bluuebunny/crossref_metadata_2025 huggingface dataset:
Endogenous Bioactive Proteins in Three-Dimensional Cultured Nucleus Pulposus Cells of Herniated Intervertebral Discs: Identification of Potential Target Proteins for Gene Therapeutic Approaches
Authors: Hegewald A. A. , Fontana J. , Beierfuß A. , Thomé C. , Mern D.
Published: May 2014

Introduction

Painful degenerative disc diseases have been targeted by different biological treatment approaches. Nucleus pulposus (NP) cells play a central role in intervertebral disc (IVD) maintenance by orchestrating catabolic, anabolic, and inflammatory factors that affect the extracellular matrix. IVD degeneration is associated with imbalances of these factors, resulting in a catabolic inflammatory metabolism. Therefore, accurate knowledge about their quantity and quality with regard to matrix synthesis is vital for a rational gene therapeutic approach.

Materials and Methods

NP cells were isolated from 63 patients operated due to lumbar disc herniation (mean age 56/range 29-84 years). Then, three-dimensional culture with low-glucose was completed in a collagen type I scaffold for 4 weeks. Subsequently, cell proliferation evaluation was performed using 3-(4, 5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide and intracellular concentration of 28 endogenously expressed anabolic, catabolic, inflammatory factors and relevant matrix proteins was determined by enzyme-linked immunosorbent assay. Specimen-related grades of degeneration were confirmed by preoperative magnetic resonance imaging.

Results

Independent from gender, age, and grade of degeneration proliferation rates remained similar in all groups of NP cells. Progressive grades of degeneration, however, showed a significant influence on accumulation of selective groups of factors such as disintegrin and metalloproteinase with thrombospondin motifs 4 and 5, matrix metalloproteinase 3, metalloproteinase inhibitor 1 and 2, interleukin-1β, and interleukin-1 receptor. Along with these changes, the key NP matrix proteins aggrecan and collagen II decreased significantly. The concentration of anabolic factors bone morphogenetic proteins 2, 4, 6, and 7; insulin-like growth factor 1; and transforming growth factor β1 and 3, however, remained below the minimal detectable quantities.

Conclusion

The advantage of the relative mass value evaluation method is the ability to perform precise quantifications of protein concentrations. To our knowledge, this method has not been applied to analyze a broad array of endogenously expressed bioactive factors in NP cells from a larger number of human specimens. The findings indicate that progressive degenerative changes in NP may be problematic with regard to biologic treatment strategies. Hence, gene therapeutic interventions regulating relevant bioactive factors identified in this work might contribute to the development of regenerative treatment approaches for degenerative disc diseases. Disclosure of Interest None declared
Effects of Initial Boost with TGF-Beta 1 and Grade of Intervertebral Disc Degeneration on 3D Culture of Human Annulus Fibrosus Cells
Authors: Hegewald A. A. , Kaps C.
Published: May 2014

Introduction

Three-dimensional (3D) culture in porous biomaterials and stimulation with growth factors are known to be supportive for intervertebral disc cell differentiation and tissue formation. Unless sophisticated releasing systems are used, however, effective concentrations of growth factors are maintained only for a very limited amount of time in in vivo applications. Therefore, we investigated if an initial boost with transforming growth factor-β1 (TGF-β1) is capable to induce a lasting effect of superior cartilaginous differentiation in slightly and severely degenerated human annulus fibrosus (AF) cells.

Materials and Methods

Human AF tissue was harvested during surgical treatment of six adult patients with lumbar spinal diseases. Grading of disc degeneration was performed with magnet resonance imaging. AF cells were isolated and expanded in monolayer culture and rearranged three-dimensionally in a porous biomaterial consisting of stepwise absorbable poly-glycolic acid and poly-(lactic-co-glycolic) acid and a supportive fine net of nonabsorbable poly vinylidene fluoride. An initial boost of TGF-β1 or TGF-β1 and hyaluronan was applied and compared with controls. Matrix formation was assessed at days 7 and 21 by (1) histological staining of the typical extracellular matrix molecules proteoglycan, type I and type II collagens and by (2) real-time gene expression analysis of aggrecan, decorin, biglycan, type I, II, III, and X collagens as well as of catabolic matrix metalloproteinases MMP-2 and MMP-13.

Results

An initial boost with TGF-β1 or TGF-β1 and hyaluronan did not enhance the expression of characteristic AF matrix molecules in our 3D culture system. AF cells showed high viability in the progressively degrading biomaterial. Stratification by grade of intervertebral disc degeneration showed that AF cells from, both, slightly degenerated or severely degenerated tissue, are capable of significant upregulations of characteristic matrix molecules in 3D culture. AF cells from severely degenerated tissue, however, displayed significantly lower upregulations in some matrix molecules such as aggrecan.

Conclusion

We failed to show a supportive effect of an initial boost with TGF-β1 in our 3D culture system. This underlines the need for further investigations on growth factor releasing systems. Disclosure of Interest A. A. Hegewald has no conflict of interest and C. Kaps is an employee of TransTissue Technologies GmbH, which develops products in the field of regenerative medicine.
Biomechanical Evaluation of the Monoaxial Pedicle Screw and Plate Construct for Minimally Invasive Transforaminal Lumbar Interbody Fusion after Decompressive Surgery
Authors: Zhou Y. , Li J. , Zhu Q. , Li C. , Liu H. , Huang Z. , Shang J.
Published: May 2014

Introduction

Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is one popular posterior lumbar fusion surgery. The immediately biomechanical stability after unilateral or bilateral facetectomy of direct decompression is dependent on the type of supplement pedicle screw fixation used. The monoaxial pedicle screw and plate (PSP) has been approved for clinical use for added stabilization after cage instrumentation, especially for axial rotation stabilization. However, little biomechanical data exist comparing PSP fixation with bilateral multiaxial pedicle screw and rod (PSR) fixation.

