bluuebunny/crossref_metadata_2025 huggingface dataset:
Research of Compare Unilateral Fixation with Bilateral Fixation MIS-TILF Technique
Authors: Liang Y.
Published: May 2014

Introduction

Unilateral fixation MIS-TLIF has less trauma, fewer scar, and shorter operation time than standard bilateral fixation MIS-TLIF. But the debatement of fixation on biomechanical strength and clinical effects is not stopped. So, in our research, we tried to confirm safety and effectivity of unilateral fixation MIS-TLIF.

Materials and Methods

Our research retrospectively reviewed 17 cases undergoing unilateral fixation MIS-TLIF in Ruijin Hospital during August 2010 to March 2012, and chose 21 cases undergoing bilateral fixation MIS-TLIF randomly during that period as control group. The operation time, intraoperative blood volume, duration of hospital stay, and complications were recorded in both the two groups. Preoperative and postoperative ODI scores were compared between both the two groups and the statistical differences of ODI score at final follow-up was compared. Especially in cases having low back pain/leg pain, pre- and postoperative VAS scores were compared between the two groups and the statistical differences of VAS score at final follow-up was compared. Also, radiation exposure dose and time in both groups were compared; X-ray and 2D CT image reconstruction were used to evaluate whether bony infusion or not.

Results

The average follow-up was 24.2 months. All cases achieved bony infusion confirmed by radiography. The intraoperative blood loss volume in unilateral fixation group was 25.50 ± 15.20 mL, whereas which was 43.30 ± 8.25 mL in bilateral fixation group. The duration of hospital stay was 5 days in unilateral fixation group, whereas 7.9 days in bilateral fixation group. At the aspect of complications, one case suffered in unilateral fixation group (one case of dural laceration) and two cases suffered in bilateral fixation group (one case of dural laceration, one case of incision infection). The preoperative ODI score was 77.23 ± 12.40 and the final follow-up ODI score was 12.34 ± 9.34 in unilateral fixation group; the preoperative VAS score for low back pain/leg pain cases was 6.3 ± 2.1 and the final follow-up VAS score was 2.3 ± 1.1. The preoperative ODI score was 79.14 ± 9.21 and the final follow-up ODI score was 13.34 ± 11.28 in bilateral fixation group; the preoperative VAS score for low back pain/leg pain cases was 5.4 ± 2.3 and the final follow-up VAS score was 2.4 ± 1.2. Radiation exposure dose and time were significantly lower in unilateral fixation group than that in bilateral fixation group. There was a significant statistical difference between the two groups in intraoperative blood loss, duration of hospital stay, and radiation exposure dose, but no statistical difference was confirmed at the aspect of function score, pain score, and complications.

Conclusion

Unilateral fixation MIS-TLIF is similar to bilateral fixation MIS-TLIF in clinical effectivity and safety. Unilateral fixation MIS-TLIF has obvious advantage in intraoperative blood loss, duration of hospital stay, and radiation exposure. Disclosure of Interest None declared
Correlation of Lateral Stenosis in MRI with Symptoms, Walking Capacity, and EMG Findings in Patients with Surgically Confirmed Lateral Lumbar Spinal Canal Stenosis
Authors: Kuittinen P. , Sipola P. , Aalto T. Juhani , Määttä S. , Parviainen A. , Saari T. , Sinikallio S. , Savolainen S. , Turunen V. , Kröger H. , Airaksinen O. , Leinonen V.
Published: May 2014

Introduction

The aim of this study is to evaluate the clinical significance of lateral lumbar spinal canal stenosis (LLSCS), found by magnetic resonance imaging (MRI), through correlating the imaging findings with patient symptoms, walking capacity and electromyographic (EMG) measurements. Materials and Methods A total of 80 patients with symptoms of LSS severe enough to indicate operative treatment were studied with MRI. Of these patients, subjects with distinct lateral LSS were included. Accordingly, 140 roots in 14 patients (mean age, 58 years; range, 48-76 years; male, 43%) were evaluated. In MR images, the entrance and midzones of the lateral lumbar nerve root canal were graded as normal, narrowed but not compressed, or compressed. In quantitative analysis, the minimal widths of the lateral recess and midzone area were measured. Clinical symptoms were recorded with the oswestry disability index (ODI), overall visual analogue scale (VAS), specific low back pain (LBP; NRS-11), specific leg pain (LP NRS-11), beck depression inventory (BDI), and walking distance in the treadmill test. Lumbar paraspinal (L2-S1) and lower limb needle EMG studies were performed. The findings were classified root by root as 1 = normal, 2 = abnormal. The associations between radiological, EMG, and clinical findings were tested with each other.

Results

LLSCS was confirmed in all patients during surgery. EMG findings were normal in 92 roots and abnormal in 48 roots. All of the patients had at least one abnormal nerve root finding. Severity of the midzone stenosis in MRI correlated with abnormal EMG findings ( p = 0.015). Patients with abnormal EMG had also higher scores in the VAS (41.9 ± 25.7 vs. 31.5 ± 18.1; p = 0.018), NRS leg pain (7.5 ± 1.5 vs. 6.3 ± 2.1; p = 0.000), and BDI (9.8 ± 3.8 vs. 8.0 ± 3.9; p = 0.014). However, no statistically significant correlations between MRI findings and clinical symptoms or walking capacity were found.

