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We have fabricated germanium-silicon (Si/HfSiOx) core-shell nanocrystal (NC) structures to work as charge storage nodes in NC flash memories. This core shell NC structure was made by doing silane annealing treatment before and after Ge NC deposition. This silicon(Si/HfSiOx) shell layer can separate the Ge NC from HfO2 and ambient oxidants in the following process, and reduces low-quality GeOx, HfGeOx to metallic Ge. Thus, a more robust interface with low trap density between the high-kappa dielectric and the NCs was achieved, which helps suppress the charges loss due to trap-assisted tunneling of electrons and results in better device performance.

This multicenter clinical study was performed to assess the safety and effectiveness of Trinity Evolution® (TE), a viable cellular bone allograft, in combination with a PEEK interbody spacer and supplemental anterior fixation in patients undergoing anterior cervical discectomy and fusion (ACDF). In a prospective, multi-center study, 31 patients that presented with symptomatic cervical degeneration at one vertebral level underwent ACDF with a PEEK interbody spacer (Orthofix, Inc., Lewisville, TX, USA) and supplemental anterior fixation. In addition all patients had the bone graft substitute, Trinity Evolution (Musculoskeletal Transplant Foundation, Edison, NJ, USA), placed within the interbody spacer. At 6 and 12 months, radiographic fusion was evaluated as determined by independent radiographic review of angular motion (≤4°) from flexion/extension X-rays combined with presence of bridging bone across the adjacent endplates on thin cut CT scans. In addition other metrics were measured including function as assessed by the Neck Disability Index (NDI), and neck and arm pain as assessed by individual Visual Analog Scales (VAS). The fusion rate for patients using a PEEK interbody spacer in combination with TE was 78.6 % at 6 months and 93.5 % at 12 months. When considering high risk factors, 6-month fusion rates for patients that were current or former smokers, diabetic, overweight or obese/extremely obese were 70 % (7/10), 100 % (1/1), 70 % (7/10), and 82 % (9/11), respectively. At 12 months, the fusion rates were 100 % (12/12), 100 % (2/2), 100 % (11/11) and 85 % (11/13), respectively. Neck function, and neck/arm pain were found to significantly improve at both time points. No serious allograft related adverse events occurred and none of the 31 patients had subsequent additional cervical surgeries. Patients undergoing single-level ACDF with TE in combination with a PEEK interbody spacer and supplemental anterior fixation had a high rate of fusion success without serious allograft-related adverse events.

We demonstrate a kinetically-driven patterning scheme to selectively position arrays of Ge or Si nanoparticles within lithographically defined HfO2 windows. The surface reactions enabling patterning are revealed through temperature programmed desorption experiments and selectivity of the deposition is verified by X-ray photoelectron spectroscopy and scanning electron microscopy. Patterning is possible by exploiting the different reactivity of Ge and Si on HfO2 and SiO2 surfaces and employing a sacrificial SiO2 mask on which adatoms etch the SiO2 surface and do not accumulate to form nanocrystals.

Germanium interactions are studied on HfO2 surfaces, which are prepared through physical vapor deposition (PVD) and by atomic layer deposition. X-ray photoelectron spectroscopy and temperature-programed desorption are used to follow the reactions of germanium on HfO2. Germanium chemical vapor deposition at 870 K on HfO2 produces a GeOx adhesion layer, followed by growth of semiconducting Ge0. PVD of 0.7 ML Ge (accomplished by thermally cracking GeH4 over a hot filament) also produces an initial GeOx layer, which is stable up to 800 K. PVD above 2.0 ML deposits semiconducting Ge0. Temperature programed desorption experiments of ∼1.0ML Ge from HfO2 at 400–1100 K show GeH4 desorption below 600 K and GeO desorption above 850 K. These results are compared to Ge on SiO2 where GeO desorption is seen at 550 K. Exploiting the different reactivity of Ge on HfO2 and SiO2 allows a kinetically driven patterning scheme for high-density Ge nanoparticle growth on HfO2 surfaces that is demonstrated.

GeH4 is thermally cracked over a hot filament depositing 0.7–15 ML Ge onto 2–7 nm SiO2/Si(1 0 0) at substrate temperatures of 300–970 K. Ge bonding changes are analyzed during annealing with X-ray photoelectron spectroscopy. Ge, GeHx, GeO, and GeO2 desorption is monitored through temperature programmed desorption in the temperature range 300–1000 K. Low temperature desorption features are attributed to GeO and GeH4. No GeO2 desorption is observed, but GeO2 decomposition to Ge through high temperature pathways is seen above 750 K. Germanium oxidization results from Ge etching of the oxide substrate. With these results, explanations for the failure of conventional chemical vapor deposition to produce Ge nanocrystals on SiO2 surfaces are proposed.