Materials and Methods

Eight L3-L6 calf spines were instrumented with posterior cages at L4-L5 after intact kinematic analysis. The TLIF model was generated by clinical procedure and fixed with multiaxial PSR or monoaxial PSP by randomized sequence. A pure moment (±5.0 Nm) were applied to specimens to induce flexion/extension, lateral bending (LB) (left + right), and axial rotation (AR) (left + right) while recording intact versus instrumented range of motion (ROM). Two monoaxial strain gauges were instrumented at the surface of L4 and L5 vertebrae body each, to record the strain distribution under the flexion and lateral bending motion. Destructive tests of monoaxial PSR, multiaxial PSR, and monoaxial PSP construct were used to record the modes of failure, yield strength, and yield stiffness in a static compression bending test.

Results

Monoaxial PSP fixation significantly reduced ROM ( p < 0.001) at the lumbar level (flexion/extension: 88.7%; LB: 94.7%; AR: 53.8%) relative to the intact condition. Multiaxial PSR fixation afforded the similar ROM reductions ( p < 0.001) relative to the intact condition (flexion/extension: 83.1%; LB: 92.6%; AR: 42.3%). The strain distribution with monoaxial PSP fixation is not significantly larger than that with multiaxial PSR fixation when different loading conditions were applied (flexion vs. lateral bending). The strain distribution of L4 in both fixation conditions was significantly less than that in intact condition in lateral bending. The yield stiffness of the monoaxial PSP construct is significantly less than that of the monoaxial PSR construct ( p < 0.001), while the yield strength of the monoaxial PSP construct is significantly larger than that of the monoaxial PSR construct ( p < 0.001).

Conclusion

Based on these biomechanical findings, monoaxial PSP fixation and multiaxial PSR fixation are equal to afford the immediate stability after TLIF surgery. The property of low yield stiffness in monoaxial PSP construct has the potential to reduce the stress-shielding effect of the fusion segment. Disclosure of Interest None declared
Collagen-Targeting Parathyroid Hormone-Related Peptide Promotes Collagen Binding and in Vitro Chondrogenesis in Bone Marrow-Derived MSCs
Authors: Wu X. , Huang B. , Wang J. , Li C. , Zhou Y.
Published: May 2014

Introduction

Parathyroid hormone-related peptide (PTHrP) is an important inductive factor during chondrogenesis of mesenchymal stem cells (MSCs). PTHrP induces chondrogenesis and suppresses hypertrophy, yet the lack of an efficient delivery system limits its use for cartilage tissue engineering in clinical application.

Materials and Methods

In this study, a peptide of seven amino acids was first used to engineer PTHrP to construct a collagen-targeting system. This peptide functioned as a collagen-binding domain (CBD) to specially target the PTHrP to collagen. ELISA assay was used to determine the collagen-binding ability of CBD-PTHrP. The effect of CBD-PTHrP on chondrogenesis was measured by an in vitro pellet assay in bone marrow-derived MSCs (BM-MSCs).

Results

The CBD peptide promoted the binding of CBD-PTHrP to collagen when compared with NAT-PTHrP. Furthermore, the recombinant protein CBD-PTHrP induced the expression of COL2A1 and Sox-9, inhibited the expression of COL1A1 at the mRNA and protein levels as effectively as NAT-PTHrP. Safranin-O and immunohistochemistry for collagen types I, II, X and Sox-9 generally paralleled qRT-PCR and Western blotting findings with minor variations.

Conclusion

Our study demonstrated that CBD-PTHrP is a collagen-targeting system and promotes in vitro chondrogenesis in BM-MSCs. We suggest that this is an efficient delivery system for cartilage tissue engineering in clinical application. Disclosure of Interest None declared
Selective Decompression and Interlaminar Dynamic Stabilization for the Treatment of Degenerative Lumbar Stenosis: A Perspective of 3 to 5 Years Follow-up Evaluation
Authors: Hai Y.
Published: May 2014

Introduction

To evaluate the clinical efficacy and safety of posterior Coflex dynamic stabilization for the treatment of degenerative lumbar stenosis, a perspective clinical and radiographic study was conducted and 3 to 5 years outcome was reported.

Materials and Methods

Between September 2007 and August 2009, 48 consecutive patients with degenerative lumbar stenosis were prospectively enrolled and treated with selective decompression and Coflex interlaminar dynamic stabilization. There were 23 male and 25 female (age 60.3 years; range, 48-79). Forty-six patients underwent single-level procedure and two patients with two-level procedures. The outcome evaluations were using VAS scale, modified ODI score, and radiographic results with the ROM of surgery and adjacent level as well as complications. All data were analyzed and patient's satisfaction was evaluated at final follow-up examination.