Conclusion

MRI findings correlated with abnormal EMG, indicating that a lateral stenosis seen by MRI is a clinically significant finding. However, no relationships between the MRI findings and symptoms or walking capacity were found, suggesting their multifactorial etiology. MRI and EMG may be useful in the workup of patients with suspected LLSCS. Disclosure of Interest None declared
New Development in VCFs Treatment: Vesselplasty, Vessel-Lock, and SrHA Cement
Authors: Darwono A. B.
Published: May 2014

Introduction

Vertebroplasty and kyphoplasty are used to treat VCFs with a risk of certain cement leakage. Regarding cement leakage the new technique vesselplasty use a nonstretchable PET container to prevent leakage of the injected cement and then left as an implant body expander. Instead of PMMA, the new SrHA cement (osteoinductive and osteoconductive with less 65°C heat production) is to be used. To treat a complex case (osteoporotic VCFs, multiple stenosis, and kyphotic and degenerative scoliosis), the new innovative vessel-lock system is used. The purpose of this study is to review the theory, surgical techniques, 5 years results using this new technique and compare the effect of SrHA and PMMA cement in osteoporotic bone.

Materials and Methods

A nonrandomized prospective study to treat VCFs using vesselplasty with PMMA and SrHA cement. This new technique, the Vessel-X system is a percutaneous nonfusion technique to stabilize, restore VCFs, and prevent leakage risk of cement. Instead of previously creating a void inside the vertebral body to be filled with BFMs, this system allows the delivery of a nonstretchable bone filler container (BFC) into the vertebral body in deflated configuration, then inflated by injecting viscous BFMs into the BFC, and left as an implant body expander. The volume of the injected BFMs is controlled by a controllable cement delivery (CCD) injector system with extension tube. The pressure inside the BFC is created by the resistance of the polyethylene terephthalate (PET) container which is related to the amount of layers (1 or 2 layers), the pore size 100 µm, and the container size. The optimum pressure need to lift the end plate is the amount of pressure to counteract the resistance of surrounding bone density (fresh or old fractures, young or elderly patients), and related to the amount of BFMs to be injected with pressure into a certain size of BFC. When the pressure is over the surrounding bone resistance, the BFMs stars to penetrate the pores and interdigitate, thus stabilizing the BFC to the surrounding bone. Compare the effect of SrHA and PMMA using X-ray and CT scan: just after treatment, 3 months and 6 months after treatment.

Results

A total of 250 cases consist of 298 VCFs (VT3-VL 5) that have been treated using this new technique included 178 PMMA and 120 SrHA cases is reported also the five preliminary report of vessel-lock system.

Conclusion

The vesselplasty is a new technique to treat osteoporotic vertebral fractures using BFC system. This technique allows the stabilization and restoration of vertebral body height of VCFs, with the advantage in controlling the volume of the injected BFMs, also the pressure inside BFC, and preventing the leakage of BFMs. SrHA cement is superior compared with PMMA in the elderly cases. The vessel lock could be the solving of difficult cases. But there is still a continuum of osteoporotic problems that should be treated with a specific medical treatment. Disclosure of Interest None declared
Chronicity of Back Pain: Predisposing Factor of Normal Age-Related Axonal Degeneration
Authors: Chen Jun
Published: May 2014

Back pain is extremely common in clinical setting. In the history, back pain has been believed to be seldom associated with clearly identifiable tissue damage or anatomical defect, but it is rather a normal part of life and aging.1 Back pain is also considered to have multifactorial etiology involving biological (age, sex, and genetic), psychosocial (stress), and environmental (food, toxins, infection, and trauma) factors. More recent epidemiological investigation has revealed that cooccurring pain sites in the body are linearly increased with age, suggesting important roles of age in pain. In this report, I will highlight the roles of normal age-related axonal degeneration in the nervous system that may predispose to the chronicity of pain in general and of back pain in specific conditions. First, across the lifespan, aging process results in development of polyneuropathies along the whole somatosensory system characterized by damage of both large myelinated and unmyelinated C fibers. The age-related polyneuropathies are a predisposing factor to chronicity of mechanical pain hypersensitivity (hyperalgesia and allodynia) under both inflammatory and nerve injury conditions. For example, in aged rats, mechanical pain hypersensitivity lasts much longer relative to young cohorts in a rat model of experimental inflammatory pain as well as in a rat model of radiculopathy caused by chronic compression of dorsal root ganglia/dorsal roots by placing a steel rod into intervertebral foramen. Second, age-related polyneuropathies are initiated by myelin breakdown that is likely to be caused by decline of NGF receptors and myelin proteins, subsequently leading to axonal degeneration and loss of sensory receptors. Third, age-related polyneuropathies that are characterized by myelin breakdown and axonal degeneration are accompanied by activations of both astrocytes and microglial cells in the central somatosensory system. Together, myelin breakdown and axonal degeneration in the nervous system are common features of aged spinal cord that are likely to be a predisposing factor to chronicity of back pain due to widespread neuropathies and angiopathies which normally supply the spine. Targeting and unraveling the pathogenesis of age-related myelin breakdown and axonal degeneration would shed new light on the underlying mechanisms of chronic back pain in specific and chronic pain in general.

Acknowledgments The article is supported by grants (2011CB504100, 2013BAI04B04, and 81171049). I am grateful to Fang Xie and Han Fu for performing the experiments and to our team members for collaborations.

