A catalyzing process under intense external magnetic fields is disclosed that is useful for accelerating carbon nanotube formation. A synthetic scheme is also disclosed. The nanotubes maybe magnetically aligned during the growth and formation and pose many applications.

This invention involves the use of intense magnetic fields to accelerate the chemical changes associated with the formation of graphitic nanotubes. This invention pertains to a new process and apparatus for the massive synthesis of carbon nanotubes using strong external magnetic fields to enhance the formation and growth by reinforcing the intrinsic magnetic mechanisms occurring during the formation.
The carbon nanotube is a hollow tube with walls made of graphene and a capping dome containing C6 conjugated aromatic rings and a few C5 member rings to alleviate curvaceous strain on the bonds. Such macromolecules of graphene are known as fullerenes. The carbon nanotube is a fullerene of great importance.
The mass production of carbon nanotubes for diverse applications is currently among the most challenging problems in nanochemistry, potentially revolutionizing many important areas of material science, particularly nanoelectronics and structural materials. The importance of enhanced formation and mass production follows from the rich potential for applications.
For example, the potential applications in nanoelectronics result from the atomic level perfection. Future nanoelectronic materials will require atomic level perfection for optimum device performance. Such a demand is unrealistic for most materials. However, the nanotube is an exception to this impracticality. The nanotubes exhibit intrinsic perfection due to the chemically bonded network, where thermodynamics restricts defect formation. Such perfection in the carbon nanotube allows ideal exploitation of mesoscopic and molecular properties, where atomic defects are intolerable. The perfection allows nice thermal and electrical conductivity in the direction of the tube axis due to the extended electronic resonance. The chemically bonded network also leads to the maximum possible strength among materials. The strength of nanotubes will contribute to many future structural applications. This optimum strength reflects the extremely stable, doubly covalently bonded network. Carbon nanotubes therefore exhibit the largest strength/mass ratio known for fibers. This threshold for maximum strength requires the existence of atomic perfection in these nanotubes.
Because of these and other possibilities, the large scale production of carbon nanotubes is currently being investigated for applications in nano-computers, strong structural support, catalyst support, scan tunneling microscopy tips and hydrogen storage in order to make use of these unique properties. Unfortunately, the large-scale preparation of the carbon nanotubes has been a challenge with no breakthroughs, except for the new approach described here. With all the prospective applications, large-scale production will be necessary to realize these many new applications. First, the older techniques are considered along with problems associated with these techniques. Then the new invention is described with detailed explanations as to how the new art resolves difficulties of the older art.
The carbon nanotube, C60, and other fullerenes were initially discovered in the debris of DC arc discharges. Therefore, the earlier preparations of the nanotubes used DC arc discharges with the graphite and the catalytic metal buried within the anode. In this process, the anode is packed with the metal catalyst and a carbon source. The ablation during an intense pulse of electric current produces high temperature and generates plasma, which contains ions and atoms of the eroded anode material. These ions and atoms nucleate the fullerenes. Later strategies used modified arc discharge, which synchronously arched and helium quenched plasma in an effort to increase the formation of graphite encapsulated metal particles and the formation of carbon nanotubes. Laser ablation of the anode was the next effort used to increase production.
In recent years, with the discovery of catalytic chemical vapor deposition (CCVD), the emphasis for mass production has shifted from arc discharge to CCVD techniques. CCVD involves the formation of carbon nanotubes by the catalytic decomposition of hydrocarbons on the surface of Fe, Co, and Ni nanoparticles. The CCVD technique is a continuous process, whereas the arc discharge process is a batch process. The continuous CCVD process is an ideal approach for the industrial synthesis of nanotubes, since CVD allows more strict control of processing conditions and CVD has demonstrated itself to be a useful method for industrial production of many other materials. Although the CCVD effort has increased the production rate, current CCVD methods still do not achieve the desired bulky formation rates.
Unfortunately, past attempts to increase growth rates of nanotubes by CVD have failed due to the poisoning of the catalytic nanoparticles. These attempts involved the older upscaling methods. The older upscaling methods involved changing reactor parameters such as increasing concentration, increasing temperature, and changing catalyst content so as to increase growth rate. These efforts have not been very fruitful for achieving commercial growth rates. Higher hydrocarbon concentrations cause poisoning of the catalyst. Poisoning is the loss of catalytic activity due to carbiding. Carbiding is the formation of metal-carbon chemical bonds on and within the catalytic metal nanoparticle. Supersaturation is the state of the metal nanocatalyst in which the carbon concentration exceeds the equilibrium concentration for carbon precipitation. High concentrations also contribute to multi-walled carbon nanotubes and the accumulation of amorphous carbon along the tube backbone. High growth temperature leads to impractical production cost. The adulteration of the catalyst can introduce impurities into the nanotube and broaden the size distribution. These problems of traditional upscaling arise because the catalytic mechanism of carbon nanotube growth involves novel phenomena alien to the older art.
The following synopsis provides a condensed overall disclosure of references on many of these difficulties associated with trying to apply the traditional art to the carbon nanotube mass production. The current state of understanding of the nanotube formation in terms of the older chemical mechanisms and the history behind developing strategies for addressing these difficulties are disclosed. The current level of technology for nanotube formation and growth is disclosed. Finally, the new revelation from this invention for mass production is presented. The new revelation is considered in details, giving a detailed account of: 1) the new process in comparison to older processes, 2) the new mechanism based upon the intrinsic magnetic field and the consequences of superposing and reinforcing by an external magnetic field and 3) the new design and apparatus. But, first the references are given below:
R. T. K. Baker et al., xe2x80x9cNucleation and Growth of Carbon Deposits from the Nickel Catalyzed Decomposition of Acetylene,xe2x80x9d Journal of Catalysis vol. 266, pp. 51-62 (1972) discloses the growth of graphite laminae from nickel particles (300 nm diameter) by the catalytic decomposition of acetylene at 1300K. Furthermore, they disclose terminated growth after 15 seconds at 870K upon the accumulation of amorphous carbon about the catalyst. The regeneration is reported after adding H2 at 1100K or O2 at 1000K. The filament formation is accounted for by acetylene adsorption and decomposition at one facet of the catalyst with subsequent internal carbon diffusion to and precipitation at an opposite facet of the particle. The diffusion process is disclosed as temperature and concentration driven.
J. C. Shelton et al., xe2x80x9cEquilibrium Segregation of Carbon to Nickel(111) Surface: A Surface Phase Transition,xe2x80x9d Surface Science vol. 43, pp. 493-520 (1974) discloses the precipitation on the (111) surface of Ni of at least three carbonaceous states: a high temperature dilute carbon phase, a condensed graphitic monolayer and a multilayered epitaxial graphite precipitate.
S. E. Stein and A. Fahr, xe2x80x9cHigh Temperature Stabilities of Hydrocarbon,xe2x80x9d Journal of Physical Chemistry vol. 89, pp. 3714-3725 (1985) discloses the thermodynamic stability of polyaromatic species relative to saturated hydrocarbons at 1500-3000K and further discloses possible pathways for hydrocarbon decomposition to polyaromatic species.
G. G. Tibbets et al., xe2x80x9cAn Adsorption-Diffusion Isotherm and Its Application to the Growth of Carbon Filaments on Iron Catalyst Particles,xe2x80x9d Carbon vol. 25, pp. 367-375 (1987) discloses that the concentration gradient drives the carbon diffusion through the catalyst particle. They further disclose the poisoning by the collision of the catalyst particle with a viscous hydrocarbon particle.