Results

Follow-up examinations were conducted at 1, 3, 6, 12, 24, and 36 months postoperatively and clinical and radiographic evaluations were performed. All patients were followed up at least 36 months (36-60 months, average 45.2 months). The average VAS scale was 8.1 pre-op, 2.9 post-op, and 2.5 at latest follow-up. The ODI score was 54.3 pre-op, 21.8 post-op, and 24.5 at the latest follow-up. All data mentioned above were statistically significantly improved. During follow-up, the range of motions (ROM) of operated levels were maintained (2-6 degrees, average 3.6 degrees) and there was no significant increase of ROM in adjacent level. Seven cases of Coflex device-related complications (14.6%) were occurred, but no patient underwent revision surgery for it.

Conclusion

From this prospective study from single institute, mid- to long-term satisfactory clinical outcome could be achieved in patients with single level of DLS treated by selective decompression and posterior Coflex interlaminar dynamic stabilization, with few device-related complications and ASD occurred. Disclosure of Interest None declared
Comparison between Posterior Laminectomy and Discectomy Followed by Coflex and Transforaminal Lumbar Interbody Fusion in Treating Lumbar Disc Herniation: A Minimum 2-year Follow-up Study
Authors: Wang Z. , Luo Z. , Shangguan L.
Published: May 2014

Introduction

The aim of the study is to compare the clinical outcomes of posterior decompression combined with interlaminar dynamic reconstruction-Coflex or transforaminal lumbar interbody fusion in treating lumbar disc herniation with instability.

Materials and Methods

A comparative study was performed on 13 male and 31 female patients (L3/4 18, L4/5 26) diagnosed as lumbar disc herniation with instability, with an average age of 53.6 years (range, 39-73 years), of which all cases were followed up at least 2 years. All patients were treated with interlaminar dynamic fixation with Coflex system (Coflex group, 19 cases) or transforaminal lumbar interbody fusion (TLIF group, 25 cases). The results were assessed by medical cost, operation time, blood loss, and Oswestry disability index (ODI). The range of motion (ROM) and intervertebral height of index and adjacent segments and the Lordosis of lumbar spine were measured before operation and last follow-up.

Results

The medical cost operative time and blood loss were significantly decreased in Coflex group than those in TLIF group. At the last follow-up, the ODI of groups Coflex and TLIF were significantly improved when compared with the preoperative values ( p < 0.05). At last follow-up, a better range of motion and intervertebral height of index and adjacent segments were found in Coflex group. However, the reoperation rate of Coflex group was higher than that of TLIF group ( p < 0.05).

Conclusion

Posterior decompression combined with Coflex has the same midterm effectiveness as transforaminal lumbar interbody fusion in treating degenerative lumbar disc herniation with instability and Coflex has less traumatic and recovery time, somewhat protective effect on the adjacent segments. However, the rate of reoperation is slightly higher in Coflex Group. Disclosure of Interest None declared
Modified Plate-Only Open-Door Laminoplasty versus Laminectomy and Fusion for Treatment of Cervical Stenotic Myelopathy: A Comparative Analysis on Decompression and Complications
Authors: Yang L.
Published: May 2014

Introduction

In this study, we compared modified plate-only laminoplasty with laminotomy and fusion to confirm which of the two surgical modalities could achieve a better decompression outcome, and whether there was any significant difference in postoperative complications between the two techniques.

Materials and Methods

Clinical data of 141 patients with cervical stenotic myelopathy who underwent plate-only laminoplasty and laminectomy from November 2007 to June 2010 were reviewed retrospectively. The extent of decompression was assessed by measuring the cross-sectional area of the dural sac and the distance of spinal cord drift at 3 most narrowed levels on T2-weighed MRI. Clinical outcomes and complications were also recorded and compared.

Results

Significant enlargement of dural sac area and spinal cord drift was achieved and well maintained in both groups, while the extent of decompression was greater in patients who underwent laminectomy and fusion. However, a greater decompression extent did not seem to produce a better clinical outcome. No significant difference was observed in JOA scores and Nurick scores between the two groups. Patients who underwent plate-only laminoplasty showed a better improvement in NDI scores and VAS scores. In addition, limited decompression, rigid reconstruction of the spinal canal, preservation of cervical mobility together with preservation of the posterior structure resulted in a lower rate of postoperative C5 palsy and axial pain in modified laminoplasty group.

Conclusion

Modified laminoplasty may be a more viable option for patients with cervical stenotic myelopathy. Disclosure of Interest None declared
Moderately Degenerative Disc with Annular Rupture is a Source of Low Back Pain
Authors: Zheng Z. , Yang H. , Liu H.
Published: May 2014

Introduction

Difficulty remains in identification of the sources of low back pain (LBP) due to spinal degenerative disorders. Degenerative intervertebral disc (IVD) may contribute to pain generation. However, the relationship of disc degeneration and occurrence of LBP is still unclear, which makes it difficult to locate a surgical target for a discectomy and predict the clinical outcome. The purpose of the present study was to explore the characteristic changes of a painful disc in MRI and attempt to clarify the underlying role of inflammatory mediators and AF tears in disc degeneration and LBP occurrence.

Materials and Methods

Human disc specimens and MRI from 57 single segment IVD protrusion patients with radiculopathy were collected by discectomy. VAS of low back pain were recorded before and postsurgery for all patients. All patients were grouped according to the LBP occurrence or the disc degeneration Pfirrmann grades. Degenerated disc inflammatory mediators (IL-1β, TNF-α, iNOS, and substance P) expression were compared with immunohistochemical analysis and real-time polymerase chain reaction (RT-PCR) among different groups. The relationship of IVD degeneration severity, incidence of HIZ, and occurrence of LBP was investigated via MRI.

