Search

Acceleration of energetic particles is a fundamental and ubiquitous mechanism in space and astrophysical plasmas. One of the open questions is the role of the sheath region behind the shock in the acceleration process. We analyze observations by Solar Orbiter, BepiColombo and the L1 spacecraft to explore the structure of a coronal mass ejection (CME)-driven sheath and its relation to enhancements of energetic ions that occurred on April 19-20, 2020. Our detailed analysis of the magnetic field, plasma and particle observations show that the enhancements were related to the Heliospheric Current Sheet crossings related to the reconnecting current sheets in the vicinity of the shock and a mini flux rope that was compressed at the leading edge of the CME ejecta. This study highlights the importance of smaller-scale sheath structures for the energization process. These structures likely formed already closer to the Sun and were swept and compressed from the upstream wind past the shock into the sheath. The upcoming observations by the recent missions (Solar Orbiter, Parker Solar Probe and BepiColombo) provide an excellent opportunity to explore further their role.

Sheaths ahead of coronal mass ejections (CMEs) are large heliospheric structures that form with CME expansion and propagation. Turbulent and compressed sheaths contribute to the acceleration of particles in the corona and in interplanetary space, but the relation of their internal structures to particle energization is still relatively little studied. In particular, the role of sheaths in accelerating particles when the shock Mach number is low is a significant open problem. This work seeks to provide new insights on the internal structure of CME sheaths with regard to energetic particle enhancements. A good opportunity to achieve this aim was provided by observations of a sheath made by radially aligned spacecraft at 0.8 and $\sim$ 1 AU (Solar Orbiter, Wind, ACE and BepiColombo) on 19-21 April 2020. The sheath was preceded by a weak shock. Energetic ion enhancements occurred at different locations within the sheath structure at Solar Orbiter and L1. Magnetic fluctuation amplitudes at inertial-range scales increased in the sheath relative to the upstream wind. However, when normalised to the local mean field, fluctuation amplitudes did not increase significantly; magnetic compressibility of fluctuation also did not increase. Various substructures were embedded within the sheath at the different spacecraft, including multiple heliospheric current sheet (HCS) crossings and a small-scale flux rope. At L1, the ion flux enhancement was associated with the HCS crossings, while at Solar Orbiter, the enhancement occurred within the rope. Substructures that are swept from the upstream solar wind and compressed in the sheath can act as particularly effective acceleration sites. A possible acceleration mechanism is betatron acceleration associated with the small-scale flux rope and the warped HCS in the sheath., 14 pages, 12 figures; published in Astronomy & Astrophysics, Solar Orbiter First Results (Cruise Phase) special issue

We present the results of experiments on dynamic nuclear polarization and relaxation of 75As in silicon crystals. Experiments are performed in strong magnetic fields of 4.6 T and temperatures below 1 K. At these conditions donor electron spins are fully polarized, and the allowed and forbidden electron spin resonance transitions are well resolved. We demonstrate effective nuclear polarization of 75As nuclei via the Overhauser effect on the time scale of several hundred seconds. Excitation of the forbidden transitions leads to a polarization through the solid effect. The relaxation rate of donor nuclei has strong temperature dependence characteristic of Orbach process.

We report on a study of the exchange tunneling reaction D + HD → D2 + H in a pure solid HD matrix and in a D2 matrix with a 0.23% HD admixture at temperatures between 130 mK and 1.5 K. We found that the exchange reaction rates, kexHD ∼ 3 × 10-27 cm3 s-1 in the pure HD matrix, and kexD2 = 9(4) × 10-28 cm3 s-1 in the D2 matrix, are nearly independent of temperature within this range. This confirms the quantum tunnelling nature of these reactions, and their ability to proceed at temperatures down to absolute zero. Based on these observations we concluded that exchange tunneling reaction H + H2 → H2 + H should also proceed in a H2 matrix at the lowest temperatures. On the other hand, the recombination of H atoms in solid H2 and D atoms in solid D2 is substantially suppressed at the lowest temperatures as a result of a decreased probability of resonant tunneling of atoms when they approach each other.

