist profile for nanoscale features while reducing the critical dimension (CD) error. In this paper, it is shown that, in order to achieve a vertical sidewall of nanoscale feature with the minimum total dose, a dose distribution of a shape other than the V-shape must be used. This is due to the fact that the lateral development of resist becomes comparable to the vertical development for nanoscale features and the exposure varies along the depth dimension with high and low contrasts at the top and bottom layers of resist, respectively. Based on these characteristics, new types of dose distributions, i.e., “M-shape” and “A-shape,” have been derived to achieve a target resist profile of a vertical sidewall while minimizing the total dose. The simulation results show that the new dose distribution types lead to a more vertical sidewall, a smaller CD error, and a lower total dose.
Infrared thermal imaging as a novel evaluation method for deep vein thrombosis in lower limbs
Authors: Deng Fangge , Tang Qing , Zheng Yujiang , Zeng Guangqiao , Zhong Nanshan
Published: November 2012

Purpose:

Early detection of deep vein thrombosis (DVT) is critical to prevent clinical pulmonary thromboembolism. However, most conventional methods for diagnosing DVT are functionally limited and complicated. The aim of this study was to evaluate the value of infrared‐thermal‐imaging (IRTI), a novel imaging detection or screening technique, in diagnosis of DVT in animal models.

Methods:

DVT model of femoral veins was established in nine New Zealand rabbits. The right hind femoral vein was embolized and the contralateral one served as a nonembolized control. Measurements of IRTI, compression ultrasonography (CPUS), and angiography under ultrasonic observation (AGUO) were performed at three time points: T1 (baseline, 10 min prior to surgery), T2 (2 h after thrombin injection), and T3 (48 h postoperatively). Qualitative pseudocolor analysis and quantitative temperature analysis were performed based on mean area temperature (Tav) and mean curvilinear temperature (Tca) of the region of interest as shown in IRTI. Temperature differences (TD) in Tav (TDTav) and Tca (TDTca) between the DVT and control sides were computed. Comparative statistical analysis was carried out by paired t‐test and repeated measure, while multiple comparisons were performed by using Greenhouse‐Geisser and Bonferroni approach. Values of P < 0.05 and P < 0.01 were considered statistically significant and highly significant.

Results:

Modeling of DVT was successful in all rabbits, as confirmed by CPUS and AGUO and immediately detected by IRTI. IRTI qualitative analysis of pseudocolor revealed that the bilateral temperatures were apparently asymmetrical and that there were abnormally high temperature zones on the DVT side where thrombosis formed. The results of pairedt‐test of Tav and Tca between DVT side and control sides did not reveal statistical difference at T1 (Tav: P = 0.817; Tca: P = 0.983) yet showed statistical differences at both T2 (Tav: P = 0.023; Tca: P = 0.021) and T3 (Tav: P = 0.016; Tca: P = 0.028). Results of repeated measure and multiple comparisons of TDTav and TDTca were highly different and significant differences across the T2 (TDTav: P = 0.009; TDTav: P = 0.03) and T3 (TDTav: P = 0.015; TDTav: P = 0.021).

Conclusions:

IRTI temperature quantitative analysis may help further detection of DVT. Additionally, IRTI could serve as a novel detection and screening tool for DVT due to its convenience, rapid response, and high sensitivity.
Temperature and temporal dependence of the optical response for a radiochromic dosimeter
Authors: Skyt Peter S. , Wahlstedt Isak , Muren Ludvig P. , Petersen Jørgen B. B. , Balling Peter
Published: November 2012

Purpose:

Both temporal and thermal dependencies of the dose response have been observed in radiochromic dosimeters. As these dependencies may be influenced by the dose level, the present study investigates the temperature dependence during irradiation and the temporal change of the optical response following irradiation of radiochromic dosimeters at a range of doses.

Methods:

Cuvette samples of the PRESAGE™ radiochromic dosimeter were irradiated within a dose range of 0–10 Gy at irradiation temperatures within 5–35 °C and postirradiation storage within 6–30 °C. The optical response due to irradiation was measured using a standard spectrophotometer and the data were analyzed in terms of thermal and temporal change.

