Search

Power handling capability of a tunable plasma-based multilayer absorber is studied using multiphysics analysis, then validated by experimental data. The proposed two-pole absorber is based on conductor-backed thickness customizable high-order bandpass frequency-selective surfaces (FSSs). Such technique allows simple integration of the tuning elements, while simultaneously providing the option to realize FSSs (including absorbers) with specific/desired thicknesses and transfer responses. Lossy magnetodielectric slabs, used to absorb electromagnetic (EM) energy in the $C$ -band, are added between the metallic layers. The lossy slabs are perforated to host discrete, electrically tunable, ceramic gas-encapsulating chambers (plasma-shells), enabling dynamic control of the absorption spectral band. To study the power handling capability of the proposed multilayered tunable absorber, dielectric and air breakdowns within the device are numerically emulated using EM simulation by quantifying the maximum field enhancement factor (MFEF). Furthermore, a comprehensive thermal analysis using a simulation method that couples EMs and heat transfer is performed for the absorber under high-power continuous microwave excitations. Since the heat generated within the absorber is a primary concern, the steady state as well as transient state temperature distributions have been evaluated for various incident power densities. The performance of the proposed absorber is validated for a prototype having a finite size of $13\times13$ cm2.

This article presents a comprehensive study on shorted dipole antennas aiming for low-cost radio frequency identification (RFID) reader applications. Starting from a low-profile shorted bowtie dipole antenna, it is found that by varying the shorting wall position, three different types of resonant antennas could be realized with different radiation features. A low-profile planar inverted F antenna (PIFA) -type dipole is obtained by moving the shorting wall toward the feeding, which exhibits a low resonance frequency without obvious back lobe radiation or sidelobes. When the shorting wall is placed in the middle of the radiating patch, a mushroom-type dipole antenna can be built. A zeroth-order mode is also observed. This structure differs from the magnetoelectric dipole due to a low-profile structure. Placing the wall toward the end of the dipole arm leads to a loop-type antenna with a broader beam and a reduced gain. It also shifts the resonance toward the higher frequency. Based on the PIFA- and mushroom-type structures, two circularly polarized antennas with crossed shorted dipoles are designed and investigated carefully. Finally, two optimized, compact, and low-cost RFID reader antennas based on simple metal stamping process and screws are designed, fabricated, and tested, showing an excellent RF reading range. This study demonstrates that for the shorted dipole antennas, miniaturization and bandwidth control can be achieved simultaneously. Particularly, for higher gain and smaller size, the shorting wall should be placed close to the feeding to suppress the loop mode. For omnidirectional radiation, the loop mode should be enhanced by moving the shorting wall close to the end of the dipole arm.

The capability of the capacitively loaded loop (CLL) metamaterial (MTM) superstrate to attenuate surface waves thereby reducing the back radiation of microstrip patch antennas is examined. To understand the surface wave suppression mechanism, theoretical approaches of a grounded dielectric slab waveguide is provided. Both theoretical and numerical analyses show that the proposed superstrate causes a drastic attenuation of surface wave propagation. To confirm the numerical simulations, the proposed antenna is fabricated and tested. The dimensions of the CLL-MTM covered patch antenna are 0.6λ × 0.8λ × 0.14λ. The radiated gain and efficiency are measured at 7.8 dB and 95%, respectively. Measurements show that the front-to-back ratio is enhanced by more than 12 dB. In comparison with the patch antenna without the CLL-MTM superstrate, the proposed antenna reduces the gain and efficiency by less than 0.1 dB and 2%, respectively.

This paper presents the feasibility of deploying a large-scale tunable absorber based on discrete plasma-shells. The proposed conductor-backed absorber is realized by integrating ceramic gas-encapsulating chambers (plasma-shells) and a closely coupled lossy resonant layer that also serves as a biasing electrode to sustain the plasma. Two topologies comprising lossy inductive or capacitive layers are investigated to realize tunable microwave absorbers. The plasma is sustained by a sinusoidal radio frequency (RF) voltage source coupled directly through the walls of the plasma-shells. These active frequency-selective absorbers are analyzed using a transmission line approach to provide the working principle and its frequency tuning capability. By varying the voltage of the sustainer, the plasma can be modeled as a lossy, variable, frequency-dependent inductor, providing a dynamic tuning response of the absorption spectral band. A prototype plasma-tuned absorber is fabricated and measured in a free space environment to validate the concept. A good agreement between the equivalent circuit model, full-wave electromagnetic simulation, and the measurement results is obtained.