We report on the measurements of electrons trapped in solid molecular films of H $$_{2}$$ , HD, and D $$_{2}$$ . A narrow ESR line associated with the trapped electrons was detected with $$g=2.00233(5)$$ , which turned out to be shifted by $$-$$ 0.3 G from the free electron resonance. Comparison is made with earlier measurements where a similar line has been seen. In addition, for a $$\text {D}_{2}{:}\text {H}_{2}$$ mixture, after raising the temperature above 1 K, we observe a strong line at the location of the electron cyclotron resonance. The line amplitude is dependent on temperature and has an activation energy of 26 K. We believe that at elevated temperatures, electrons diffuse from the bulk of the film to the surface.

We report on the first ESR study of atomic hydrogen and tritium stabilized in solid T

Efficient manipulation of nuclear spins is important for utilizing them as qubits for quantum computing. In this work we report record high polarizations of ${}^{31}\mathrm{P}$ and $^{29}\mathrm{Si}$ nuclear spins in P-doped silicon in a strong magnetic field (4.6 T) and at temperatures below 1 K. We reached ${}^{31}\mathrm{P}$ nuclear polarization values exceeding $98%$ after 20 min of pumping the high-field electron spin resonance (ESR) line with a very small microwave power of 0.4 $\ensuremath{\mu}\mathrm{W}$. We evaluate that the ratio of the hyperfine-state populations increases by three orders of magnitude after 2 hours of pumping, and an extremely pure nuclear spin state can be created, with less than 0.01 ppb impurities. A negative dynamic nuclear polarization has been observed by pumping the low-field ESR line of ${}^{31}\mathrm{P}$ followed by the flip-flip cross relaxation, the transition which is fully forbidden for isolated donors. We estimate that while pumping the ESR transitions of ${}^{31}\mathrm{P}$ also the nuclei of $^{29}\mathrm{Si}$ get polarized, and polarization exceeding $60%$ has been obtained. We performed measurements of relaxation rates of flip-flop and flip-flip transitions which turned out to be nearly temperature independent. Temperature dependence of the ${}^{31}\mathrm{P}$ nuclear relaxation was studied down to 0.75 K, below which the relaxation time became too long to be measured. We found that the polarization evolution under pumping and during relaxation deviates substantially from a simple exponential function of time. We suggest that the nonexponential polarization dynamics of ${}^{31}\mathrm{P}$ donors is mediated by the orientation of $^{29}\mathrm{Si}$ nuclei, which affect the transition probabilities of the forbidden cross-relaxation processes.

We report on a study of the exchange tunneling reaction D + HD → D

We report on the first ESR study of atomic hydrogen and tritium stabilized in a solid T$_{2}$ and T$_{2}$:H$_{2}$ matrices down to 70$\,$mK. The concentrations of T atoms in pure T$_{2}$ approached $2\times10^{20}$cm$^{-3}$ and record-high concentrations of H atoms $\sim1\times10^{20}$cm$^{-3}$ were reached in T$_{2}$:H$_{2}$ solid mixtures where a fraction of T atoms became converted into H due to the isotopic exchange reaction T+H$_2\rightarrow$TH+H. The maximum concentrations of unpaired T and H atoms was limited by their recombination which becomes enforced by efficient atomic diffusion due to a presence of a large number of vacancies and phonons generated in the matrices by $\beta$-particles. Recombination also appeared in an explosive manner both being stimulated and spontaneously in thick films where sample cooling was insufficient. We suggest that the main mechanism for H and T migration is physical diffusion related to tunneling or hopping to vacant sites in contrast to isotopic chemical reactions which govern diffusion of H and D atoms created in H$_{2}$ and D$_{2}$ matrices by other methods.