Disclosure of Interest

None declared

Reference

Fordyce WE. Back Pain in Workplace. Seattle, WA: IASP Press; 1995
Pathological End Plate Alterations in Disc Degeneration
Authors: Lotz Jeffrey C.
Published: May 2014

Discogenic pain accounts for approximately 40% of chronic low back pain cases, affecting 1 to 2 million adults between age 45 and 64 years in the United States. The putative pain generator in discogenic pain patients is usually considered intrinsic to the disc. Crock defined internal disc disruption as damage of internal disc structures while the external shape remains essentially normal, and no nerve root compression is present. However, the vertebral end plate is also a source of pain. It is the weak link during spinal compression, can sustain damage at loads well below those that cause disc herniation or vertebral fracture, and is innervated comparable to the outer annulus. Further evidence of the clinical importance of the vertebral end plate is the association between vertebral marrow abnormalities and discogenic pain. Data from multiple independent studies suggest that Modic Types I and II adjacent to the end plate are among the most specific of all MRI observations for predicting concordant discography-induced pain. In one prospective study, moderate-to-severe Modic Types I or II end plate abnormalities correlated 100% of the time with positive concordant pain at the adjacent disc. Recently, increased end plate innervation has also been reported for end plates with Modic changes.

End plates serve as the interface between rigid vertebral bodies and pliant intervertebral discs. Because the lumbar spine carries significant forces and discs do not have a dedicated blood supply, end plates must balance conflicting requirements of being strong to prevent vertebral fracture and porous to facilitate transport between disc cells and vertebral capillaries. Consequently, end plates are particularly susceptible to damage, which can increase communication between proinflammatory disc constituents and vascularized vertebral bone marrow. End plate damage regions can be sites of reactive bone marrow lesions that include proliferating nerves, which are susceptible to chemical sensitization and mechanical stimulation. While several lines of evidence indicate that innervated end plate damage can be a source of chronic low back pain, its role in patients is likely underappreciated because innervated damage is poorly visualized with diagnostic imaging. This literature review summarizes end plate biophysical function and aspects of pathologic degeneration that can lead to vertebrogenic pain.

Disclosure of Interest

Consultant for Relievant MedSystems

Consultant for Nocimed, LLC
In Vivo Imaging of NF-κB Activity, Pain Sensitivity, and Serum Cytokines in a Rodent Model of Neuropathy
Authors: Setton Lori A , Kraus Virginia B , Bowles Robby D.
Published: May 2014

Herniation of the intervertebral disc may be associated with a painful neuropathy (sciatica) or motor weakness that is partly mediated by inflammatory cell infiltration and proinflammatory cytokine expression. Much of the cytokine-mediated signaling and inflammatory events falls downstream of activation of the transcription factor, NF- κB. We have previously demonstrated an ability to visualize NF- κB activity in a transgenic NF-κB luciferase reporter mouse, following induction of arthritis in the knee joint.1 The temporal and spatial pattern of NF-κB-luc correlated with development of painful sensitivities in the arthritis model suggesting an ability to use in vivo imaging to rapidly screen progression of pathology and therapeutic interventions.

Here, we investigate the temporal and spatial development of NF-κB activity in the NF-κB-luc reporter mouse following induction of peripheral nerve injury (sciatic nerve constriction) and test for relationships amongst pain-related sensitivities, serum levels of NF-κB-related cytokines, and regional measures of NF-κB activity. Our work in this model system revealed that NF-κB B activity following nerve injury is elevated in the region of the affected nerve, with luciferase production specifically from the sciatic nerve and the surrounding musculature. Temporal elevations in NF-κB activity were noted beginning at 3 days after surgery, and correlated with mechanical (von Frey testing, Spearman ρ-0.84) and thermal (hyperalgesia at paw, Spearman ρ -0.80) sensitivity in a distinctly nonlinear fashion. NF- κB activity also correlated with serum interleukin 6 levels (Spearman ρ 0.75), but not with other measured cytokines. Delivery of the NF- κB specific inhibitor, NEMO-binding domain peptide NBD, was able to reduce NF- κB-luc signal, restore thermal sensitivity to sham levels, and restore mechanical sensitivity to near sham levels. These findings are important for demonstrating a direct link between the NF- κB-luc signal and pain-related measures. Together this work suggests that longitudinal and spatially resolved in vivo imaging can be useful to characterize cytokine-related sensitivities in neuropathy, with implications for radiculopathy associated with intervertebral disc herniation.

Disclosure of Interest

None declared

Reference

Bowles RD, Mata BA, Bell RD, et al. In vivo luminescent imaging of NF-κB activity and serum cytokine levels predict pain sensitivities in a rodent model of osteoarthritis. Arthritis Rheum 2013; November 18 (Epub ahead of print); doi: 10.1002/art.38279
Roles of Biomaterials in Cell-based Therapies for Disc Degeneration
Authors: Chan Barbara
Published: May 2014

Degenerative disc disease poses an increasing threat to our quality of life as we age. Existing treatments have limitations. New treatment modalities using biological approaches are appealing. While cells including mesenchymal stem cells (MSC) are proving themselves potential candidates for treating disc degeneration, biomaterials are demonstrating their important roles in supporting and potentiating such therapies.