R. T. K. Baker et al., xe2x80x9cCatalytic Growth of Carbon Filaments,xe2x80x9d Carbon vol. 27, pp. 315-323() discloses that the adulteration of the catalyst with Cu leads to an increased rate of nanotube formation with branch nanotube nucleation and growth on a single catalyst particle. The symmetrical branching suggests the carbon filament develop from specific crystallographic planes of the catalyst particle.
Haddon et al., xe2x80x9cExperimental and Theoretical Determination of the Magnetic Susceptibility of C60 and C70,xe2x80x9d Nature vol. 350, pp. 46(1991) discloses the differing diamagnetic susceptibilities of C60, C70 and graphite. They disclose that the difference results from the 5 member paramagnetic rings, which counter the ring current of the diamagnetic C6 member ring. This opposing paramagnetic effect of the C5 member ring causes the following relative diamagnetic susceptibility: Graphite greater than C70 greater than C60. This decrease reflects the increasing ratio of 5 to 6 member rings.
Schnabel et al., xe2x80x9cEvidence of Low Pressure Catalysis in the Gas Phase by a Naked Metal Cluster: The Growth of Benzene Precursors on Fe4+,xe2x80x9d Journal of Physical Chemistry vol. 95, pp. 9688-9694(1991) discloses the catalytic capacity for Fe4+ to form benzene from ethylene and cyclopropane. Hence, the polynuclear aromatics can be formed from hydrocarbons at lower decomposition temperature due to catalysis.
Pan et al., xe2x80x9cReaction of Co1-4+ and Co4(CO)n with Cyclohexane: Cxe2x80x94H Activation as a Function of Cluster Size and Ligand Substitution,xe2x80x9d Journal of the American Chemical Society vol. 113, pp. 2406-2411(1991) discloses that the catalytic capacity of Co clusters depends on the cluster size, which reflects the nature of the frontier orbitals. They disclose the increased reactivity of the 3d transition metal clusters as being due to the lower spin in the frontier orbitals, which results in the greater influence of s orbitals. For second and third series transition metals, d orbitals play a stronger role. The accepting ability of the S orbital of the catalyst leads to the conversion of saturated hydrocarbons to polycylic aromatic hydrocarbon (PAH).
Endo and Koto, xe2x80x9cFormation of Carbon Nanofibers,xe2x80x9d Journal of Physical Chemistry,xe2x80x9d vol. 96, pp. 6941-6944(1992) discloses the existence of giant fullerenes and the growth by the insertion of sp2 carbon in the arc discharge process.
Saito et al., xe2x80x9cTopological Defects in Large Fullerenes,xe2x80x9d Chemical Physics Letters, vol. 195, pp. 537-541(1992) disclose the efficient bond rearranging reactions wherein the motions of five member and seven member ring pairs are demonstrated with subsequent annihilation by collision with a second five member ring.
Rodriquez et al., xe2x80x9cA Review of Catalytically Grown Carbon Nanofibers,xe2x80x9d Journal of Materials Res. Vol. 8, pp. 3233-3250(1993) discloses the preferential decomposition and graphitization on certain facets of the catalyst, discloses the hydrogen and sulfur promotion of catalysis, discloses the absence of carbide and discloses the importance of wetting of metal by graphite precipitate.
Ivanov et al., xe2x80x9cThe Study of Carbon Nanotubules Produced by Catalytic Methods,xe2x80x9d Chemical Physics Letters vol. 223, pp. 329-335 (1994) discloses the catalytic chemical vapor deposition of carbon nanotubes with Co as the best catalyst among Co, Fe and Ni catalysts.
Rose and Shore, xe2x80x9cElastic Constants of the Transition Metals from a Uniform Electron Gases,xe2x80x9d Physical Review B vol. 49 (17) pp. 11566(1994) discloses the trends in bond strength among the transition metals, demonstrating experimentally and computationally the unusual behavior of the ferro-metals.
Guerret-Piecourt et al., xe2x80x9cRelation between Metal Electronic Structure and Morphology of Metal Compounds Inside Carbon Nanotubes,xe2x80x9d Nature vol. 372, pp.761-764 (1994) discloses that the ability to encapsulate transition metals within carbon nanotubes depends on the incompleteness of the electronic shell in the most stable ionic state of the metal.
I. M. Billas et al., xe2x80x9cMagnetism from the Atom to the Bulk in Iron, Cobalt and Nickel Clusters,xe2x80x9d Science vol. 265, pp. 1682-1684(1994) discloses the atomic like magnetic moments of small Fe, Co and Ni clusters containing less than 30 atoms. Moreover, they disclose the oscillating moments in these nanoparticles due to surface induced spin density waves (Friedel waves). Furthermore, Fe clusters exhibit a temperature dependent phase transition between a high moment BCC phase and a low moment FCC phase.
H. Hjiki and T. Ando, xe2x80x9cEnergy Bands of Carbon Nanotubes in Magnetic Fields,xe2x80x9d Journal of Physical Society of Japan vol. 65, pp. 505(1995) discloses the splitting of electronic bands of carbon by a magnetic field normal to the tube axis.
Wang et al., xe2x80x9cCarbon Nanotube Synthesized in a Hydrogen Arc Discharge,xe2x80x9d Applied Physics Letters vol. 66, pp. 2430-2432(1995) discloses the formation of opened ended carbon nanotubes in the presence of H2.
Setlur et al., xe2x80x9cA Method for Synthesizing Large Quantities of Carbon Nanotubes and Encapsulated Copper Nanowires,xe2x80x9d Applied Physics Letters, vol. 63, pp. 345-347(1996) discloses the role of H2 in generating polycylic aromatic hydrocarbons during arc discharge and the ability of Cu to graphitize polycylic aromatic hydrocarbons (PAH).
Jia et al., xe2x80x9cPreparation and Properties of Ferromagnetic Carbon-Coated Fe, Co and Ni Nanoparticles,xe2x80x9d Journal of Applied Physics, vol. 80, pp. 103-108 (1996) discloses the interaction between Fe, Co and Ni catalysts and the graphite precipitate with graphitization occurring at 600xc2x0 C. for Fe and Co. But graphitization occurs at 900xc2x0 C. for Ni (in comparison to 3000K for xc2x0C.).
Chambers et al., xe2x80x9cInfluence of Copper on the Structural Characteristics of Carbon Nanofibers Produced from the Cobalt-Catalyzed Decomposition of Ethylene,xe2x80x9d Journal of Materials Res. Vol.11 pp. 430-437 (1996) discloses the ability of Cu in a Co/Cu alloy to enhance the growth rate of smaller nanotubes relative to the rate formed by pure Co. The enhanced formation of the smaller tubes is disclosed as resulting from the facilitation of surface reconstruction by carbide formation allowing multi-faceted particle surface morphology leading to bimodal growth and smaller nanotubes. Cu prevents graphitic overlayer and catalyst poisoning.
Colbert et al., xe2x80x9cGrowth and Sintering of Fullerenes Nanotubes,xe2x80x9d Science vol. 266, pp. 1218-1222(1995) discloses a mechanism for nanotube formation in arc discharge where in the absence of catalyst the tube opening is stabilized by the strong electric field of the plasma.
Seraphin et al., xe2x80x9cFilling the Carbon Nanocage,xe2x80x9d Journal of Applied Physics vol.80, pp. 2097-2104(1996) discloses the propensity for graphitic encapsulation of transition metals depends on the existence of its carbide, interfacial interaction and stability with the graphite shell and the processing conditions: 1) weak carbides are encapsulated as carbides, 2) unstable carbides are not encapsulated but form a graphitic cage, 3) stable carbides are not encapsulated, and 4) metastable carbides are not encapsulated but form nanotubes.
Host et al., xe2x80x9cGraphite Encapsulated Nanocrystals Produced Using a Low Carbon: Metal Ratio,xe2x80x9d Journal of Material Res. Vol. 12, pp. 1268-1273(1997) discloses the ability to encapsulate rather than form nanotubes by using high metal/carbon concentrations. The effect of particle size on the structure (high temperature fcc or low temperature phase) is also disclosed.
Kanzow et al., xe2x80x9cLaser Assisted Production of Multi-Walled Carbon Nanotubes from Acetylene,xe2x80x9d Chemical Physics Letters vol. 295, pp. 525-529 (1998) discloses the effect of freezing point depression by carbon on the catalyst and the effect of particle size on nanotube formation (smaller favor) to graphitic encapsulation (larger favor).
Kong et al., xe2x80x9cChemical Vapor Deposition of Methane for Single Walled Carbon Nanotubes,xe2x80x9d Chemical Physics Letters vol. 292, pp. 567-574(1998) discloses the importance of carbon source (CH4) to favoring single over multi walled nanotubes. This result is related to the effect low carbon concentration on increasing single wall nanotube formation.
Kanzow et al., xe2x80x9cFormation Mechanism of Single Walled Carbon Nanotubes on Liquid-Metal Particles,xe2x80x9d Physical Review B vol. 60, pp. 11180-11186(1999) discloses a nucleation model for carbon nanotube formation wherein the nanotubes nucleate from graphitic sheets parallel to the catalyst. The sheets undergo bending at the high synthesis temperature by coordinated vibrations to form domes, which grow by adding carbon from the catalyst.
Yokomichi et al., xe2x80x9cEffects of High Magnetic Field on the Morphology of Carbon Nanotubes and Selective Synthesis of Fullerenes,xe2x80x9d Applied Physics Letters vol. 74, pp. 1827(1999) discloses that magnetic fields up to 10T affect curvature of nanotubes and increase the ratio of C70 to C60.