A method is presented to synthesize wideband linear-phase FIR filters with a piecewise-polynomial-sinusoidal impulse response. The proposed method is based on merging the earlier synthesis scheme proposed by the authors with the method proposed by Chu and Burrus and by modifying it by using an arbitrary number of separately generated center coefficients instead of only one used in the method by Chu-Burrus. The desired impulse response is created by using a parallel connection of several filter branches and by adding an arbitrary number of center coefficients to form it. The arithmetic complexity of these filters is proportional to the number of branches, the common polynomial order for each branch, the number of separate center coefficients, and the number of complex multipliers. The filter coefficients are optimized by using linear programming. An example shows the benefits of these filters with regard to reducing the number of coefficients as well as the arithmetic complexity.

In the experiments to be described two congenic inbred lines CB and CC and two recombinant lines CB.R1 and CC.R1 were used. All four lines differ only in regard to the major histocompatibility complex (MHC). To determine the percentage distributions of the two cell subsets in peripheral blood lymphocytes (PBL) in these lines, monoclonal antibodies to these two antigens were used. By FACScan there were more CD4+PBL in CB and CB.R1 lines (share B-F/B-L region, controlling class I/class II antigens with line CB) than CC and CC.R1, while the reverse was true with CD8+ subsets. There were more CD8+ PBL in the CC and CC.R1 lines and less in CB and CB.R1 lines. The ratio of CD4+ to CD8+ in CB chickens was 3.4 +/- 0.2 and in CC chickens 1.6 +/- 0.1.

We demonstrate an efficient control of $^{29}\mathrm{Si}$ nuclear spins for specific lattice sites near $^{31}\mathrm{P}$ donors in silicon at temperatures below 1 K and in a high magnetic field of 4.6 T. Excitation of the forbidden electron-nuclear transitions leads to a pattern of well-resolved holes and peaks in the electron spin resonance (ESR) lines of $^{31}\mathrm{P}$. The pattern originates from dynamic polarization (DNP) of the $^{29}\mathrm{Si}$ nuclear spins near the donors via the solid effect. DNP of $^{29}\mathrm{Si}$ is demonstrated also with the Overhauser effect where the allowed ESR transitions are excited. In this case mostly the remote $^{29}\mathrm{Si}$ nuclei having weak interaction with the donors are polarized, which results in a single hole and a sharp peak pair in the ESR spectrum. Our work shows that the solid effect can be used for initialization of $^{29}\mathrm{Si}$ nuclear spin qubits near the donors.

We introduce a genetic algorithm-based method for structural optimization of multiplicative general parameter (MGP) finite impulse response (FIR) filters. These computationally efficient reduced-rank adaptive filters are robust, suitable for predictive configurations, and they have numerous applications in 50/60 Hz power systems instrumentation. The design process of such filters has three independent stages: Lagrange multipliers-based optimization of the sinusoid-predictive basis filter, genetic algorithm-based search of optimal FIR tap cross-connections and, finally, the online MGP-adaptation phase guided by variations in signal statistics. Thus, our multistage design procedure is a complementary fusion of hard computing (HC) and soft computing (SC) methodologies. Such advantageous fusion (or symbiosis) thinking is emerging among researchers and practicing engineers, and it can potentially lead to competitive combinations of individual HC and SC methods.

We introduce an evolutionary-programming-based method for designing robust and computationally efficient adaptive bandpass filters. These predictive filters are optimized for generating current references in active power filters (APFs). The accuracy (phase/amplitude) of the reference current is crucial in current-injection-type systems, because it directly affects the harmonics reduction ability of the APF. Our digital filtering approach has the following advantages: selective bandpass response, efficient attenuation of specific harmonic components, capability to handle typical frequency alteration, small number of multiplications, and structural simplicity. In addition, practically no prior knowledge of the electricity distribution network and its loading characteristics is needed for designing the current reference generator. In an illustrative example, the total harmonic distortion of an artificial current waveform was reduced from 36.7% to less than 3.7% within the line frequency range 49-51 Hz. The proposed scheme is a combination of the hard-computing (HC)-type multiplicative general parameter method and evolutionary programming that, on the other hand, is a constituent of soft computing (SC). Such open-minded fusion thinking is emerging among researchers and engineers, and it can potentially lead to efficient combinations of HC and SC methodologies*both on the algorithm level and on the system level.