Results

RT-PCR and immunohistochemical analysis showed no significant differences in inflammatory mediators expression between the disc samples with and without LBP. Moderately degenerative IVD according to Pfirrmann grade demonstrated the highest inflammatory mediators expression compared with mildly and severely degenerative IVD. For LBP patients, the postoperative VAS of LBP was significantly decreased. The LBP occurrence in moderately degenerated patients was the highest (70.8%). The HIZ incidence was 75% in moderately degenerated patients, while 61.9% in severely degenerated patients. The patients who demonstrated both moderate disc degeneration and HIZ had 83.3% LBP occurrence, higher than the rest of the patient population.

Conclusion

Moderately degenerative disc with AF tear is a source of LBP. MRI showing moderately degenerative disc with HIZ could be an indication of discectomy and may predict good prognosis. Disclosure of Interest None declared
Different Sites of L5 Nerve Root Compression Cause Different Phenotypes of Sensory Deficit
Authors: Lin J. H. , Chiang Y. H.
Published: May 2014

Introduction

Identifying the pathology responsible for the clinically presenting symptoms and signs on the image of lumbar spine is critical for a success of lumbar spine surgery. A nerve root could be compressed within the spinal canal at its preganglion segment, dorsal root ganglion, or both, depending on the pathoanatomy, such as central disc herniation, lateral recess stenosis, or foraminal stenosis. The responsible pathology required to be decompressed has a high impact on the decision of surgical strategy. For a given L5 nerve compression by central disc herniation (L4/5), a simple discectomy is capable to relieve the compression, whereas total facetectomy followed by spinal fusion is required for foraminal stenosis. Sensory deficit in lumbar radiculopathy provides a useful information helping the surgeons identifying the corresponding pathology and planing the surgical strategy. This study is devoted to elucidate the role of the phenotype of sensory deficit in different sites of nerve root compression and to see if the phenotype of sensory deficit is able to predict the compression site on the images.

Materials and Methods

The study prospectively included patients who had degenerative spinal disorders on L4/5 or L5/S1 levels with/without L5 radicular pain. The compressing pathologies on L5 nerve root were divided into three categories: the disc level (L4/5), the pedicle level (L5), and the foremen level (L5/S1). The sensory examination included warm, cold, static mechanical, and dynamic mechanical sensation on the foot dorsum ipsilateral to the pathology, and the foot dorsum contralateral to the pathology on the images served as the control. The association between the sensory examination and the compression sites was analyzed.

Results

A total of 48 patients met the inclusion criteria. The incidences of compressing pathology were 52% (25/48) in the disc level, 43% (21/48) in the pedicle level, and 20% (10/48) in the foramen level. There were 54% (26/48) patients with impaired warm sensation, 45% (22/48) with impaired cold sensation, 27.78% (10/36) with impaired static mechanical stimuli, and 39.58% (19/48) with impaired dynamic mechanical stimuli. The sensory deficit in cold or warm was highly associated with the compressing pathology at the pedicle or foramen level ( p = 0.0023) with 78.5% sensitivity and 65% specificity.

Conclusion

Based on our results, different sites of L5 nerve root compression caused different phenotypes of sensory deficit. One should cautiously look for compressing pathology at pedicle/foramen level if the patient presents sensory deficit. Disclosure of Interest None declared
Basic Research on Neuronal Activation Induced by Intradiscal Pain Stimulation into Degenerative ?Intervertebral Disc Using Capsaicin
Authors: Orita S. , Nishiori H. , Yamauchi K. , Sakuma Y. , Kubota G. , Oikawa Y. , Inage K. , Sainoh T. , Sato J. , Fujimoto K. , Takahashi K. , Ohtori S.
Published: May 2014

Introduction

Previously, it was reported that pain perception is related to not only DRG but also to the reaction of the central nervous system; however, the reaction of the dominant nervous system to pain stimulus in the intervertebral discs is unknown. The purpose of this research was to verify the mechanism of reaction of the nervous system, which controls the intervertebral discs, using chemical pain stimulus.

Materials and Methods

We used 6-week-old Sprague Dawley rats, and injected 20 µL capsaicin solution, which contains 2% Fluoro-Gold (FG), into the L5/6 intervertebral disc. FG is an antidromic neuronal tracer. Seven days after injection, we prepared perfusion fixation of the rats and extracted DRGs from L1 to L6 along with the lumbar enlargement of spinal cord. At the DRG, we detected CGRP, which is a nociceptive pain-related protein, by immunostaining, and measured the distribution of the expression. At the lumbar enlargement of the spinal cord, we detected Iba1, which is a marker for pain stimulus-activated micro glia, and compared Iba 1 expression in the capsaicin group and vehicle group, in which we injected only 20 µL saline solution (each is n = 5).