High-density (>1×1012 cm−2) Si nanoparticles have been successfully grown on Si3N4 and SiO2 thin films by hot-wire chemical vapor deposition (HW-CVD) using disilane, in which Si atoms are generated on a heated tungsten filament and, after desorbing, impinge on the substrate. The highest density, 1.1×1012 cm−2 as measured by scanning electron microscopy (SEM) and 2.1×1012 cm−2 by scanning tunneling microscopy, is achieved by depositing 1.8 monolayer Si on Si3N4 at 600 °C and a disilane pressure of 1.2×10−6 Torr. The corresponding Si nanoparticles have an average size of about 5 nm. Different densities are reported because scanning tunneling microscopy imaged Si nanoparticles of ∼4 nm, beyond the resolution of SEM. At temperatures above 600 °C, parallel thermal chemical vapor deposition (CVD) during HW-CVD becomes important. Parallel thermal CVD broadens the size distribution of Si nanoparticles and causes coalescence of neighboring nanoparticles, leading to a decrease of nanoparticle density. High densitie...

Intermittent pneumatic compression (IPC) is effective in deep venous thrombosis prophylaxis. IPC prevents venous stasis by collapsing the peripheral venous plexus in an extremity leading to increased venous return. It has been suggested that IPC has an additional effect of enhancing fibrinolysis. This study was designed to evaluate the effect of IPC on both systemic and local fibrinolysis in normal volunteers by measuring the activity of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-type 1 (PAI-1). In addition, tissue factor pathway inhibitor (TFPI) was measured to assess changes in the extrinsic coagulation cascade. IPC was applied in the foot and calf of 10 healthy subjects and blood was drawn from the antecubital fossa to determine systemic fibrinolytic activity. Local fibrinolysis was assessed in 15 healthy subjects by placing an IPC cuff on the forearm and drawing blood 2 cm above the cuff The IPC maximum inflation pressure was 120 mm Hg lasting for 3 seconds at three cycles per minute. Blood samples were taken at rest, on the 10th minute of active IPC, and 5 minutes after cessation of IPC for both systemic and local measurements. The plasma was analyzed for TFPI, t-PA, and PAI-1 antigen by use of enzyme-linked immunosorbent assays. There were no significant changes in systemic or local fibrinolytic activity before, during, or after application of IPC. TFPI systemic activity before, during, and after was 111 ±24, 118 + 18, and 116 ±22, respectively. Local TFPI activity was 91 ±32, 93 +36, and 91 ± 24, respectively. The t-PA systemic activity before, during, and after was 4.1 ± 1.9, 4.7 ± 2.3, and 5 + 2.8, respectively. Local t-PA activity was 4.5 ± 1.3, 4.5 ± 1.4, and 4.2 ± 1.4, respectively. Systemic PAI-1 activity was 11 ± 9.2, 17 ± 19, and 17 ±31, respectively. Local PAI-I activity was 3.7 ± 3.1, 3 ± 1, and 2.8 + 1, respectively, p > 0.38 for all comparisons in both groups. No evidence was found that IPC enhances systemic and local fibrinolysis or TFPI release. Irrespective of the length of IPC application or the inflation pressure, several studies have reported increased fibrinolysis, whereas others have not found any changes. Although, according to the literature, there is a trend toward increased fibrinolytic activity, further controlled studies with adequate sample size should be performed to provide an answer to this controversial topic.

Peptides have been shown to mediate the reduction and clustering of inorganic ions during biomineralization processes to build nanomaterials with well-defined shape, size, and composition. This precise control has been linked to specific amino acid sequence; however, there is a lack of information about the role of peptides during mineralization. Here, we investigate the nucleation and growth behavior of Au nanocrystals that are mediated by the engineered peptide AYSSGAPPMPPF. Unlike other nanocrystal synthesis schemes, this peptide produces Au nanocrystals from Au(III) ions at very low relative peptide concentrations, at ambient temperature, and in water at neutral pH. Our data show that (i) the peptide AYSSGAPPMPPF actually inhibits nucleation and growth of nanocrystals, (ii) HEPES plays an active chemical role as the reducing agent, and (iii) HAuCl4 accelerates the kinetics of nanoparticle nucleation and growth. Herein, we propose empirical rate laws for nucleation and growth of Au nanocrystals and compare kinetic rate laws for this peptide, citrate, and various other polymer ligands. We find that the peptide belongs to a unique class of nonreducing inhibitor ligands regulating the surface-reaction-limited growth of nanocrystals.