Adaptive filters are often used in signal processing tasks related to line-frequency signals in power distribution systems. In this paper, we discuss a computationally efficient adaptive algorithm for transversal discrete-time filters. The algorithm, which is based on the so-called general parameter method, uses only two dynamically adjusted parameters, each to be added to a block of coefficients of a fixed basis finite-impulse response filter. The parameter updating formula involves running addition of the data samples, causing suppression of certain frequencies. Therefore, the algorithm can be designed to adapt mainly according to the primary input frequency while being tolerant against specific harmonic components. This is advantageous, for instance, when processing 50/60-Hz line-frequency signals. The properties and stability of the algorithm are analyzed.

We report on magnetic resonance studies of high-density atomic hydrogen and deuterium in solid hydrogen matrices at temperatures below 1 K. Average concentrations of H atoms $\ensuremath{\approx}3\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}3}$ are obtained in chemical tunneling reactions of isotope exchange with D atoms. The products of these reactions are closely located pairs of H atoms near ${\mathrm{D}}_{2}$ molecules with strong exchange interactions. We discovered a dynamic nuclear polarization effect on H atoms created by pumping the center of the H electron spin resonance spectrum, similar to the Overhauser effect in metals. Our results indicate that H atoms may be arranged inside molecular matrices at separations equivalent to local concentrations of $2.6\ifmmode\times\else\texttimes\fi{}{10}^{21}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}3}$. This opens up a way to build a metallic state of atomic hydrogen at zero pressure.

An in vivo thymus reconstitution assay based on intrathymic injection of hematopoietic progenitors into irradiated chicks was used to determine the number of T-cell progenitors in peripheral blood, paraaortic foci, bone marrow (BM), and spleen during ontogeny. This study allowed us to analyze the regulation of thymus colonization occurring in three waves during embryogenesis. It confirmed that progenitors of the first wave of thymus colonization originate from the paraaortic foci, whereas progenitors of the second and the third waves originate from the BM. The analysis of the number of T-cell progenitors indicates that each wave of thymus colonization is correlated with a peak number of T-cell progenitors in peripheral blood, whereas they are almost absent during the periods defined as refractory for colonization. Moreover, injection of T-cell progenitors into the blood circulation showed that they homed into the thymus without delay during the refractory periods. Thus, thymus colonization kinetics depend mainly on the blood delivery of T-cell progenitors during embryogenesis.

We have cloned and sequenced the first nonmammalian CD4 cDNA from the chicken using the COS cell expression method. Chicken CD4 contains four extracellular Ig domains that, in analogy to mammalian CD4, are in the order V, C2, V, and C2. The molecule is 24% identical with both human and mouse sequences. The extracellular domains were modeled using human and rat CD4 crystal structures as templates. In the first domain there are two extra Cys residues that are at suitable distance to form an intra-β-sheet disulfide bridge in addition to the canonical one in the V domain. The region responsible for the interaction with MHC class II is relatively nonconserved in chicken. However, there are positively charged amino acids in the C″ region of the N-terminal domain that may mediate the association to the negatively charged residues of the MHC class II β-chain. Molecular modeling also implies that the membrane-proximal domain mediates dimerization of chicken CD4 in a similar way as it does for human CD4. Furthermore, the cytoplasmic tail is highly conserved, containing the protein tyrosine kinase p56lck recognition site that is preceded by an adjacent di-leucine motif for the internalization of the molecule. Interestingly, there are no Ser residues in the cytoplasmic part, which may explain the slow down-regulation of chicken CD4 after phorbol ester stimulation.

A digital filter design and optimization method for sampling rate alteration of narrow-band signals is presented. The resulting predictive finite-duration impulse-response filters are used to remove the aliasing or imaging frequency components when the sampling rate is changed. The sampling rate can be changed either by an integer factor or a rational factor. A least-squares-based generalization is developed for optimal wide-band noise attenuation.