During intradiscal injection, the vast majority of cells leaked out via back flow from the injection portal, reducing the efficacy of treatment. Recent evidence even suggests that annulus puncture is associated with cell leakage and contributes to osteophyte formation, leading to an undesirable side-effect of MSC-based therapy. This suggests the significance of developing appropriate cell carriers and effective approaches to prevent leakage and associated osteophyte formation before MSC-based therapies can be applied in a clinical setting. Using a collagen microencapsulation platform, we fabricated collagen microspheres entrapping MSCs, supporting their survival, proliferation, differentiation and matrix remodeling. Using a rabbit disc degeneration model, we showed that, comparing with delivering MSC in saline, delivering MSC in collagen microspheres significantly reduced the risk of osteophyte formation. Using a photochemical crosslinking technology, we further fabricated an injectable collagen-based annulus plug to block the injection portal during intradiscal delivery. Ex vivo studies showed that the plug survived physiologically relevant loadings and significantly reduced leakage and enhanced retention of the injected materials. In vivo rabbit disc degeneration model showed that the plug significantly reduced osteophyte formation, suggesting the potential of the annulus plug as an adjunct or annulus closure device for intradisc delivery of cells and materials.

Apart from facilitating cell delivery as shown in the above mentioned example, biomaterials play important roles in immobilizing soluble signals such as growth factors, providing structural and mechanical support to cells and tissues, presenting microenvironmental clues or niches, and acting as the template for functional remodeling of cells and tissues. Detailed discussion and examples on these functions of biomaterials will be given in this study.

Disclosure of Interest

None declared
LINK between Degeneration and Regeneration of Human Intervertebral Discs
Authors: Mwale Fackson , Gawri Rahul , Ouellet Jean , Önnerfjord Patrik , Alkhatib Bashar , Steffen Thomas , Heinegård Dick , Roughley Peter , Antoniou John , Haglund Lisbet
Published: May 2014

Back pain affects a large portion of the population across all ages and intervertebral disc (IVD) degeneration is its most implicated common cause. Presently, there are no established treatments to prevent, stop, or even retard disc degeneration, and surgery is often the offered option. Previous studies have shown that Link N can act as a growth factor and stimulate the synthesis of proteoglycans and collagens in bovine IVD in vitro and in intact human IVDs ex vivo, as well as increase disc height in a rabbit model of disc degeneration. However, the sequences in Link N involved in modulating cellular activity are not well understood. To determine if disc cells can proteolytically process Link N, human disc cells in monolayer were exposed to native Link N over a 48-hour period and mass spectrometric analysis revealed that a peptide spanning residues 1 to 8 was generated in the presence of AF cells but not NP cells. Link N 1-8 significantly induced proteoglycan production in the presence of IL-1β in both NP and AF cells, confirming that the biological effect is maintained in the first eight amino acids of the peptide and indicating that the effect is sustained in an inflammatory environment. Thus Link N 1-8 could be a promising candidate for biologically induced disc repair, and the identification of such a stable specific peptide may facilitate the design of compounds to promote disc repair and provide alternatives to surgical intervention for early stage disc degeneration.

Acknowledgments The authors thank Ms. Areej Khabut for her assistance with mass spectrometry. This work would not have been possible without funding from the Faculty of Medicine McGill University, AO Spine, North American Spine Society and Canadian Institutes of Health Research. We also thank Transplant Quebec for coordinating the retrieval of human lumbar spines through their organ donation program. Lastly, we thank The Crafoord Foundation and the Inga-Britt & Arne Lundberg Foundation for funding the mass spectrometers used in this study.

Disclosure of Interest

None declared
Pulsed Electromagnetic Field Stimulation of Intervertebral Disc Cells
Authors: Ferguson Stephen J. , Franco-Obregón Alfredo , Wuertz Karin
Published: May 2014

Pulsed electromagnetic field (PEMF) stimulation has been proposed for the noninvasive treatment of a variety of musculoskeletal disorders. PEMF is most commonly applied in the treatment of fracture nonunions or delayed fusion. PEMF stimulation devices are FDA approved as a complimentary therapy and there is clinical evidence of effectiveness for bone stimulation. More recently, potential therapeutic effects of PEMF on muscle and cartilage have been reported, with also an increasing interest in the application for the treatment of disc disorders.

We have studied the influence of PEMFs in the mT range on isolated intervertebral disc cells in both 2D monolayer and 3D cell culture models, exploring the influence of parameters such as field strength, pulsing frequency, and daily exposure. Depending on the nature of the PEMF stimulation, we have demonstrated a mild anabolic effect, mostly of mitogenic nature, and also the potential to decrease the expression of catabolic enzymes, including matrix metalloproteinases and aggrecanases. A full and detailed understanding of the pathway(s) by which PEMFs influence cellular metabolism remains the topic of current investigations.

Information on the optimal strategy for PEMF stimulation of the IVD is scarce. BMP-2 has been shown to mediate the response of disc cells to PEMF, suggesting a potential benefit of combined therapy. However, in vitro studies have also highlighted the highly variable nature of the response of disc cells to PEMF stimulation. Further work is required to elucidate the optimal parameters for PEMF therapy, to validate the process in vivo before translating the process to clinical practice.