Results

The rate of distribution of CGRP positive cells in the FG positive rats was highest at the L2 DRG, and the rate was higher in the capsaicin group (54.9%) than in vehicle group (27.1%), with a statistically significant difference ( p < 0.05). The number of Iba1 positive micro glia cells per 1.4 × 10 mm2 was also larger in the capsaicin group (31.7 cells) than in the vehicle group (14.8 cells), with a statically significant difference ( p < 0.05)

Conclusion

The results of this experiment suggested that the chemical stimulus to the L5/6 intervertebral disc resulted in an elevated CGRP expression that caused pain around the L2 DRG area, and the mechanism of pain perception is strongly related to the activation of microglia at the posterior horn of the spinal cord. Disclosure of Interest None declared
Unilateral Tubular Approach for Bilateral Laminectomy: Effect on Ipsilateral and Contralateral Buttock and Leg Pain
Authors: Alimi M. , Hofstetter C. P. , Torres J. M. , Cong G. T. , Njoku I. , Hartl R.
Published: May 2014

Introduction

Tubular laminectomy is an effective treatment for lumbar spinal stenosis (LSS) with neurogenic claudication and leg pain. Many surgeons agree that tubular approach results in a more complete decompression of the contralateral thecal sac and nerve root, as compared with the ipsilateral side. With this study, we sought to answer the question whether this is reflected in clinically significant differences between right- and left-sided postoperative leg pain.

Materials and Methods

First, all patients with LSS who underwent MIS laminectomy through tubular retractors between 2004 and 2011 were identified (110 patients). Among those, two groups of patients were included in the study: patients with equal preoperative leg VAS scores and paint s with unequal leg VAS scores. At the latest follow-up, in the equal pain group the extent of VAS score improvement on the approach side was compared with the extent of improvement on the contralateral side. Also, at the latest follow-up, in the unequal pain group, the extent of dominant side pain improvement was compared between the patients who were approached ipsilaterally to the painters who were approached contralaterally.

Results

In the equal pain group, at the latest follow-up of 25.8 ± 3.4 months, leg VAS scores were significantly improved both on the ipsilateral and the contralateral side compared with before surgery ( p < 0.001 and p = 0.001, respectively). In the unequal pain group, at the latest follow-up of 31.3 ± 3.7 months, leg VAS scores were significantly improved only on the contralateral side of the approach ( p < 0.001). In the equal pain group, there were no statistically significant differences between the extent of pain improvement on the ipsilateral and on the contralateral side.

Conclusion

Minimally invasive tubular laminectomy through a unilateral approach results in effective bilateral decompression. Disclosure of Interest None declared
Anatomy of Failure in Lumbar Disc Herniation. An in Vivo, Multimodal, Prospective Study of 181 Subjects
Authors: Rajasekaran S. , Bajaj Nipun , Tubaki Vijay , Kanna Rishi M. , Shetty Ajoy Prasad
Published: May 2014

Study Design

A prospective clinical study including radiological, serial postcontrast magnetic resonance imaging, intraoperative findings, and histopathological study.

Objective

The objective of this study is to document in vivo, the site of anatomical failure in lumbar disc herniation (LDH) in patients requiring disc excision surgery.

Summary of Background Data

In vitro mechanical disruption studies have demonstrated both the end plate junction (EPJ) and the annulus fibrosus (AF) as the site of failure in LDH depending upon the type of force used. However, corroborative studies in vivo to document the exact anatomy of failure have not been done in humans.

Methods

A total of 185 consecutive patients requiring microdiscectomy at a single level formed the study group. The status of the end plate and AF in the operated level (study discs) and the other discs (control) were evaluated by plain radiograph, thin slice computed tomographic scan, plain and contrast magnetic resonance imaging, intraoperative examination, and histopathological analysis.

Results

LDH due to EPJ failure (EPJF- type I herniation) was more common (117; 65%) than annulus fibrosis rupture. Herniated discs had a significantly higher incidence of EPJF than control discs ( p < 0.0001) The EPJF was evident radiologically as vertebral corner defect in 30 patients, rim avulsion in 46, frank bony avulsions in 24, and avulsion at both upper and lower EP in 4. Thirteen discs with normal EP radiologically had cartilage or bone avulsion intraoperatively. Sixty-four discs (35%) had intact EP of which annular high intensity zone was found in 21 (11%) suggesting a disruption of AF (type II herniation). Postcontrast magnetic resonance image of 20 patients showed dye leak at the EPJ proving EPJF as main cause of LDH.

Conclusion

Our study is the first in vivo evidence that LDH in humans is more commonly the result of EPJF than AF rupture in patients requiring disc surgery. Our results offer clinical validation of previous in vitro mechanical disruption studies. Future research must focus on the EPJ as a primary area of interest in LDH. Disclosure of Interest None declared
$\!\!\!{\cal N}{=}\,4$
N
=
4
mechanics with diverse (4, 4, 0) multiplets: Explicit examples of hyper-Kähler with torsion, Clifford Kähler with torsion, and octonionic Kähler with torsion geometries
Authors: Fedoruk Sergey , Ivanov Evgeny , Smilga Andrei
Published: May 2014

We present simple models of \documentclass[12pt]{minimal}\begin{document}${\cal N}{=}\,4$\end{document}N=4 supersymmetric mechanics with ordinary and mirror linear (4, 4, 0) multiplets that give a transparent description of Hyper-Kähler with Torsion (HKT), Clifford Kähler with Torsion (CKT), and Octonionic Kähler with Torsion (OKT) geometries. These models are treated in the \documentclass[12pt]{minimal}\begin{document}${\cal N}{ = }\,4$\end{document}N=4 and \documentclass[12pt]{minimal}\begin{document}${\cal N}{ = }2\,$\end{document}N=2 superfield approaches, as well as in the component approach. Our study makes manifest that the CKT and OKT supersymmetric sigma models are distinguished from the more simple HKT models by the presence of extra holomorphic torsion terms in the supercharges.
Compact, compression-free, displaceable, and resealable vacuum feedthrough with built-in strain relief for sensitive components such as optical fibers
Authors: Buchholz B. , Ebert V.
Published: May 2014

