A filter network demultiplexes a frequency division multiplexed input signal which involves a reduced number of multiplier or multiplying steps. The filter network comprises Lxe2x88x921 Zxe2x88x92N shift registers in series receiving the multiplexed input signal Y(n) to produce Lxe2x88x921 corresponding shifted signals, pairs of which are added. The filter network further comprises a set of q multiplier sections including p first multiplier sections each being coupled to the added signals for combining each output of a corresponding set of N transformed filter coefficients gi. There are provided a set of N second adder sections each being coupled to distinct outputs of the multiplier sections for producing a corresponding set of N transformed signals, and a set of t third adders each receiving a distinct pair of signals {CT(n),CTxe2x80x2(n)} from the transformed signals Ck(n) for producing a first filtered signal Ao(n) and a set of Nxe2x88x921 filtered signals Ak(n+k), with k=1, . . . , Nxe2x88x921.

1. Field of the Invention
The invention relates to telecommunication field, and more particularly to apparatus and method for demultiplexing a frequency division multiplexed signal using a polyphase digital filter network.
2. Description of Prior Art
The use of satellites with multiple spot beam is a major step in increasing the capabilities of satellite communication. Multiple beam satellites have the advantage of having high gain and allowing the reuse of the same frequency band in geographically separated beams. The use of multiple spot beams requires additional switching on-board the satellite. This switching can be done either in the RF, IF or the baseband. Switching at the RF and IF necessitates the use of Time Division Multiple Access (TDMA) in the uplink which could lead to high rate modems in the earth stations, therefore increasing the cost of earth stations. On-board switching in the baseband requires down-conversion, demultiplexing and demodulation of the uplink data prior to switching and remultiplexing, remodulation and upconversion after switching to form the downlink. The part of the signal processing in the baseband is called On-board Baseband Processing (OBP). The use of the OBP results in a considerable flexibility in the choice of the access scheme and either TDMA or Frequency Division Multiple Access (FDMA) can be used. For the payloads with OBP, the use of FDMA is considered on the uplink to reduce ground station cost. On the other hand, Time Division Multiplexing (TDM) is used for its power efficiency on the downlink.
Moreover, use of FDMA on the uplink reduces the size of the earth terminal as compared to TDMA. However, the price paid is the increased complexity of the spacecraft payload. While a single demodulator is sufficient for demodulation of high bit rate TDMA on the uplink, several demodulators are required for the demodulation of the FDMA carriers received by the satellite. A solution to this problem is the use of a multi-carrier demodulator, referred to as a group demultiplexer/demodulator. Group demultiplexing is needed, for example, in the digital signal processing payloads if the uplink uses FDMA or some other type of spectrum sharing such as MF-TDMA or MF-CDMA. The more important and computational intensive section, referred to as the group demultiplexer, divides the incoming composite spectrum into separate channels. The second section, the demodulator, recovers the digital data for each individual channel.
There are several techniques for the group demultiplexer design. A straightforward method is per-channel filtering. In this method, a separate filter is used for each channel. This is only feasible for a small number of channels. For a large number of channel, sharp filters with many taps are required. Another method is the FFT/IFFT or frequency-domain filtering. In this method, a Fast Fourier Transform (FFT) is used to find the frequency spectrum of the composite FDM signal. Following the FFT, the frequency-domain coefficients are multiplied by coefficients of a filter in order to determine the frequency-domain samples falling into each of the carrier channels. For each set of frequency-domain coefficients, an Inverse FFT (IFFT) is used to recover the time-domain samples of the modulated carriers. This method is much less complex than the per-channel approach, while having a great degree of flexibility.
Another method for the implementation of the group demultiplexer is the polyphase/FFT method. In this method, a digital filter bank is implemented in cascade with an DFT processor, and preferably a FFT processor to provide better efficiency. This technique can be used when the bandwidths of the channels are equal and fixed. FIG. 1 is a block diagram of a polyphase/FFT group demultiplexer according to the prior art and generally designated at 10. Input Y(z) at 12, 12xe2x80x2 and outputs Xk(zN) at 14, 14xe2x80x2 with k=0, . . . , Nxe2x88x921, are in complex sampled form, as well known in the art, with solid lines 12, 14 representing the In-phase (or I) and dotted lines 14, 14xe2x80x2 representing the Quadrature-phase (or Q) components of different signals. The notation used for the representation of the signals and delay elements is in the Z-domain. The elements specified by Zxe2x88x92k in FIG. 1 represent a delay of rT, normally implemented using shift registers of length r. That is, if the input to Zxe2x88x92k is a sample of a time signal u(t) at time kT, denoted by u[n], its output will be a sample of the signal u(t) at time nTxe2x88x92kT, denoted by u[nxe2x88x92k], where T is the time duration between two consecutive samples. The symbol Y(z) represents the Z-transform of a composite signal y[n] consisting of N frequency multiplexed signals represented as follows:                               Y                                (            z            )                          =                              ∑                          n              =                              -                ∞                                                    +              ∞                                                                    y                                            [                n                ]                                                                z                              -                n                                                                        (        1        )
The outputs Xi(zN), i=0,1, . . . , Nxe2x88x921 represent the N individual signals after demultiplexing. The Z-transform being represented as a function of ZN rather than z represents a decimation of the outputs by N, i.e., only every Nth sample of xi[n] is retained. This is consistent with the Nyquist sampling theorem, relating the number of samples required for discrete representation of a signal to its bandwidth. That is, since the bandwidth of each of the N individual channels is 1/Nth of the total bandwidth occupied by the composite signal y(t), to represent each of these individual signals, we need only to have 1/Nth of the samples required for perfect reconstruction of y(t).
The digital filter network 15 comprises a filter bank 16 shown in FIG. 1 consisting of sub-filters Hi(zN), i=0,1, . . . , Nxe2x88x921, designated at 17, which is derived from a single prototype Finite Impulse Response (FIR) filter, H(z), through a decimation by N. That is, each sub-filter Hi(ZN) consists of 1/Nth of the coefficients of H(z). Denoting the coefficients of the prototype filter by hi, i=0,1, . . . , NLxe2x88x921, the coefficients of the sub-filter, H0(zN), are h0, hN, h2N, . . . , hN(Lxe2x88x921), and the coefficients of the sub-filter, H1(zN), are h1, hN+1, h2N+1, . . . , hN(Lxe2x88x921)+1. In general, the coefficients of the ith sub-filter, Hi(zN), are hi, hN+i, h2N+i, . . . , hN(Lxe2x88x921)+i. The derivation of the sub-filters from the prototype filter is based on the following factorization:                               H                                (            z            )                          =                                            ∑                              n                =                0                                            NL                -                1                                                                                h                n                                                          z                                  -                  n                                                              =                                                    ∑                                  i                  =                  0                                                  N                  -                  1                                                                                z                                      -                    i                                                                                ∑                                          k                      =                      0                                                              L                      -                      1                                                                                h                                              kN                        +                        i                                                                                z                                              -                        kN                                                                                =                                          ∑                                  i                  =                  0                                                  N                  -                  1                                                                                z                                      -                    i                                                                                H                      i                                                                                (                                              z                        N                                            )                                                        .                                                                                (        2        )
The switches 18, 18xe2x80x2 at the input of the sub-filters 17 close every N samples connecting the outputs of the shift registers 20 to different sub-filters. That is, each sub-filter operates at a rate which is 1/Nth that of the sample rate of the input signal, y[n]. Multiplication of output signals Ai(n) by wi, i=0,1, . . . , Nxe2x88x921 generated at outputs 19, 19xe2x80x2, where w=exe2x88x92ixcfx80/N is performed by a set of N multipliers 22 and results in a phase shift of ixcfx80/N to produce filtered output signals A*i(n) at outputs 21, 21xe2x80x2, from which the FFT processor 23 finds the Discrete Fourier Transform (DFT) as defined by:                               B          k                =                              ∑                          i              =              0                                      N              -              1                                                                    A              i                                                  ⅇ                              j                                                                      2                                        π                                    N                                                ik                                                                        (        3        )
Finally, the alternate samples of each of the N outputs 25, 25xe2x80x2 of the FFT processor are inverted by the multipliers 24 to produce demultiplexed output signals Xk(ZN) at outputs 14, 14xe2x80x2.
From the foregoing, it can be seen that the number of multipliers required for the implementation of the polyphase filter network is NL, which correspond to coefficients h0, h1, h2, . . . , hNLxe2x88x921 of the prototype filter. Such a number of multipliers may represents a limiting factor in the context of payload optimization especially where a high number of channels is to be handled by a satellite On-board demultiplexer.
It is therefore an object of the present invention to provide apparatus and method for demultiplexing a frequency division multiplexed input signal which involves a reduced number of multipliers or multiplying steps.
According to the above object, from a broad aspect of the present invention, there is provided a polyphase digital filter network based on a linear phase prototype filter for use in a group demultiplexer for generating N output data signals associated with N channels from a corresponding Frequency Division Multiplexed input signal Y(n), said linear phase prototype filter comprising N sub-filters being characterized by L coefficients forming NL coefficients for said prototype filter. The polyphase digital filter network comprises Lxe2x88x921 Zxe2x88x92N shift registers in series receiving the multiplexed input signal Y(n) to produce Lxe2x88x921 corresponding shifted signals Y(nxe2x88x92rN), with r=1, . . . , Lxe2x88x921, and a set of p first adder sections each receiving a distinct pair of signals from the multiplexed input signal Y(n) and the shifted signals Y(nxe2x88x92rN). The filter network further comprises a set of q multiplier sections including p first multiplier sections each being coupled to a respective output of a corresponding one of the first adder sections for combining each said output with a corresponding set of N transformed filter coefficients gi derived from the coefficients of the linear phase prototype filter, the set of q multiplier sections including a further multiplier section receiving shifted signal   Y        (          n      -                        (                                    L              -              1                        2                    )                        N              )
where L is odd for combining thereof in parallel with a corresponding set of s further transformed filter coefficients gi derived from the coefficients of the linear phase prototype filter. The filter network further comprises a set of N second adder sections each being coupled to distinct outputs of the multiplier sections for producing a corresponding set of N transformed signals Ck(n), with k=0, . . . , Nxe2x88x921; and a set of t third adders each receiving a distinct pair of signals {CT(n),CTxe2x80x2(n)} from the transformed signals Ck(n) for producing a first filtered signal A0(n) and a set of Nxe2x88x921 filtered signals Ak(n+k), with k=1, . . . , Nxe2x88x921.
According to a further broad aspect of the present invention, there is provided a polyphase/DFT digital group demultiplexer for generating N output data signals associated with N channels from a corresponding Frequency Division Multiplexed input signal Y(n), comprising a polyphase digital filter network based on a linear phase prototype filter formed by N sub-filters being characterized by L coefficients forming NL coefficients for said prototype filter. The polyphase digital filter network comprises Lxe2x88x921 Zxe2x88x92N shift registers in series receiving the multiplexed input signal Y(n) to produce Lxe2x88x921 corresponding shifted signals Y(nxe2x88x92rN), with r=1, . . . , Lxe2x88x921; and a set of p first adder sections each receiving a distinct pair of signals from the multiplexed input signal Y(n) and the shifted signals Y(nxe2x88x92rN). The filter network further comprises a set of q multiplier sections including p first multiplier sections each being coupled to a respective output of a corresponding one of the first adder sections for combining each said output with a corresponding set of N transformed filter coefficients gi derived from the coefficients of the linear phase prototype filter, the set of q multiplier sections including a further multiplier section receiving shifted signal   Y        (          n      -                        (                                    L              -              1                        2                    )                        N              )
where L is odd for combining thereof with a corresponding set of s further transformed filter coefficients gi derived from the coefficients of said linear phase prototype filter. The filter network further comprises a set of N second adder sections each being coupled to selected outputs of the multiplier sections for producing a corresponding set of N transformed signals Ck, with k=0, . . . , Nxe2x88x921; and a set of t third adders each receiving a distinct pair of signals {CT(n),CTxe2x80x2(n)} from the transformed signals Ck(n) for producing a first filtered signal A0(n) and a set of Nxe2x88x921 filtered signals Ak(n+k), with k=1, . . . , Nxe2x88x921. The filter network further comprises a set of Nxe2x88x921 shift registers Zxe2x88x92k receiving said. filtered signals Ak(n+k) to produce Nxe2x88x921 corresponding filtered signals Ak(n), with k=1, . . . , Nxe2x88x921. The group demultiplexer further comprises a set of N phase offset multipliers receiving the filtered signals A0(n) and Ak(n) forming a set of filtered signals Ak(n), with k=0, . . . , Nxe2x88x921, for combining thereof with a corresponding set of N phase offset parameter wk, with k=0, . . . , Nxe2x88x921, to produce a corresponding set of phase offset filtered signals A*k(n); Discrete Fourier Transform processor means for generating a set of N processed output signals Bk(n) from said corresponding set of phase offset filtered signals A*k(n), with k=0, . . . , Nxe2x88x921; and a set of N output alternate inverting multipliers each receiving a corresponding one of the set of processed output signals Bk(n) to generate the N output data signals associated with the N channels.
According to a still further broad aspect of the present invention, there is provided a method of demultiplexing a Frequency Division Multiplexed input signal Y(n) for generating N output data signals associated with N channels, the method comprising the steps of: i) generating Lxe2x88x921 shifted signals Y(nxe2x88x92rN), with r=1, (lxe2x88x921)N, from the multiplexed input signal Y(n); ii) coupling p pairs of distinct signals from the multiplexed input signal Y(n) and the shifted signals Y(nxe2x88x92rN) to produce p corresponding pairs of coupled output signals; iii) combining each said pair of output signals with a corresponding set of N transformed filter coefficients derived from coefficients of a linear phase prototype filter; iv) combining shifted signal   Y        (          n      -                        (                                    L              -              1                        2                    )                        N              )
with a corresponding set of s further transformed filter coefficients derived from the coefficients of the linear phase prototype filter, whenever L is odd; v) coupling the results of the combining steps to produce N transformed signals Ck, with k=0, . . . , Nxe2x88x921; vi) coupling distinct pair of signals {CT(n),CTxe2x80x2(n)} from the transformed signals Ck(n) for producing a first filtered signal A0(n) and a set of Nxe2x88x921 filtered signals Ak(n+k), with k=1, . . . , Nxe2x88x921; vii) shifting the filtered signals Ak(n+k) to produce Nxe2x88x921 corresponding filtered signals Ak(n), with k=1, . . . , N-xe2x88x921; viii) phase offsetting the filtered signals A0(n) and Ak(n) forming a set of filtered signals Ak(n), to produce a corresponding set of phase offset filtered signals A*k(n); ix) applying a Discrete Fourier Transform on the phase offset filtered signals A*k(n) to generate a set of N output signals Bk(n), with k=0, . . . , Nxe2x88x921; and x) alternately inverting the output signals Bk(n) to generate the N output data signals associated with the N channels.