Results:

The initial dose response was linear over the applied dose range independent of irradiation temperature. However, the optical response to a specific dose increased exponentially with irradiation temperature corresponding to an activation energy of 0.114 ± 0.007 eV. The temporal change in dose response after irradiation consisted of an offset, an auto‐oxidation rate with activation energy 0.84 ± 0.03 eV, and an initial exponential increase in optical response (1.6 ± 0.2 eV) followed by an exponential decrease in optical response (0.98 ± 0.08 eV). These contributions depended on both storage temperature and the dose given, leading to a nonlinear dose response with time at low storage temperatures and a high auto‐oxidation rate at high storage temperatures.

Conclusions:

Thermal equilibration is important to the radiochromic dosimeter investigated due to an exponential change in dose response with irradiation temperature and a considerable postirradiation temporal change in response. For the dosimeter version investigated in this study, a compromise in storage temperature has to be made between increasing the nonlinearity of the dose response with time and inducing a high auto‐oxidation rate.
Free‐breathing MOLLI: Application to myocardial T1 mapping
Authors: Tsai Jyun‐Ming , Huang Teng‐Yi , Tseng Yu‐Shen , Lin Yi‐Ru
Published: November 2012

Purpose:

Of the myocardial T1 mapping techniques, the modified Look‐Locker inversion recovery (MOLLI) sequence is accurate and highly reproducible. The MOLLI sequence requires patients to hold their breath for 17 heartbeats during the scanning process to minimize respiratory motion‐related artifacts. However, some patients are unable to hold their breath because of illness or limited breath‐hold capacity. This study, therefore, aimed to develop a robust myocardial T1 mapping method based on the MOLLI sequence for patients unable to perform voluntary breath‐holds.

Methods:

This study presents a free‐breathing MOLLI (FB‐MOLLI) sequence and an optimized reconstruction method to allow myocardial T1 mapping in vivo without breath‐hold. Nine healthy volunteers participated in this study after providing institutionally approved consent. The FB‐MOLLI sequence acquires 20 images within 29 heartbeats. The reconstruction program employs a two‐step automatic image registration technique and an image selection method inspired by the self‐gating cardiac imaging method.

Results:

Results indicate that the proposed reconstruction method increases the accuracy and reproducibility of free‐breathing T1 measurements significantly (p < 0.001).

Conclusions:

The FB‐MOLLI method provides a robust tool for clinical application in free‐breathing myocardial T1 mapping, and could greatly facilitate acquisition procedures during routine examinations.
Multiple applicator hepatic ablation with interstitial ultrasound devices: Theoretical and experimental investigation
Authors: Prakash Punit , Salgaonkar Vasant A. , Clif Burdette E. , Diederich Chris J.
Published: November 2012

Purpose:

To evaluate multiple applicator implant configurations of interstitial ultrasound devices for large volume ablation of liver tumors.

Methods:

A 3D bioacoustic‐thermal model using the finite element method was implemented to assess multiple applicator implant configurations for thermal ablation with interstitial ultrasound energy. Interstitial applicators consist of linear arrays of up to four 10 mm‐long tubular ultrasound transducers, each under separate and dynamic power control, enclosed within a water‐cooled delivery catheter (2.4 mm OD). The authors considered parallel implants with two and three applicators (clustered configuration), spaced 2–3 cm apart, to simulate open surgical placement. In addition, the authors considered two applicator implants with applicators converging and diverging at angles of ∼20°, 30°, and 45° to simulate percutaneous placement. Heating experiments (10–15 min) were performed and compared against simulations employing the same experimental parameters. To estimate the performance of parallel, multiple applicator configurations in anin vivo setting, simulations were performed taking into account a range of blood perfusion levels (0, 5, 12, and 15 kg m−3 s−1) that may occur in tumors of varying vascularity. The impact of tailoring the power supplied to individual transducer elements along the length of applicators is explored for applicators inserted in non‐parallel (converging and diverging) configurations. Thermal dose (t43 > 240 min) and temperature thresholds (T > 52 °C) were used to define the ablation zones, with dynamic changes to tissue acoustic and thermal properties incorporated within the model.

Results:

Experiments inex vivo bovine liver yielded ablation zones ranging between 4.0–5.6 cm × 3.2–4.9 cm, in cross section. Ablation zone dimensions predicted by simulations with similar parameters to the experiments were in close agreement (within 5 mm). Simulations of in vivo heating showed that 15 min heating and interapplicator spacing less than 3 cm are required to obtain contiguous, complete ablation zones. The ability to create complete ablation zone profiles for nonparallel implants was illustrated by tailoring applied power levels along the length of applicators.