Additional delay is an unavoidable drawback of conventional filters used frequently in industrial electronics. This delay is particularly harmful if the filtered primary signal is to be used for time-critical feedback or synchronization purposes. Therefore, predictive signal processing methods can offer significant advantages for these real-time applications. Polynomial predictive filters are specified without explicit passbands and stopbands, and they are behaving delaylessly or predictively for smoothly varying signal components. The degree of smoothness of the incoming signal sets the requirements for the applied filtering scheme and its parameters. Smoothness of a signal is a fuzzy and application-specific concept: the degree of smoothness depends on the ratio of the bandwidth of the primary signal and the applied sampling rate, as well as the noise component. In this paper, the authors review the most important polynomial predictive filtering methods and algorithms, their design and implementation techniques, and a collection of successful applications.

The authors describe two adaptive multistage digital filters for 50/60-Hz line-frequency signal processing in zero-crossing detectors and synchronous power systems. These filters combine a median filter with adaptive predictors, either finite-impulse response (FIR)- or infinite-impulse response (IIR)-based, thus making it possible to extract the sinusoidal signals from noise and strong disturbances without phase shifting the primary frequency signal. The median filter is used as a prefilter because it can remove deep commutation notches from the waveform. Adaptation allows the filters to track the exact instantaneous line frequency and avoids the selectivity problem encountered with a fixed filter.

Computing time delay may have greatly degrading effects on control system performance. The effects of nonzero computing delay can be classified as delay or loss problems. This delay problem occurs when the time-varying computing delay is less than the constant sampling interval, and the loss problem exists when the computing delay is greater than the sampling interval. We propose a nearly all-pass narrow-band predictor to be used as a predictive compensator of the computing delay. The presented add-on prediction scheme is practical when the output of the controller can be approximated by a piecewise low-degree polynomial. An illustrative design example is presented, demonstrating the predictor's performance.

A class of analog continuous-time filters is introduced, having predictive properties for specified narrow-band signal models, such as low-order polynomials or sinusoids. Such filters are designed by using model transfer functions designed in the discrete-time domain. Z-to-s-domain mapping is done using the inverse bilinear transformation. The analog filters are implemented with active-RC structures, using the state-variable structure for biquads and a single-op-amp structure for real poles and zeros. The application examples include a filter for zero-crossing detectors, polynomial predictors for sensor signal smoothing, and an optimized sixth-order ramp-tracking filter for anti-aliasing and anti-imaging in digital signal processor (DSP) systems where high selectivity is required.

We have examined the emigration of chicken thymocytes after intrathymic fluorescein isothiocyanate (FITC) labelling in situ. In this paper we show that in young birds about 0.7% and 0.4% of thymocytes emigrate from the thymus to the blood and the spleen, respectively, per day. This suggests that, as in mammals, most thymocytes die within the thymus. At 3 weeks of age gamma delta and alpha beta T cells leave the thymus in comparable levels to their appearance in the blood. The phenotype of recent emigrants in peripheral tissues is similar to that of mature T cells. Interestingly, recent emigrants contain relatively much higher numbers of CD4+ and fewer CD8+ cells than is observed in peripheral tissues in a steady-state situation.

An improved digital filtering method for line frequency zero-crossing detectors is proposed. The multistage filter efficiently attenuates harmonics, wide-band noise, commutation notches, and other impulsive disturbances without causing any phase shift on the primary sinusoidal waveform. Our novel signal-processing system is a cascade of a median filter and an adaptive sinusoid predictor, followed by up-sampling and interpolation. The three-point median filter effectively removes impulses, and the predictor provides wide-band noise attenuation while compensating for delays in the other processing steps. The predictor adapts to possible line frequency variations within the specified range by changing the set of coefficients, based on an estimate of the instantaneous line frequency. The adaptive approach allows the use of highly selective IIR bandpass predictors.