Apparatus and method for demultiplexing a frequency division multiplexed input signal and polyphase digital filter network therefor


An animal, e.g., transgenic mouse, in which the MSH5 gene is misexpressed. The animal is useful for screening treatments for a number of conditions. Methods for identifying contraceptive agents are also described.

MutS homolog 5 (MSH5) is a member of a family of proteins that are known to be involved in DNA mismatch repair (Modrich, P. & Lahue (1996) Annu. Rev. Biochem. 65, 101–133; Kolodner, R. (1996) Genes Dev. 10, 1433–1442). Germ line mutations in MSH2, MLH1 and MSH6 cause hereditary non-polyposis colon cancer (HNPCC) or Lynch syndrome (Leach, F. S. et al. (1993) Cell 75, 1215–1225; Bronner, C. E. et al. (1994) Nature 368, 258–261; Papadopoulos, N. et al. (1994) Science 263, 1625–1629; Akiyama, Y. et al. (1997) Cancer Res. 57, 3920–3923; Miyaki, M. et al. (1997) Nature Genet. 17, 271–272). Inactivation of Msh2, Mlh1, Msh6 and Pms2 in mice leads to hereditary predisposition to intestinal and other cancers (de Wind, N. et al. (1995) Cell 82, 321–330; Reitmair, A. H. et al. (1995) Nature Genet. 11, 64–70). Early studies in yeast revealed a role for some of these proteins, including MSH5, in meiosis (Hollingsworth, N. M., et al. (1995) Genes & Development 9, 1728–1739; Ross-Macdonald, P. & Roeder, G. S. (1994) Cell 79, 1069–1080). Gene targeting studies in mice confirmed roles for MLH1 and PMS2 in mammalian meiosis (Baker, S. M. et al. (1995) Cell 82, 309–320; Edelmann, W. et al. (1996) Cell 85, 1125–1134; Baker, S. M. et al. Nature Genet. 13, 336–342).

Methods for identifying compounds which modulate the activity of MSH5

Albert Einstein College of Medicine of Yeshiva University


Featured are methods for non-invasive assessment of a vascular physiological parameter including but not limited to central arterial stiffness, vascular reactivity and/or local arterial stiffness. The methods of the invention use any one of a number of magnetic resonance imaging techniques known in the art to acquire image data so as to arrive at these vascular physiological parameters. Also such methods include locating the detector or imaging coil proximal to a single artery and external to the body/specimen. According to one aspect, the methodology determines the central arterial stiffness from image data acquired at the single arterial location. In another aspect, image data is acquired so that one or more of central arterial stiffness, vascular reactivity and/or local arterial stiffness can be determined from the acquired image data alone or in combination with other acquired data/information. The disclosed methods of the invention allow for reproducible, non-invasive diagnosis of early stage indicators of atherosclerosis.