Conclusions:

Parallel implants consisting of three interstitial ultrasound applicators in a triangular configuration yield complete ablation zones measuring up to 6.2 cm × 5.7 cm after 15 min heating. At larger interapplicator spacing, the level of blood perfusion in the tumor may yield indentations along the periphery of the ablation zone. Tailoring applied power along the length of the applicator can accommodate for nonparallel implants, without compromising safety.
Effect of a carbohydrate mouth rinse on simulated cycling time-trial performance commenced in a fed or fasted state
Authors: Lane Stephen C. , Bird Stephen R. , Burke Louise M. , Hawley John A.
Published: November 2012

It is presently unclear whether the reported ergogenic effect of a carbohydrate (CHO) mouth rinse on cycling time-trial performance is affected by the acute nutritional status of an individual. Hence, the aim of this study was to investigate the effect of a CHO mouth rinse on a 60-min simulated cycling time-trial performance commenced in a fed or fasted state. Twelve competitive male cyclists each completed 4 experimental trials using a double-blinded Latin square design. Two trials were commenced 2 h after a meal that contained 2.5 g·kg−1body mass of CHO (FED) and 2 after an overnight fast (FST). Prior to and after every 12.5% of total time during a performance ride, either a 10% maltodextrin (CHO) or a taste-matched placebo (PLB) solution was mouth rinsed for 10 s then immediately expectorated. There were significant main effects for both pre-ride nutritional status (FED vs. FST; p < 0.01) and CHO mouth rinse (CHO vs. PLB; p < 0.01) on power output with an interaction evident between the interventions (p < 0.05). The CHO mouth rinse improved mean power to a greater extent after an overnight fast (282 vs. 273 W, 3.4%; p < 0.01) compared with a fed state (286 vs. 281 W, 1.8%; p < 0.05). We concluded that a CHO mouth rinse improved performance to a greater extent in a fasted compared with a fed state; however, optimal performance was achieved in a fed state with the addition of a CHO mouth rinse.
QSAR studies for the computational prediction of HMG-CoA reductase inhibitors by genetic function approximation technique
Authors: Awad Mohamed K. , El-Bastawissy Eman A. , Atlam Faten M.
Published: November 2012

Two-dimensional quantitative structure−activity relationship (2D-QSAR) models are useful in understanding how chemical structure is related to the biological activity of natural and synthetic chemicals. Also, they could be usefully employed for designing newer and better therapeutics. A 2D-QSAR study was performed for 52 compounds of a series of thiophenyl quinolines and α-asarone derivatives as potential hypocholesterolemic inhibitors using different types of physicochemical descriptors, which correlated significantly with the activity. Linear QSAR models were developed using multiple linear regression, where the genetic algorithm (genetic function approximation technique) was adopted for selecting the most appropriate descriptors. The results are discussed on the basis of regression data and the cross-validation technique. Model A is the best 2D-QSAR model describing the inhibition efficiency of HMG-CoA reductase with cross-validated squared correlation coefficient (Q 2 = 0.700) and the squared correlation coefficient (R 2 = 0.752), which is able to describe 70% of the variance in the experimental activity. The good agreement between the experimental and the predicted values of pIC50 (micromoles per litre) (R = 0.876) confirms the reliability and the predictability of the proposed model. The results obtained from the present QSAR study explained the importance of the electronic, structural, spatial, and electrotopological descriptors in enhancing the biological activity of the investigated inhibitors.
The implications of spatially varying catchability on bottom trawl surveys of fish abundance: a proposed solution involving underwater vehicles
Authors: Thorson James T. , Clarke M. Elizabeth , Stewart Ian J. , Punt André E.
Published: November 2012

Bottom trawl sampling is used to estimate trends in stock abundance for groundfishes worldwide, including Pacific rockfishes (Sebastes spp.). However, trawl sampling efficiency varies spatially and the distribution of groundfish populations may change among easy- and difficult-to-survey areas over time. These concerns have prompted interest in using underwater vehicles (UVs), for which catchability is likely to decrease less in rocky habitats. In this study, we use simulation modeling to evaluate the abundance trends arising from bottom trawl sampling given density-dependent habitat selection and spatially varying catchability. We first demonstrate that relative abundance indices in this case will generally be biased measures of changes in population abundance. We also propose and evaluate a sampling design that combines data from bottom trawl and UV gears. Combined sampling has greater precision than UV sampling, lower bias than bottom trawl sampling, and is robust to moderately violated assumptions regarding sampling strata or spatial catchability. We conclude by recommending future research that could test the assumptions under which combined sampling is a feasible solution to spatially varying catchability.
Metabolic engineering for enhanced hydrogen production: a review
Authors: Goyal Yogesh , Kumar Manish , Gayen Kalyan
Published: November 2012

