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Chronic obstructive pulmonary disease (COPD) causes sarcopenia and osteoporosis. However, the mechanisms underlying muscle and bone loss as well as the interactions between muscle and bone in the COPD state remain unclear. Therefore, we herein investigated the effects of the COPD state on muscle and bone in mice intratracheally administered porcine pancreatic elastase (PPE). The intratracheal administration of PPE to mice significantly reduced trabecular bone mineral density (BMD), trabecular bone volume, trabecular number, cortical BMD and cortical area. It also significantly decreased grip strength, but did not affect muscle mass or the expression of myogenic differentiation-, protein degradation- or autophagy-related genes in the soleus and gastrocnemius muscles. Among the myokines examined, myostatin mRNA levels in the soleus muscles were significantly elevated in mice treated with PPE, and negatively related to grip strength, but not bone parameters, in mice treated with or without 2 U PPE in simple regression analyses. Grip strength positively related to bone parameters in mice treated with or without PPE. In conclusion, we showed that a PPE model of COPD in mice exerts dominant effects on bone rather than skeletal muscles. Increased myostatin expression in the soleus muscles of mice in the COPD state may negatively relate to a reduction in grip strength, but not bone loss. [ABSTRACT FROM AUTHOR]

Matrix vesicles (MtVs) are one of the extracellular vesicles (EVs) secreted by osteoblasts. Although MtVs have a classically-defined function as an initiator of ossification and recent findings suggest a role for MtVs in the regulation of bone cell biology, the effects of MtVs on bone repair remain unclear. In the present study, we employed collagenase-released EVs (CREVs) containing abundant MtVs from mouse osteoblasts. CREVs were administered locally in gelatin hydrogels to damaged sites after a femoral bone defect in mice. CREVs exhibited the characteristics of MtVs with a diameter <200 nm. The local administration of CREVs significantly promoted the formation of new bone with increases in the number of alkaline phosphatase (ALP)-positive cells and cartilage formation at the damaged site after the femoral bone defect. However, the addition of CREVs to the medium did not promote the osteogenic differentiation of ST2 cells or the ALP activity or mineralization of mouse osteoblasts in vitro. In conclusion, we herein showed for the first time that MtVs enhanced bone repair after a femoral bone defect partly through osteogenesis and chondrogenesis in mice. Therefore, MtVs have potential as a tool for bone regeneration. [ABSTRACT FROM AUTHOR]

The interactions between muscle and bone are noted in the clinical relationships between sarcopenia and osteoporosis. Myokines secreted from the skeletal muscles play roles in muscle-bone interactions related to various physiological and pathophysiological states. Although numerous evidence suggests that growth hormone (GH) influences both muscle and bone, the effects of GH on the muscle-bone interactions have remained unknown. We, therefore, investigated the influences of GH administration for 8 weeks on muscle and bone, including myokine expression, in mice with or without ovariectomy (OVX). GH administration significantly increased muscle mass in the whole body and lower limbs, as well as tissue weights of the extensor digitorum longus (EDL) and soleus muscles in mice with or without OVX. Moreover, it markedly increased grip strength in both mice. As for femurs, GH administration significantly increased cortical thickness and area in mice with or without OVX. Moreover, GH significantly blunted the decrease in the ratio of bone volume to tissue volume at the trabecular bone in mice with OVX. GH administration significantly decreased follistatin mRNA levels in the EDL, but not the soleus, muscles in mice with or without OVX, although it did not affect the other myokines examined. However, GH administration significantly elevated serum follistatin levels in mice. In conclusion, this study indicates that GH administration increases skeletal muscle mass and grip strength and cortical and trabecular bone-related parameters obtained by micro-computed tomography analyses in mice. However, myokine regulation might not be critical for the effects of GH on muscle and bone. [ABSTRACT FROM AUTHOR]

In power electronics, diode rectifiers are often regarded as the counterpart of a power amplifier. That is plausible because a power amplifier converts dc energy into RF, and a rectifier works in the reverse. In fact, wireless power transfer systems employ a power amplifier for transmission and a diode rectifier for reception. Therefore, the design theory of rectifiers is supposed to be analogous to that of power amplifiers. Is it straightforward to adapt the amplifier theory for rectifiers? [ABSTRACT FROM AUTHOR]