The capability of a magnetodielectric superstrate to suppress the surface wave propagation is investigated. It is shown that the capacitively loaded loop (CLL) metamaterial (MTM) superstrate exhibits a high degree of surface wave attenuation. One of the important applications of such structure is to reduce the mutual coupling between the microstrip patch elements in array antennas. The results of numerical simulations show a significant reduction in the mutual coupling between the antenna elements. To verify and confirm the simulation results, a prototype of the CLL-MTM superstrate incorporating an array of rectangular patch antennas are fabricated and tested. The proposed two-element array antenna has a dimension of approximately $1.6\lambda \times 0.9\lambda \times 0.16\lambda $ while achieving a gain and an efficiency of 8.2 dB and 97%, respectively. Measurement shows the mutual coupling reduction of over 55 dB. The CLL-MTM superstrate provides the gain and efficiency almost the same of unloaded array antennas with 0.1 dB and 2% changes, respectively.

Although B-cell acute lymphoblastic leukemia (B-ALL) is the most common malignancy in children and while highly curable, it remains a leading cause of cancer-related mortality. The outgrowth of tumor subclones carrying mutations in genes responsible for resistance to therapy has led to a Darwinian model of clonal selection. Previous work has indicated that alterations in the epigenome might contribute to clonal selection, yet the extent to which the chromatin state is altered under the selective pressures of therapy is unknown. To address this, we performed chromatin immunoprecipitation, gene expression analysis, and enhanced reduced representation bisulfite sequencing on a cohort of paired diagnosis and relapse samples from individual patients who all but one relapsed within 36 months of initial diagnosis. The chromatin state at diagnosis varied widely among patients, while the majority of peaks remained stable between diagnosis and relapse. Yet a significant fraction was either lost or newly gained, with some patients showing few differences and others showing massive changes of the epigenetic state. Evolution of the epigenome was associated with pathways previously linked to therapy resistance as well as novel candidate pathways through alterations in pyrimidine biosynthesis and downregulation of polycomb repressive complex 2 targets. Three novel, relapse-specific superenhancers were shared by a majority of patients including one associated with S100A8, the top upregulated gene seen at relapse in childhood B-ALL. Overall, our results support a role of the epigenome in clonal evolution and uncover new candidate pathways associated with relapse. Significance: This study suggests a major role for epigenetic mechanisms in driving clonal evolution in B-ALL and identifies novel pathways associated with drug resistance.

The feasibility of realizing an adaptive absorber subject to high-power microwave/electromagnetic (EM) pulse is investigated. To achieve this goal, a passive absorber based on circuit analog topology is designed and then embedded with active components to enable tunability/adaptivity of the absorption bandwidth. This tuning mechanism can be achieved using discrete plasma shells embedded in a low-profile frequency selective surface-based absorber. The absorption center frequency and bandwidth can be tuned by controlling the plasma frequency. A systematic design guide is presented to explain the working principle of the proposed absorber. The proposed design is insensitive to the polarization, and the absorption bandwidth is enhanced by controlling two spectrally overlapped resonances. A full wave EM simulation is performed to present the performance of the proposed absorber. Finally, the peak power handling capability of the active absorber has been investigated.