Disclosure of Interest

None declared
Note on specific chiral ensembles of statistical hydrodynamics: “Order function” for transition of turbulence transfer scenarios
Authors: Zhu Jian-Zhou
Published: May 2014

Hydrodynamic helicity signatures the parity symmetry breaking, chirality, of the flow. Statistical hydrodynamics thus respect chirality, as symmetry breaking and restoration are key to its fundamentals, such as the spectral transfer direction and its mechanism. Homochiral sub-system of three-dimensional (3D) Navier-Stokes isotropic turbulence has been numerically realized with helical representation technique to present inverse energy cascade [Biferale et al., Phys. Rev. Lett. 108, 164501 (2012)]. The situation is analogous to 2D turbulence where inverse energy cascade, or more generally energy-enstrophy dual cascade scenario, was argued with the help of a negative temperature state of the absolute equilibrium by Kraichnan. Indeed, if the helicity in such a system is taken to be positive without loss of generality, a corresponding negative temperature state can be identified [Zhu et al., J. Fluid Mech. 739, 479 (2014)]. Here, for some specific chiral ensembles of turbulence, we show with the corresponding absolute equilibria that even if the helicity distribution over wavenumbers is sign definite, different ansatzes of the shape function, defined by the ratio between the specific helicity and energy spectra s(k) = H(k)/E(k), imply distinct transfer directions, and we could have inverse-helicity and forward-energy dual transfers (with, say, s(k) ∝ k−2 resulting in absolute equilibrium modal spectral density of energy \documentclass[12pt]{minimal}\begin{document}$U(k)=\frac{1}{\alpha +\beta k^{-2}}$\end{document}U(k)=1α+βk−2, exactly the enstrophy one of two-dimensional Euler by Kraichan), simultaneous forward transfers (with s(k) = constant), or even no simply-directed transfer (with, say, non-monotonic s(k) ∝ sin 2k), besides the inverse-energy and forward-helicity dual transfers (with, say, s(k) = k as in the homochiral case).
Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers
Authors: Fedorov Dmitry A. , Derevianko Andrei , Varganov Sergey A.
Published: May 2014

We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X1Σ+ electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-ζ basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-ζ quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm−1 for LiNa and by no more than 114 cm−1 for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm−1, and the discrepancies for the anharmonic correction are less than 0.1 cm−1. We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrational energies and wave functions the vibrational Schrödinger equation is solved with the B-spline basis set method. The transition dipole moments between all vibrational states, the Einstein coefficients, and the lifetimes of the vibrational states are calculated. We analyze the decay rates of the vibrational states in terms of spontaneous emission, and stimulated emission and absorption induced by black body radiation. In all studied heteronuclear alkali dimers the ground vibrational states have much longer lifetimes than any excited states.
Connectivity and critical current density of in-situ processed MgB2 superconductors: Effect of excess Mg and non-carbon based additives
Authors: Bhadauria P. P. S. , Gupta Anurag , Kishan Hari , Narlikar A. V.
Published: May 2014

In a sequel to our previous paper (J. Appl. Phys. 113, 036908 (2013)), where we reported comprehensive analysis of inter-grain connectivity (AF), pinning, percolation threshold (Pc), and anisotropy (γ) in a series of ex-situ processed MgB2, we address the same issues in in-situ processed samples. MgB2 samples with stoichiometric composition, excess Mg (5 wt. %) and further 3 wt. % addition of various non-carbon based additives like nano-Ag, nano-Ni, and YBCO are synthesised by the in-situ route. Detailed investigations of X-ray diffraction, magnetization (M), and resistivity (ρ) as a function of temperature (T) and field (B) in the range 5–300 K and 0–8 T are carried out in all the samples. The resistive superconducting onset Tcon ∼ 38.6 ± 0.3 K and offset (where ρ goes to zero) Tc0 ∼ 38.1 ± 0.3 K of the samples stay nearly unchanged. The inter-grain connectivity (AF) of the samples varies between 11%–20%. All the additives result in a critical current density (Jc) higher than the stoichiometric MgB2 sample, where the highest values (e.g., Jc(1 T, 5 K) ∼ 1.2 × 109 A/m2) are observed for the sample with 5 wt. % excess Mg. The major findings based on quantitative analysis of ρ (T, B) and Jc (B, T) data in all the samples are: (1) along with previously studied ex-situ samples, the Jc(AF) shows a significant increase at AF ∼ 7%; (2) the irreversibility lines lie lower than the characteristic Tc0(B) lines in the B-T phase diagram; (3) a universal core pinning (δl- and/or δTc- type) mechanism is revealed in the entire T range 5–30 K; and (4) typical values of Pc ∼ 0.57 ± 0.04 is indicative of weak link networks.
Studies on gas breakdown in pulsed radio frequency atmospheric pressure glow discharges
Authors: Huo W. G. , Jian S. J. , Yao J. , Ding Z. F.
Published: May 2014

In pulsed RF atmospheric pressure glow discharges, the gas breakdown judged by the rapid drop in the amplitude of the pulsed RF voltage is no longer universally true. The steep increment of the plasma-absorbed RF power is proposed to determine the gas breakdown. The averaged plasma-absorbed RF power over a pulse period is used to evaluate effects of the preceding pulsed RF discharge on the breakdown voltage of the following one, finding that the breakdown voltage decreases with the increment in the averaged plasma-absorbed RF power under constant pulse duty ratio. Effects of the pulse off-time on the breakdown voltage and the breakdown delay time are also studied. The obtained dependence of the breakdown voltage on the pulse off-time is indicative of the transitional plasma diffusion processes in the afterglow. The breakdown voltage varies rapidly as the plasma diffuses fast in the region of moderate pulse off-time. The contribution of nitrogen atom recombination at the alumina surface is demonstrated in the prolonged memory effect on the breakdown delay time vs. the pulse off-time and experimentally validated by introducing a trace amount of nitrogen into argon at short and long pulse off-times.
Development of silicon electrode enhanced by carbon nanotube and gold nanoparticle composites on silicon neural probe fabricated with complementary metal-oxide-semiconductor process
Authors: Zhang Songsong , Tsang Wei Mong , Srinivas Merugu , Sun Tao , Singh Navab , Kwong Dim-Lee , Lee Chengkuo
Published: May 2014