For the direct fiber coupling of small optical measurement cells, we developed a new compact vacuum feedthrough for glass fibers and other similarly shaped objects that are compact and that offer the possibility of adjusting the fiber in longitudinal and in circular direction. The feedthrough assembly avoids compression or torsion on the fiber and thus protects, e.g., highly frangible fiber materials. In the following, we will present a brief simulation of the tightness requirements for low-pressure and low-concentration water vapor measurements and we will explain an integrated concept for a displaceable and self-adjustable, compression-free, compact, ultra-high vacuum, resealable feedthrough with good strain relief. The feedthrough has been successfully tested in a laboratory test facility and in several extractive airborne tunable diode laser absorption spectroscopy hygrometers. The leakage rate of the feedthrough presented here was tested via a helium leak searcher and was quantified further in an 8-week vacuum measurement campaign. The leakage rate is determined to be 0.41 ± 0.04 × 10−9 hPa l/s, which – to our knowledge – is the first time a leakage rate for such a feedthrough has been quantified.
A self-reconfiguring metamorphic nanoinjector for injection into mouse zygotes
Authors: Aten Quentin T. , Jensen Brian D. , Burnett Sandra H. , Howell Larry L.
Published: May 2014

This paper presents a surface-micromachined microelectromechanical system nanoinjector designed to inject DNA into mouse zygotes which are ≈90 μm in diameter. The proposed injection method requires that an electrically charged, DNA coated lance be inserted into the mouse zygote. The nanoinjector's principal design requirements are (1) it must penetrate the lance into the mouse zygote without tearing the cell membranes and (2) maintain electrical connectivity between the lance and a stationary bond pad. These requirements are satisfied through a two-phase, self-reconfiguring metamorphic mechanism. In the first motion subphase a change-point six-bar mechanism elevates the lance to ≈45 μm above the substrate. In the second motion subphase, a compliant folded-beam suspension allows the lance to translate in-plane at a constant height as it penetrates the cell membranes. The viability of embryos following nanoinjection is presented as a metric for quantifying how well the nanoinjector mechanism fulfills its design requirements of penetrating the zygote without causing membrane damage. Viability studies of nearly 3000 nanoinjections resulted in 71.9% of nanoinjected zygotes progressing to the two-cell stage compared to 79.6% of untreated embryos.
Formulation of the undertow using linear wave theory
Authors: Guannel G. , Özkan-Haller H. T.
Published: May 2014

The undertow is one of the most important mechanisms for sediment transport in nearshore regions. As such, its formulation has been an active subject of research for at least the past 40 years. Still, much debate persists on the exact nature of the forcing and theoretical expression of this current. Here, assuming linear wave theory and keeping most terms in the wave momentum equations, a solution to the undertow in the surf zone is derived, and it is shown that it is unique. It is also shown that, unless they are erroneous, most solutions presented in the literature are identical, albeit simplified versions of the solution presented herein. Finally, it is demonstrated that errors in past derivations of the undertow profile stem from inconsistencies between (1) the treatment of advective terms in the momentum equations and the wave action equation, (2) the expression of the mean current equation and the surface shear stress, and (3) the omission of bottom shear stress in the momentum equation.
Coherent and incoherent contributions to the carrier-envelope phase control of wave packet localization in quantum double wells
Authors: Hader K. , Engel V.
Published: May 2014

We study laser excitation processes in a double well potential. The possibility to influence localization via the carrier-envelope phase (CEP) of a laser pulse is investigated for various situations which differ in the nature of the initial state prior to the laser interactions. In more detail, the CEP-dependence of asymmetries in the case where initially the system is described by localized wave packets, eigenstates, or incoherent mixtures are calculated and interpreted within time-dependent perturbation theory. It is investigated which contributions to the asymmetry exist and how they can be modified to reveal a more or less pronounced CEP-effect.
Decay dynamics of nascent acetonitrile and nitromethane dipole-bound anions produced by intracluster charge-transfer
Authors: Yandell Margaret A. , King Sarah B. , Neumark Daniel M.
Published: May 2014

Decay dynamics of nascent dipole bound states of acetonitrile and nitromethane are examined using time-resolved photoelectron imaging of iodide-acetonitrile (I−·CH3CN) and iodide-nitromethane (I−·CH3NO2) complexes. Dipole-bound anions are created by UV-initiated electron transfer to the molecule of interest from the associated iodide ion at energies just below the vertical detachment energy of the halide-molecule complex. The acetonitrile anion is observed to decay biexponentially with time constants in the range of 4–900 ps. In contrast, the dipole bound state of nitromethane decays rapidly over 400 fs to form the valence bound anion. The nitromethane valence anion species then decays biexponentially with time constants of 2 ps and 1200 ps. The biexponential decay dynamics in acetonitrile are interpreted as iodine atom loss and autodetachment from the excited dipole-bound anion, followed by slower autodetachment of the relaxed metastable ion, while the dynamics of the nitromethane system suggest that a dipole-bound anion to valence anion transition proceeds via intramolecular vibrational energy redistribution to nitro group modes in the vicinity of the iodine atom.
Low-frequency inelastic light scattering in a ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) glass
Authors: Adichtchev S. V. , Malinovsky V. K. , Ignatieva L. N. , Merkulov E. B. , Surovtsev N. V.
Published: May 2014