Atherosclerotic cardiovascular disease is the leading cause of death in developed nations. Traditional risk factors predict atherosclerotic disease in populations but lack specificity in predicting atherosclerosis severity in individuals.
Since modifiable risk factors account for most myocardial infarctions worldwide, early and accurate identification of high-risk individuals would allow better targeting of aggressive preventive strategies. Yusuf S, Hawken S, Ounpuu S, et al. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study. Lancet 2004; 364:937-52. The incidence of coronary heart disease can be predicted in populations based on traditional risk factors [Wilson P W, D'Agostino R B, Levy D, Belanger A M, Silbershatz H, Kannel W B. Prediction of coronary heart disease using risk factor categories. Circulation 1998; 97:1837-47], but these factors lack specificity in predicting severity of atherosclerosis and likelihood of cardiovascular events in individuals [Greenland P, LaBree L, Azen S P, Doherty T M, Detrano R C. Coronary artery calcium score combined with Framingham score for risk prediction in asymptomatic individuals. Jama 2004; 291:210-5; Desai M Y, Nasir K, Braunstein J B, et al. Underlying risk factors incrementally add to the standard risk estimate in detecting subclinical atherosclerosis in low- and intermediate-risk middle-aged asymptomatic individuals. Am Heart J 2004; 148:871-7]. Consequently, other noninvasive methods are needed beyond traditional risk factors for early and accurate identification of individuals at high risk for atherosclerosis.
As is known to those skilled in the art, abnormalities of two arterial properties—endothelial function and central arterial stiffness—are associated with increased risk of atherosclerosis and cardiovascular events [Schroeder S, Enderle M D, Ossen R, et al. Noninvasive determination of endothelium-mediated vasodilation as a screening test for coronary artery disease: pilot study to assess the predictive value in comparison with angina pectoris, exercise electrocardiography, and myocardial perfusion imaging. Am Heart J 1999; 138:731-9; Neunteufl T, Katzenschlager R, Hassan A, et al. Systemic endothelial dysfunction is related to the extent and severity of coronary artery disease. Atherosclerosis 1997; 129:111-8; Teragawa H, Kato M, Kurokawa J, Yamagata T, Matsuura H, Chayama K. Usefulness of flow-mediated dilation of the brachial artery and/or the intima-media thickness of the carotid artery in predicting coronary narrowing in patients suspected of having coronary artery disease. Am J Cardiol 2001; 88:1147-51; Oliver J J, Webb D J. Noninvasive assessment of arterial stiffness and risk of atherosclerotic events. Arterioscler Thromb Vase Biol 2003; 23:554-66; Sutton-Tyrrell K, Najjar S S, Boudreau R M, et al. Elevated aortic pulse wave velocity, a marker of arterial stiffness, predicts cardiovascular events in well-functioning older adults. Circulation 2005; 111:3384-90].
Furthermore, endothelial dysfunction and increased central arterial stiffness precede atherosclerosis by years or even decades [Celermajer D S, Sorensen K E, Gooch V M, et al. Non-invasive detection of endothelial dysfunction in children and adults at risk of atherosclerosis. Lancet 1992; 340:1111-5; Iannuzzi A, Licenziati M R, Acampora C, et al. Preclinical changes in the mechanical properties of abdominal aorta in obese children. Metabolism 2004; 53:1243-6; Wildman R P, Mackey R H, Bostom A, Thompson T, Sutton-Tyrrell K. Measures of obesity are associated with vascular stiffness in young and older adults. Hypertension 2003; 42:468-73].
Hence, there is much interest in developing noninvasive techniques for assessing endothelial function and/or central arterial stiffness in order to enhance cardiovascular risk stratification [Taylor A J, Merz C N, Udelson J E. 34th Bethesda Conference: Executive summary—can atherosclerosis imaging techniques improve the detection of patients at risk for ischemic heart disease? J Am Coll Cardiol 2003; 41:1860-2; Corretti M C, Plotnick G D, Vogel R A. Technical aspects of evaluating brachial artery vasodilatation using high-frequency ultrasound. Am J Physiol 1995; 268:H1397-404; Kuvin J T, Patel A R, Sliney K A, et al. Peripheral vascular endothelial function testing as a noninvasive indicator of coronary artery disease. J Am Coll Cardiol 2001; 38:1843-9; Moens A L, Goovaerts I, Claeys M J, Vrints C J. Flow-mediated vasodilation: a diagnostic instrument, or an experimental tool? Chest 2005; 127:2254-63]. Thus, evaluating either or both of these arterial properties may enable early and accurate identification of high-risk individuals.
A standard approach to assessing central arterial stiffness is to measure central pulse wave velocity—pulse waves travel faster in stiffer arteries. There are two particular methods of assessing central pulse wave velocity that typically measure transit time between two different aortic sites [Mohiaddin R H, Firmin D N, Longmore D B. Age-related changes of human aortic flow wave velocity measured noninvasively by magnetic resonance imaging. J Appl Physiol 1993; 74:492-7; Rogers W J, Hu Y L, Coast D, et al. Age-associated changes in regional aortic pulse wave velocity. J Am Coll Cardiol 2001; 38:1123-9] or two peripheral arterial sites [Davies J I, Struthers A D. Pulse wave analysis and pulse wave velocity: a critical review of their strengths and weaknesses. J Hypertens 2003; 21:463-72].
When assessing central pulse wave velocity by measuring transit time between two different aortic sites, the aorta—the major artery in the chest—is imaged using MRI and the arrival time of the pulse wave at two or more aortic locations is determined. The distance between each of two points is typically determined using the acquired image and the pulse wave velocity is determined using the difference between the arrival times at two locations and the distance between these two points (i.e., Vpw=distance/time, where the distance and time is that between the two locations). This particular methodology can involve breath-holding and can involve time-consuming scanning and data analysis.
In the other methodology where two peripheral sites are used, the difference in pulse-wave arrival times at two different peripheral arterial locations, such as the radial and femoral arteries is determined. Also, the distance between these two peripheral arterial locations is determined. In the common technique often called applanation tonometry, two transducer or sensors are located external to the body and in proximity to the peripheral arterial locations. The transducers can be used to generate a time history of pressure changes and thereby sense the arrival of a pulse wave. The distance between these two peripheral arterial locations is typically determined by extending a tape measurer between the locations of the two sensors.
As indicated above, vascular physiology can be assessed, in part, through measurements of endothelial function. Changes in the diameter of an artery in response to a stimulus such as change in blood flow velocity through the artery (arterial wall shear stress, WSS) are indicative of endothelial function, known as flow mediated dilation (FMD). Endothelial function can be measured by inflating a blood pressure cuff around a subject's arm and monitoring velocity of blood flowing through a brachial artery while measuring the artery's diameter before, during and after the inflation of the cuff.
Vascular endothelium, the inner lining of blood vessels, is crucially important to maintaining vascular health. Endothelial cells regulate thrombosis, inflammation, vasomotion, and cell proliferation through the synthesis and release of substances including nitric oxide and endothelin-1. Cardiovascular risk factors are associated with endothelial dysfunction, and agents that reduce cardiovascular risk also improve endothelial function. Hence, endothelial dysfunction is considered to be an important common pathway by which risk factors promote atherosclerosis. Furthermore, endothelial dysfunction is associated with coronary events. Consequently, there is much interest in assessing endothelial function non-invasively.
It thus would be desirable to provide new non-invasive methods for assessing central arterial stiffness using a non-invasive imaging technique such as Magnetic Resonance Imaging (MRI) as well as applications programs embodying such methods. It would be particularly desirable to provide such methods that would assess central arterial stiffness by use of image data acquired at a single peripheral arterial location such as for example, the femoral artery. It also would be desirable to provide new non-invasive methods whereby one acquires image data to assess one or more vascular properties, such as central arterial stiffness, local arterial stiffness and/or vasculature reactivity using a non-invasive technique (e.g., MRI) at a single peripheral arterial location such as for example, the femoral artery, as well as applications programs embodying such methods. Such a method would be particularly adaptable so that the image data for these one or more vascular properties is obtained without having to reposition or relocate the detector or imaging coil used to acquire the image data.
The references referred to herein and discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate such disclosure by virtue of prior invention.

Method of assessing central arterial stiffness using MRI, method of assessing vascular function including arterial stiffness, applications program and media embodying same


A process for removal of Group 13 and/or 15 elements from an organosilane containing Group 13 and/or 15 elements as contaminants comprising contacting the organosilane with a reagent substantially soluble in the organosilane and capable of forming a complex with the Group 13 and/or Group 15 element which is less volatile than the organosilane, wherein the reagent is selected from the group consisting of thiols, alcohols, carboxylic acids, amines or mixtures thereof and separating the organosilane from the complex by distillation.