Exercise is important for the prevention and treatment of sarcopenia and osteoporosis. Although the interactions between skeletal muscles and bone have recently been reported, the myokines linking muscle to bone during exercise remain unknown. We previously revealed that chronic exercise using treadmill running blunts ovariectomy‐induced osteopenia in mice. We herein performed an RNA sequence analysis of the gastrocnemius and soleus muscles of male mice with or without chronic exercise to identify the myokines responsible for the effects of chronic exercise on the muscle/bone relationship. We extracted peripheral myelin protein 22 (PMP22) as a humoral factor that was putatively induced by chronic exercise in the soleus and gastrocnemius muscles of mice from the RNA sequence analysis. Chronic exercise significantly enhanced the expression of PMP22 in the gastrocnemius and soleus muscles of female mice. PMP22 suppressed macrophage‐colony stimulating factor and receptor activator factor κB ligand‐induced increases in the expression of osteoclast‐related genes and osteoclast formation from mouse bone marrow cells. Moreover, PMP22 significantly inhibited osteoblast differentiation, alkaline phosphatase activity, and mineralization in mouse osteoblast cultures; however, the overexpression of PMP22 did not affect muscle phenotypes in mouse muscle C2C12 cells. A simple regression analysis revealed that PMP22 mRNA levels in the gastrocnemius and soleus muscles were positively related to cortical bone mineral density at the femurs of mice with or without chronic exercise. In conclusion, we identified PMP22 as a novel myokine induced by chronic exercise in mice. We first showed that PMP22 suppresses osteoclast formation and the osteoblast phenotype in vitro. [ABSTRACT FROM AUTHOR]

A frame-splitting (FS) scheme is proposed to exploit spatial diversity in the downlink wireless transmission from a base station (BS) to a mobile station (MS) that has multiple receive antennas. The BS has multiple geographically distributed arrays, each consisting of multiple transmit antennas. The scenario comprises a number of downlink multiple-input-multiple-output (MIMO) channels from different BS arrays to an MS with mutually independent Rayleigh-fading processes. A data frame from the BS for the MS is split into portions, which are consecutively transmitted from multiple BS arrays. For the FS transmission scheme, the distribution of information capacity is formulated on the basis of the FS fractional lengths of the portions. Analytical evaluation of the outage probability reveals the optimal setting of FS fractional lengths for the maximum diversity advantage based on knowledge of the long-term average signal-to-noise ratios (SNRs) of the downlink MIMO channels. Index Terms--Distributed antennas, diversity, multiple-input multipleoutput (MIMO), outage capacity, Rayleigh fading, Wishart matrices.

Effects of gravitational loading or unloading on the growth-associated increase in the cross-sectional area and length of fibers, as well as the total fiber number, in soleus muscle were studied in rats. Furthermore, the roles of satellite cells and myonuclei in growth of these properties were also investigated. The hindlimb unloading by tail suspension was performed in newborn rats from postnatal day 4 to month 3 with or without 3-too reloading. The morphological properties were measured in whole muscle and/or single fibers sampled from tendon to tendon. Growth-associated increases of soleus weight and fiber cross-sectional area in the unloaded group were ~68% and 69% less than the age-matched controls. However, the increases of number and length of fibers were not influenced by unloading. Growth-related increases of the number of quiescent satellite cells and myonuclei were inhibited by unloading. And the growth-related decrease of mitotically active satellite cells, seen even in controls (20%, P > 0.05), was also stimulated (80%). The increase of myonuclei during 3-too unloading was only 40 times vs. 92 times in controls. Inhibited increase of myonuclear number was not related to apoptosis. The size of myonuclear domain in the unloaded group was less and that of single nuclei, which was decreased by growth, was larger than controls. However, all of these parameters, inhibited by unloading, were increased toward the control levels generally by reloading. It is suggested that the satellite cell-related stimulation in response to gravitational loading plays an essential role in the cross-sectional growth of soleus muscle fibers. gravitational loading/unloading; antigravity muscle