T. Ando, xe2x80x9cSpin-Orbit Interaction in Carbon Nanotubes,xe2x80x9d Journal of the Physical Society of Japan vol. 69(6), pp. 1757(1999) discloses the use of effective mass Hamiltonian in the presence of a weak spin-orbit interaction in order to demonstrate a spin Zeeman energy due to magnetic field in both the circumference and axial directions.
M. F. Lin, xe2x80x9cMagnetic Properties of Chiral Carbon Toroids,xe2x80x9d Physica B vol. 269, pp. 43-48(1999) discloses the dependence of magnetic properties of chiral carbon toroids reflects the character of xcfx80 electronic states and discloses that at high magnetic fields the Zeeman effect strongly affects low energy electronic structures, causing drastic diamagnetic to paramagnetic transitions.
Grossman et al. xe2x80x9cTransition Metals and their Carbides and Nitrides: Trends in Electronic and Structural Properties,xe2x80x9d Physical Review B vol. 60, pp. 6343 (1999) discloses the increase in moduli of transition metals with increasing number of electrons for a given principle quantum number, discloses similar moduli for n=3,4 with increase for n=5 and discloses the similarity trends of moduli pure metal and the corresponding metal carbides.
B. W. Smith et al.,xe2x80x9cStructural Anisotropy of Magnetically Aligned Single Wall Carbon Nanotube Films,xe2x80x9d Applied Physics Letters vol. 77(5) pp. 663(2000) discloses the nanotubular alignment occurs using a 25T strong magnetic field; the alignment is such that the axis orients parallel with the external field; and the nanotubular annealing in the strong magnetic field at high temperature.
Van der Wal et al., xe2x80x9cDiffusion Flame Synthesis of Single Walled Carbon Nanotubes,xe2x80x9d Chemical Physics Letters vol.323, pp. 217-223(2000) discloses the importance of C2 species in the molecular path toward soot formation.
Andriotis et al. xe2x80x9cCatalytic Action of Ni Atoms in the Formation of Carbon Nanotubes: A Molecular Dynamics Study,xe2x80x9d Physical Review Letters vol. 85, pp.3193-3196 (2000) discloses the theoretically predicted ability of Ni atoms to stabilize defects along a nanotube backbone until carbon atoms displace the Ni to eliminate the defect. Ni mobility within and without the nanotube and the curvature effects on Ni binding are disclosed.
On the basis of these references, the understanding of the phenomena of carbon formation from hydrocarbon decomposition on metal surfaces has enormously evolved. During the last 25 years, these investigations have determined processing conditions leading to differing phenomena such as graphitic fiber formation, graphitic nanotubular formation, fullerene formation and graphitic encapsulation of metal particle. This progress has resulted in a larger scale selective production of carbon nanotubes with the exclusion of these undesired carbon products. However, currently the nanotubular production rate is not practical for commercialization. Furthermore, the detail mechanism is still unknown. The deficits in the older art result from attempts to understand this complex process by models that are too simple. Previous efforts to increase rates have failed, because new complicating factors are not accounted for by extending the older model to this more complicated system.
On the basis of these previous investigations, the mechanism has been interpreted by the older art consisting of a simpler chemical catalytic model involving: an adsorption of hydrocarbon to a catalytic facet of the catalyst; the decomposition of the hydrocarbon on this facet; the desorption of H2 from this decomposing facet; the diffusion of carbon into and through the catalyst; and finally the precipitation of graphite at some other facet of the crystal. The older art does not recognize the extreme sensitivity of these processes to temperature. The diffusion of carbon within the catalyst has been determined as the rate-limiting step. The carbon diffusion has been attributed to concentration and temperature gradients between the decomposing and graphitizing facets of the catalyst. The diffusion bottleneck to faster nanotube formation results in carbon supersaturation with subsequent carbiding and poisoning of the catalyst. Large temperature fluctuations cause supersaturation and poisoning under high carbon-concentration conditions. Currently during CCVD extended growth is interrupted by sporadic temperature fluctuation and poisoning, shortening growth time and productivity. Hence, efforts to increase reaction and formation rates by classical strategies of increasing the temperature and the concentration gradients have failed. Catalytic deactivation occurs as a result of the supersaturation caused by these older strategies. The supersaturation causes global precipitation with the formation of a carbonaceous overlayer at the catalytic facet. Although promoters such as S, Cu and H2 reduce the poisoning they still do not eliminate the poisoning. In addition to catalytic poisoning, these mass production efforts of the older art have failed due to competing formations of multiwalled nanotubes and amorphous carbon deposits, whereby the system alleviates the supersaturation by nucleating internal tubes and unhybridized amorphous carbon. These limitations of the existing nanotube preparation technology have limited the process to the formation of large quantities of shorter nanotubes with efforts to sinter the tubes to form longer tubes.
I have discovered a new CVD technique to reduce the poisoning, thereby allowing bulky formation of nanotubes. This discovery reduces carbon concentration in the catalyst and increases the carbon diffusion through the catalyst by slowing the carbon production, lowering the activation energy for carbon diffusion, and increasing the driving force for carbon diffusion rather than introducing supersaturating temperature and concentration conditions. This new approach therefore lowers interior and surface carbon concentrations and increases carbon flux, thereby reducing the tendency for supersaturation and poisoning. Furthermore, this new method binds the growing nanotube to the metal nanoparticle for a more extended growth period. This new art of CCVD is based upon my new mechanism. My new mechanism accounts for complicating factors, not included in the traditional upscaling strategies. My new mechanism modifies the previous model by accounting for magnetic effects of the catalyst.
The most efficient catalysts for nanotube formation are all ferromagnetic: Fe, Ni and Co. Paramagnetism is the attraction of a substance to a magnetic field due to unpaired electrons of atoms in the material. However, the atoms of paramagnetic substances do not self-orient. Diamagnetism is the repulsion of a substance by a magnetic field due to the pairing of electrons in the atoms making up the material. Ferromagnetism is a special case of paramagnetism where in the magnetic moment and exchange between atoms lead to the spontaneous orientation in the absence of an external magnetic field. The magnetic forces are usually weaker than the electric forces, so these magnetic effects have been ignored. This reasoning accounts for the exclusion of the magnetic factor by the older art. However, I attribute the unique catalytic abilities of Co, Fe and Ni for nanotubular formation to the large magnetic moments of these metals as nanoparticles. Such large moments produce an intrinsic magnetic field which decelerates decomposition of the hydrocarbon, lowers surface and interior carbon concentration below saturation limit, forces the H2 product away from the surface after the decomposition, pulls the resulting carbon atoms on the surface into the interior of the catalyst particle, increases and directs carbon mobility by lowering activation energy for diffusion, promotes graphitic crystallization at some lateral facet of the catalyst particle, bends the graphene sheet nucleating the nanotube, inhibits multi walled formation relative to single wall nanotubular growth and binds the growing tube to the nanoparticle. The magnetic field also restricts the graphitization to only one facet of the particle. Because of these serious effects of the magnetic field on the mechanism, the magnetic factor cannot be neglected. The new art is based upon a novel magnetic model and incorporates enhancing the phenomena by externally driving the phenomena by applying an external, strong magnetic field.
Based on my new mechanism, the magnetic field is crucial for nanotube formation and growth. Therefore, any effort to substantially increase growth rate must modify the magnetic field. My discovery pertains to using a strong external magnetic field to enhance the individual processes occurring during the formation and growth. Because the carbon diffusion is the rate-limiting step and the magnetic properties of the catalyst accelerate diffusion, this invention focuses upon using an external magnetic field to lower interior carbon concentration and lower the activation energy and increase the directional driving force for carbon mobility beyond the reductions caused by the intrinsic magnetic field. This technique is called MAGNETO CATALYTIC CHEMICAL VAPOR DEPOSITION.