This paper presents a design guide for the implementation of thickness customizable high-order ( $N \ge 2$ ) bandpass frequency-selective surface (FSS). Admittance inverters are used to synthesize the filter response given desired characteristics such as filter type, center frequency, and bandwidth. The spatial inverter layers are essentially electromagnetic coupling interlayers that can be adjusted to customize the thickness of multilayered FSS without degrading the desired filter performance. A generalized equivalent circuit is used to provide physical insights of the proposed design. This synthesized technique can be adopted to deliver a versatile implementation capability of high-order FSS filters using various dielectric spacers with arbitrary thicknesses. Such a technique enables the realization of spatial filters with variable weight and size, while maintaining the desired filter response. To highlight its thickness controllability, a third-order bandpass FSS operating at the X-band (center frequency at $f_{0} = 10$ GHz) with $\approx 10$ % fractional bandwidth is synthesized in four different thickness configurations (electrical size varying from $\lambda _{0}$ /12 to $\lambda _{0}$ /6). The simulation results of all the four thickness customized configurations deliver the same filter response. To validate the proposed technique, two prototypes among the four design configurations are fabricated and measured in a free-space environment. Simulated and measured results show good agreement.

A planar 2-D antenna array capable of mapping a full-hemisphere space to frequencies around 6 GHz is presented. It was designed using composite right-/left-handed transmission lines for the series feed network as well as for the radiating elements, thus achieving size reduction and beam steering control simplification compared to other approaches. Stripline fabrication technology is utilized to eliminate the undesired feed network radiation. A via-less unit cell reduces sensitivity to via misplacement. The result is an antenna that can be used for radar or imaging applications with the appropriate transmit/receive circuitry. Validation is provided by pattern measurements and successful detection of reflective targets.

In this paper, series feed networks based on composite right/left-handed transmission line for dual-polarized frequency scanning phased array antenna are presented. The proposed all-passive feed networks provide unique frequency dispersion and adjustable current amplitude distribution, which enable continuous backward-to-forward beam scanning capability as well as the directivity, beamwidth, and sidelobe level controllability of the incorporated array antenna. The working mechanisms are demonstrated through broadband dual-polarized aperture-coupled antenna elements and series feed networks that support uniform/binomial current amplitude distributions. Backward-to-forward frequency beam scanning and wide range beam shaping capability for dual-polarization states of the proposed phased array are validated in both simulation and measurement.

L-section matching circuits are used for various applications. Such circuits can be advanced to provide notch responses to suppress undesired spurious signals. The design guide that allows integration of notch responses in the L-section matching circuits is presented. With given impedance at the targeted matching frequency and notch frequencies, a matching circuit with the spurious signal suppressing notches can be simply designed based on the closed-form equations provided. A composite lowpass filter (LPF) based on the image parameter method is composed of two matching sections and two filter sections. Replacing conventional matching sections with the proposed L-section matching circuits, an LPF with spurious signal notches can be realised. The proposed matching circuit and filter with spurious suppression notches will bring an added dimension of design freedom for modern communication systems that demand stringent out-of-band requirements.

Background: The treatment paradigm of adult patients with acute lymphoblastic leukemia (ALL) is primarily derived from successful pediatric chemotherapy regimens. Pegasparagase (PEG) is a key component of pediatric therapy and is the backbone of cytotoxic ALL regimens. However, among the adult population the use of PEG has been limited by the difficulty in tolerating prolonged asparagine depletion. Hepatotoxicity is among the most common adverse events reported with the use of PEG, with grade 3/4 hepatotoxicity seen in 20% of young adults compared to 40-60% of older adults. Incorporating PEG into the treatment of ALL patients under 40 remains an accepted practice despite some studies that report up to 75% of patients have grade 3/4 adverse events as a result of asparagine depletion. In a study of 85 patients with ALL, 3-year overall survival (OS) was significantly different between patients older and younger than 35 (52% vs 83% p = 0.003). Whether this difference is due to PEG toxicity or to other factors remains to be determined. At NYU hospitals, PEG-containing protocols are frequently deployed to treat adult ALL. In our study, we sought to look at the difference in PEG toxicity and response rate (RR) in patients older and younger than 35 and whether these toxicities contributed to a delay in subsequent treatments and to a worse outcome. Methods: We conducted a retrospective chart review of patients older than 18 diagnosed with ALL or lymphoblastic lymphoma, who received at least 1 dose of PEG at our institution between 2014 and 2018. All patients received PEG as part of their first line treatment protocol. Our main objective was to compare the tolerability and toxicity profile of intravenous PEG in patients ≥35 years old versus Results: Out of a total of 50 patients, 23 were age ≥ 35 (46%). Mean age was 34.4 (Range: 18.9-63.1). The 2 groups shared similar distributions in gender, race, and Philadelphia chromosome (Ph) subtypes (Table 1). The older group received significantly less PEG, 5114.8 vs. 25353.7 units (p=0.0007) and 1.65 vs. 3.59 doses (p Conclusions: Patients aged ≥ 35 received significantly less PEG during their treatments but were more likely to develop severe grade 3-4 hepatotoxicity compared to their younger counterparts. The response rates were similar with comparable MRD negativity rates after induction regardless of total amount of PEG administered. However, relapse occurred more frequently in the older group, possibly resulting from more frequent delays in administering other chemotherapy agents due to PEG toxicity. Incorporation of PEG is important in the treatment of ALL but should be used with caution in patients ≥35 years old, and will likely require dose and schedule modifications. A larger prospective trial investigating adequate dosing and scheduling of PEG in this age group is warranted, specifically comparing delays in chemotherapy, relapse, and survival rates in regimens with and without PEG. Disclosures No relevant conflicts of interest to declare.