Hydrogen gas exhibits potential as a sustainable fuel for the future. Therefore, many attempts have been made with the aim of producing high yields of hydrogen gas through renewable biological routes. Engineering of strains to enhance the production of hydrogen gas has been an active area of research for the past 2 decades. This includes overexpression of hydrogen-producing genes (native and heterologous), knockout of competitive pathways, creation of a new productive pathway, and creation of dual systems. Interestingly, genetic mutations in 2 different strains of the same species may not yield similar results. Similarly, 2 different studies on hydrogen productivities may differ largely for the same mutation and on the same species. Consequently, here we analyzed the effect of various genetic modifications on several species, considering a wide range of published data on hydrogen biosynthesis. This article includes a comprehensive metabolic engineering analysis of hydrogen-producing organisms, namely Escherichia coli, Clostridium, and Enterobacter species, and in addition, a short discussion on thermophilic and halophilic organisms. Also, apart from single-culture utilization, dual systems of various organisms and associated developments have been discussed, which are considered potential future targets for economical hydrogen production. Additionally, an indirect contribution towards hydrogen production has been reviewed for associated species.
Lifestyle impact on meal-induced insulin sensitization in health and prediabetes: A focus on diet, antioxidants, and exercise interventions
Authors: Chowdhury Kawshik K. , Legare Dallas J. , Lautt W. Wayne
Published: November 2012

The augmented whole-body glucose uptake response to insulin during the postprandial state is described as meal-induced insulin sensitization (MIS). MIS occurs when the presence of food in the upper gastrointestinal tract activates 2 feeding signals (activation of hepatic parasympathetic nerves and elevation of hepatic glutathione level), and causes insulin to release hepatic insulin sensitizing substance (HISS), which stimulates glucose uptake in skeletal muscle, heart, and kidneys. HISS action results in nutrient storage, primarily as glycogen. Impairment of HISS release results in the absence of meal-induced insulin sensitization (AMIS), which causes postprandial hyperglycemia and hyperinsulinemia, and chronically leads to the progression to a cluster of metabolic, vascular, and cardiac dysfunctions, which we refer to as components of the AMIS syndrome. Manipulation of the MIS process in health and in disease, by pharmacological and nonpharmacological interventions, is outlined in this review. High fat or sugar supplemented diet reduces MIS; exercise elevates MIS; and antioxidants protect MIS against reductions associated with diet and age.
Divergent reproductive life histories in Haida Gwaii stickleback (Gasterosteusspp.)
Authors: Oravec T.J. , Reimchen T.E.
Published: November 2012

To assess intraspecific variability in fecundity of threespine stickleback (Gasterosteus aculeatus L., 1758) as a test of life-history trade-offs, we quantified egg traits, morphological characters, and habitat variables in 43 allopatric and morphologically diverse populations from Haida Gwaii off the west coast of Canada. Mean mature egg size and total egg count (12 eggs per female and 8 gravid females per locality) were both positively and significantly correlated with standard length (SL) of the fish (r = 0.58 and 0.84, respectively). Egg size was ∼10% larger in freshwater localities than in similar-sized stickleback in adjacent marine localities (P < 0.02). Multiple regression and Akaike’s information criterion (AIC) analyses of residual egg size against morphological and lake habitat variables yields a negative correlation with lake pH (partial r = –0.34, P < 0.05) and no association with lake size, aquatic spectra, gill raker number, defense armor, or predation regime. Relative to stickleback from continental regions, Haida Gwaii stickleback life histories appear to be K-shifted (large but few eggs) possibly because of cool temperatures, low aquatic productivity, low community diversity, predation regime, and occasional iteroparity.
Assessing and modeling standing deadwood attributes under alternative silvicultural regimes in the Acadian Forest region of Maine, USA
Authors: Russell Matthew B. , Kenefic Laura S. , Weiskittel Aaron R. , Puhlick Joshua J. , Brissette John C.
Published: November 2012