We present the fabrication of highly P-doped single crystal silicon electrodes on a silicon probe through complementary metal-oxide-semiconductor (CMOS)-compatible processes. The electrode with diameter of 50 μm and a separation of 200 μm is designed for recording/stimulating purposes. Electrochemical impedance spectroscopy indicates that the interfacial impedance of silicon electrodes at 1 KHz is 2.5 ± 0.4 MΩ, which is equivalent to the result reported from the gold (Au) electrode. To further enhance the charge storage capacity, composites of multi-wall carbon nanotubes (MWCNTs) and Au nanoparticles are electroplated onto the highly P-doped silicon electrode after surface roughness treatments. With optimized electroplating processes, MWCNTs and Au nanoparticles are selectively coated onto the electrode site with only a minimum enlargement in physical diameter of electrode (<10%). However, the typical impedance is reduced to 21 ± 3 kΩ. Such improvement can be explained by a boost in double-layer capacitance (Cdl) and the reduction in faradic resistances. The measurement of cyclic voltammetry (CV) shows that the cathodal charge storage capacity is up to 35 mC cm−2, which proves the superior performance of composite coatings on silicon electrodes and validates the functionality of reported CMOS-compatible silicon probe.
Field-effect passivation and degradation analyzed with photoconductance decay measurements
Authors: Chen Yi-Yang , Hsin Pi-Yu , Leendertz Caspar , Korte Lars , Rech Bernd , Du Chen-Hsu , Gan Jon-Yiew
Published: May 2014

In this article, an expression for the surface passivation has been derived in terms of the surface recombination velocity and the field-effect exponential. The analytical solutions provide a comprehensive understanding of the injection dependency of minority charge carrier lifetime as measured by photoconductance decay. The model has been utilized to analyze the field-effect passivation of silicon exerted by the fixed dielectric charge in an overlying dielectric film. Possible limitations and restrictions of the technique are also addressed.
A low-order decomposition of turbulent channel flow via resolvent analysis and convex optimization
Authors: Moarref R. , Jovanović M. R. , Tropp J. A. , Sharma A. S. , McKeon B. J.
Published: May 2014

We combine resolvent-mode decomposition with techniques from convex optimization to optimally approximate velocity spectra in a turbulent channel. The velocity is expressed as a weighted sum of resolvent modes that are dynamically significant, non-empirical, and scalable with Reynolds number. To optimally represent direct numerical simulations (DNS) data at friction Reynolds number 2003, we determine the weights of resolvent modes as the solution of a convex optimization problem. Using only 12 modes per wall-parallel wavenumber pair and temporal frequency, we obtain close agreement with DNS-spectra, reducing the wall-normal and temporal resolutions used in the simulation by three orders of magnitude.
Random telegraph noise in metallic single-walled carbon nanotubes
Authors: Chung Hyun-Jong , Woo Uhm Tae , Won Kim Sung , Gyu You Young , Wook Lee Sang , Ho Jhang Sung , Campbell Eleanor E. B. , Woo Park Yung
Published: May 2014

We have investigated random telegraph noise (RTN) observed in individual metallic carbon nanotubes (CNTs). Mean lifetimes in high- and low-current states, τhigh and τlow, have been studied as a function of bias-voltage and gate-voltage as well as temperature. By analyzing the statistics and features of the RTN, we suggest that this noise is due to the random transition of defects between two metastable states, activated by inelastic scattering with conduction electrons. Our results indicate an important role of defect motions in the 1/f noise in CNTs.
Correlation between nanocrystalline and magnetic structure of Co-based alloys with the induced transverse magnetic anisotropy
Authors: Kolano-Burian A. , Kolano R. , Hawełek Ł. , Szynowski J. , Włodarczyk P.
Published: May 2014

The magnetic domain structure is a specific property of ferromagnetic materials influencing their main magnetic properties. The aim of this work was to determine a relationship between nanocrystalline and the domain structure observed by means of magneto-optic Kerr effect on the surface of the Fe14.7Co58.8Cu1Nb3Si13.5B9 and Fe13.8Co65Cu0.6Nb2.6Si9B9 toroidal cores, and the induced transverse magnetic anisotropy Ku. The transverse magnetic anisotropy was induced in the Fe14.7Co58.8Cu1Nb3Si13.5B9 and Fe13.8Co65Cu0.6Nb2.6Si9B9 amorphous cores by annealing them at the temperature of 460 °C, under an external magnetic field of 500 kA/m. It was found that the appearance of nanocrystalline phase in the Fe13.8Co65Cu0.6Nb2.6Si9B9 alloy resulted in considerable increase of the magnetic anisotropy constant to 900 J/m3 already after 40 minutes of heating, whereas the nanocrystallization process in the Fe14.7Co58.8Cu1Nb3Si13.5B9 alloy proceeded much slower (after 240 minutes of heating the content of nanocrystalline phase was at the level of about 18%, and the induced magnetic anisotropy constant reached 190 J/m3). Observations of the domain structure were also made showing that the 180° domains were obtained in the Fe14.7Co58.8Cu1Nb3Si13.5B9 alloy only after 240 min of heating, whereas similar structure was observed in the Fe13.8Co65Cu0.6Nb2.6Si9B9 alloy already after 40 min of treatment.
Molecular dynamics simulations of the melting curve of NiAl alloy under pressure
Authors: Zhang Wenjin , Peng Yufeng , Liu Zhongli
Published: May 2014