A retrodirective array (RDA) capable of retransmitting predictable polarization with respect to any received polarization state is presented. RDAs have the unique ability to scatter the received signal back to the interrogator without prior knowledge of the source location. In addition to this unique feature, the proposed system can receive any polarization and always retransmits the signal that is orthogonally polarized with respect to the received polarization state. This added feature helps to maintain a more stable communication link between the RDA and the interrogator by mitigating the polarization mismatch loss. The proposed system shows excellent retrodirectivity for various received linear and circular polarizations. © 2013 IEEE.

The λ/2 strip-resonator directional filter has good balance between compactness and robustness against manufacturing error. However, there have been difficulties in generalizing the strip-resonator directional filter to realize multipole filtering responses. This paper presents the theory, experiments, and improvement of a new structure of strip-resonator directional filter based on a band-reject filter. This new structure allows the realization of multipole responses and theoretically does not limit the types of filter responses. A three-pole elliptic directional filter prototype is studied thoroughly to show that its performance can be predicted accurately by a conventional filter structure. We also propose a modification of the delay-line part using composite right-/left-handed transmission line to improve the isolation. An isolation level of 30 dB is shown to be achieved consistently.

Clinical and preclinical studies indicate that early postnatal exposure to anesthetics can lead to lasting deficits in learning and other cognitive processes. The mechanism underlying this phenomenon has not been clarified and there is no treatment currently available. Recent evidence suggests that anesthetics might cause persistent deficits in cognitive function by disrupting key events in brain development. The hippocampus, a brain region that is critical for learning and memory, contains a large number of neurons that develop in the early postnatal period, which are thus vulnerable to perturbation by anesthetic exposure. Using an in vivo mouse model we demonstrate abnormal development of dendrite arbors and dendritic spines in newly generated dentate gyrus granule cell neurons of the hippocampus after a clinically relevant isoflurane anesthesia exposure conducted at an early postnatal age. Furthermore, we find that isoflurane causes a sustained increase in activity in the mechanistic target of rapamycin pathway, and that inhibition of this pathway with rapamycin not only reverses the observed changes in neuronal development, but also substantially improves performance on behavioral tasks of spatial learning and memory that are impaired by isoflurane exposure. We conclude that isoflurane disrupts the development of hippocampal neurons generated in the early postnatal period by activating a well-defined neurodevelopmental disease pathway and that this phenotype can be reversed by pharmacologic inhibition.

© 2001-2012 IEEE. A planar electromagnetic bandgap (EBG) structure designed for broadband common-mode suppression is proposed. A uniplanar compact photonic-bandgap (UC-PBG) structure with periodic center slots is etched on the ground plane to obtain broadband common mode suppression while minimally disturbing the differential signal within the designed bandwidth. Dispersion analysis has been conducted for both common (even) and differential (odd) mode signals. Good signal integrity is observed in both simulated and measured results. The fractional bandwidth of the proposed EBG ground plane is around 70% with common-mode suppression below - 20 dB. The proposed EBG ground planes may be applicable for systems requiring low-cost and simple solutions in designing high-speed differential interlinks operating above 5 Gbps.