Two new approaches to the design of predictive FIR filters are presented. First, we discuss the design of predictors and estimators for narrow-band signals based on the interpolated FIR (IFIR) filter approach. The transfer function of the IFIR predictor is of the form H(z)=P(z/sup L/)G(z) where P(z) is a predictor and G(z) is an interpolating estimator. The general-purpose design procedure for efficient IFIR predictors is described, and demonstrated for polynomial predictors. The resulting predictors, optimized for white noise attenuation, have much lower computational complexity than the corresponding direct-form FIR predictors. Secondly, an IIR filter-based implementation of sinusoidal FIR predictors is presented. As an application, a zero-crossing detector for 50 Hz thyristor drives is designed. >

A simple combination of nonlinear and linear digital signal processing methods is proposed for efficient noise reduction in zero crossing detectors. The method is very robust against strong impulsive noise, typically encountered in thyristor power converters, where reliable zero crossing detection is required for firing synchronization. A systematic design procedure is described for the proposed filter-based synchronization method, taking into account the specified line frequency tolerance. The fully digital signal processing approach allows compact implementations, and supports flexible interfacing to digital motor control systems. >

An adaptive, robust, and computationally efficient disturbance reduction method for line-frequency zero-crossing detectors is proposed. Our adaptive system consists of a fixed finite-impulse response filter block and two multiplicative general parameters. The predictive filter is able to handle wide variations in the line frequency without harmfully adapting to the harmonic components.

We present a high magnetic field study of electron spin waves in atomic hydrogen gas compressed to high densities of 10^18 cm^-3 at temperatures ranging from 0.26 to 0.6 K. We observed a variety of spin wave modes caused by the identical spin rotation effect with strong dependence on the spatial profile of the polarizing magnetic field. We demonstrate confinement of these modes in regions of strong magnetic field and manipulate their spatial distribution by changing the position of the field maximum., Comment: 5 pages, 4 figures

Lymphocytes and their subset counts were determined in 30 cardiac surgery patients during cardiopulmonary bypass (CPB) with or without use of an autotransfusion device. In the autotransfusion group, centrifuged and washed autoiogous red blood cells (median 400 mL [range 200–770 mL]) and in the control group corresponding amounts of homologous packed red blood cells (median 500 mL [range 250–750 mL]) were transfused after declamping the aorta. The percentages of T lymphocytes (CD3) and T cytotoxic cells (CD8) increased in both groups (CD3 up to 5%, P < 0.05 and CD8 up to 35%, P < 0.01), but the percentage of T helper cells (CD4) did not change. The ratio of CD4/CD8 cells decreased (up to 34%, P < 0.01). The percentage of naive resting T cells (CD45RA) increased slightly (up to 8%, P < 0.05) whereas the percentages of memory T cells (CD45RO), T cells with IL-2 receptor (CD25), and natural killer cells (CD16) remained unaltered. The percentage of HLA-DR positive lymphocytes increased during CPB (up to 18%,P < 0.05), but it was decreased thereafter (up to 16%, P < 0.05). The percentage of monocytes (CD14) decreased first during CPB in both groups (up to 32%, P < 0.01), but it was higher in the autotransfusion device group (decreased 29% from initial value) than in the control group (decreased 65% from initial value) at the end of CPB (P < 0.05). This study shows that extracorporeal circulation has an effect on lymphocytes and their subset counts. The changes were slightly immunosuppressive. By contrast, use of autotransfusion devices had only minor effects.

A mAb recognizing a 40- to 44-kDa monomeric molecule on the surface of chicken T cells was used to screen a cDNA expression library made from Con A-stimulated chicken spleen cells. The sequence of the cDNA obtained encoded a molecule having 50% amino acid sequence identity with mammalian CD28, but the cysteine residue involved in the inter-chain bridge of the mammalian CD28 homodimer was not conserved in the chicken sequence. The molecule produced in transfected COS-7 cells was also recognized by another mAb that had previously been thought to recognize an avian homologue of CD2. The sequence data establish that this molecule is a homologue of mammalian CD28 in the strict evolutionary sense.