The melting curve of B2-NiAl alloy under pressure has been investigated using molecular dynamics technique and the embedded atom method (EAM) potential. The melting temperatures were determined with two approaches, the one-phase and the two-phase methods. The first one simulates a homogeneous melting, while the second one involves a heterogeneous melting of materials. Both approaches reduce the superheating effectively and their results are close to each other at the applied pressures. By fitting the well-known Simon equation to our melting data, we yielded the melting curves for NiAl: 1783(1 + P/9.801)0.298 (one-phase approach), 1850(1 + P/12.806)0.357 (two-phase approach). The good agreement of the resulting equation of states and the zero-pressure melting point (calc., 1850 ± 25 K, exp., 1911 K) with experiment proved the correctness of these results. These melting data complemented the absence of experimental high-pressure melting of NiAl. To check the transferability of this EAM potential, we have also predicted the melting curves of pure nickel and pure aluminum. Results show the calculated melting point of Nickel agrees well with experiment at zero pressure, while the melting point of aluminum is slightly higher than experiment.
Role of chemical termination in edge contact to graphene
Authors: Gao Qun , Guo Jing
Published: May 2014

Edge contacts to graphene can offer excellent contact properties. Role of different chemical terminations is examined by using ab initio density functional theory and quantum transport simulations. It is found that edge termination by group VI elements O and S offers considerably lower contact resistance compared to H and group VII element F. The results can be understood by significantly larger binding energy and shorter binding distance between the metal contact and these group VI elements, which results in considerably lower interface potential barrier and larger transmission. The qualitative conclusion applies to a variety of contact metal materials.
Dielectric breakdown properties of hot SF6-CO2 mixtures at temperatures of 300–3500 K and pressures of 0.01–1.0 MPa
Authors: Zhong Linlin , Yang Aijun , Wang Xiaohua , Liu Dingxin , Wu Yi , Rong Mingzhe
Published: May 2014

Recently, much attention has been paid to SF6-CO2 mixtures as one of substitutes for pure SF6 gas. In this paper, the dielectric breakdown properties of hot SF6-CO2 mixtures are investigated at temperatures of 300–3500 K and pressures of 0.01–1.0 MPa. Under the assumptions of local thermodynamic equilibrium and local chemical equilibrium, the equilibrium compositions of hot SF6-CO2 mixtures with different CO2 proportions are obtained based on Gibbs free energy minimization. The cross sections for interactions between electrons and neutral species are presented. Some unknown ionization cross sections are determined theoretically using Deutsch–Märk (DM) formalism based on quantum chemistry. Two-term Boltzmann equation is adopted to calculate the electron energy distribution function, reduced ionization coefficient, reduced attachment coefficient, and reduced effective ionization coefficient. Then the reduced critical electric field strength of mixtures, corresponding to dielectric breakdown performances, is determined when the generation and loss of electrons are balanced. Finally, the influences of temperature, pressure, and CO2 proportion on the reduced critical electric field strength are studied. It is found that a large percentage of CO2 can obviously reduce concentrations of high-energy electrons. At temperatures above 1750 K, an addition of CO2 to SF6 gas can enhance dielectric breakdown performances. However, at low temperatures, too much CO2 added into mixtures can reduce dielectric breakdown abilities. In addition, increasing gas pressure can improve dielectric breakdown performances. But the influence will be no more significant if pressure is over 0.8 MPa.
Kinetics of oxygen interstitial injection and lattice exchange in rutile TiO2
Authors: Gorai Prashun , Hollister Alice G. , Pangan-Okimoto Kristine , Seebauer Edmund G.
Published: May 2014

The existence of a facile surface pathway for generation of O interstitials (Oi) in rutile that can facilitate annihilation of O undesirable vacancies has been demonstrated recently. Through isotopic self-diffusion experiments, the present work determines a value of approximately 1.8 eV for the activation energy of Oi injection from TiO2 (110). The mean path length for Oi diffusion decreases by nearly an order of magnitude upon adsorption of 0.1 monolayer of sulfur. Sulfur apparently inhibits the surface annihilation rate of Ti interstitials, lowering their bulk concentration and the corresponding catalytic effect they seem to exert upon Oi exchange with the lattice.
Structural, electronic transport and magnetoresistance of a 142nm lead telluride nanowire synthesized using stress-induced growth
Authors: Dedi  , Chien Chia-Hua , Hsiung Te-Chih , Chen Yu-Chieh , Huang Yi-Cheng , Lee Ping-Chung , Lee Chih-Hao , Chen Yang-Yuan
Published: May 2014