An enhanced reactance-domain estimation of signal parameters via rotational invariance techniques (RD-ESPRIT) algorithm is proposed for direction-of-arrival (DoA) estimation in the full-azimuth plane. Unlike the classical RD-ESPRIT algorithm, the proposed method employs a generalized RD correlation matrix combined with soft selection. The proposed algorithm is expected to allow estimating more than one signal DoA with improved estimation precision. The generalized RD correlation matrix is formed by utilizing a number of beam patterns greater than or equal to the number of array elements. The soft selection employed in the enhanced RD-ESPRIT consists of two steps. First, the estimates obtained by applying the generalized RD-ESPRIT to three translational-invariance configurations are gathered to form a set of DoA estimate candidates. Second, selection functions based on a modified MUSIC function are used to select the DoA estimates from among the estimate candidate set. The proposed algorithm is investigated through computer simulations with a seven-element electronically steerable parasitic array radiator (ESPAR) antenna. The simulation showed that the proposed algorithm can perform effective DoA estimation of up to four incoming signals in the full-azimuth plane with slightly improved DoA-estimation precision. So far, the classical RD-ESPRIT is not effective because it can estimate up to one signal DoA. Moreover, the proposed method showed robust estimation capability for up to two incoming signals. A robust estimation refers to the fact that a number of DoA estimates equal to the number of incoming signals can always be selected from trial to trial. A one-signal estimation experiment was conducted in an anechoic chamber with a fabricated seven-element ESPAR antenna. In general, the proposed algorithm showed as accurate estimation precision as the classical algorithm. In particular, using soft selection instead of hard selection increases the estimation precision, whereas augmenting the number of beam patterns brings an increase in the estimation precision only when used with hard selection. Index Terms--Cramer-Rao lower bound (CRB), direction-of-arrival (DoA) estimation, electronically steerable parasitic array radiator (ESPAR) antenna, estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm, reactance domain (RD), selection criteria.

Quality factor (Q-factor) and stability criterion of sinusoidal oscillators are formulated from the viewpoints of energy equilibrium and spectrum purity. Complex power works as an objective function to determine the steady-state oscillation amplitude and frequency. Conjugate product of amplitude and frequency slopes of the function dominates equilibrium stability. Logarithmic derivative of oscillator's output impedance defines active Q-factor, which takes into account effects of positive power generated by active devices, while keeping its non-divergent property. Transfer Q-factor is also defined for oscillating networks involving noise sources on different branches from the port of spectrum observation. Presented formulas can be applied to the entire oscillator circuit without de-embedding active devices, and thus they enable frequency-domain CAD simulators to numerically evaluate oscillator performance. Index Terms--Complex power, frequency slope, oscillator, Q-factor, stability, stored energy.

An extraction and calibration technique is proposed that allows electronically steerable parasitic array radiator (ESPAR) antennas to achieve high efficiency and precision in performance characterization. The proposed technique is based on a reactive-near-field measurement or direct acquisition of RF current. We present a simple formulation that requires minimal current measurements to successfully extract the mutual impedance. Currents are predicted for an arbitrary combination of bias voltages that are used to control the reactance of varactor diodes integrated with the antenna's parasitic elements. These predicted currents are compared by conducting an experiment with a seven-element ESPAR. For the bias voltage combinations that have reasonably good symmetry, the differences in relative gain, beam direction and half power beam width (HPBW) actually fall within 0.5 dB, 4[degrees] and 9[degrees], respectively. Directivity patterns obtained by calculating the predicted currents are verified with those obtained by calculating the directly measured currents. Furthermore, the calculated patterns are verified through comparison with far-field measurements in a conventional anechoic chamber. The differences in beam direction and HPBW are also found to be acceptable. Using the proposed technique, the required number of measurements is reduced from 85,766,121 to just 149 for a seven-element array. Index Terms--Adaptive arrays, anechoic chambers, antenna measurements, antenna radiation patterns, calibration, current measurement.

The necessary and sufficient condition for constructing a spreading set with decodability is investigated. It is proved that for a given [delta]-decodable spreading set and a q x q square matrix H with components 1 or -1, a q[delta]-decodable spreading set [S.sup.*] is obtained if and only if H is a Hadamard matrix. In addition, a decoding rule with error correction and message data detection is provided. Index Terms--Error-correcting code, Hadamard matrix, multiple-access communication (MAC), multiuser code, spreading set.