Magnetic production of carbon nanotubes and filaments


A control unit that includes a braking system for fixing the position of an endoscope tip is provided. The control system includes an up-down control knob and a right-left control knob. The brakes are engaged by rotating the control knob itself counter-clockwise from a free wheeling position. After the brakes have been engaged, a sufficient amount of force applied to the control knobs will move the endoscope tip slightly in the corresponding direction, allowing for fine tuning of tip position after braking.

An endoscope is a medical instrument used for examining and treating internal body parts such as the alimentary canals, airways, the gastrointestinal system, and other organ systems. Conventionally used endoscopes have at least a flexible tube carrying a fiber optic light guide for directing light from an external light source situated at a proximal end of the tube to a distal tip. Also, most endoscopes are provided with one or more channels, through which medical devices, such as forceps, probes, and other tools, are passed. Further, during an endoscopic procedure, fluids, such as water, saline, drugs, contrast material, dyes, or emulsifiers are often introduced or evacuated via the flexible tube. A plurality of channels, one each for introduction and suctioning of liquids, may be provided within the flexible tube.
Endoscopes have attained great acceptance within the medical community since they provide a means for performing procedures with minimal patient trauma while enabling the physician to view the internal anatomy of the patient. Over the years, numerous endoscopes have been developed and categorized according to specific applications, such as cystoscopy, colonoscopy, laparoscopy, and upper GI endoscopy among others. Endoscopes are usually inserted into the body's natural orifices or through an incision in the skin.
In many endoscopes the distal end of an insertion tube is capable of being articulated by a steering mechanism that includes a pair of external control wheels coupled to steering cables mounted inside the insertion tube. Rotation of one of the control wheels produces an up or down deflection of the distal tip of the insertion tube while rotation of the second control wheel produces a left or right deflection of the insertion tube tip. By operating the two control wheels, the distal end of the insertion tube can be pointed at a desired target within the range of the instrument or maneuvered through a tortuous path of travel.
Further, the control wheels or knobs are locked through respective braking mechanisms, thereby causing the distal end of the insertion tube to be fixed in a desired position.
For example, German patent application DE 20 2011 109 769 UI, filed on Jul. 1, 2011 and assigned to the applicant of the present specification, discloses an endoscope having an articulation unit. The deflection of the articulation unit (also called curvature device), and thus of the distal end of the endoscope is effected by means of cables. In each case, two cables arranged opposite each other on the outer circumference of the articulation unit are connected to form a cable pair. The cable pairs are attached in such a way to cable drums that can be adjusted by rotary knobs so that the distal end of the articulation unit carries out a movement upwards or downwards (up/down; U-D) or a movement in a direction right or left (right/left; R-L).
When a human body is examined using an endoscope having an articulation unit, on occasions it can be advantageous to fix the deflection of the articulation unit. As mentioned, usually this is accomplished by means of a locking device, also called a brake, that prevents the cable drum(s) from rotating.
Known braking or locking devices often are of a complicated design. What is needed is an efficient braking system that enables an operating physician to easily fix the endoscope insertion tube tip in a desired position when required and just as easily move the tip in a desired direction.
There is therefore a need for a system that ensures smooth directional readjustment of right and left (or up and down) movement of the insertion tube tip after applying a brake for fixing the end position. There is also need for a watertight braking system that provides a complete separation of free movement and locking operations.

This patent is subject to a terminal disclaimer.

Endoscope control unit with braking system


Disclosed are reticle assemblies for use in electron-beam microlithography. An exemplary reticle assembly includes a scattering-stencil reticle portion and a scattering-membrane reticle portion that define respective portions of the overall pattern defined by the reticle assembly. The reticle portions desirably are mounted to a reticle frame to provide strength and rigidity to the assembly. By combining both types of reticles in a single reticle assembly, the shortcomings of each are minimized compared to a single reticle type by which the entire pattern is defined. Because fabrication processes for the two reticle types are different, the reticle types can be fabricated separately and then bonded to the reticle frame to form the reticle assembly. Also disclosed are electron-beam microlithography apparatus and methods that include use of such reticle assemblies. Compared to conventional reticle assemblies as well as conventional apparatus and methods using them, reticle assemblies as disclosed herein can reduce the need to stitch together complementary pattern portions and reduce chromatic aberrations.

This disclosure pertains to microlithography, which involves projection-transfer of a pattern, defined by a reticle or mask, to a xe2x80x9csensitivexe2x80x9d substrate using an energy beam. By xe2x80x9csensitivexe2x80x9d is meant that the substrate is imprintable with an image carried from the reticle to the substrate by the energy beam. More specifically, this disclosure pertains to reticles as used in microlithography in which the energy beam is an electron beam.
As noted above, in projection microlithography the pattern is defined on a reticle or mask (termed a xe2x80x9creticlexe2x80x9d herein) and is projected onto the sensitive substrate. For electron-beam (EB) microlithography, various types of reticles have been devised, including xe2x80x9cabsorptionxe2x80x9d reticles and several types of xe2x80x9cscatteringxe2x80x9d reticles.
Scattering reticles generally are of two types: xe2x80x9cscattering-stencilxe2x80x9d reticles and xe2x80x9cscattering-membranexe2x80x9d reticles. A scattering-stencil reticle comprises an electron-beam-scattering (EB-scattering) membrane, usually made of silicon (Si), that defines pattern elements by corresponding EB-transmissive through-holes in the membrane. A scattering-membrane reticle comprises a thin EB-transmissive membrane, usually made of silicon nitride (SiN), on which pattern elements are defined by corresponding portions (xe2x80x9cscattering bodiesxe2x80x9d) of a thin EB-scattering layer (e.g., tungsten (W) or chromium (Cr)) on the SiN membrane. An xe2x80x9cabsorptionxe2x80x9d reticle is constructed similarly to the scattering-membrane reticle, except that pattern elements are defined by corresponding xe2x80x9cabsorption bodiesxe2x80x9d of a EB-absorbing material (e.g., heavy metal) on a EB-transmissive membrane.
A scattering reticle is used in a different manner than an absorption reticle. With an absorption reticle, portions of the incident beam are absorbed by the EB-absorbing bodies, which can cause localized heating of the reticle. With a scattering reticle, in contrast, the incident electron beam is scattered (mostly forward-scattered) as it passes through various portions of the reticle, rather than being absorbed by the reticle. The resulting scattering contrast defines pattern elements as imaged on the substrate. Since few of the incident electrons are absorbed, the temperature of a scattering reticle can be kept relatively low compared to an absorption reticle, with a corresponding increase in the accuracy of pattern transfer.
With a scattering-stencil reticle, the incident electrons that pass through the through-holes of the reticle (and that do not interact with the reticle and become scattered, for example) are used for transfer and exposure. Hence, the full capacity of the EB-optical system can be used, with a corresponding increase in imaging resolution. A disadvantage of scattering-stencil reticles, however, is the fact that certain pattern elements (e.g., donut-shaped elements, peninsular-shaped elements, certain longitudinally extended elements) cannot be defined entirely in a single corresponding portion of the reticle. Rather, complete definition of such a pattern element on the reticle requires use of complementary portions of the reticle each defining a respective portion of the element. As exposed onto the substrate, the images of the complementary pattern portions must be xe2x80x9cstitchedxe2x80x9d together properly to create the entire respective pattern element. The unusually high stitching accuracy required poses a problem with using this type of reticle.
Scattering-membrane reticles also have problems, notably the fact that some of the energy of the incident electrons passing through the thin EB-transmissive membrane is absorbed by the scattering bodies. This energy absorption not only increases the temperature of the reticle but also results in increased chromatic aberration of the electron beam propagating downstream of the reticle. I.e., the chromatic aberration arises from energy of the incident beam being absorbed by certain regions of the reticle relative to other regions.
In view of the foregoing, an object of the invention to provide, inter alia, scattering-reticle assemblies for use in electron-beam (EB) microlithography of a pattern, defined by the reticle assembly, to a substrate. An embodiment of such a reticle assembly comprises at least one scattering-stencil reticle portion defining a respective portion of the pattern, and at least one scattering-membrane reticle portion defining a respective portion of the pattern. Typically, the reticle assembly is of a xe2x80x9cdividedxe2x80x9d reticle, wherein each of the scattering-stencil reticle and scattering-membrane reticle portions is segmented into respective subfields. Also, the reticle assembly desirably further comprises a support frame, wherein the at least one scattering-stencil reticle portion and the at least one scattering-membrane reticle portion are bonded to respective locations on the support frame.
Each scattering-stencil reticle portion typically comprises a respective reticle membrane made of silicon, wherein pattern elements are defined by respective through-holes in the reticle membrane. Each scattering-membrane reticle portion typically comprises a respective reticle membrane made of Si, SiC, SiN, carbon, diamond, BN, or a mixture thereof. Each scattering-membrane reticle portion typically further comprises a respective pattern-defining layer on the respective reticle membrane. The pattern-defining layer desirably is made of a material such as chromium (Cr), tungsten (W), tantalum (Ta), or a mixture thereof. Further desirably, each respective pattern-defining layer has a transmittance to electrons of an incident electron beam of no more than one-tenth of the respective reticle membrane.
The reticle assembly can comprise a first scattering-stencil reticle portion, a second scattering-stencil reticle portion, and a scattering-membrane reticle portion. In such a configuration, the second scattering-stencil reticle portion usually comprises subfields defining respective pattern features that are complementary to respective pattern features defined in subfields of the first scattering-stencil reticle portion.
Also provided are EB microlithography apparatus. An embodiment of such an apparatus includes an illumination system, a projection system, and a scattering-reticle assembly. The illumination system is situated and configured to receive an illumination beam from an EB source and to direct the illumination beam to a selected region on the reticle assembly. The projection system is situated and configured to direct a portion of the beam passing through the reticle assembly to a substrate. The scattering-reticle assembly is situated on a reticle stage so as to be illuminated by the illumination beam. The scattering-reticle assembly comprises at least one scattering-stencil reticle portion defining a respective portion of the pattern, and at least one scattering-membrane reticle portion defining a respective portion of the pattern. Each of the scattering-stencil reticle and scattering-membrane reticle portions of the reticle assembly can be configured as summarized above with respect to reticle assemblies.
Also provided are improvements to EB microlithographic exposure methods in which an electron beam is directed to a reticle assembly (that defines a pattern) by which the beam acquires an ability to form an image of the pattern on a substrate. On the reticle assembly a first pattern portion is defined on at least one scattering-stencil reticle portion, and a second pattern portion is defined on at least one scattering-membrane reticle portion. Using the electron beam, the pattern portions from each reticle portion are transferred to the substrate so as to produce a stitched-together image of the pattern on the substrate.
Characteristic of a divided reticle assembly, each of the reticle portions typically is divided into respective subfields each defining a respective portion of the pattern. With such a reticle assembly, the step of transferring the pattern portions comprises exposing the subfields individually to respective locations on the substrate so as to stitch together images of the respective portions of the pattern on the substrate. Also, each of the scattering-stencil reticle and scattering-membrane reticle portions of the reticle assembly can be configured as summarized above with respect to reticle assemblies. In general, each scattering-stencil reticle portion comprises a respective reticle membrane defining pattern elements by respective through-holes in the reticle membrane, and each scattering-membrane reticle portion comprises a respective reticle membrane including a pattern-defining layer made of a material different from a material used to form the respective reticle membrane.
Also provided are apparatus for performing a fabrication process on a wafer as required to produce a microelectronic device on the wafer. An embodiment of such an apparatus comprises an EB optical system and a scattering-reticle assembly situated relative to the EB optical system and defining a pattern that is projection-transferred to a substrate by an energy beam passing through the EB optical system. The scattering-reticle assembly comprises at least one scattering-stencil reticle portion defining a respective portion of the pattern, and at least one scattering-membrane reticle portion defining a respective portion of the pattern. The scattering-reticle assembly can further comprise a support frame, wherein the at least one scattering-stencil reticle portion and the at least one scattering-membrane reticle portion are bonded to respective locations on the support frame. Each of the scattering-stencil reticle and scattering-membrane reticle portions of the reticle assembly can be configured as summarized above with respect to reticle assemblies.
Also provided are methods for fabricating a reticle assembly defining a pattern to be transferred microlithographically to a substrate using an electron beam. In an embodiment of such a method, a scattering-stencil reticle portion is fabricated that defines a first portion of the pattern. Also, a scattering-membrane reticle portion is fabricated that defines a second portion of the pattern. The scattering-stencil reticle portion and the scattering-membrane reticle portion are attached to a reticle frame. Each of the scattering-stencil reticle and scattering-membrane reticle portions of the reticle assembly can be configured as summarized above with respect to reticle assemblies.
With any of the reticle assemblies summarized above, the need to stitch together complementary pattern portions on the reticle is not increased over the need experienced with conventional reticles. In fact, the need for such stitching usually is reduced compared to what is encountered with conventional scattering-stencil reticles. In addition, reticle assemblies as summarized above do not produce increased chromatic aberrations. Hence, by including at least one of each type of scattering reticle on a single reticle assembly, it is now possible to compensate for the shortcomings of the two types of scattering reticles.
The foregoing and additional features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.

