Pulsations and eclipse-time analysis of HWVir

We analysed recent K2 data of the short-period eclipsing binary systemHWVir,which consists of a hot subdwarf-B type primary with an M-dwarf companion.We determined the mid-times of eclipses, calculated O-C diagrams, and an average shift of the secondary minimum. Our results show that the orbital period is stable within the errors over the course of the 70 days of observations. Interestingly, the offset from mid-orbital phase between the primary and the secondary eclipses is found to be 1.62 s. If the shift is explained solely by light-travel time, the mass of the sdB primary must be 0.26M⊙, which is too low for the star to be core-helium burning. However, we argue that this result is unlikely to be correct and that a number of effects caused by the relative sizes of the stars conspire to reduce the effective light-travel time measurement. After removing the flux variation caused by the orbit, we calculated the amplitude spectrum to search for pulsations. The spectrum clearly shows periodic signal from close to the orbital frequency up to 4600 μHz, with the majority of peaks found below 2600 μHz. The amplitudes are below0.1 part-per-thousand, too lowto be detected with groundbased photometry. Thus, the high-precision data from the Kepler spacecraft has revealed that the primary of the HWVir system is a pulsating sdBV star. We argue that the pulsation spectrum of the primary in HWVir differs from that in other sdB stars due to its relatively fast rotation that is (nearly) phase-locked with the orbit

Fraction size in radiation therapy for breast conservation in early breast cancer (Review)

Background: Shortening the duration of radiation therapy would benefit women with early breast cancer treated with breast conserving surgery. It may also improve access to radiation therapy by improving efficiency in radiation oncology departments globally. This can only happen if the shorter treatment is as effective and safe as conventional radiation therapy. This is an update of a Cochrane Review first published in 2008 and updated in 2009. Objectives: To assess the effect of altered radiation fraction size for women with early breast cancer who have had breast conserving surgery. Search methods: We searched the Cochrane Breast Cancer Specialised Register (23 May 2015), CENTRAL (The Cochrane Library 2015, Issue 4), MEDLINE (Jan 1996 to May 2015), EMBASE (Jan 1980 to May 2015), the WHO International Clinical Trials Registry Platform (ICTRP) search portal (June 2010 to May 2015) and ClinicalTrials.gov (16 April 2015), reference lists of articles and relevant conference proceedings. No language or publication constraints were applied. Selection criteria: Randomised controlled trials of altered fraction size versus conventional fractionation for radiation therapy in women with early breast cancer who had undergone breast conserving surgery. Data collection and analysis: Two authors performed data extraction independently, with disagreements resolved by discussion. We sought missing data from trial authors. Main results: We studied 8228 women in nine studies. Eight out of nine studies were at low or unclear risk of bias. Altered fraction size (delivering radiation therapy in larger amounts each day but over fewer days than with conventional fractionation) did not have a clinically meaningful effect on: local recurrence-free survival (Hazard Ratio (HR) 0.94, 95% CI 0.77 to 1.15, 7095 women, four studies, high-quality evidence), cosmetic outcome (Risk ratio (RR) 0.90, 95% CI 0.81 to 1.01, 2103 women, four studies, high-quality evidence) or overall survival (HR 0.91, 95% CI 0.80 to 1.03, 5685 women, three studies, high-quality evidence). Acute radiation skin toxicity (RR 0.32, 95% CI 0.22 to 0.45, 357 women, two studies) was reduced with altered fraction size. Late radiation subcutaneous toxicity did not differ with altered fraction size (RR 0.93, 95% CI 0.83 to 1.05, 5130 women, four studies, high-quality evidence). Breast cancer-specific survival (HR 0.91, 95% CI 0.78 to 1.06, 5685 women, three studies, high quality evidence) and relapse-free survival (HR 0.93, 95% CI 0.82 to 1.05, 5685 women, three studies, moderate-quality evidence) did not differ with altered fraction size. We found no data for mastectomy rate. Altered fraction size was associated with less patient-reported (P < 0.001) and physician-reported (P = 0.009) fatigue at six months (287 women, one study). We found no difference in the issue of altered fractionation for patient-reported outcomes of: physical well-being (P = 0.46), functional well-being (P = 0.38), emotional well-being (P = 0.58), social well-being (P = 0.32), breast cancer concerns (P = 0.94; 287 women, one study). We found no data with respect to costs. Authors' conclusions: We found that using altered fraction size regimens (greater than 2 Gy per fraction) does not have a clinically meaningful effect on local recurrence, is associated with decreased acute toxicity and does not seem to affect breast appearance, late toxicity or patient-reported quality-of-life measures for selected women treated with breast conserving therapy. These are mostly women with node negative tumours smaller than 3 cm and negative pathological margins