Most studies on the relationship between corporate social performance (CSP) and corporate financial performance (CFP) have focused on large enterprises and archival tests for SMEs have been relatively few. There is a need for SME studies that are comparable to the research on large enterprises. In this study, we tested the CSP-CFP relationship of SMEs in Korea using a massive archival database. Although common theories on corporate social responsibility (CSR) in SMEs describe SMEs as non-strategic performers, we found a strong positive relationship between CSP-CFP for the larger or hi-tech SMEs. Therefore, some SMEs are similar to multinational companies in that they approach CSR effectively. This study makes a contribution to the literature on both CSR and SMEs because it empirically demonstrates the heterogeneity of SMEs and it presents a CSR-SME study that is methodologically comparable to the research on big corporations.

A circularly polarized (CP) CRLH-inspired leaky-wave antenna (LWA) based on substrate-integrated waveguide (SIW) and microstrip delay line is presented. The unit-cell of the proposed periodic antenna consists of two conventional CRLH SIW cells and two quarter-wavelength microstrip lines. The interdigital slots on the CRLH SIW are rotated at $+ 45^\circ $ and $- 45^\circ $ with respect to the wave propagation direction and separated by 90° to create circular polarization. Utilizing the microstrip line instead of the SIW delay section, the total size of the five unit-cell antenna is reduced by 24.4% in comparison to the previous single radiator CP LWA. Furthermore, microstrip lines provide improved matching for broadside radiation as well as better CP purity. The unit-cell characteristics are investigated in detail through dispersion and Bloch impedance analysis. In addition, space harmonic analysis is carried out to explain the radiation mechanism of the proposed antenna. The proposed CRLH-inspired SIW CP antenna operates from 4.2 to 4.85 GHz and frequency scans from $- 25^\circ $ to 26° along the elevation angle. Axial ratio is maintained below 3 dB throughout the operating frequency. The measured results show good agreement with the simulated results.

In this letter, a novel dipole antenna based on substrate integrated waveguides (SIWs) is presented. The dipole antenna radiates through the equivalent magnetic current loops on the top and bottom annular ring slot that is excited by the fundamental mode of the SIW cavity. Therefore, the proposed dipole possesses a vertical polarization perpendicular to the metallic plane. Moreover, thanks to normal electric field, the proposed dipole is less affected by the ground plane size and surrounding metal. The proposed antenna topology provides a very easy way to realize vertical dipole antenna by just using planar circuits and is promising to be used as a fundamental element to realize antenna arrays. © 2002-2011 IEEE.

This paper presents an all-passive phased-array feed network based on composite right/left handed (CRLH) transmission lines (TLs). A CRLH TL enables systematic engineering of the phase response providing phase advance in addition to phase delay. When utilized in a phased-array feed network, an all-passive 1-D frequency-scanning array can be designed with a large scanning angle range toward both positive and negative elevation angles. This unique feature cannot be realized using conventional delay lines or dispersive lines that do not contain left-handed properties. Also, unlike the previously studied CRLH-based leaky-wave antennas that provide similar 1-D continuous frequency-scanning functionality, the proposed method completely decouples the radiating antenna element from the array factor; thereby providing extra design freedom and enhanced radiation performance. To validate the added advantage, we use the proposed CRLH-based phased-array feed network to demonstrate simultaneous controllability of the radiated polarization and array current amplitude distribution. © 1963-2012 IEEE.