We examine that an inductively loaded dipole becomes electrical invisible showing that the influence on a nearby antenna's input impedance and on its radiation pattern (scattering) are minimized. We also verify that the direction of the current reverses on the electrically invisible dipole so that the integral of the dipole current becomes zero. By making an inductive load with a distributed constant line, we fabricate an electrically invisible dipole without using chip devices and evaluate its performance. Furthermore, we propose electrically invisible conductor lines formed by connecting these electrically invisible dipoles in series using open stubs as connectors, and analytically examine their invisible state. Index Terms--Current, dipole, inductive, load, scatter.

A technique to efficiently characterize the azimuth radiation patterns of monopole arrays based on evanescent reactive-near-field measurement in a compact anechoic box is presented. We describe a desktop-size measurement setup for determining the azimuth far-field pattern of an electronically steerable parasitic array radiator (ESPAR) at 2.5 GHz, and present a thorough statistical evaluation of the ESPAR antenna characterization technique. In addition, the sensitivity to probe position and the errors caused by possible fluctuations in the probe position are investigated. Furthermore, comparisons among patterns obtained by the proposed method, simulations and conventional far-field measurements are carried out, and a good agreement among them is obtained. We also provide a statistical evaluation of the proposed desktop-size measurement setup using forty ESPAR antennas and conclude that the proposed setup can be an inexpensive candidate to replace the conventional measuring system. Index Terms--Anechoic chamber, antenna arrays, antenna measurements, monopole arrays, probe antennas.

This brief characterizes one-and two-port passive networks from the viewpoint of oscillator design. A linear circuit theory derives the spectral spread due to RF noise from active devices. The formulation finds a frequency derivative function of logarithmic immittance that plays the key role of dominating the spectrum behavior. This leads to an explicit definition of the Q factor by referring to Leeson's basic oscillator model. The derived definition can provide an effective criterion for circuit topology and parameter optimization in low-noise oscillator design. Index Terms--Controlled source, immittance, negative resistance (NR), noise, oscillator, Q factor, resonator, spectrum.

We describe a secure communication scheme that uses the random fluctuation of the natural environment of communication channels. Only the transmitter and the receiver share the communication channel characteristics. From reciprocity between a transmitter and a receiver, it is possible for them to share one-time information of their fluctuating channel. This can provide a secret key agreement scheme without key management and key distribution processes. In this paper, we propose a new secret key generation and agreement scheme that uses the fluctuation of channel characteristics with an electronically steerable parasitic array radiator (ESPAR) antenna. This antenna, which has been proposed and prototyped, is a smart antenna designed for consumers. Using the beam-forming technique of the ESPAR antenna, we can increase the fluctuation of the channel characteristics. From experimental results, we conclude that the proposed scheme has the ability to generate secret keys from the received signal strength indicator (RSSI) profile with sufficient independence. Index Terms--Beam-forming, channel characteristics, electronically steerable parasitic array radiator (ESPAR), key distribution, key management, received signal strength indicator (RSSI), secret key agreement.

A direction-of-arrival (DoA) method that combines the reactance-domain (RD) technique and the ESPRIT algorithm is proposed for use with the 7-element electronically steerable parasitic array radiator (ESPAR) for the estimation of noncoherent sources. Simulations show that the method could resolve up to three incoming signals with an estimation performance that depends on the signal's angle of arrival. Moreover, the method is compared with the Cramer-Rao lower bound (CRB) and the MUSIC asymptotic error variance, both modified for the RD technique. Numerical comparison between this lower bound and the MUSIC algorithm confirmed that the proposed method can achieve the CRB and provide high-precision DoA estimation with a level of performance that is sufficient for many DoA finding applications. The proposed method could be demonstrated by means of experiments on DOA estimation conducted in an anechoic chamber. Index Terms--Cramer-Rao lower bound (CRB), direction-of-arrival (DOA) estimation, electronically steerable parasitic array radiator (ESPAR) antenna, ESPRIT algorithm, MUSIC algorithm, reactance-domain (RD).