Low-frequency (down to 30 GHz) inelastic light scattering is studied in a multicomponent glass ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) in a wide temperature range. The contributions of the THz vibrational spectrum (boson peak) and of the fast relaxation are extracted and analyzed. It is shown that the fast relaxation spectrum is described by a distribution of relaxation times leading to a power-law να dependence in the frequency range 30–300 GHz. Temperature dependence of α(T) is well described by the Gilroy-Phillips model, while the integrated intensity of the fast relaxation increases significantly with the temperature. This feature distinguishes the fast relaxation in ZBLAN from the case of most single-component glasses. Thermodynamic and kinetic fragility indexes are significantly different for the ZBLAN glass. The correlations between the boson peak intensity, elastic moduli, and fragility index, found earlier for single-component glasses, are fulfilled for the thermodynamic fragility index of ZBLAN. In contrast, the correlation between the fast relaxation intensity at Tg and the fragility holds better for the kinetic fragility index of ZBLAN. We propose that thermodynamic and kinetic fragilities reflect different aspects of glassy dynamics in the case of glass formers with the complex chemical composition and structure topology: the former correlates with the elastic properties and the boson peak, the latter with the relaxation.
Phonons and magnetic excitation correlations in weak ferromagnetic YCrO3
Authors: Sharma Yogesh , Sahoo Satyaprakash , Perez William , Mukherjee Somdutta , Gupta Rajeev , Garg Ashish , Chatterjee Ratnamala , Katiyar Ram S.
Published: May 2014

Here, we report the temperature dependent Raman spectroscopic studies on orthorhombically distorted perovskite YCrO3 over a temperature range of 20–300 K. Temperature dependence of DC-magnetization measurements under field cooled and zero field cooled protocols confirmed a Néel transition at TN ∼ 142 K. Magnetization isotherms recorded at 125 K show a clear loop opening without any magnetization saturation up to 20 kOe, indicating a coexistence of antiferromagnetic (AFM) and weak ferromagnetic (WFM) phases. Estimation of exchange constants using mean-field approximation further confirm the presence of a complex magnetic phase below TN. Temperature evolution of Raman line-shape parameters of the selected modes (associated with the octahedral rotation and A(Y)-shift in the unit-cell) reveal an anomalous phonon shift near TN. An additional phonon anomaly was identified at T* ∼ 60 K, which could possibly be attributed to the change in the spin dynamics. Moreover, the positive and negative shifts in Raman frequencies between TN and T* suggest competing WFM and AFM interactions. A close match between the phonon frequency of B3g (3)-octahedral rotation mode with the square of sublattice magnetization between TN and T* is indicative of the presence of spin-phonon coupling in multiferroic YCrO3.
Temporal instability of coflowing liquid-gas jets under an electric field
Authors: Li Guangbin , Luo Xisheng , Si Ting , Xu Ronald X.
Published: May 2014

Temporal instability of an electrified liquid jet in the core of a high-speed gas stream is studied to better understand the electro-flow focusing (EFF) technique. Two types of physical models with and without viscosities of fluids are considered. One utilizes uniform basic flow and an axial electric field, while the other one considers both the axial and radial electric fields and employs appropriate velocity profiles based on the pipe flow for inner liquid and the error function for outer gas stream. Both models demonstrate that the axisymmetric instability and the helical instability are two most unstable modes in the EFF problem. The significance of free charge initially imposed on the interface is highlighted and the effects of surface tension and liquid viscosity on the jet instability are also studied. It is shown that the increase of free charge density can definitely promote both the axisymmetric and helical instabilities and the transition between them arises for sufficiently large free charge densities when the axial electric field intensity increases. Finally, the EFF experiments are carried out to compare with theoretical predictions in the temporal instability analysis and a good agreement between them is achieved.
Non-modal analysis of the diocotron instability for cylindrical geometry with conducting boundary
Authors: Mikhailenko V. V. , Seok Kim Jin , Jo Younghyun , Mikhailenko V. S. , June Lee Hae
Published: May 2014

The temporal evolution of the linear diocotron instability of a cylindrical annular plasma column surrounded by a conducting boundary has been investigated by using the methodology of the cylindrical shearing modes. The linear solution of the initial and boundary-value problems is obtained which is valid for any time at which linear effects dominate. The solution reveals that the initial perturbations of the electron density pass through the stage of the non-modal evolution when the perturbation experiences spatio-temporal distortion pertinent to the considered geometry of the electron column. The result is confirmed by a two-dimensional cylindrical particle-in-cell simulation.
InGaAs tunnel diodes for the calibration of semi-classical and quantum mechanical band-to-band tunneling models
Authors: Smets Quentin , Verreck Devin , Verhulst Anne S. , Rooyackers Rita , Merckling Clément , Van De Put Maarten , Simoen Eddy , Vandervorst Wilfried , Collaert Nadine , Thean Voon Y. , Sorée Bart , Groeseneken Guido , Heyns Marc M.
Published: May 2014