Scattering-reticle assemblies for electron-beam microlithography including a scattering-stencil reticle portion and a scattering-membrane reticle portion


A method for performing a corneal ablation procedure on an eye of a patient including determining a refractive correction for the eye and determining a first parameter corresponding to the refractive correction or a condition of the patient. An ablation profile is selected that includes a refractive correction component and a pre-compensating component that is selected based on the first parameter. The ablation profile is configured to promote a controlled induction of a higher order aberration, where the pre-compensating component limits the induction of the higher order aberration to be within a predefined range. The cornea is ablated using the selected ablation profile.

Spherical aberration (SA) and other higher order aberrations (HOA) can be beneficial to a person's vision because it can result in an increase in depth of field. SA is a naturally occurring aberration in all human eyes, and as a result, the visual cortex has developed the ability to process a retinal image that has been slightly degraded by the presence of spherical aberration to sharpen the perceived image. Depth of field is increased by the ability of the visual cortex to process spherical aberration, and allow objects to be perceived to be in focus over a greater range of focal distances. Both negative and positive spherical aberration have a similar effect of increasing depth of field.
While some SA is beneficial, too much spherical aberration can be detrimental to the quality of vision. For example, patients with too much spherical aberration can experience decreased contrast sensitivity and night vision disturbances. The inventors of the present application have concluded that there is a maximum tolerable level of SA above which the brain's natural neural processing can no longer sharpen the retinal image to produce a clear perceived image in the mind.
Corneal excimer laser ablation profiles induce spherical aberration because of healing and biomechanical responses such as, e.g., paracentral stromal thickening and epithelial thinning, and to a lesser extent uncertainties in the ablation, e.g., due to fluence and projection. The amount of induced spherical aberration caused by the laser ablation profile is correlated to the magnitude of refraction treated, where higher refractions induce more spherical aberration. The correction of myopic refraction induces negative spherical aberration, whereas the correction of hyperopic refraction induces positive spherical aberration (using Malacara notation).
The effects of inducing spherical aberration and other higher order aberrations can also be important in patients that have been implanted with an intraocular lens (IOL). An IOL is an implanted lens in the eye to typically replace the existing crystalline lens because it has been clouded over by a cataract. Alternatively, an IOL may be implanted as a form of refractive surgery to change the optical power of the eye and correct for refractive errors. The IOL usually consists of a small synthetic lens with side struts, which are commonly referred to as haptics and are useful in holding the lens in place within the capsular bag or posterior chamber or anterior chamber of the eye. Modern IOL are made of flexible materials and are typically configured as fixed monofocal lenses designed to correct distance vision to plano although other types are available, such as multifocal IOLs and accommodative IOLs. Even though IOLs enable many patients to reduce their dependence on glasses, most patients still rely on glasses for certain activities, such as reading.
U.S. Patent Application Publication No. 2006/0195074 A1, to Bartoli describes an excimer LASER unit and relative control method for performing corneal ablation for partially correcting presbyopia that includes introducing an amount of SA to the eye of a subject. Although this and other similar methods are generally supportive to patient's vision, the uncontrolled induction of SA, for example, as described by Bartoli, has been known to result in poor contrast sensitivity for some patients, un-tolerated loss of visual acuity for far vision, or non-beneficial blur at different viewing distances.

Method for increasing ocular depth of field


The present disclosure provides a disinfecting device for a central air conditioner, which uses high-powered ultraviolet rays to efficiently and rapidly eliminate viruses, and uses two sets of parallel reflectors to reflect and overlap light curtains of the high-powered ultraviolet rays back and forth. In this way, small-sized aerosols with viruses can be eliminated, and no secondary pollutants such as ozone are produced in a process of purifying and disinfecting air by the ultraviolet rays. The entire device has a simple structure and can be used in the central air conditioner with an existing architecture. The entire device only needs to be provided in an air supply duct of the central air conditioner.

Dust in a central air-conditioning system can serve as media for viruses and bacteria to spread pathogens to rooms with people, causing epidemic of respiratory infectious diseases via airborne transmission. In addition, particulate matters in ventilation ducts, microbial aerosols produced by cooling towers and humidifiers, dust mites deposited on a surface of air filters, and the like are also very likely to spread in crowded office buildings, endangering the health of people.
Conventional indoor disinfection methods are performed by using disinfectant, ultraviolet lamps, air purifiers, and the like. In the disinfecting device for the central air conditioner, a plasma photocatalytic method using nanomaterials is often used. The principle is to dispose a nanomaterial of titanium dioxide (TiO2) on an electrode plate of the purification device to form a titanium dioxide film with a high specific surface area and high oxidability. Ultraviolet rays with a wavelength (350 to 400 nm) emitted when the plasma is discharged under a low temperature are used to generate active substances with high performance, and the active substances are combined with the hydroxyl radicals of the plasma, causing a composite catalytic oxidation effect. The device has a complex structure and a better function of removing large suspended particles in the air, but it cannot effectively extinguish the extremely tiny suspended particles with viruses in the air, for example, aerosols. In addition, the entire device is very complex and needs professional maintenance, and its functions of air purification and disinfection will also fade away with time.
Currently, common indoor disinfection devices are the ultraviolet lamps and the air purifiers. The ultraviolet lamps eliminate viruses by using ultraviolet rays emitted by mercury lamps. The ultraviolet rays emitted by mercury lamps contain a larger amount of power, and if no protective measures are taken, great harms are likely to be caused to the human body. In addition, the ultraviolet lamps will also generate ozone, causing secondary pollution. Therefore, the ultraviolet lamps are often used at night with no humans around, and cannot work uninterruptedly around the clock. Currently, purification technologies using plasmas and powerful filters are usually applied to the air purifiers with disinfection functions on the market. This method is only suitable for a condition with large suspended particles in the air, and the purification efficiency is low. In large crowded offices, air purification and disinfection effects are poor, and therefore, the method is not suitable for the central air conditioner.
An effective disinfection device applicable to the central air conditioner urgently needs to be provided.