Estimating the amount of standing deadwood in forests is crucial for assessing wildlife habitat and determining carbon stocks. In this analysis, snags (standing dead trees) in various stages of decay were inventoried across eight silvicultural treatments in eastern spruce–fir forests in central Maine nearly 60 years after treatments were initiated. Several modeling strategies were developed to estimate number of snags per hectare in various stages of decay. An unmanaged reference area displayed the highest basal area and volume of snags (5.4 ± 3.1 m2·ha–1 and 29.4 ± 23.6 m3·ha–1, respectively, (mean ± standard deviation)), while the lowest basal area and volume (0.9 ± 1.0 m2·ha–1 and 3.1 ± 5.2 m3·ha–1) were observed in selection system with a 5-year cutting cycle. Models indicated that snag abundance was related to stand density, depth to water table, and the average harvest interval of the treatment. At a fixed stand density, approximately 140% more snags were predicted to occur in treatments with an average harvest interval of 55 compared with 5 years. An index of error reflecting the number of snags found in certain decay classes was reduced by 40% when predictions from count regression models fit with a mixed modeling strategy were used over ordinal regression. Results from these analyses can help to reduce the disparities between observed and modeled snag stocking levels and further our understanding of the relationships between live and standing dead trees inherent to eastern spruce–fir forests.
Moving towards carbon neutrality: CO2 exchange of a black spruce forest ecosystem during the first 10 years of recovery after harvest
Authors: Coursolle Carole , Giasson Marc-André , Margolis Hank A. , Bernier Pierre Y.
Published: November 2012

Disturbances control the landscape-level C dynamics of boreal forests, but post-disturbance C dynamics are usually poorly quantified. In the current study, we use 10 years of CO2 flux measurements at a boreal black spruce ( Picea mariana (Mill.) B.S.P.) cutover in eastern Canada to estimate time to C neutrality, quantify the relative role of respiration versus photosynthesis during recovery, and determine the agreement between cumulated CO2 fluxes and plot-level changes in C content. The site was a net source of 139 g C·m–2·year–1 2 years post-harvest, dropped further to a source of 173 g C·m–2·year–1 4 years post-harvest, following a scarification treatment, and was nearly C neutral 10 years post-harvest. Gross ecosystem productivity (GEP) increased by 50 g C·m–2·year–1 post-scarification, while ecosystem respiration (ER) increased by only 23 g C·m–2·year–1. The resulting net rate of increase of 27 g C·m–2·year–1 in net ecosystem productivity was driven by changes in increasing leaf area. In fact, vegetation regrowth had a much greater impact on annual fluxes than did interannual variability in climate. Biometric-based measurements of total C losses after harvest were in relatively good agreement with eddy-covariance-based estimates 8 years after the harvest.
Predicting and calibrating tree attributes by means of airborne laser scanning and field measurements
Authors: Maltamo Matti , Mehtätalo Lauri , Vauhkonen Jari , Packalén Petteri
Published: November 2012

This paper examines the calibration of airborne laser scanning based tree attribute models to separate data by applying a best linear unbiased predictor. Firstly, single Scots pine ( Pinus sylvestris L.) trees were identified from dense airborne laser scanning data. Secondly, seemingly unrelated mixed-effects models for diameter at breast height, tree height, volume, dead branch height, and crown base height were constructed using airborne laser scanning based height metrics as predictors at both the area and individual tree level. Finally, these models were calibrated to validation stands using field measurements of some of the five abovementioned tree attributes. The models were calibrated by applying the best linear unbiased predictor to predict the random stand effects for the validation stand. In a system of several models, the correlation of random effects enabled the prediction of stand effects for all models, providing the response of at least one of the models was known for one or more sample trees of the validation stand. The results showed that the accuracy of tree attribute prediction improved in most cases as the number of sample trees increased. The level of improvement was highest for volume and dead branch height. The practical importance of the results of this study lies in applications where forest stands are visited in the field, for example, before making cutting decisions.
Balancing equity and efficiency of goal programming for use in forest management planning
Authors: Eyvindson Kyle
Published: November 2012

Developing forest management plans from a multicriteria perspective requires the decision maker to state preferences regarding the criteria and their importance. This article demonstrates the feasibility of merging the weighted goal programming formulation and the minimax goal programming formulation as a means to provide the decision maker the opportunity to decide which goals are to be treated in a weighted goal programming (the efficient solution) manner or in a minimax goal programming (the equitable solution) manner. The combination of these two goal planning variants is done through partitioning the criteria into sets to be treated by the different variants. The two methods proposed in this paper assign different criteria to a set where the balance of the achievements is desired or to a different set where the maximum aggregated achievement is desired. The first method is designed to create alternative plans, based only on the assignment of criteria to different partitions. The second method requires that the decision maker has a clear understanding of how he/she wishes to deal with each criterion. The functionality of these methods of goal planning is shown with an example derived from a forest management planning situation.
Patterns of flammability of the California oaks: the role of leaf traits
Authors: Engber Eamon A. , Varner J. Morgan
Published: November 2012