Promising predictions are made for III-V tunnel-field-effect transistor (FET), but there is still uncertainty on the parameters used in the band-to-band tunneling models. Therefore, two simulators are calibrated in this paper; the first one uses a semi-classical tunneling model based on Kane's formalism, and the second one is a quantum mechanical simulator implemented with an envelope function formalism. The calibration is done for In0.53Ga0.47As using several p+/intrinsic/n+ diodes with different intrinsic region thicknesses. The dopant profile is determined by SIMS and capacitance-voltage measurements. Error bars are used based on statistical and systematic uncertainties in the measurement techniques. The obtained parameters are in close agreement with theoretically predicted values and validate the semi-classical and quantum mechanical models. Finally, the models are applied to predict the input characteristics of In0.53Ga0.47As n- and p-lineTFET, with the n-lineTFET showing competitive performance compared to MOSFET.
Resistance and passivation of metal contacts using n-type amorphous Si for Si solar cells
Authors: Labie Riet , Bearda Twan , El Daif Ounsi , O'Sullivan Barry , Baert Kris , Gordon Ivan
Published: May 2014

A low fill factor remains one of the critical issues for successful implementation of amorphous Si layers in back-contact solar cells. In this work, the metal-phosphorous doped hydrogenated amorphous silicon (a-Si:H) contact is studied in terms of contact resistance while maintaining a high passivation level of the crystalline silicon bulk material after metal deposition and during long-term solar cell operation. On top of these contacting and passivation-preservation requirements, the metal back-surface reflection has to be large in order to reflect as much light as possible to generate high output current densities. Two different contact metals, Al and Ti, with Ti being combined in a stack with either Al, Pd/Ag or Cu, are investigated. For these two metals with comparable metal work function, the material choice shows only a minimal effect on the contact resistance value. The main parameters for obtaining a low-resistive, ohmic contact lie in the tuning of the n+ a-Si:H layer thickness and the application of a thermal annealing step. Contact resistance values down to 10 mΩ cm2 are obtained on an intrinsic/n+ a-Si:H layer stack with a remaining effective lifetime of several milliseconds after metallization and anneal. It is shown that a thin Ti (5 nm) layer is needed in order to obtain a thermally stable contact that guarantees a reliable long-term solar cell operation. The optical disadvantage of having Ti at the backside of a Si solar cell can be compensated by combining this very thin Ti layer with Cu. This results in an improvement of the back-reflectance compared to a direct Al contact.
G-centers in irradiated silicon revisited: A screened hybrid density functional theory approach
Authors: Wang H. , Chroneos A. , Londos C. A. , Sgourou E. N. , Schwingenschlögl U.
Published: May 2014

Electronic structure calculations employing screened hybrid density functional theory are used to gain fundamental insight into the interaction of carbon interstitial (Ci) and substitutional (Cs) atoms forming the CiCs defect known as G-center in silicon (Si). The G-center is one of the most important radiation related defects in Czochralski grown Si. We systematically investigate the density of states and formation energy for different types of CiCs defects with respect to the Fermi energy for all possible charge states. Prevalence of the neutral state for the C-type defect is established.
Dielectric spectroscopy at the nanoscale by atomic force microscopy: A simple model linking materials properties and experimental response
Authors: Miccio Luis A. , Kummali Mohammed M. , Schwartz Gustavo A. , Alegría Ángel , Colmenero Juan
Published: May 2014

The use of an atomic force microscope for studying molecular dynamics through dielectric spectroscopy with spatial resolution in the nanometer scale is a recently developed approach. However, difficulties in the quantitative connection of the obtained data and the material dielectric properties, namely, frequency dependent dielectric permittivity, have limited its application. In this work, we develop a simple electrical model based on physically meaningful parameters to connect the atomic force microscopy (AFM) based dielectric spectroscopy experimental results with the material dielectric properties. We have tested the accuracy of the model and analyzed the relevance of the forces arising from the electrical interaction with the AFM probe cantilever. In this way, by using this model, it is now possible to obtain quantitative information of the local dielectric material properties in a broad frequency range. Furthermore, it is also possible to determine the experimental setup providing the best sensitivity in the detected signal.
High-performance hybrid organic-inorganic solar cell based on planar n-type silicon
Authors: Chi Dan , Qi Boyuan , Wang Jizheng , Qu Shengchun , Wang Zhanguo
Published: May 2014

Hybrid organic-inorganic solar cells were fabricated by spin coating the hole transporting conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film on n-type crystalline silicon (n-Si). By incorporating different additives into the PEDOT:PSS, the conductivity and wettability of PEDOT:PSS film are markedly improved, and the device performance is greatly enhanced accordingly. To further optimize the device performance, poly(3-hexylthiophene) (P3HT) layer was inserted between the n-Si and PEDOT:PSS layer. The P3HT layer blocks electrons from diffusing to the PEDOT:PSS, and hence reduces recombination at the anode side. The device eventually exhibits a high power conversion efficiency of 11.52%.
Communication: Acceleration of coupled cluster singles and doubles via orbital-weighted least-squares tensor hypercontraction
Authors: Parrish Robert M. , Sherrill C. David , Hohenstein Edward G. , Kokkila Sara I. L. , Martínez Todd J.
Published: May 2014

We apply orbital-weighted least-squares tensor hypercontraction decomposition of the electron repulsion integrals to accelerate the coupled cluster singles and doubles (CCSD) method. Using accurate and flexible low-rank factorizations of the electron repulsion integral tensor, we are able to reduce the scaling of the most vexing particle-particle ladder term in CCSD from \documentclass[12pt]{minimal}\begin{document}${\cal O}(N^6)$\end{document}O(N6) to \documentclass[12pt]{minimal}\begin{document}${\cal O}(N^5)$\end{document}O(N5), with remarkably low error. Combined with a T1-transformed Hamiltonian, this leads to substantial practical accelerations against an optimized density-fitted CCSD implementation.