Although caspase activation is generally thought to be necessary to induce apoptosis, recent evidence suggests that apoptosis can be activated in the setting of caspase inhibition. In this study, we tested the hypothesis that caspase-independent apoptotic pathways contribute to the development of heart failure in the absence of caspase activation. Acute cardiomyopathy was induced using a single dose of doxorubicin (Dox, 20 mg/kg) injected into male wild-type (WT) and transgenic (Tg) mice with a cardiac-specific expression of cytokine response modifier A (CrmA), a known caspase inhibitor. Early (6 day) survival was significantly better in CrmA Tg (81%) than WT (38%) mice. Twelve days after Dox injection, however, the mortality benefit had dissipated, and increased cardiac apoptosis was observed in both groups. There was, however, a significantly greater release of apoptosis-inducing factor (AIF) from mitochondria to cytosol in CrmA Tg compared with WT mice, which suggests that an enhancement of activation in caspase-independent apoptotic pathways had occurred. The administration of a poly(ADP-ribose) polymerase-1 inhibitor, 4-amino-1,8-naphthalimide (4-AN), to Dox-treated mice resulted in significantly improved cardiac function, a significant blockade of AIF released from mitochondria, and decreased cardiac apoptosis. There were also significantly improved survival in WT (18% without 4-AN vs. 89% with 4-AN) and CrmA Tg (13% without 4-AN vs. 93% with 4-AN) mice 12 days after Dox injection. In conclusion, these findings suggest that apoptosis can be induced in the heart lacking caspase activation via caspase-independent pathways and that enabling the inhibition of AIF activation may provide a significant cardiac benefit.

Aims The caspases are thought to be central mediators of the apoptotic program, but recent data indicate that apoptosis may also be mediated by caspase-independent mechanisms such as apoptosis-inducing factor (AIF). The role of AIF-induced apoptosis in heart, however, is currently not well understood. The aim of this study was to investigate the presence of and conditions for AIF-induced cardiac apoptosis in vitro . Methods and results Hypertrophic cardiomyocyte (H-CM) cultures were prepared from the hearts of Dahl salt-sensitive rats fed a high salt diet. Apoptotic stimulation induced by hypoxia/reoxygenation or staurosporine (1 µM) enhanced AIF release in H-CMs compared with non-hypertrophic cardiomyocytes (N-CMs). Caspase inhibition using zVAD.fmk (25 µM) or overexpression of CrmA using recombinant adenovirus only partially protected N-CMs from apoptosis (63 ± 0.93%) and provided no significant protection against apoptosis in hypertrophic cells (23 ± 1.03%). On the other hand, poly-ADP-ribose polymerase inhibition using 4-AN (20 µM) during apoptotic stimulation blocked the release of AIF from mitochondria and significantly improved cell viability in hypertrophied cardiomyocytes (74 ± 1.18%). Conclusion A caspase-dependent, apoptotic pathway is important for N-CM death, whereas a caspase-independent, AIF-mediated pathway plays a critical role in H-CMs.

The phosphoinositide 3-kinase (PI3-kinase)-protein kinase B (Akt) signaling pathway is essential in the induction of physiological cardiac hypertrophy. In contrast, protein kinase C beta2 (PKCbeta2) is implicated in the development of pathological cardiac hypertrophy and heart failure. Thus far, no clear association has been demonstrated between these two pathways. In this study, we examined the potential interaction between the PI3-kinase and PKCbeta2 pathways by crossing transgenic mice with cardiac specific expression of PKCbeta2, constitutively active (ca) PI3-kinase, and dominant-negative (dn) PI3-kinase. In caPI3-kinase/PKCbeta2 and dnPI3-kinase/PKCbeta2 double-transgenic mice, the heart weight-to-body weight ratios and cardiomyocyte sizes were similar to those observed in caPI3-kinase and dnPI3-kinase transgenic mice, respectively, suggesting that the regulation of physiological developmental hypertrophy via modulation of cardiomyocyte size proceeds through the PI3-kinase pathway. In addition, we observed that caPI3-kinase/PKCbeta2 mice showed improved cardiac function while the function of dnPI3-kinase/PKCbeta2 mice was similar to that of the PKCbeta2 group. PKCbeta2 protein levels in both dnPI3-kinase/PKCbeta2 and PKCbeta2 mice were significantly upregulated. Interestingly, however, PKCbeta2 protein expression was significantly attenuated in caPI3-kinase/PKCbeta2 mice. PI3-kinase activity measured by Akt phosphorylation was not affected by PKCbeta2 overexpression. These data suggest a potential interaction between these two pathways in the heart, where PI3-kinase is predominantly responsible for the regulation of physiological developmental hypertrophy and may act as an upstream modulator of PKCbeta2 with the potential for rescuing the pathological cardiac dysfunction induced by overexpression of PKCbeta.