In this study, structurally uniform single crystalline PbTe nanowires (NWs) were synthesized using a stress-induced growth. Selected-area electron diffraction patterns show that the PbTe NWs were grown along the [100] direction. The electrical conductivity σ of a NW with 142 nm in diameter exhibited a semiconducting behavior at 50–300 K. An enhancement of electrical conductivity σ up to 2383 S m−1 at 300 K is much higher than σ [0.44–1526 S m−1, Chen et al., Appl. Phys. Lett. 103, p023115, (2013)] in previous studies. The room temperature magnetoresistance of the 142 nm NW was ∼0.8% at B = 2 T, which is considerably higher than that [0.2% at B = 2 T, Ovsyannikov et al., Sol. State Comm. 126, 373, (2003)] of the PbTe bulk reported.
Ultrasensitive surface-enhanced Raman scattering based gold deposited silicon nanowires
Authors: Peng Mingfa , Xu Hongyan , Shao Mingwang
Published: May 2014

Surface-enhanced Raman scattering effect was demonstrated on nanomaterial array, which was fabricated by Au deposition on the profile of etched Si nanowires. Ultrasensitive surface-enhanced Raman scattering signals from the nanoside array structures were observed with the enhancement factor of 2.3 × 109, even though the concentration of the R6G was as low as 1 × 10−11 M. Moreover, the Raman enhancement effect of nanoside array was proved to be 6.2 times compared with the counterpart of nanoplane array, which suggested the potential applications in ultrasensitive surface-enhanced Raman detection.
Cantilevered carbon nanotube hygrometer
Authors: Kuroyanagi Toshinori , Terada Yuki , Takei Kuniharu , Akita Seiji , Arie Takayuki
Published: May 2014

We investigate the effects of humidity on the vibrations of carbon nanotubes (CNTs) using two types of CNT cantilevers: open-ended and close-ended CNT cantilevers. As the humidity increases, the resonant frequency of the open-ended CNT cantilever decreases due to the adsorption of water molecules onto the CNT tip, whereas that of the close-ended CNT cantilever increases probably due to the change in the viscosity of the air surrounding the CNT cantilever, which is negatively correlated with the humidity of air. Our findings suggest that a close-ended CNT cantilever is more suitable for a quick-response and ultrasensitive hygrometer because it continuously reads the viscosity change of moist air in the vicinity of the CNT.
Seismic metamaterials based on isochronous mechanical oscillators
Authors: Finocchio G. , Casablanca O. , Ricciardi G. , Alibrandi U. , Garescì F. , Chiappini M. , Azzerboni B.
Published: May 2014

This Letter introduces a seismic metamaterial (SM) composed by a chain of mass-in-mass system able to filter the S-waves of an earthquake. We included the effect of the SM into the mono dimensional model for the soil response analysis. The SM modifies the soil behavior and in presence of an internal damping the amplitude of the soil amplification function is reduced also in a region near the resonance frequency. This SM can be realized by a continuous structure with inside a 3d-matrix of isochronous oscillators based on a sphere rolling over a cycloidal trajectory.
Monitoring the Impacts of Extraction: Science and Participation in the Governance of Mining in Peru
Authors: Himley Matthew
Published: May 2014

In Peru the recent growth of the mining economy has generated conflicts that often revolve around the environmental impacts of extraction. This paper examines a regulatory mechanism that has emerged as a response to these conflicts: participatory environmental monitoring. Focusing on a monitoring committee in the region of Ancash, I assess the committee's efforts to generate shared understandings about mining's environmental impacts, while also analyzing the consequences of the committee's work for the claims-making efforts of affected populations. I find that, while the work of the committee has not led to a cohesive environmental knowledge community, it has shaped the dynamics of mining-related struggle. Through its privileging of an expert framework for knowing and judging water quality, the committee has helped to demarcate the boundaries of credible environmental knowledge in ways that tend to constrain the capacity of area residents to hold the mining firm accountable for observed impacts on downstream water resources. My analysis points to the ongoing need to examine the uneven social effects that may flow from the privileging of particular knowledge systems and administrative rationalities within resource governance frameworks.
Compact Development without Transit: Life-Cycle GHG Emissions from Four Variations of Residential Density in Vancouver
Authors: Senbel Maged , Giratalla Waleed , Zhang Kevin , Kissinger Meidad
Published: May 2014

Numerous studies have shown that compact, mixed-use, transit-oriented developments contribute to reduced use of automobiles and in turn contribute to lower greenhouse gas emissions. When everyday destinations are within walking distance, people are more likely to walk or cycle, and if transit is within walking distance people are more likely to use it. Other studies have shown that compact development enables reductions in building energy consumption that contribute further to emissions savings. The reduced emissions are assumed to rely on the combination of compactness and transit connectedness. However, this combination requires an extensive transit network covering large areas both of residential and of employment destinations. Such networks often do not exist and are too costly to construct. When they do exist, the transit networks often do not reach those outlying neighbourhoods with the greatest potential for future growth and densification. This paper therefore asks what emissions savings compact development can achieve in the absence of high-frequency transit. In an examinination of the life-cycle emissions of four variations of density in three different neighbourhoods in Vancouver, none of which is well served by transit, we found a wide range of emissions profiles. A mixed-use new urbanist development produced 22% fewer emissions than an adjacent development of large single-family homes, both of which were in a transit-poor area on the far edge of a suburban city. A high-density neighbourhood adjacent to a suburban city centre, and one adjacent to a central city centre, produced 50% and 67% fewer emissions than the neighbourhood of large single-family homes. Findings suggest that, while compactness may be most effective when it is coupled with high frequency transit, decoupling the pair and building compactness before or without transit can still yield considerable household emissions reductions.