Terahertz on-chip antenna based on metasurface and SIW with stacked layers of resonators on GaAs substrate

This paper presents a 100μm GaAs-based 0.45-0.50 THz on-chip antenna based on metasurface and substrate integrated waveguide (SIW) technologies to realize a high-performance antenna. The antenna design consists of 2×4 array of circular slot resonators embedded in rectangular ground-plane segments in a horizontal arrangement. The ground-plane segments are separated from each other by a narrow channel to create a coplanar waveguide which is used to excite the structure. This antenna structure, which is constructed on GaAs substrate, reduces substrate loss and surface waves. In addition, the metasurface essentially enlarges the effective aperture area of the antenna to enhance the gain and radiation efficiency of the antenna. The dimensions of the metasurface on-chip antenna is 0.8×0.8×0.13 mm3. The antenna exhibits an average gain and efficiency of 6.9dBi and 61.82%, respectively, which makes it a promising candidate for packaging in terahertz components

Amalgamation of metamaterial and SIW technologies for realizing wide-bandwidth and high-radiation properties of on-chip antennas for application in packaging of terahertz components

This paper shows that by employing a combination of metamaterial (MTM) and substrate integrated waveguide (SIW) technologies, the drawbacks of narrow-bandwidth and low radiation properties encountered in terahertz on-chip antennas can be overcome. In addition, an effective feeding mechanism is introduced to excite the on-chip antenna. The proposed antenna is constructed on the three stacked layers comprising Silicon-metal-Silicon substrates. Dimensions of on-chip antenna are 1×1×0.265 mm3. The on-chip antenna is shown to have an average impedance match, gain, and efficiency parameters of -35dB, 8.5dBi, and 67.5%, respectively, over a wide frequency range of 0.20-0.22 THz

High‑isolation antenna array using SIW and realized with a graphene layer for sub‑terahertz wireless applications

This paper presents the results of a study on developing an effective technique to increase the performance characteristics of antenna arrays for sub-THz integrated circuit applications. This is essential to compensate the limited power available from sub-THz sources. Although conventional array structures can provide a solution to enhance the radiation-gain performance however in the case of small-sized array structures the radiation properties can be adversely affected by mutual coupling that exists between the radiating elements. It is demonstrated here the effectiveness of using SIW technology to suppress surface wave propagations and near field mutual coupling effects. Prototype of 2 × 3 antenna arrays were designed and constructed on a polyimide dielectric substrate with thickness of 125 μm for operation across 0.19–0.20 THz. The dimensions of the array were 20 × 13.5 × 0.125 mm3. Metallization of the antenna was coated with 500 nm layer of Graphene. With the proposed technique the isolation between the radiating elements was improved on average by 22.5 dB compared to a reference array antenna with no SIW isolation. The performance of the array was enhanced by transforming the patch to exhibit metamaterial characteristics. This was achieved by embedding the patch antennas in the array with sub-wavelength slots. Compared to the reference array the metamaterial inspired structure exhibits improvement in isolation, radiation gain and efficiency on average by 28 dB, 6.3 dBi, and 34%, respectively. These results show the viability of proposed approach in developing antenna arrays for application in sub-THz integrated circuits

High-performance 50μm Silicon-based on-chip antenna with high port-to-port isolation for THz integrated systems

A novel 50μm Silicon-based on-chip antenna is presented that combines metamaterial (MTM) and substrate integrated waveguide (SIW) technologies for integration in THz circuits operating from 0.28 to 0.30 THz. The antenna structure comprises a square patch antenna implemented on a Silicon substrate with a ground-plane. Embedded diagonally in the patch are two T-shaped slots and the edges of the patch is short-circuited to the ground-plane with metal vias, which convert the structure into a substrate integrated waveguide. This structure reduces loss resulting from surface waves and Silicon dielectric substrate. The modes in the structure can be excited through two coaxial ports connected to the patch from the underside of the Silicon substrate. The proposed antenna structure is essentially transformed to exhibit metamaterial properties which enlarges the effective aperture area of the miniature antenna and significantly enhances its impedance bandwidth and radiation characteristics between 0.29 THz to 0.3 THz. It has an average gain and efficiency of 4.5dBi and 65.32%, respectively. In addition, it is a self-isolated structure with high isolation of better than 30dB between the two ports. The on-chip antenna has dimensions of 800×800×60 μm