Organosilanes are widely used in the electronics industry. For example, tetraethylorthosilicate (TEOS) is used as a major source for depositing silicon dioxide. Group 13 (IIIA) and 15 (VA) elements behave as impurities in obtaining silicon dioxide films. One of the challenges for the industry involves removal of impurities effectively from TEOS to make ultrahigh purity TEOS (see Hawley's Condensed Chemical Dictionary, 11th ed., N. Irving Sax, et al. (1987) for the current numbering in the Periodic Table of the Elements).
J. M. Rosamilia, 1994 Proceedings Institute of Environmental Sciences, pp156 demonstrate some of the methods of analysis and impurity levels in TEOS. They also describe the difficulty in removing boron impurities because it forms volatile triethoxyboron complex which distills along with TEOS.
Ultra high purity precursors are extremely important for the fabrication of high performance devices in the semiconductor industry. As the device density increases with the number of transistors, the dimensions of the device decrease to submicroscopic features. At 0.25 .mu.m technology and beyond, even very low levels of impurities (ppb to parts per trillion) effect the device in high failure rates and low performance.
In addition to the miniaturization and design of multilevels, the thickness of the dielectric layers between the levels is continuously reduced. This reduction in thickness of the dielectric layers is required for devices to operate at high speeds in the gigahertz regime. As a result even small amounts of impurities diffuse readily at high temperatures through these dielectric layers and cause device failures. In the case of boron and phosphorus impurities, this effect is dramatic at high process temperatures. This is because light atoms, such as boron (B.sup.11) impurities, easily diffuse through shallow junctions.
Some of the other problems which are caused by the presence of impurities are:
1) Leakage current at junctions.
2) Unstable electrical characteristics of silicon dioxide.
3) Localized eutectic points with silicon o form undesirable alloys.
Highly sensitive techniques are routinely utilized in analyzing all the materials. Instrumentation such as atomic pressure ionization mass spectroscopy (APIMS) Inductively coupled plasma mass spectrometer (ICPMS) and Inductively coupled plasma atomic emission (ICPAE) are used to detect low levels of impurities in the range of <5 ppb.
Typical reactions that can be expected with boron are described in Advanced Inorganic Chemistry, 5th ed., F. Albert Cotton and Geoffrey Wilkinson, 1988, pp. 162-207.
Removal of boron and other impurities in water was earlier demonstrated by use of a boron specific resin (Amberlite IRA -173 Ion Exchange Resin Separation Technology bulletin, Rohm & Haas (1989). Ion exchange resins which contain N-methylglucamine have been used specifically to bind boron as boric acid. This technique has been used in removing boron from irrigation waters and solutions, see Robert Kunin and Albert F. Preuss, I&EC Product Research Development, Vol 3., No 4., (1964). pp 304.
High purity alkoxysilanes have been purified by using chelating resins such as Chitosan followed by vacuum distillation and diffusion with inert gases. The chelating resin contained groups such as HN(CH.sub.2 COOH).sub.2, see Japanese Patent JP 04082892 A2 920316 (1990). Here, they demonstrate removal of impurities such as Na, K, Ca and Cu.
Typically, TEOS is manufactured using ultra high purity starting materials to minimize contaminants. Chlorine, sodium and potassium are some of the common impurities. Halides were removed in alkoxysilanes by reacting with zinc metal to provide purified alkoxysilanes, see U.S. Pat. No. 5,104,999.
The synthesis and manufacture of TEOS for the semiconductor industry is carefully monitored by using high purity silicon containing starting materials and impurity free reagents. The product thus obtained is further purified by fractional distillation. These fractional distillations result in loss of yield in the form of prefractions (25-30%). Even after several repeated distillations TEOS may still contain contamination above 50 ppb.
The prior art generally involves use of ion exchange resins to reduce Group 13 impurities. Other techniques involve separation of boron impurities from aqueous media and purification of alkoxysilanes involved repeated fractional distillation and use of high purity starting materials.
The present invention overcomes the deficiencies in the prior art purification of organosilanes of Group 13 and 15 impurities by providing a technique for producing high purity products using reagents soluble in the product which are less volatile than the product. This results in decreased distillation losses and higher purities, as described in greater detail below.

Purification of organosilanes of group 13 (IIIA) and 15 (VA) impurities


In a method and apparatus of aligning liquid crystal, a first ion beam is formed. The first ion beam is transformed into a second ion beam having transformed cross-section. The second ion beam advances toward a thin film including carbon-carbon double bond. The second ion beam forms a first angle with respect to the thin film. The second ion beam is transformed into an atomic beam. The atomic beam is irradiated onto the thin film to break the carbon-carbon double bond. The carbon-carbon double bond is broken to form a polarized functional group for aligning a liquid crystal molecule.

1. Field of the Invention
The present invention relates to a method of manufacturing a liquid crystal display device, and more particularly to a method of manufacturing a liquid crystal display device having a reduced time for manufacturing the liquid crystal display device and an enhanced productivity.
2. Description of the Related Art
In general, a liquid crystal display device is lighter and smaller in comparison with other display devices. The liquid crystal display devices are manufactured via many manufacturing processes.
A first process for manufacturing the liquid crystal display device includes forming thin film transistor (TFT) unit cells on a first mother substrate and forming color filter unit cells on a second mother substrate. One example of the first process for manufacturing the liquid crystal display device is disclosed in U.S. Pat. No. 6,391,137 (entitled 'method for manufacturing display device').
A second process for manufacturing the liquid crystal display device includes a rubbing process. Liquid crystal layer disposed between the thin film transistor unit cell and the color filter unit cell is aligned via the rubbing process on the thin film transistor unit cells and the color filter unit cells. One example of the second process is disclosed in U.S. Pat. No. 5,879,497 (entitled 'alignment device and rubbing cloth for alignment with respect to liquid crystal display device-use substrate, and method for manufacturing a liquid crystal display device'). A cylindrical roller covered by a piled fabric (or rubbing cloth) having pile rolls on the alignment film, so that an alignment groove is formed on the alignment film. The alignment groove creates pre-tilt angles of liquid crystal molecules of the liquid crystal layer.
One example of a third process for manufacturing the liquid crystal display device is disclosed in the U.S. Pat. No. 6,397,137. The third process includes an assembly process for assembling the first mother substrate and the second mother substrate. The first mother substrate and second mother substrate are assembled such that the thin film transistor unit cells of the first mother substrate face the color filter unit cells of the second mother substrate unit cell. Hereinafter, the first mother substrate and second mother substrate are referred to as an 'assembled substrate', and the thin film transistor unit cell and color filter unit cell are referred to as a 'liquid crystal display device unit cell'.
One example of a fourth process for manufacturing the liquid crystal display device is disclosed in the U.S. Pat. No. 6,397,137. The fourth process includes a scribe-and-break process for scribing and separating the liquid crystal display device unit cells from the assembled substrate. One liquid crystal display device unit cell separated from the assembled substrate is referred to as a 'liquid crystal display panel'.
A fifth process for manufacturing the liquid crystal display device includes a test process. A test driving signal is applied to the liquid crystal display panel for testing the liquid crystal display panel.
A sixth process for manufacturing the liquid crystal display device includes a liquid crystal injection process for injecting liquid crystal into a cell gap disposed between the first mother substrate and the second mother substrate, and cell gap modulating process for modulating the size of the cell gap.
A seventh process for manufacturing the liquid crystal display device includes a polarizing plate attaching process and module process. A polarizing plate (or polarizing plates) is (are) attached on the liquid crystal display panel via the polarizing plate attaching process. A driving module for driving the liquid crystal display panel is installed on the liquid crystal display panel via the module process. Hereinafter, the liquid crystal display device having the driving module is referred to as a 'liquid crystal display panel assembly'.
Generally, the sequence of the conventional manufacturing processes has been maintained, and the failures occurring during each of the processes has been reduced.
However, the conventional manufacturing processes has some critical problems.
For example, a process speed of each of processes is different from each other. In detail, a process speed of the first through the third processes is different from that of the fourth through the seventh processes. In general, the process speed of the first through the third processes is faster than that of the fourth through the seventh processes. Namely, the process speed of the processes of manufacturing the thin film transistor unit cell, the color filter unit cell and the assembled substrate is faster than the process speed of the scribe process, separation process, the test process, the liquid crystal injection process, polarizing plate attaching process and the module process.
Therefore, the assembled substrate that has passed through the third process should stand by for a predetermined time so as to undergo the fourth process. The longer the assembled substrate stands by, the lower is the productivity of the liquid crystal display device.
More equipment may be established in the fourth through the seventh processes in order to solve above problem. In other word, extensions of equipment may increase the productivity of the liquid crystal display devices. However, the more equipment greatly increases manufacturing cost.
Further, the conventional manufacturing processes have many problems.
A first problem occurs in the rubbing process. The rubbing process for aligning the liquid crystal molecules has the following problem. The roller covered by a piled fabric having pile rolls on the alignment film, so that an alignment groove is formed on the alignment film. The alignment groove creates pre-tilt angles of liquid crystal molecules of the liquid crystal layer.
However, many particles are generated as a byproduct in the conventional rubbing process. The particles may induce failures during the rubbing process. In order to eliminate the particles, a cleaning process is needed. The cleaning process includes a chemical cleaning process in which chemical cleaning agent resolves the particles and the particles are removed, a process for removing the chemical cleaning agent by pure water, and a dry process for removing the pure water. Accordingly, the time for manufacturing the liquid crystal display device may be increased due to the cleaning process.
Further, according to the conventional rubbing process, the rubbing cloth is replaced by a new rubbing cloth or the rubbing cloth is cleaned periodically. Therefore, the conventional rubbing process cannot be successively performed and the efficiency of manufacturing the liquid crystal display device is lowered.
Moreover, in the conventional rubbing process, the piled fabric (rubbing cloth) having pile forms alignment grooves on the alignment film. Therefore, defects of the alignment grooves are seldom detected, when the alignment grooves are already formed. The defects of the alignment grooves may be detected in the reliability test of the liquid crystal display device after the liquid crystal display device is completely manufactured. The liquid crystal display device having a defect of the alignment groove lowers image display quality.
A second problem occurs after the assembled substrate is manufactured. When the assembled substrate is manufactured, the liquid crystal display device unit cells are separated from the assembled substrate, and each of the liquid crystal display panels are manufactured using each of the liquid crystal display device unit cells. Input terminals and (or) output terminals are exposed to the air, and the input/output terminals are oxidized, so that a thin oxidation film may be formed on the surface of the input/output terminals. The thin oxidation film deteriorates electrical characteristics of the input/output terminals. Therefore, display quality of the liquid crystal display device is lowered.
A fourth problem occurs in the module process. Liquid crystal is injected into liquid crystal display panel and a polarizing plate is attached onto the liquid crystal display panel. The polarizing plate is attached onto each of the liquid crystal display panels separated from the assembled substrate one by one. Therefore, much time is required so as to attach the polarizing plate onto the assembled substrate.
In order to overcome above problem, the polarizing plate may be attached onto the assembled substrate. Then, the polarizing plate attached onto the assembled substrate is cut off, so that a liquid crystal display device unit cell having a polarizing plate on is manufactured. However, it is hard to detect the defect of the liquid crystal display device unit cell before cutting off the assembled substrate. When a polarizing plate is attached onto a defective liquid crystal display unit cell, the polarizing plate is wasted.