Disinfecting device for central air conditioner

HUAZHONG UNIVERSITY OF SCIENCE AND TECHNOLOGY


Embodiments include devices and methods for providing secure communications between a first computing device and a second computing device are disclosed. A processor of the first computing device may determine in a first application software first security key establishment information. The processor may provide the first security key establishment information to a communication layer of the first computing device for transmission to the second computing device. The processor may receive, in the first application software from the communication layer of the first computing device, second security key establishment information received from the second computing device. The processor may determine a first security key by the first application software based at least in part on the second security key establishment information. The processor may provide the first security key to the communication layer for protecting messages from the first application software to the second computing device.

ProSe is a protocol that has been standardized by 3GPP to provide secure negotiation and set up of secure communications, including identifiers (IDs) to identify the security credentials or keys used in establishing secure communication links. However, ProSe has not yet addressed the emerging vehicle-to-anything (V2X) use cases for authenticating devices interested in establishing secure direct (or unicast) communication links and establishing necessary keys to protect the communication links.

Providing secure communications between computing devices


A method and system to help address this issue. When a device is within coverage of a cell that operates with a particular TDD configuration, the device will determine based on its location a set of one or more TDD frame configurations that the device would support, which could be based on maximum uplink transmission power of the UE, permitted maximum transmission power in the location, and uplink duty cycle defined by each of the various TDD configurations. The UE will then control whether or not it will be served by the cell based on whether the TDD configuration of the cell is within the determined set.

A typical wireless communication system includes one or more base stations, each radiating to define one or more cells in which user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped devices (whether or not user-operated) can operate. Further, each base station of the system may then be coupled or communicatively linked with network infrastructure such as a switch and/or a gateway that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a UE within coverage of the system may thus engage in air interface communication with a base station and thereby communicate via the base station with various remote network entities or with other UEs served by the system.
In general, a wireless communication system may operate in accordance with a particular air interface protocol or radio access technology (RAT), with communications from a base station to UEs defining a downlink or forward link and communications from the UEs to the base station defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Long Term Evolution (LTE) (using Orthogonal Frequency Division Multiple Access (OFDMA) on the downlink), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), Global System for Mobile Communication (GSM), WI-FI, and BLUETOOTH. Each protocol may define its own procedures for registration of UEs, initiation of communications, handover between cells, and other functions related to air interface communication.
In accordance with the air interface protocol, each of the one or more cells of such a system may operate on a respective carrier, which could be frequency division duplex (FDD) or time division duplex (TDD), defining one or more frequency channels each typically within an industry standard frequency band. An FDD carrier defines separate frequency channels for downlink and uplink communication, so that UEs can engage in downlink and uplink communication. Whereas, a TDD carrier defines a frequency channel multiplexed over time (e.g., on a recurring basis) between downlink and uplink use, so that UEs can engage in downlink communication in only particular time intervals and uplink communication in only other time intervals.
Each carrier in such a system may also define a number of sub-channels for carrying information between the base station and UEs. For instance, each carrier may define a pilot channel, reference channel or other resource on which the base station can broadcast a pilot signal, reference signal, or the like that UEs may detect as an indication of coverage and may measure to evaluate coverage. Further, each carrier may define a downlink control channel for carrying scheduling directives and other control signaling from the base station to UEs, and an uplink control channel for carrying service requests and other control signaling from UEs to the base station, and each carrier may define downlink and uplink traffic channels or the like for carrying bearer traffic between the base station and UEs.
When a UE initially enters into coverage of a wireless communication system (e.g., powers on in coverage of the system), the UE may scan for a strongest (e.g., highest signal-to-noise ratio) reference signal, defining a strongest cell. Further, the UE may read system information broadcast from the base station in that cell and may engage in a process to register itself to be served by the base station's cell and generally by the system.
In an example process, for instance, the UE and base station may first engage in signaling to establish a radio-link-layer connection between the UE and the base station, the UE may then transmit an attach, registration, or association request message on an uplink control channel of the cell, and the base station and/or supporting infrastructure may then authenticate and authorize the UE for service, establish a record indicating where in the system the UE is operating, establish local profile or context records for the UE, and provide an attach accept message to the UE. The UE may then be served by the base station's cell in an idle mode or a connected mode.
Further, while a UE is served by a base station's cell, the UE may also monitor the signal strength of that cell and of other cells in an effort to ensure that the UE continues to operate in a best (e.g., strongest) cell. If the UE detects that its serving cell becomes threshold weak and/or that another cell is threshold strong (e.g., threshold stronger than the serving cell), then the UE may hand over from being served by its current cell to being served by the other cell. For instance, the UE may transmit to its serving base station a measurement report indicating the other detected cell, and the base station and/or supporting network infrastructure may responsively process handover of the UE from the serving cell to the other cell. Alternatively, the UE may engage in idle handover by itself to the other cell and possibly transmit a location area update or tracking area update to the network to notify the network where the UE is now operating.

Method and system for controlling UE operation based on TDD configuration support per location


The device which forms the object of the present invention comprises flat element (1) more than half of which is subdivided longitudinally into two parts (2 and 3). The external faces of the element (1) are provided with longitudinal grooves (4) and the internal faces are provided with longitudinal parallel ribs (5). The element (1) is embraced by a bridge piece (6) with laterally projecting wings (7) and a number of inner ribs (8) which slide within the grooves (4). To seal the opening of the container the lips of the opening are simply fitted between the two parts (2 and 3). Once in this position, the bridge piece (6) is simply pushed along by pressing the projections (7) with the fingers such that as it advances, guided by the coupling which exists between the ribs (8) and the grooves (4), it applies pressure on the opening until it is perfectly sealed, the presence of the ribs (5) eliminating any tendency of the new seal to slip.

In recent years the industry of containers for domestic liquids, such as milk, wine, water, fruit juices etc., has undergone significant developments, allowing it to move on from the traditional glass bottle to other types of container.
Among these, the one which appears to have received greatest acceptance is the polyhedral, generally prismatic container made of a sandwich of cardboard or other materials and known by the name "tetrapak".
This container has a number of advantages in terms of both containing the liquid and transporting it, as well as its resistance to breakage. One inconvenience, and perhaps the only one, is the fact that once the container has been opened by cutting one of its vertices it is not possible to close it again. For this reason the liquid it contains remains in permanent contact with the outside until it has been completely consumed.
This causes problems in the case of some of the liquids contained such as fruit juices which are oxidised by contact with the air and lose their properties.
There is also the danger of spillage of the contents due to the fact that the container is always open, meaning that it is better that the liquid be consumed as soon as possible.


The invention comprises a catalyst compound of formula Zr(L)(A1)(A2)(A3) where L represents a ketoamide ligand, A1, A2 & A3 may be the same or different and each represent a ligand derived from a compound selected from the group consisting of:—an alcohol, a polyol, an alkyl acetoacetate, a diketone, a ketoamide, a carboxylic acid or ester thereof, an alkanolamine, a phosphoric acid ester and a sulphonic acid or ester thereof. The compound may be made by the reaction of a zirconium alkoxide or haloalkoxide with a ketoamide. The compound is useful as a catalyst for the reaction of a polyisocyanate with a hydroxyl-containing compound, e.g. for the manufacture of polyurethanes or composite cellulosic materials such as fibre-boards.

Polyurethanes are typically made by reacting a polyisocyanate compound with a polyol in the presence of an organometallic catalyst. Catalysts for polyurethane manufacture are conventionally based on tin compounds such as dibutyl tin dilaurate or compositions of mercury such as phenyl mercuric neodecanoate. More recently, compounds based upon metals such as titanium or nickel have been used.
Compounds of titanium, zirconium, hafnium, iron (III), cobalt (III) or aluminium were described in WO2004/044027. Such compounds are of general formula RO-M(L1)x(L2)y(L3)z where R is alkyl or a hydroxy-alkyl, hydroxyalkoxyalkyl, or (hydroxy)polyoxyalkyl group and up to 2 of L1 to L3 may represent an amide of acetoacetic acid. These compounds have a single labile —OR ligand and were believed to function as a cure catalyst by exchange or insertion of the polyol or of the isocyanate at the labile site on the organometallic composition, by displacement of the OR group.
U.S. Pat. No. 5,846,897 discloses zirconium compounds with diketones or alkylacetoacetates which catalyse the isocyanate—alcohol reaction having the chemical structure: Me (X1, X2, X3, X4) wherein Me is zirconium (Zr) or hafnium (Hf) and X1, X2, X3, and X4, are the same or different and selected from the group consisting of a diketone and an alkylacetoacetate having the structures: R1COCH2COR2 and R1OCOCH2COR2 wherein each of R1 and R2 is a branched or linear C1-C20 hydrocarbon and at least one of X1, X2, X3, and X4 is a diketone with structure (II) wherein the total number of carbons in R1+R2 is at least 4. Patil et al (J. Mater Chem 2003, 13, 2177-2184) have used zirconium bis(isopropoxide)bis(N,N-diethylacetoacetamide) as a precursor for the metal-organic chemical vapour deposition of zirconium dioxide.
It is an object of the invention to provide an alternative catalyst for making polyurethanes.