An approach for estimating direction-of-arrival (DoA) based on power output cross-correlation and antenna pattern diversity is proposed for a reactively steerable antenna. An 'estimator condition' is proposed, from which the most appropriate pattern shape is derived. Computer simulations with directive beam patterns obtained from an electronically steerable parasitic array radiator antenna model are conducted to illustrate the theory and to inspect the method performance with respect to the 'estimator condition.' The simulation results confirm that a good estimation can be expected when suitable directive patterns are chosen. In addition, to verify performance, experiments on estimating DoA are conducted in an anechoic chamber for several angles of arrival and different scenarios of antenna adjustable reactance values. The results show that the proposed method can provide high-precision DoA estimation. Index Terms--Adjustable reactance, cross-correlation, direction-of-arrival (DoA), directive beam patterns, electronically steerable parasitic array radiator (ESPAR) antenna, Gaussian noise, high precision.

Conventional adaptive array antenna processing must observe signals on all of the array antenna elements. However, because the low-cost electronically steerable parasitic array radiator (ESPAR) antenna has only a single-port output, none of the signals on the antenna's parasitic elements can be observed. A direct application of most of the algorithms for the conventional adaptive array antenna is impractical. In this paper, a new technique of estimation of direction-of-arrivals (DoAs) is proposed for the ESPAR antenna. This technique is based on the modified MUltiple Signal Classification (MUSIC) algorithm. The correlation matrix used in the MUSIC algorithm is estimated from the signal received through the single-port output of the ESPAR antenna as it switches over a set of antenna patterns. Simulation results show that DoAs can be estimated by the reactance domain MUSIC algorithm for ESPAR antennas. Furthermore, the statistical performance on estimation error variance of the reactance domain MUSIC estimator is analyzed and compared with the Cramer-Rao lower bound. Analytic and empirical results show that high-resolution DoAs estimation can be achieved by using the reactance domain MUSIC algorithm for ESPAR antennas. Index Terms--Direction finder, electronically steerable parasitic array radiator (ESPAR) antenna, reactance domain MUltiple Signal Classification (MUSIC) algorithm.

A low-power consumption, small-size smart antenna, named electronically steerable parasitic array radiator (ESPAR), has been designed. Beamforming is achieved by tuning the load reactances at parasitic dements surrounding the active central element. A fast beamforming algorithm based on simultaneous perturbation stochastic approximation with a maximum cross correlation coefficient criterion is proposed. The simulation and experimental results validate the algorithm. In an environment where the signal-to-interference-ratio is 0 dB, the algorithm converges within 50 iterations and achieves an output signal-to-interference-plus-noise-ratio of 10 dB. With the fast beamforming ability and its low-power consumption attribute, the ESPAR antenna makes the mass deployment of smart antenna technologies practical. Index Terms--Ad hoc network, aerial beamforming (ABF), digital beamforming (DBF), electronically steerable parasitic array radiator (ESPAR), simultaneous perturbation stochastic approximation (SPSA), smart antennas, spatial division multiple access (SDMA).

The objective of the beamforming with the exploitation of a sensor array is to enhance the signals of the sources from desired directions, and to suppress the noises and the interfering signals from other directions. A higher order cumulant-based beamforming algorithm, namely, the super-exponential blind adaptive beamforming algorithm is presented.

In this paper, we introduce generation of multiplexed signals on the millimeter-wave bands for fiber-radio systems where an optical millimeter-wave generator is based on a two-mode locked Fabry-Perot (FP) slave laser, whose injection current is directly modulated by a signal source. We qualitatively consider the distortion of the millimeter-wave signals from the FP slave laser. The distortion components on the millimeter-wave bands are induced from the simultaneous modulation of the locked modes and the nonlinear modulation response of the FP laser. Two-tone modulation of the locked FP laser is examined to evaluate the dynamic range of the millimeter-wave signals against the second-and third-order distortion components. We also perform fiber transmission of three 156-Mb/s-BPSK signals on the 60-GHz band to demonstrate fiber-radio down-link systems. The total capacity of the down-link system is discussed. In addition, two methods for multicarrier generation on the millimeter-wave bands are proposed. Multicarrier generators supported by these methods can be used as local signals for up-link millimeter-wave signals. The first method is based on multitone modulation of the FP slave laser. We attempt the down-conversion of a 52-Mb/s ASK signal on the 60-GHz band by using the millimeter-wave local signals. The second method depends on the distorted modulation of the FP slave laser by using a single continuous wave signal where the dc-bias level of the FP laser's injection current is partly under the threshold value. We confirm that five carriers on the 60-GHz band are effectively generated by using the second method. Furthermore, the influences of the chromatic dispersion effects on the millimeter-wave local signals are investigated for both methods. Index Terms--Fabry-Perot (FP) lasers, fiber-radio systems, millimeter-wave links, optical generation of multicarriers.