Method and apparatus of alligning liquid crystal


A method for preventing or inhibiting fouling in a gas-phase polyolefin polymerization process. The method includes maintaining the inside surface temperature of the process equipment below the dew point temperature of the gas mixture passing through the equipment.

In a continuous gas-phase, fluidized-bed polyolefin polymerization process, it was found that process equipment such as the gas loop piping and heat exchangers would foul to such an extent that a shutdown was periodically required to clean the equipment. Investigation into this problem led to the surprising discovery that internal equipment surfaces that were made to "sweat" (i.e., condense liquids on the internal surfaces) and kept wet had a reduced tendency to foul and remained clean for long periods of time. Modification of equipment and/or operating conditions such that the surfaces of the equipment that are exposed to the process gas could be made to "sweat" or condense liquids on all or nearly all of their surfaces has greatly reduced the rate of fouling experienced in the loop and the loop heat exchangers. In addition, "sweating" of the internal pipe surfaces of a tubular, loop, gas-phase polymerization reactor greatly reduces the fouling rate experienced in the reactor.

Method for preventing or inhibiting fouling in a gas-phase polyolefin polymerization process


A method for making a spin valve includes providing a substrate; depositing a first ferromagnetic layer having a first surface on the substrate; depositing a spacer layer having a second surface; depositing a second ferromagnetic layer, wherein the spacer layer is disposed between the first and second ferromagnetic layers; and exposing one or more of the first and second surfaces to an oxygen partial pressure, then decreasing the oxygen partial pressure before depositing a subsequent layer. One or more of the first and second surfaces may be exposed to an oxygen partial pressure of between about 1×10−7 Torr and about 5×10−5 Torr.

A spin valve or a magnetoresistive (MR) sensor detects magnetic field signals through the resistance changes of a read element, fabricated of a magnetic material, as a function of the strength and direction of magnetic flux being sensed by the read element. The conventional MR sensor operates on the basis of the anisotropic magnetoresistive (AMR) effect in which a component of the read element resistance varies as the square of the cosine of the angle between the magnetization in the read element and the direction of sense current flow through the read element. Such a MR Sensor can be used to read data from a magnetic medium. An external magnetic field from the magnetic medium (the signal field) causes a change in the direction of magnetization in the read element, which in turn causes a change in resistance (ΔR/R) in the read element and a corresponding change in the sensed current or voltage.
A spin valve has been identified in which the resistance between two uncoupled ferromagnetic layers varies as the cosine of the angle between the magnetizations of the two layers and is independent of the direction of current flow.
An external magnetic field causes a variation in the relative orientation of the magnetization of neighboring ferromagnetic layers in a spin valve. This in turn causes a change in the spin-dependent scattering of conduction electrons and thus the electrical resistance of the spin valve. The resistance of the spin valve thus changes as the relative alignment of the magnetizations of the ferromagnetic layers changes.
Typically, a conventional simple spin valve comprises a ferromagnetic free layer, a spacer layer, and a single-layer pinned ferromagnetic layer, which is exchange-coupled with an anti-ferromagnetic (AF) layer. In an anti-parallel (AP) pinned spin valve, the single-layer pinned ferromagnetic layer is replaced by a laminated structure comprising at least two ferromagnetic pinned sublayers separated by one or more thin non-ferromagnetic anti-coupling sublayers.
In general, the larger the value of ΔR/R and the smaller the coupling field Hf, the better the performance of the spin value. The ΔR/R value of a spin valve conventionally increases as the thickness of the spacer layer decreases due to the reduced shunting of the sense current in the spacer layer of the spin valve. For example, a spin valve with a copper spacer layer having a thickness of 28 Å will achieve a ΔR/R of about 5%. If the thickness of copper spacer is reduced to 20 Å, a ΔR/R of 8% will be obtained. However, the ferromagnetic coupling field Hf also increases as the thickness of the spacer layer decreases. In addition, the ferromagnetic coupling field of conventional spin valves is unstable upon annealing cycles. For example, the ferromagnetic coupling field of spin valves changes from about +5 Oe at the beginning of the annealing process to +20 Oe after annealing cycles.
An article entitled "Oxygen as a Surfactant in the Growth of Giant Magnetoresistance Spin Valve" published Dec. 15, 1997 by Journal of Applied Physic to Egelhoff et al. discloses a method for increasing the giant magnetoresistance of ΔR/R of Co/Cu spin valves with use of oxygen. In this method, oxygen is introduced in an ultrahigh vacuum deposition chamber with an oxygen partial pressure of 5×10−9 Torr during deposition of the spin valve layers, or the top copper surface is exposed to the oxygen to achieve an oxygen coverage, after which growth of the sample is completed. The oxygen acts as a surfactant during film growth to suppress defects and to create a surface that scatters electrons more specularly. Oxygen coverage decreases the ferromagnetic coupling between magnetic layers, and decreases the sheet resistance of spin valves.
Unfortunately, this technique requires a very small oxygen partial pressure window around 5×10−9 Torr, since when the oxygen partial pressure is increased to only 10−8 Torr, all GMR (ΔR/R) gain due to oxygen is lost, and at oxygen pressures higher than this, the fall-off in GMR is rapid. This very small oxygen partial pressure is very difficult to achieve or to maintain in a large manufacturing type system. Also, oxygen exposure of only one surface of the copper spacer layer does not optimize the ferromagnetic coupling field. Furthermore, the use of oxygen for all spin valve layer depositions may result in oxidation of Mn in anti-ferromagnetic materials, such as FeMn, PtMn, IrMn, PdPtMn and NiMn, and thus kills the spin valve effect. Therefore this technique can not be applied for spin valve deposition.
In addition, adsorbing oxygen only on the copper surface does not improve the GMR, and produces only a positive coupling field. Furthermore, this technique results in a decrease in sheet resistance, which reduces the overall signal. Finally, prior art oxygen treatment does not show stabilization of the ferromagnetic coupling field upon hard bake annealing cycles.
There is a need, therefore, for an improved method of making spin valves that overcomes the above difficulties.

Method to achieve low and stable ferromagnetic coupling field

International Business Machines Corporation


A method of driving an electric motor includes generating a periodic, driving voltage. The driving voltage comprises a sequence of first, second, and third waveforms. The first waveform in the sequence is a generally constant, high voltage. The second waveform in the sequence is a down hook voltage. The third waveform in the sequence is an up hook voltage. The method also includes applying the driving voltage to a coil of the motor to generate a generally sinusoidal current through the coil of the motor.

A mass storage device, such as a hard disk drive, utilizes a spindle motor to rotate platters that store information. The spindle motor generally rotates the platters at a constant angular speed while electromagnetic heads read from or write to circular tracks on the platters. The spindle motor is often implemented as a three phase motor.
A typical, three-phase motor includes a magnetic rotor and three electric coils. The three electric coils are related to the three phases of the motor. A separate current, called a phase current, flows through each of the three electric coils of the motor. The rotor rotates in response to an electrical field created by the phase currents.
The phase currents flowing through the three electric coils generally interact with the magnetic elements in the motor to produce acoustic noise. In some traditional drives, each of the motor's three electric coils cycles through three states: each electric coil can be held at ground, driven to some positive voltage, or floated. As a result, the phase currents flowing through the electric coils have very abrupt transitions. Because torque is proportional to current, the abrupt changes in the phase currents cause the torque also to change abruptly. If the harmonics in the torque waveform excite mechanical resonances, the motor structure may vibrate and generate audible noise.