Zirconium compound, catalyst and its use for polyurethane manufacture


Apparatus and systems, as well as methods and articles, may operate to detect radio-frequency energy at a frequency associated with at least one wireless networking channel and to transmit a data frame responsive to determining that the radio-frequency energy is not associated with a wireless networking transmission.

Wireless networking devices may contend for access to a shared radio-frequency (RF) spectrum by following protocol rules. The rules may be designed to increase the likelihood of access by active devices. For example, some devices, such as those operating according to protocols including an Institute of Electrical and Electronic Engineers (IEEE) 802.11 protocol, may perform a transmission back-off operation that includes delaying transmission when a busy communications medium is detected. To reduce the probability of data collisions (caused by two or more transmitters operating at the same time during an idle period following a busy period), such devices may randomly choose a particular back-off delay period (one or more time "slots") within a maximum delay period, referred to as the "contention window."
The contention window may grow exponentially according to the protocol as the wireless networking device senses recurring instances of a busy medium condition and/or performs a back-off in response to each instance. The device may sense the busy medium condition by detecting RF energy in a received spectrum, perhaps originating from other wireless networking devices transmitting on the same channel(s), utilizing the same modulation technique, and/or obeying the same protocol (hereinafter referred to as "coherent energy"). On the other hand, in-band received energy may originate from an interference source (e.g., a microwave oven) not participating in the protocol. Such interference source operation may cause the contention window associated with the device to reach a maximum value, preventing and/or reducing transmissions from the device. System throughput may decrease as a result.
For more information regarding IEEE 802.11 standards, please refer to "IEEE Standards for Information Technology—Telecommunications and Information Exchange between Systems—Local and Metropolitan Area Network—Specific Requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY), ISO/IEC 8802-11: 1999" and related amendments.

Interference adaptation apparatus, systems, and methods


Provided are multi-tread vehicles and methods of operating such vehicles to access small interior spaces. A multi-tread vehicle may include two or more tread sections such that each pair of adjacent tread sections is interconnected by a connector section. Furthermore, each pair may have one or more degrees of articulations, such as being pivotable with respect to each other around one or more axis and/or being bendable with respect to each other around one or more axis. These articulation degrees may be provided by the connector section and/or by couplings between the connector section and each tread section. In some embodiments, each tread section may include two portions detachably coupled to each other. This detachable coupling may be used for disassembly of the multi-tread vehicle after or even during its use, for example, when only a portion of the vehicle needs to be retrieved from an interior space.

Accessing small interior spaces, such as wing bays, during assembly and/or maintenance can be challenging. In many cases, workers access such interior spaces through various access ports, such as ports formed in the bottom skin panels of the wings and through the wing ribs. This type of human access requires sufficient large ports, which puts limitation on scaling of various components. For example, a certain minimal wing thickness is needed for access. Furthermore, external access ports need to be closed and even sealed during operation of aircraft. Finally, many interior spaces have uneven topography such as internal ribs extending from wing skin panels, which makes it difficult to navigate robotic systems during access. What is needed is a system for accessing small interior spaces, such as wing roots and wing tips, and capable of navigating within these spaces which would allow reduction in the number and/size of access ports.

Multi-tread vehicles and methods of operating thereof


A binding method of a perfect-bound booklet includes the steps of folding each leaf of sheets forming a body to obtain multiple signatures; pressing creased parts of the multiple signatures in a thickness direction thereof; jogging a one-book bundle formed of a predetermined number of signatures forming a body, a front cover, and a back cover, or a multi-book bundle formed by stacking a plurality of one-book bundles on top of one another; applying a first adhesive that remains flexible upon curing, in a layer in a middle area 5 to 10 millimeters from both top and bottom ends of a rear face of the one-book bundle or the multi-book bundle; applying a second adhesive on the entire rear face; and drying and curing the second adhesive for a predetermined drying time.

A perfect-bound binding method, in which a body is composed of a layered product formed by jogging, stacking, and bundling a predetermined number of sheets, and then applying an adhesive on a rear face of the body, and if needed, in the vicinity of the face to attach a front cover to the body, is also adopted to bind notebooks or other kinds of booklets. As described above, in this binding method, an adhesive is applied on a face of the rear side (rear face) of the body to fix the back of the body. Hence, the booklet can be opened to the right and left from its joint, and the method is known to have advantages such as lower cost than saddle stitching binding, and more freedom in the number of sheets forming the body.
However, in this binding method, a rear end part of each sheet of the body is arranged and fixed perpendicular to the applied adhesive layer. For this reason, when an arbitrary page of the booklet is opened, normally, each sheet having its end fixed substantially perpendicular to the adhesive layer bulges upward particularly in the vicinity of the joint part, and therefore the sheets of the opened right and left pages do not open substantially 180 degrees. Thus, there has been a problem of insufficient spreading.
Additionally, in recent years, in binding of a perfect-bound booklet, a hot-melt type adhesive has been often used to attach the front cover to the rear face of the body. When the adhesive is applied, the low-viscosity adhesive melted by heating flows into the joint part between the body and the flyleaf (front cover), where the front cover and the rear end part of the first sheet in contact with the front cover are bonded. This causes a problem that the first sheet of the body cannot be opened favorably. Moreover, to improve adhesion of the sheets of the body and prevent them from dropping from the booklet, a kerf, a slit or the like substantially parallel to the thickness direction of the body is provided in the rear part of the body, and the sheets are bonded with an adhesive (notched or burst binding). Providing the kerf, slit or the like is effective in improving the adhesiveness of the sheets of the body to the inner face of the back part of the front cover. However, there has also been a problem that the adhesive infiltrates the inside of the body through the kerf to bond rear areas of the joint of adjacent sheets, whereby the pages cannot be spread 180 degrees.
As a result of extensive studies to solve the above problems, the applicant has developed a perfect-bound booklet (see Patent Literature 1) that can be spread favorably with right and left pages opened substantially 180 degrees without the vicinity of the joint part bulging upward when an arbitrary page of the body is opened, and the applicant has placed the product on the market as a flat notebook (registered trademark). The binding method described in Patent Literature 1 is aimed to bind a booklet in which an arbitrary folded signature in the body does not come off and drop from the body, and in a quality check after binding, the bonding strength of the rear glue has been checked thoroughly to see whether a signature does not come off and drop from the body.
However, recently, there have been many user requests for a perfect-bound booklet having contradictory functions of preventing a signature of the body from coming off and dropping in a normal state, but allowing a signature or a leaf to be cut off from the bottom of the joint when necessary, like a block memo pad.
Note that in the specification, "edge" of a booklet refers to a cut end (front edge) parallel to a spine of the booklet. In addition, "bundle" in "one-book bundle" or "multi-book bundle" collectively refers to a body formed of a predetermined number of sheets, a front cover, and a back cover.


In an example embodiment, cohort-based generalized linear mixed effect model (GLMIX) training is performed to identify patterns across cohorts of users, rather than slicing across all users blindly without accounting for common characteristics of users. Thus, rather than performing GLMIX training at just the finest granular level (e.g., user-level and job-level) or the highest level (global level), a “medium” level of granularity is used to train the GLMIX model at cohort-level.

The rise of the Internet has occasioned an increase in the use of these online services to perform searches for jobs that have been posted on or linked to by the online services.
These job searches may either be performed explicitly by, for example, a user typing in a search query looking for particular jobs, or implicitly, by presenting the user with job listings the system thinks the user will be interested in. The latter may be presented in an area of a graphical user interface termed "Jobs You May Be Interested In."
In either the implicit or explicit case, results are presented based on scoring of potential results using a machine-learned model. In the case of explicit searches, the explicit search query is a large factor in the scoring of the results (which would evaluate match features such as how often terms that appear in the query appear in the results). In the case of implicit searches, match features are not used as no explicit search query is provided, but other features may be evaluated to score the results. These include global features, per-user features, and per-job features.
Historically, algorithms to rank job search results in response to an explicit query have heavily utilized text and entity-based features extracted from the query and job postings to derive a global ranking. However, when such global ranking algorithms are modified to improve certain queries, other queries tend to become degraded. Specifically, the queries that often become degraded are those where personalization is desired. When such text and entity-based features are more difficult to obtain, such as where no explicit query is provided, implicit features may be used.

Cohort-based generalized linear mixed effect model


A constant velocity joint for a drive system includes: an outer joint member and an inner joint member, each having a plurality of ball grooves, the ball grooves consisting of a first group of grooves of a skewed groove shape with a first skew angle other than zero and alternately arranged in opposite directions relative to an axis of rotation of the outer and inner joint members, and a second group of grooves of a skewed groove shape with a second skew angle other than zero and alternately arranged in opposite directions relative to an axis of rotation of the outer and inner joint members, the second skew angle less than the first skew angle. In addition to the differentiated skew angles, the contact angles of the balls in the first and second group of grooves may also be differentiated.