Fire is one of the most important processes driving plant community composition and structure. Fire regimes are largely governed by climate, vegetation structure, and individual plant traits that influence flammability. We assessed the mechanistic drivers of flammability for a diverse group of 18 California Quercus and allied Chrysolepis and Notholithocarpus species, addressing variation in leaf physical traits, growth form (tree or shrub), phylogeny (Quercus subgenera), and fire regime (low, mixed, or high severity). Differences in flammability were not strongly driven by leaf habit, leaf margin type, or surface area to volume ratio; simple measures of leaf size accounted for most of the observed variation. Further, leaf size was tightly linked to fuelbed depth, a known driver of fire behavior. Litter from trees was generally more flammable than litter from shrubs, primarily a function of differences in leaf size. A hierarchical clustering analysis on the flammability data set divided the oaks into three clusters of low, intermediate, and high flammability, corresponding closely to high-, mixed-, and low-severity fire regimes, respectively. The link between plant flammability traits and fire regime provides further evidence that individual species affect ecosystem processes.
Fine and coarse root parameters from mature black spruce displaying genetic × soil moisture interaction in growth
Authors: Major John E. , Johnsen Kurt H. , Barsi Debby C. , Campbell Moira
Published: November 2012

Fine and coarse root biomass, C, and N mass parameters were assessed by root size and soil depths from soil cores in plots of 32-year-old black spruce ( Picea mariana (Mill.) Britton, Sterns & Poggenb.) from four full-sib families studied previously for drought tolerance and differential productivity on a dry and wet site. All fine and coarse root size categories had greater root biomass on the dry than on the wet site. Most of the site differences resided in 0–20 cm soil depth. The wet site had greater root N concentration than the dry site, despite the same soil N; thus, virtually no differences were observed in total fine and coarse root N mass between sites. Root N concentration declined with increases in both soil depth and root size. Fine roots (<2 mm) accounted for 73% and 38% of the total fine and coarse N and C mass, respectively. The dry site had lower needle mass and more fine root mass than the wet site, demonstrating an adaptation to moisture stress change through the rebalancing of resource-obtaining organs. Drought-tolerant families had the same quantity of fine roots as drought-intolerant families but were able to support more foliage and aboveground mass per unit fine root mass than intolerant families.
Acute ascorbic acid and hindlimb skeletal muscle blood flow distribution in old rats: rest and exercise
Authors: Copp Steven W. , Schwagerl Peter J. , Hirai Daniel M. , Poole David C. , Musch Timothy I.
Published: November 2012

Excess reactive oxygen species are implicated in the impaired peripheral vascular function evident during exercise in older individuals. We tested the hypothesis that an acute infusion of the antioxidant ascorbic acid (AA) in old rats would improve antioxidant capacity and reduce oxidative stress and, therefore, elevate hindlimb muscle blood flow at rest and during treadmill exercise in muscles containing principally type I and IIa muscle fibers. Total and individual hindlimb skeletal muscle blood flow was measured (radiolabeled microspheres) in old rats (26–28 months) at rest (n = 8) and during treadmill exercise (n = 8; 20 m·min–1, 5% grade) before and after AA treatment (76 mg·(kg body mass)–1 intra-arterial (i.a.) injection). AA elevated total antioxidant capacity (rest, ∼37%; and exercise, 31%) and reduced oxidative stress (∼26%, exercise only). AA reduced resting total hindlimb muscle blood flow (control, 25 ± 3; AA, 16 ± 2 mL·min–1·(100 g)–1; p < 0.05) and blood flow to 8 of 28 individual muscles with no fiber-type correlation (p > 0.05). During exercise there was no effect of AA on total hindlimb muscle blood flow (control, 154 ± 14; AA, 162 ± 13 mL·min–1·(100 g)–1; p > 0.05) or blood flow to any individual muscle. This disconnect between whole-body antioxidant status and skeletal muscle blood flow in old rats mandates consideration when pursuing antioxidant treatments experimentally or clinically in older populations.