Method and system for driving a three-phase motor in a mass storage device


A polyaxial bone anchoring system includes a receiving part having an accommodation space, a first anchoring element having a first head, a sleeve-like insert piece configured to be arranged around a portion of the first head and to be arranged in the accommodation space, a second anchoring element having a second head, and a pressure member configured to exert pressure onto the first head or the second head, wherein when one of the first anchoring element or the second anchoring element is connected to the receiving part, the connected anchoring element is pivotable relative to the receiving part and can be locked at an angle relative to the receiving part by exerting pressure with the pressure member onto the respective head of the connected anchoring element, and wherein the first bone anchoring element and the second bone anchoring element are configured to be interchangeably connectable to the receiving part.

1. Field of the Invention
The invention relates to a polyaxial bone anchoring system including a receiving part and at least a first bone anchoring element and, in some embodiments, a second bone anchoring element that are selectively connectable to the receiving part. Each of the first bone anchoring element and the second bone anchoring element is pivotable in the receiving part and can be fixed at a desired angle. The receiving part couples the bone anchoring element to a stabilization element such as a spinal rod. The first bone anchoring element can be pivoted in the receiving part to an enlarged maximum pivot angle that is greater than a maximum pivot angle of the second bone anchoring element. An orientation of the enlarged pivot angle can be selected within a range of 360° around a central axis of the receiving part, and may be automatically achieved by pivoting the receiving part relative to the bone anchoring element. Such a polyaxial anchoring device is a modular device, wherein the receiving part and the bone anchoring element are connectable by introducing the bone anchoring element from the bottom into the receiving part.
2. Description of Related Art
A polyaxial bone anchoring device with an enlarged pivot angle is described in U.S. Pat. No. 6,736,820. This bone anchoring device includes a bone screw and a receiving part with a seat for the head of the bone screw. The screw member can be pivoted to at least one side by an enlarged angle, because the edge bounding the free end of the receiving part is of asymmetric construction. In a modified embodiment, an insert piece is provided, which has a spherical bottom as a seat for the head of the screw member.
US 2007/0118123 A1 describes a polyaxial bone anchor with increased angulation. The polyaxial bone anchor has a locking element shaped and configured to allow an anchoring member, e.g. a screw or a hook, to polyaxially rotate at large angles about a central axis of the bone anchor before compression locking the anchoring member within an anchor head.


A laser peening process for the densification of metal surfaces and sub-layers and for changing surface chemical activities provides retardation of the up-take and penetration of atoms and molecules, particularly Hydrogen, which improves the lifetime of such laser peened metals. Penetration of hydrogen into metals initiates an embrittlement that leaves the material susceptible to cracking.

1. Field of the Invention
The present invention relates to laser peening, and more specifically, it relates to methods of laser peening a metal to prevent the absorption and adsorption by that material of deleterious atoms and molecules.
2. Description of Related Art
Hydrogen embrittlement is a major cause of metal failure especially fastener failure. The prevailing thought is that steels with a Rockwell hardness above C30 are vulnerable. Titanium and aluminum alloys are also susceptible to hydrogen reactions. The phenomenon is well known, although the precise mechanism has been elusive despite extensive research. A number of mechanisms have been proposed, and most are considered to have at least some merit. A widely held theory is that susceptibility to hydrogen embrittlement is related directly to the trapped population in the material. Generally, hydrogen embrittlement can be described as absorption and adsorption of hydrogen which promotes enhanced de-cohesion of the material (e.g., steel), primarily as an intergranular phenomenon.
Electroplating is a major cause of hydrogen embrittlement. Some hydrogen is generated during the cleaning and pickling cycles, but by far the most significant source is cathodic inefficiency, which is followed by sealing the hydrogen in the parts. Baking is often performed on high strength parts to reduce this risk. For the production plater, having to remove the parts from the production line to bake, followed by a separate chromating process, is a laborious process.
Hydrogen will penetrate into materials along grain boundaries and dislocations, hastening hydrogen embrittlement. Hydrogen diffuses along the grain boundaries and combines with the carbon, which is alloyed with the iron, to form methane gas. The methane gas is not mobile and collects in small voids along the grain boundaries where it builds up enormous pressures that initiate cracks. In nuclear power plants without aluminum components, hydrogen embrittlement is a primary reason that reactor coolant is maintained at a neutral or basic pH.
If the metal is under a high tensile stress, brittle failure can occur. At normal room temperatures, the hydrogen atoms are absorbed into the metal lattice and diffused through the grains, tending to gather at inclusions or other lattice defects. If stress induces cracking under these conditions, the path is transgranular. At high temperatures, the absorbed hydrogen tends to gather in the grain boundaries and stress-induced cracking is then intergranular. The cracking of martensitic and precipitation hardened steel alloys is believed to be a form of hydrogen stress corrosion cracking that results from the entry into the metal of a portion of the atomic hydrogen that is produced in the following corrosion reaction.
Hydrogen embrittlement is not a permanent condition. If cracking does not occur and the environmental conditions are changed so that no hydrogen is generated on the surface of the metal, the hydrogen can re-diffuse from the steel, so that ductility is restored.
To address the problem of hydrogen embrittlement, emphasis is placed on controlling the amount of residual hydrogen in steel, controlling the amount of hydrogen pickup in processing, developing alloys with improved resistance to hydrogen embrittlement, developing low or no embrittlement plating or coating processes, and restricting the amount of in-situ (in position) hydrogen introduced during the service life of a part.
Sources of hydrogen causing embrittlement have been encountered in the making of steel, in processing parts, in welding, in storage or containment of hydrogen gas, and related to hydrogen as a contaminant in the environment that is often a by-product of general corrosion. It is the latter that concerns the nuclear industry. Hydrogen may be produced by corrosion reactions such as rusting, cathodic protection, and electroplating. Hydrogen may also be added to reactor coolant to remove oxygen from reactor coolant systems. Hydrogen entry, the obvious pre-requisite of embrittlement, can be facilitated in a number of ways. Some manufacturing operations such as welding, electroplating, phosphating and pickling facilitate hydrogen entry. If a material subject to such operations is susceptible to hydrogen embrittlement, then a final baking heat treatment is employed to expel any hydrogen. Hydrogen entry may be caused as a by-product of a corrosion reaction such as in circumstances when the hydrogen production reaction acts as the cathodic reaction since some of the hydrogen produced may enter the metal in atomic form rather than be all evolved as a gas into the surrounding environment. In this situation, cracking failures can often be thought of as a type of stress corrosion cracking. If the presence of hydrogen sulfide causes entry of hydrogen into the component, the cracking phenomenon is often termed "sulphide stress cracking (SSC)". Hydrogen entry can result from the use of cathodic protection for corrosion protection if the process is not properly controlled.
Hydrogen embrittlement has been a problem for metals in a number of industries, especially in petroleum and gas production, where high concentrations of H2S are frequently encountered. Other hydrogen rich environments in which processes are employed, such as electroplating, picking, casting, corrosion and fuel cell reactions, have also been found to produce hydrogen damage in metals. Hydrogen atoms diffuse through the surface of metals into interstitial lattice sites or through microstructural channels such as grain boundaries, dislocation pile-ups, carbides, and defects. Once excessive hydrogen atoms are trapped and accumulated inside the metal several damage mechanisms may occur, including cracking, blistering, hydride formation, decarburization at elevated temperature and altering of tensile strength and lowering of ductility. Consequently, these deleterious effects lead to degradation of mechanical properties, and may result in eventual structural failure.
Austenitic stainless steels are employed in large quantities in these industries because of their high strength and good corrosion resistance. Their low diffusivity and high solubility of hydrogen in the FCC lattice structures provide generally good resistance to hydrogen damage in many aggressive aqueous environments. However, it has been found that with enough hydrogen permeation, austenitic stainless steels can become embrittled, and that brittle fracture has occurred in severe environmental conditions such as cathodic charging.
Hydrogen rich environments such as fuel cell reactors can exhibit damage caused by hydrogen permeation in the in the form of Hydrogen Induced Cracking (HIC) and Stress Oriented Hydrogen Induced Cracking (SOHIC). Both processes are known to decrease material ductility and can lead to corrosion cracking or failure in equipments. Although coatings and liners have been investigated by industry, there has been no definitive laser peening method referenced in literature with respect to preventing or retarding hydrogen embrittlement.

Laser peening for reducing hydrogen embrittlement

Lawrence Livermore National Security, LLC


A method and apparatus are provided for sensing the mass flow rate of a fluid flowing through a pipe. A light beam containing plural individual wavelengths is projected from one side of the pipe across the width of the pipe so as to pass through the fluid under test. Fiber optic couplers located at least two positions on the opposite side of the pipe are used to detect the light beam. A determination is then made of the relative strengths of the light beam for each wavelength at the at least two positions and based at least in part on these relative strengths, the mass flow rate of the fluid is determined.