The design of sampled-data polynomial estimators for noise reduction in industrial instrumentation applications is discussed. Unlike conventional lowpass filters, an estimator causes no delay on the polynomial-like primary signal. A general purpose design approach is described, incorporating notch frequencies for removal of narrow-band noise components, such as the 50/60 Hz line frequency. A 24-tap FIR estimator is optimized for tachometer signal smoothing in motor control systems. An analog circuit architecture, targeted for silicon CMOS implementation, is described and simulated. >

A VLSI implementation of a linear-phase digital filter for ECG signal processing has been designed. With a sampling rate of 100 Hz, the passband is from 0.5 Hz to 49.5 Hz with 0.5-dB ripple. The filter architecture is based on the use of recursive running-sum blocks, resulting in a very low computational complexity. Module generators have been used in the layout design for high integration density. The circuit has been designed for a 2.0-/spl mu/m double-metal CMOS technology, having about 34000 transistors and a 15.43-mm/sup 2/ chip area. >

A promoter polymorphism -174 G/C in the inflammatory cytokine interleukin-6 (IL-6) gene has been associated with differences in serum IL-6 levels and a risk for inflammatory conditions, such as cardiovascular diseases. We investigated whether this polymorphism is associated with Chlamydia pneumoniae, a common causative agent of respiratory infection with tendency for persistent infections, in 867 Finnish military recruits. IgG seropositivity in arrival and departure serum samples during 6-12 months of military service was considered as persistence of antibodies and a possible prolonged or chronic infection. The -174C allele was significantly associated with IgG seropositivity (P = 0.0002) and the persistence of IgG antibodies (P = 0.0002) as well as with slightly elevated C-reactive protein (CRP) levels (P = 0.003). In addition, the association was stronger when persistent C. pneumoniae antibodies were present together with elevated CRP than when either of them was positive alone (OR; 95% CI: 3.45; 2.00-5.98 and 1.41; 1.00-1.99, respectively). Our data suggest that IL-6 -174 G/C polymorphism is associated with persistence of C. pneumoniae antibodies and may be linked to the chronic or prolonged infection with systemic low-grade inflammation.

Viral infections and graft-versus-host disease (GVHD) render an impact on both the clinical and immunological recovery following allogeneic hematopoietic stem cell transplantation (HSCT). We studied the recuperation of the immune defence after transplant in the paediatric setting and assessed the impact of early (100 days post-HSCT) viral [cytomegalovirus (CMV), Ebstein-Barr virus (EBV) and adenovirus] reactivations/infections and GVHD. Fifty-one paediatric recipients of HSCT were enrolled. T cell recovery was evaluated on lymphocyte subpopulations using flow cytometry and functionally by measuring T cell excision circles (TRECs) and through the analysis of T lymphocyte responses to mitogens. B cell recovery was studied by flow cytometry and functionally by ELISPOT. Acute and mild chronic GVHD allowed for a brisk recovery of both cellular and humoral immunity while moderate to severe chronic graft-versus-host disease (cGVHD) associated with a significant, tampering effect on the immunological recovery after transplant. In the former group, the early viral reactivations/infections seemingly linked with a delayed recovery of T lymphocytes and low TRECs values. Moderate to severe cGVHD appears to associate with an impaired immunological recovery after HSCT. Early viral infections linked with prolonged T cell immunodeficiency and thymic dysfunction may be indicative of the presence of subclinical GVHD.

A simple heuristic method for designing frequency-selective finite impulse response (FIR) filters with prediction properties is presented. Starting from passband and stopband specifications, a linear-phase model filter is converted into a minimum phase equivalent and the zero locations are manipulated in order to achieve negative group delay at the zero frequency. The method allows us to design FIR ramp predictors with nearly equiripple stopband characteristics.

We study the output coupling of atoms from a magnetic trap into a linear potential slope of gravity using a weak radio-frequency field. We present a one-dimensional wave-packet model based on a continuous loading of a continuous spectrum of generalised eigenstates to describe the scenario. Analyzing the model, we show how the interference of the classical coupling fields maps to the interference of the resulting atomic streams., Comment: 8 pages, 9 figures, 1 table, 40 references. Submitted for publication