The design of an optimized Electronically Steerable Passive Array Radiator (ESPAR) antenna is presented. A genetic algorithm using a finite element based cost function optimized the antenna's structure and loading conditions for maximal main lobe gain in a single azimuth direction. Simulated gain results of 7.3 dBi at 2.4 GHz were attained along the antenna's elemental axis. The optimized antenna was fabricated and tested with the corresponding experimental gain better than 8 dBi. The 0.7 dB error between simulated and measured gain was constant for numerous structures and therefore did not affect the optimization. The optimized antenna reduced average main lobe elevation by 15.3[degrees] to just 9.7[degrees] above the horizontal. Index Terms--Antennas, genetic algorithm, parasitic radiator, smart antennas.

Electronically steerable passive array radiator (ESPAR) antennas are considered to have the capability to spatially form a beam toward the desired signal with the lowest cost. In this paper, we propose a method to realize space-time adaptive filtering (STAF) by employing ESPAR antennas for TDMA or CDMA signal waveforms. According to the method, the cochannel interference signals are spatially suppressed by the adaptive beamforming, and the intersymbol interference signals are suppressed by the temporal waveform-based adaptive equalization. Simulation results show the effectiveness of the proposed method in the signal environment of a local network communication system. Index Terms--Adaptive beamforming, electronically steerable passive array radiator (ESPAR) antenna, local network communication systems, space-time adaptive filtering (STAF), temporal equalization, wireless communications.

This paper concerns an optical millimeter-wave signal generator for fiber-based millimeter-wave systems. The millimeter-wave signal generator is based on two-mode injection locking of a Fabry-Perot (F-P) laser. The millimeter-wave signal can be induced by self-heterodyne detection of the locked two modes in a high-speed photodetector (PD). The locking characteristics of the F-P slave laser and the tunability for the millimeter-wave carrier frequency are demonstrated. When the F-P laser is directly modulated by data signals, the locked two modes are modulated simultaneously. The data signals can then be up-converted to the millimeter-wave band at the PD output. By this direct modulation method, the effect of fiber chromatic dispersion on the millimeter-wave signal components at the PD output can be moderate according to mixing of amplitude and phase modulation on the locked two modes. In virtue of the wide response of the F-P laser, relatively high-speed data (2.5 Gbit/s nonreturn to zero (NRZ)-ASK or 622 Mbit/s NRZ-BPSK) on the millimeter-wave band (52 or 60 GHz) can be transmitted on a 32-km single-mode fiber without bit error. A wide tunable range (56-63 GHz) for the central frequency of the millimeter-wave signals and a wide optical bandwidth (1530-60 nm) of the F-P slave laser are also confirmed by the bit-error measurements of the transmitted data signals. Index Terms--Fabry-Perot (F-P) lasers, fiber-radio systems, millimeter-wave links, optical generation of millimeter-wave signals.

A novel beamforming (BF) system that employs two switched beam antennas (SBAs) at both ends of the wireless link in an indoor double-directional radio channel (DDRC) is proposed. The distributed directivity gain (DDG) and beam pattern correlation in DDRC are calculated. The channel capacity of the BF system is obtained from an analytical model. Using the channel capacity and outage capacity as performance measures, we show that the DDG of the BF system directly increases the average signal-to-noise ratio (SNR) of the wireless link, thus achieving a direct increase of the ergodic channel capacity. By jointly switching between different pairs of transmit (Tx) and receive (Rx) directional beam patterns towards different wave clusters, the system provides diversity gain to combat against multipath fading, thus reducing the outage probability of the random channel capacity. Furthermore, the performance of the BF system is compared with that of a multiple-input multiple-output (MIMO) system that is set up using linear antenna arrays. Results show that in a low-SNR environment, the BF system outperforms the MIMO system in the same clustering DDRC.