Cryogenic systems are used throughout industry and research alike. Although the invention is not limited to such an application, of particular interest here is the application of cryogenic systems to space-related propulsion research. In this regard, most types of propulsion research rely heavily on the use of cryogenic fluids. Generally, these fluids include liquid oxygen (O2), liquid nitrogen (N2) and liquid hydrogen (H2). These cryogenic fluids are used for a variety of propulsion related requirements, such as cooling and combustion fuel/additives.
Cryogenic systems usually operate at high flow or nozzle pressures. For example, flow rates of up to 16 liters per second are common in pipes with 5 centimeter diameters. Fundamental data on physical attributes within the cryogenic liquid flow are difficult to measure. In this regard, even basic questions such as how much cryogenic liquid is actually traveling through the system are difficult to answer. At the operating temperatures of these cryogenic systems there is a constant mixing between the gaseous and liquid states. This can lead to turbulent flow and cavitation and make flow measurement difficult.
Current techniques for determining mass flow assume that there is no turbulence, which also precludes the presence of any gaseous medium in the flow. Due to the very nature of the low temperatures involved, the basic, conventional engineering measurement techniques normally used are either not available or inapplicable, or, if used, are error ridden. These conventional techniques include the use of direct contact thermocouple and thermoresistor measurements, as well as of flow-driven mechanical flow meters.

Fiber optic liquid mass flow sensor and method

The United States of America as represented by the Administrator of the National Aeronautics and Space Administration


A data transmission method in a telecommunication system utilizing frequency hopping and the system having a limit for allowable interference. The method includes performing at least two frequency hopping layers, each layer comprising one or more frequency hopping areas, the frequency hopping layers having frequency hopping parameters divergent from each other, setting the frequency hopping layers one on the other in such a way that the overlapping of the border zones of the frequency hopping areas is minimized, estimating interference in the system or in a predetermined part of the system, and if the interference is too high, transferring one or more users to another frequency hopping layer.

1. Field of the Invention
The invention relates to a data transmission method and a network element such as a base station controller in a telecommunication system, the system utilizing frequency hopping.
2. Description of the Related Art
Frequency hopping consists of changing the frequency used by a channel at regular intervals. Frequency hopping is used to attenuate the influence of attenuation due to, for instance, Rayleigh fading. One advance achieved is interferer diversity: in high traffic areas the capacity of a cellular system is limited by its own interference caused by frequency reuse. The carrier-to-interference ratio may vary considerably between calls. The carrier level changes with the mobile station position relative to the base station, with the number of obstacles between them, etc. The interference level changes depending on whether the frequency is being used by another call in a nearby cell, and it also varies according to the distance to the interfering source, its level, etc. With frequency hopping, it is possible to circulate channels between users and thus shorten the time each user has a connection of poor quality.
Typically, in cellular networks, when frequency hopping is used, the interference is most considerable in the areas, where several cells having similar frequency hopping lists (MA list, mobile allocation frequency list) and different random hopping sequences are bordering each other. Another problem is due to the fact that cellular networks usually consist of multiple separate cell clusters. The interference is usually highest in the proximity of cell border areas where there are cells belonging to different cell clusters.

Data transmission method, system and network element


A superconducting tunnel junction radiation sensing device includes first and second superconductor electrodes and a tunnel barrier layer interposed therebetween. The tunnel barrier layer is made up of a thin-wall portion and a thick-wall portion each formed of a semiconductor or an insulator, and each having opposite surfaces respectively contacting the first and second superconductor electrodes, and each extending adjacent each other in a same horizontal plane between the first and second electrodes. The thick-wall portion has a vertical thickness which is at least twice that of the thin-wall portion. Furthermore, the thickness of the thin-wall portion is such that a tunnel effect is enabled therethrough form the first electrode to the second electrode, and the thickness of the thick-wall portion is such that a tunnel effect is substantially prohibited therethrough from the first electrode to the second electrode. The thin-wall portion along the same horizontal plane is substantially evenly distributed in a cross-sectional pattern within the tunnel barrier layer, the cross-sectional pattern being either an intermittent pattern or a continuous pattern. Furthermore, the cross-sectional area along the same horizontal plane of the thin-wall portion is less than that of the thick-wall portion.