We present an experimental study of H atoms embedded in thin films of solid ${\text{H}}_{2}$ at temperatures below 1 K. ${\text{H}}_{2}$ films up to 50 nm thick were first grown as a result of slow recombination of atomic hydrogen gas on the sample cell walls. If the recombination occurred in three-body atomic collisions in the gas phase, small concentrations of atoms could be captured inside the films during the film deposition. As a second method of generating atomic populations inside the ${\text{H}}_{2}$ films, we used a direct dissociation by a low power rf discharge in the sample cell. With this latter method, we achieved record high atomic concentrations exceeding $2\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }{\text{cm}}^{\ensuremath{-}3}$. The samples were characterized by means of magnetic resonance: electron spin resonance (ESR) and electron-nuclear double resonance (ENDOR) in a magnetic field of 4.6 T. We observed density-dependent broadening and shifts of the ESR lines due to the dipolar interactions, and resolved these effects for like and unlike atoms. Relaxation of the relative hyperfine populations was measured as a function of temperature for H in ${\text{H}}_{2}$ films grown on different substrates. For ${\text{H}}_{2}$ films on Mylar substrates, the relative equilibrium populations of the two lowest hyperfine states of H were found to deviate substantially from the prediction of Boltzmann statistics. We also found two narrow lines in the ENDOR spectra of H in ${\text{H}}_{2}$ films shifted to the red from the position for free atoms. This indicates two possible substitutional positions of the atoms in ${\text{H}}_{2}$ matrices, both characterized by very homogeneous crystalline fields.

In chickens from congenic inbred lines CB and CC that differ only in the major histocompatibility complex (MHC), we observed significantly different percentages of CD4+ and CD8+ cells in peripheral blood lymphocytes (PBL) and spleen. Positive cells were detected by indirect immunofluorescence test as analysed by flow cytometry. In both PBL and spleen cell suspensions, the number of CD4+ cells was significantly higher in CB than in CC chickens, whereas in CC birds there was a higher percentage of CD8+ cells than in CB. These statistically significant differences were under the MHC control. We found no statistically significant influence of regressions or progression of Rous sarcoma virus-induced tumours on the percentage of peripheral T cells and on the interleukin-2 production in vitro.

Newton predictors have considerable gain at the higher frequencies, which reduces their applicability to practical signal processing where the narrowband primary signal is often corrupted by additive wideband noise. Two modifications that can be used to extrapolate low-order polynomials have been proposed. In both approaches, the highest order difference of successive input samples, approximating the constant nonzero derivative, is smoothed before it is added to the lower order differences, reducing the undesired noise gain. The linear smoothed Newton (LSN) predictor is extended in this work by including a recursive term in the basic transfer function and cascading the rest of the successive difference paths with appropriately delayed extrapolation filters of corresponding polynomial orders. This leads to computationally efficient IIR predictors with significantly lowered gain at the higher frequencies. The recursive predictor is analyzed in the time and frequency domains and compared to the other predictors. >

Discrete-time computational models of squirrel-cage AC motors are derived and analyzed for the purpose of advanced motor control. The starting point is a continuous-time model defined by a pair of simultaneous complex-coefficient differential equations. Discrete-time models are derived using both the bilinear transformation and the forward-difference approximation. The exact dependence between stability and the minimum sampling rate in the forward-difference approach is shown. The responses of the two discretized models are compared using real-world motor parameters. Using the forward difference method, a more compact implementation is obtained (although a higher sampling rate is required) as compared to the bilinear transformed model of equivalent performance and 2.7 times higher computational complexity. A 16/24-b DSP-ASIC coprocessor prototype implementing the AC motor model is introduced. >

The stabilization of high densities of atomic hydrogen $(2\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }{\text{cm}}^{\ensuremath{-}3})$ embedded in solid ${\text{H}}_{2}$ films has been achieved by employing a method for producing the samples involving a direct dissociation of ${\text{H}}_{2}$ molecules by a cold plasma discharge in the sample cell at temperatures below 0.5 K. High stabilities against recombination were obtained. We observed density-dependent shifts and widths of the electron spin resonance lines resulting from the dipolar interactions between like and unlike spins. We discuss the possibilities for further increasing the H density and studying possible supersolid behavior.