A cross groove type constant velocity joint (hereinafter to be referred as a "cross groove joint") is one type of constant velocity universal joints used for transmitting rotational torque between the rotating shafts (i.e., the driving shaft and the driven shaft), typically for the drive system of automobiles. The cross groove joint includes an outer joint member with a plurality of ball grooves formed on the inner surface thereof, and an inner joint member with a plurality of ball grooves formed on the outer surface thereof, in which the corresponding ball grooves of the outer joint member and the inner joint member are configured to pair with each other and slanted with the same skew angle and in opposite directions with respect to the center or rotating axis of the joint.
FIGS. 1-2 illustrate one example of a conventional cross groove type joint which retains six balls in the ball grooves for transmitting the rotational torque between the outer and inner joint members to drive the drive system. This cross groove joint includes an outer joint member 1 with six grooves formed on the inner surface thereof, an inner joint member 3 with six grooves formed on the outer surface thereof, six balls 2 retained in the pared grooves of the outer and inner joint members for torque transfer between the outer and inner joint members 1 and 3, and a cage 4 configured to support the balls 2 to a plane bisecting the angle of articulation between the axes of rotation of the outer and inner joint members 1 and 3.
In the structure of the conventional cross groove joint as shown in FIG. 2, the outer joint member 1 has a plurality of (i.e., six) inwardly facing outer ball grooves 1a alternately skewed with a skew angle δ in opposite directions relative to an axis of rotation of the outer joint member 1. The inner joint member 3 positioned inside the outer joint member 1 has a plurality of (i.e., six) outwardly facing inner ball grooves 3a alternately skewed with the same skew angle δ in opposite directions relative to an axis of rotation of the inner joint member 3. The outer and inner ball grooves 1a and 3a face each other in crossed pairs with each of the balls 2 positioned between each crossed pair for torque transfer between the inner and outer joint members 1 and 3. As the ball 2 is retained in the cage 4, the ball 2 is limited in a ball movement range L2 in the circumferential direction of the joint, and the outer joint member 1 has a minimum thickness L1 on one side of the member. To secure the movement of the balls 2, the cage 4 includes a plurality of (i.e., six) cage windows 4awith a dimension sufficient to accommodate the ball movement L2. As a result, the width L4 of each cage web 4b must be designed to have a dimension at least the same or less than the minimum thickness L1 of outer joint member 1.
In an attempt to reduce a transmission error and to make the design of the joint more compact, the cross groove joints retaining eight balls have been suggested. The eight-ball type cross groove joint known in the art typically has a basic structure generally the same or similar to that shown in FIGS. 1-2, however, with the number of the balls and the number of the ball grooves of the outer and inner joint members respectively increased from six to eight. FIGS. 3(a) and (b) illustrate a conventional cross groove joint with eight balls. Like the six ball cross groove joint, the eight ball cross groove joint includes an outer joint member 11, an inner joint member 33, balls 22 for torque transfer between the outer and inner joint members, and a cage 44 configured to support the balls to a plane bisecting the angle of articulation between the axes of rotation of the outer and the inner joint member.
In the structure of the conventional eight ball type cross groove joint as shown in FIG. 4, the outer joint member 11 has a plurality of inwardly facing outer ball grooves 11a alternately skewed with a skew angle δ in opposite directions relative to an axis of rotation of the outer joint member. The inner joint member 33 placed inside the outer joint member 11 similarly has a plurality of (i.e., eight) outwardly facing inner ball grooves 33a alternately skewed with the same skew angle δ, however, oriented in opposite directions relative to an axis of rotation of inner joint member 33. The outer and inner ball grooves 11a and 33a face each other in crossed pairs with each of the balls 22 retained between each crossed pair for torque transfer between the inner and outer joint members. As the ball 22 is retained in the cage 44, the ball 22 is limited in a ball movement range L22 in the circumferential direction of the joint, and the outer joint member 11 has a minimum (least) thickness L11 on one side of the member. To secure the movement of the balls 22, the cage 44 includes a plurality of (i.e., eight) cage windows 44a with a dimension sufficient to accommodate the ball movement L22. As a result, the width L44 of each cage web 44b must be designed to have a dimension the same or less than the minimum thickness L11 of outer joint member 11.
As the cross groove joint with higher balls (e.g., eight or more balls) can provide more compact design and secure a smoother and reliable operation as compared to the cross groove joint with six balls, it would be desirable to produce a higher ball (e.g., eight or more balls) type cross groove joint which has the same or equivalent durability as that having six balls. More specifically, if the cross groove joint with eight balls, for example, is designed to have the same pitch circle diameter (PCD) as the joint having six balls, the ball diameter of the eight ball joint can be reduced because the load on each ball groove and the stress onto the cage web 44b decreases by the increase of the number of the balls. In addition, the size of each cage window 44a can also be reduced compared to the joint containing six balls.
However, the higher ball (e.g., eight ball) type cross groove joint may also include certain shortcomings or disadvantages as described below, for example. Because the eight ball type joint includes more (i.e., eight) cage windows 44a, the thickness of the cage web 44b is also reduced, and thus, the stress on the cage web 44b becomes greater than that of the six ball type. Comparing to the joint with six balls having the same PCD, the increased amount of stress on the cage web (due to the reduction of cage web thickness) exceeds that of the decreased amount of stress owing to the increase of the number of balls. Therefore, the higher ball (e.g., eight ball) type cross groove joint may have a weakened strength and durability in the cage web, and thus, the load bearing capacity of the joint can be deteriorated than that of the conventional six ball type joint.

Cross groove type constant velocity joint


A multipole unit normally consists of a support tube, a threaded ring, a plurality of magnetic rings, a plurality of spacer rings and a spring ring. According to the present invention, the structural design of a multipole unit is simplified in that the threaded ring is modified in such a way that the spring ring becomes superfluous. In order to achieve this the threaded ring or a stop arranged on the support tube is provided with spring elements which fulfil the function of the conventional spring ring.

1. Field of the Invention
The present invention relates to a multipole unit for a color picture tube of the type including a support tube, a retaining ring, and at least one magnetic ring.
2. Description of the Related Art
Color picture tubes for color television sets and color monitors are provided with a multipole unit by means of which static convergence adjustment is carried out. Convergence adjustment guarantees that the three color separation images which are produced in a color picture tube appear on the front screen with raster superposition, i.e. that the three electron beams of the electron gun impinge on respective neighbouring, associated phosphor dots over the whole screen area. This will only be the case if the electron beams cross in a common shadow mask opening of the shadow mask provided on the inner side of the front screen in the picture tube. In the case of static convergence adjustment minor deviations of the electron beams are corrected with the aid of so-called multipole fields. These multipole fields are produced by permanent-magnetic rings consisting of a slightly permeable material so that the deflection field will not be influenced.
Hitherto known multipole units consist of a support tube, a threaded ring which can be screwed onto the support tube, and a plurality of (permanent-) magnetic rings. The magnetic rings are arranged between the threaded ring and a flange on the opposite end of the support tube. For static convergence adjustment of a color picture tube, the magnetic rings can be rotated on the support tube. When the adjustment has been finished, the magnetic rings are fixed at the position in question by fully tightening the threaded ring. The static convergence adjustment for the color picture tube will be preserved permanently in this way.
In order to permit adjustment with the aid of the magnetic rings before said rings are fixed completely, said magnetic rings must be rotatably supported on the support tube without rotating on their own. They must always be held at their respective position in this adjustment phase. As soon as all the magnetic rings have been brought to their final position, the threaded ring is tightened firmly so as to fix the magnetic rings completely.
In the adjustment phase, the magnetic rings are held in a clamped condition. For this purpose, an additional spring ring is normally used between the magnetic rings. By means of a force acting in the axial direction, this spring ring clamps the magnetic rings between the threaded ring and the flange in the adjustment phase. The spring ring is provided with axially effective spring elements for this purpose.
Such a conventional structural design is disadvantageous insofar as an additional spring ring is required.
It is the object of the present invention to provide an improved multipole unit having a simplified structural design.
This object is achieved by providing a multipole unit for a color picture tube comprising a support tube, a retaining ring and at least one magnetic ring. The magnetic ring is attachable to the support tube and a spring element is provided between the retaining ring and a stop on the outer circumference of the support tube. The spring element acts in axial direction and is integrated in the stop or the retaining ring.
According to the present invention, a spring element is integrated in the retaining ring or in the flange of the support tube. A separate spring ring is therefore no longer necessary.
The structural design of the multipole unit according to the present invention has been simplified substantially in comparison with conventional multipole units, since the production as well as the mounting of an additional spring ring can be dispensed with.
Further advantageous embodiments of the present invention are disclosed below and in the claims.

Multipole unit for a color picture tube with integrated spring element

Matsushita Display Devices (Europe) GmbH