1. Field of the Invention
This invention relates to a radiation sensing device and a Josephson device. More particularly, this invention relates to a device for the detection of nuclear radiation, light energy, etc. using a superconducting tunnel junction, an arithmetic device, and a Josephson device as used for the detection of microwaves.
2. Description of the Prior Art
The radiation sensing device using a superconducting tunnel junction can possibly have more than a ten times greater energy-resolution than that of the conventional high-resolution semiconductor-detectors. The development of this radiation sensing device has been under way in recent years [Applied Physics, Vol. 53, No. 6, pages 532-537 (1984) and A. Barone "Superconductive Particle Detectors," (1988), World Scientific].
The common term "light" actually denotes an electromagnetic wave, similar to the X ray radiation. The photosensor using a superconducting tunnel junction may become highly sensitive to a wide spectrum of light i.e. light having wavelengths from the far-infrared to the ultraviolet spectrum.
Heretofore, for the detection of radiation energy such as X ray radiation and light energy, by the use of a superconducting tunnel junction, a device configured as illustrated in FIG. 23 and FIG. 24 has been developed.
In the sensing device illustrated in FIG. 23 and FIG. 24, a thin insulating layer (tunnel barrier layer) 113 is disposed throughout the entire junction between a superconductor 111 serving as a lower electrode and a superconductor 112 serving as a counter electrode and shaped so as to enclose the upper surface and one lateral surface of the superconductor 111 serving as the lower electrode. In FIG. 24, the reference numeral 127 denotes an upper wiring and the reference numeral 128 a lower wiring.
To improve the performance of the radiation sensing device or the photosensor, the surface area of the superconductor destined to serve as an absorbent for the radiation energy or photon energy must be increased for enhancing the detection efficiency of the impinging radiation or photons. In the device configured as illustrated in FIG. 23 and FIG. 24, such an increase in the surface area entails a problem in that the electric capacitance of the tunnel junction increases and the radiation or photon energy detection signal decreases.
Booth, for the purpose of solving this problem, has proposed a device having a vertical sectional structure as illustrated in FIG. 25 (Applied Physics Letters, Vol. 50, No. 5, pages 293-295 (1987)). Specifically, a superconducting tunnel junction device is produced having a lower electrode side superconductor 111 which is a composite having superposed on the central part of a large surface area of a superconductive layer 116 a superconductive layer 117 having a small surface area and having a smaller energy gap than the superconductive layer 116. An insulating layer 113 is formed on the upper surface of the superconductive layer 117, and superposed on the insulating layer 113 is a superconductor 112 which serves as a counter electrode. This device reduces the electric capacitance and provides for a large detection signal because the insulating layer 113 has a smaller surface area than the superconductive layer 116 serving as the absorbent of the radiation or photon energy. Further, since the superconductive layer 117 having a smaller energy gap than the superconductive layer 116 is joined to the insulating layer 113, the electrons or holes excited in the superconductive layer 116 by the absorption of radiation or photon energy 120 (hereinafter collectively referred to as "excited electrons" for the sake of simplicity) 121, after being diffused inside the superconductive layer 116 and then passed into the superconductive layer 117, are not appreciably returned again to the superconductive layer 116 but are instead contained within the superconductive layer 117. Since the superconductive layer 117 functions as a trapping layer and continues to trap the excited electrons close to the insulating layer 113, the probability that the excited electrons 121 will penetrate the insulating layer 113 by virtue of the tunnel effect and contribute to a single before recombination is improved.
In the device of such a structure as illustrated in FIG. 25 and as proposed by Booth, the efficiency of the collection of the excited electrons in the superconductive layer 117 is high when the mean free path of the excited electrons within the superconductive layer 116 is not very small as compared with the representative length of the plane of the superconductive layer 116 (such as, for example, the diameter where the plane has a circular shape or the length of the side where the plane has a square shape). Generally, however, it is quite difficult to increase the mean free path of excited electrons within a superconductor beyond the level of some tens of .mu.m. Even if the mean free path could be sufficiently increased in a superconductor having a bulky form, once the superconductor is finished in the form of a thin film, the mean free path is substantially limited by the thickness of the thin film. Thus, it is impossible to approximate the mean free path to the representative length of the plane of the superconductive layer 116 in the case of thin film detectors.
In the structure illustrated in FIG. 25, since the surface area of the superconductive layer 117 destined to serve as a trapping layer is smaller than that of the superconductive layer 116 destined to serve as an absorbent of energy, it is inferred that the excited electrons 121 produced as a consequence of the absorption of radiation or photon energy 120 in a portion of the superconductive layer 116 remote from the superconductive layer 117 require a much longer time to reach the superconductive layer 117 by diffusion than those produced in a portion relatively close to the superconductive layer 117 as illustrated in FIG. 26. In fact, it is well known that the average time required for the excited electrons 121 to depart from a certain point to a certain distance by diffusion is proportional to the square of this distance. It is also well known that in a superconductor, the electrons excited by radiation or photon energy eventually recombine (S. B. Kaplan et al, Physical Review B., Vol. 14, pages 4,854-4,873 (1976)). In the tunnel junction device, the excited electrons no longer contribute to detection signals when they recombine before they penetrate the insulating layer by virtue of the tunnel effect. Thus, even when the radiation or photon energy is constant, the rise time and magnitude of the detection signal varies according to the location of the impingement of the radiation or photon energy. Further, concerning the electrons excited in the portion 116 close to the superconductive layer 117, many of the excited electrons diffuse to the portion of the superconductive layer 116 remote from the superconductive layer 117 before they reach the superconductor layer 117.
In the device structure of FIG. 25, when the surface areas of the insulating layer 113 and that of the superconductor 112 are fixed and the surface area of the superconductive layer 117 is enlarged so as to equal that of the superconductive layer 116, the average time required for the electrons excited within the superconductive layer 116 to be diffused in the superconductive layer 117 is decreased. In this case, however, the time required by the excited electrons in traveling from the superconductive layer 117 of a larger surface area to the insulating layer 113 of a smaller surface area is increased and, as the result, the probability that they will recombine before they penetrate the insulating layer 113 by virtue of the tunnel effect increases.
The conventional radiation sensing device is disadvantageous in that a generous increase in the surface area for the enhancement of the efficiency of detection is difficult to obtain, in that a large increase in the surface area results in a decrease in the response speed, and in that the rise time and magnitude of the detection signal varies according to the location of the impingement of the radiation or photon energy.
Further, in the radiation sensing device or the photosensor, it is considered that an increase in the thickness of the superconductor serving as an energy absorbent is effective in enhancing the detection efficiency of radiation or light energy.
It is plain from the above description that in order for the radiation sensing device or the photosensor to be highly sensitive, however, the excited electrons produced in the sensor by the impingement of radiation or photon energy must efficiently pass through the tunnel barrier layer by virtue of the tunnel effect and then output from the junction in the form of signal charges. If the excited electrons require a long time period in tunneling the barrier layer, most of the excited electrons will recombine in this time period and are thus not output in the form of signal charges.
When the thickness of the superconductor is increased for the purpose of improving the detection efficiency of the radiation or light energy and, as the result, the time required by the excited electrons in tunneling the tunnel barrier layer increases, there ensues a disadvantage in that the collection efficiency of the excited electrons is degraded.
In fact, in the conventional radiation sensing device, the energy resolution is seriously degraded by an increase in the thickness of the superconductive layer alone. This phenomenon is ascribable in a large measure to the fact the conventional radiation sensing device configured as illustrated in FIGS. 23 and 24 or FIGS. 25 and 26 utilizes superconductors formed invariably of polycrystals.
Specifically, in order for the excited electrons 121 produced in response to the incident radiation or photon energy 120 to achieve efficient tunneling through the tunnel barrier layer 113, it is desirable that the excited electrons 121 be capable of quickly migrating about within the superconductive layer and easily reaching the tunnel barrier layer. As easily understood from FIG. 27 and FIG. 28 which, depict the manner of diffusion of excited electrons 121, it is desirable that the superconductive layer on which the radiation or photon 120 impinges not be the polycrystalline superconductor 111 but instead be a single-crystal superconductor 131 in which the mean free path of excited electrons 121 is long. Incidentally, this fact has been pointed out in literature (Nuclear Instruments and Method in Physics Research, Vol. 277, P 483 (1984)).
Forming the energy absorbent superconductor of the single-crystal superconductor 131, therefore, is advantageous for enhancing the collection efficiency of the excited electrons. In a device as illustrated in FIG. 28 which is formed using a single-crystal superconductor 131 as a lower superconductive layer and superposing thereon a tunnel barrier layer 113 and an upper superconductive layer 112, there arises a disadvantage in that there is an increase in the leak current, i.e. the electric current which flows through defects in the tunnel barrier layer 131 or in the terminal of the tunnel barrier layer 113. The leak current itself constitutes a major source of electric noise. For the radiation sensing device which measures individual components of radiation or light energy from weak signal charges, this drawback is fatal.
The superconducting tunnel junction type radiation sensing device relies on excited electrons as already described and not on the Josephson effect. The operating principle and the method of use of this radiation sensing device are entirely different from those of the microwave sensor using a Josephson junction, for example. In fact, the radiation sensing device as used is maintained under a magnetic field for the purpose of suppressing the Josephson effect. The wiring for this device also necessitates a peculiar construction which is not required in the Josephson junction. Exclusively in terms of the basic configuration of the junction, however, the superconducting tunnel junction device and the tunnel type Josephson junction are substantially identical to each other.
Heretofore, in the tunnel type Josephson device, polycrystalline superconductors have also been used as superconductors. In a device which uses polycrystalline superconductors only as superconductors, however, when the temperature above the transition temperature is lowered below that temperature in a weak magnetic field, such as in geomagnetism, the superconductor is not easily cooled evenly or uniformly in one direction because of the numerous grain boundaries present in the polycrystalline. Thus, there ensues the possibility that the magnetic field which has been expelled by the Meissner effect from a location already vested with superconductivity is trapped in a location not yet vested with superconductivity and the magnetic flux is consequently trapped in the device (magnetic flux trap). Since the occurrence of the magnetic flux trap depends on a delicate change in the manner of cooling occurring in the device, it cannot be easily controlled.
When magnetic flux is trapped, the Josephson device cannot achieve an optimum operation because the DC Josephson current decreases.
For the elimination of this problem, the use of single crystals as a superconductor layer has been tried in the tunnel type Josephson device (IEEE Transactions on Magnetic, Vol. MAG-21, No. 2, p 539 (1985)).
In the tunnel type Josephson device which uses single crystals as superconductors on the input side, it is considered that the magnetic flux trap does not easily occur because the device is liable to be cooled even or uniformly in one direction and, as the result, the magnetic flux is completely expelled from the device. Where the Josephson device is formed as illustrated in FIG. 28 by using a single-crystal superconductor 131 as a lower superconductive layer and superposing thereon a tunnel barrier layer 113 and an upper superconductive layer 112, there inevitably ensues a disadvantage in that there is an increase in the leak current, i.e. the electric current which flows through the defects in the tunnel barrier layer 113 or in the terminal part of the tunnel barrier layer 113, similar to the aforementioned radiation sensing device. Even in the Josephson device, the leak current poses a serious problem in that the probability of the device producing an erroneous operation will be increased.

Radiation sensing device and Josephson device


A method of preparing .alpha.-APM derivatives without using an expensive L-phenylalanine is provided, wherein 2,5-dioxopiperazine-3-acetamide is reacted with acetic anhydride to give N,N'-diacetyl-6-cyanomethyl-2,5-dioxopiperazine, which is then reacted with benzaldehyde in the presence of a strong base to give 1-acetyl-3-benzylidene-6-cyanomethyl-2,5-dioxopiperazine. This is treated with hydrazine to give 3-benzylidene-6-cyanomethyl-2,5-dioxopiperazine, which is then reduced to prepare 3-benzyl-6-cyanomethyl-2,5-dioxopiperazine, which is converted by reaction with methanol in the presence of a strong acid to an .alpha.-APM derivative for use as a sweetener.

1. Field of the Invention
The present invention relates to a method of preparing 3-benzyl-6-cyanomethyl-2,5-dioxopiperazine, which is an intermediate in the preparation of an .alpha.-L-aspartyl-L-phenylalanine methyl ester derivative and to a method of preparing an .alpha.-L-aspartyl-L-phenylalanine methyl ester (.alpha.-APM) derivative.
2. Discussion of the Background
.alpha.-L-aspartyl-L-phenylalanine methyl ester (Aspartame, .alpha.-APM) is in heavy demand as a good low-calorie sweetener. The .alpha.-APM derivative as referred to herein is a generic name for a group of compounds which include .alpha.-APM, .alpha.-L-aspartyl-L-phenylalanine dimethyl ester, .alpha.-L-aspartyl-L-phenylalanine-.beta.-methyl ester and .alpha.-L-aspartyl-L-phenylalanine, each of which can be converted to .alpha.-APM with relative ease by conventional methods (see Japanese Patent Application Laid-open Nos. 59-219258 and 59-225152 and U.S. Pat. No. 4,173,562). A variety of methods have previously been proposed for preparing .alpha.-APM, which are based on chemically or enzymatically condensing L-aspartic acid or a derivative thereof and L-phenylalanine or a derivative thereof (see Kirk-Othmer's Encyclopedia of Chemical Technology, vol. 22, pp 453-458 (1983); R. H. Mazur et al, J. Med. Chem., 91, 2684 (1969); Y. Ariyoshi et al. Bull Chem. Soc. SpA. 46, 1893 (1973); Y. Ariyoshi Kagakuto Seibutsu 12, 189 (1974); Chem. Abstr. 82, 1120u (1975); F. J. Vinick, U.S. Pat. No. 4,256,897; F. J. Vinick et al, Tetrahedron Lett 23, 1315 (1982); W.H.J. Boesten, U.S. Pat. No. 3,879,372; G. L. Bachman, U.S. Pat. No. 3,933,781, A. Yasutake et al, Bull. Chem. Soc. Jpn. 50, 2413 (1977); Isowa et al., Tetrahedron Lett. 20, 7611 (1979)). However, no method of preparing .alpha.-APM has been proposed which does not involve the use of L-phenylalanine or a derivative thereof. Such a method would be desirable in order to reduce the production cost of .alpha.-APM by eliminating the need to use the expensive L-phenylalanine as raw materials.

2,5-dioxopiperazine compounds and method for preparing .alpha.-aspartyl-L-phenylalanine methyl ester derivatives