We investigate the utility of Langmuir adsorption measurements for characterizing nanoparticle-substrate interactions. Spherical CdSe/ZnS core-shell nanoparticles were chosen as representative particles because of their widespread use in biological labeling measurements and their relatively monodisperse dimensions. In particular, the quantum dots were functionalized with 11-mercaptoundecanoic acid, and we utilized an amine-terminated self-assembled monolayer (SAM) as a model substrate. SAMs with different end-groups (-CH(3) and -COOH) were also considered to contrast with the adsorption behavior on the amine-terminated SAM substrates. We followed the kinetics of nanoparticle adsorption on the aminosilane layer by quartz crystal microgravimetry (QCM) over a range of particle concentrations and determined the corresponding Langmuir adsorption isotherms. Analysis of both equilibrium adsorption and kinetic adsorption data allowed us to determine a consistent value of the Langmuir adsorption equilibrium constant for the amine-terminated SAM at room temperature (K(L) approximately 2.7 (micromol/L)(-1)), providing a useful characterization of the nanoparticle-substrate interaction. The effect of varying solution pH on Langmuir adsorption was also investigated in order to gain insight into the role of electrostatic interactions on nanoparticle adsorption. The equilibrium extent of adsorption was found to be maximum at about pH 7. These changes of nanoparticle adsorption were further quantified and validated by X-ray photoelectron spectroscopy (XPS) and confocal fluorescence microscopy measurements. We conclude that Langmuir adsorption measurements provide a promising approach for quantifying nanoparticle-substrate interactions.

This paper presents a new germanium-silicon core-shell nanoparticle structure for nonvolatile memory applications. This core-shell can help to passivate Ge dots from oxidation, create more favorable interface between nanoparticle and high K dielectric materials and improve device performance.

Germanium nanoparticle nucleation was studied in organized arrays on HfO2 using a SiO2 thin film mask with ~20-24 nm pores and a 6×1010 cm-2 pore density. Poly(styrene-b-methyl methacrylate) diblock copolymer was employed to pattern the SiO2 film. Hot wire chemical vapor deposition produced Ge nanoparticles using 4-19 monolayer Ge exposures. By seeding adatoms on HfO2 at room temperature before growth and varying growth temperatures between 725-800 K, nanoparticle size was demonstrated to be limited by Ge etching of SiO2 pore walls.

Ge is deposited on HfO2 surfaces by chemical vapor deposition (CVD) with GeH4. 0.7-1.0 ML GeHx (x = 0-3) is deposited by thermally cracking GeH4 on a hot tungsten filament. Ge oxidation and bonding are studied at 300-1000 K with X-ray photoelectron spectroscopy (XPS). Ge, GeH, GeO, and GeO2 desorption are measured with temperature programmed desorption (TPD) at 400-1000 K. Ge initially reacts with the dielectric forming an oxide layer followed by Ge deposition and formation of nanocrystals in CVD at 870 K. 0.7-1.0 ML GeHx deposited by cracking rapidly forms a contacting oxide layer on HfO2 that is stable from 300-800 K. Ge is fully removed from the HfO2 surface after annealing to 1000 K. These results help explain the stability of Ge nanocrystals in contact with HfO2.

This paper discusses a kinetically-driven patterning scheme to marry top-down and bottom-up assembly of nanoparticle arrays. We explain how Ge atoms interact with different dielectric surfaces to either etch the surface or to accumulate and self assemble into nanocrystals during chemical vapor deposition. By exploiting the different reactivity of these dielectrics, the accumulation of adatoms is controlled and thus subsequent self assembly of nanocrystals is controlled. Scanning electron microscopy and atomic force microscopy are used to determine particle densities. We have achieved dense (>1011 cm-2) arrays of self-assembled Ge nanocrystals within ∼100 µm sized features (defined by optical lithography) with no Ge deposition on the adjacent SiO2 sacrificial mask region. Electron beam lithography was used to pattern smaller (100 µm to 500 nm) features in which to direct the self assembly. As features shrink below 10 µm, nanoparticle nucleation within the feature is sharply affected. Finally, diblock copolymers are used to pattern 20 nm features to template self assembly of nanoparticles at a scale useful for device applications.

STUDY DESIGN The authors conducted an in vitro biomechanical flexibility study of T2-S1 specimens in flexion-extension under compressive follower preloads of physiological magnitudes. OBJECTIVES The objectives of this study were to test the hypotheses that 1) the thoracolumbar spine will support compressive preloads of in vivo magnitudes and 2) allow physiological mobility under flexion-extension moments if the preload is applied along an optimized follower load path that approximates the kypholordotic curve of the thoracolumbar spine. SUMMARY OF BACKGROUND DATA In the absence of muscle forces, the ligamentous thoracolumbar spine specimens cannot support the compressive loads expected in vivo. As a result, the flexibility of the thoracolumbar spine in flexion-extension has not been studied in vitro under physiological compressive preloads. METHODS Seven human thoracolumbar spines (T2-sacrum) were subjected to flexion and extension moments (up to 8 and 6 Nm, respectively) under compressive preloads from 0 to 800 N applied along an optimized follower preload path. The experimental technique applied the compressive preload such that: 1) it minimized the internal shear forces and bending moments resulting from the preload application, 2) made the internal force resultant compressive, and 3) caused the preload path to approximate the tangent to the curve of the thoracolumbar spine. The range of motion was measured in the T2-sacrum, T2-T11, T11-L1, and L1-sacrum regions. RESULTS All thoracolumbar specimens supported the compressive follower preload up to 800 N without damage or instability. At 800 N preload, the total flexion-extension range of motion of the T2-sacrum region decreased by 22%, from a mean of 73 degrees to 57 degrees (P < 0.05). The range of motion of the T2-T11 and L1-sacrum regions decreased from the baseline value by 23% and 30%, respectively, at a preload of 800 N. The sagittal mobility of the thoracolumbar junction (T11-L1) was not affected by the preload. The follower preload did not significantly affect the proportion of the total T2-sacrum flexion-extension range of motion contributed by the T2-T11 and L1-sacrum regions of the thoracolumbar spine. CONCLUSIONS The optimized follower preload vector minimizes the effects of artifact moment and shear force on the range of motion of the thoracolumbar spine in flexion-extension. This model allows the entire thoracolumbar spine to be investigated under physiological loading for different clinical applications.

GeH4 is thermally cracked over a hot filament depositing 0.7–15 ML Ge onto 2–7 nm SiO2/Si(100) at substrate temperatures of 300–970 K. Ge, GeHx, GeO, and GeO2 desorption is monitored through temperature programmed desorption in the temperature range 300–1000 K. Ge bonding changes are analyzed during annealing from 300–1000 K with X-ray photoelectron spectroscopy (XPS). Low temperature desorption features are attributed to GeO and GeH4. No GeO2 desorption is observed, but GeO2 decomposition to Ge through high temperature pathways is seen above 700 K. Germanium oxidization results from Ge etching of the oxide substrate, which is demonstrated through XPS. Ge nanoparticle formation on SiO2 is demonstrated using the agglomeration process. With these results, explanations for the difficulties of conventional chemical vapor deposition to produce Ge nanocrystals on SiO2 surfaces are proposed.

Oxidation of the Ag nanoparticle surface has a dramatic effect on the adsorption, orientation, and SERS detection limit of nitroaromatic molecules in aqueous solutions. Ultrasensitive SERS detection of p-nitrophenol can be achieved when oxidation of surface-immobilized Ag nanoparticles is inhibited by replacing the oxygen dissolved in water with argon gas. The presence of silver oxide at the nanoparticle surface hinders charge transfer between the aromatic ring and the underlying Ag metal surface and drastically decreases the overall detection sensitivity.

We present a comprehensive study of Si∕SiO2∕Hf(1−x)SixO2 structures using optical second-harmonic generation (SHG), supported by spectroscopic ellipsometry, photoelectron spectroscopy, and noncontact electrical measurements. Rotationally anisotropic and spectroscopic SHG depend strongly on dielectric composition and on postdeposition annealing in NH3. Spectroscopic SHG shows that these variations are linked to variations in charge trapped in the high-κ material, which influences SHG via electrostatic-field-induced SH (EFISH) generation. Supporting measurements corroborate this interpretation. Noncontact electrical measurements and x-ray photoelectron spectroscopy show annealing-dependent trends in interface charge and nitrogen incorporation, respectively, that mirror annealing-dependent trends in EFISH generation. The results show that SHG can potentially be used as an in situ, real-time monitor of internal electric fields attributable to composition- and annealing-dependent fixed charge in the oxide layers.

Germanium nanoparticle nucleation was studied in organized arrays on HfO2 using a SiO2 thin film mask with ∼20–24nm pores and a 6×1010cm−2 pore density. Poly(styrene-b-methyl methacrylate) diblock copolymer was employed to pattern the SiO2 film. Hot wire chemical vapor deposition at 800K produced Ge nanoparticles using 6–19 monolayer Ge exposures. By seeding adatoms on HfO2 at room temperature before growth, nanoparticle density is approximately one particle per pore.

Field-emission studies on Si nanowires (Si NWs) grown by the vapor-liquid-solid (VLS) technique are presented. The field-emission properties of the Si NWs were characterized in ultrahigh vacuum following several postgrowth processes such as catalyst etching, in situ annealing, and cesiation. The average threshold field of cesiated Si NWs was found to be ∼7.76±0.55V∕μm and showed a significant improvement over that of as-grown NWs (average threshold field ∼11.58V∕μm). The superior field-emission characteristics are attributed to the combination of cesiation and quality of the NWs’ surface grown via hydrogen reduction of silicon tetrachloride.