HERA Phase I Limits on the Cosmic 21 cm Signal: Constraints on Astrophysics and Cosmology during the Epoch of Reionization

Recently, the Hydrogen Epoch of Reionization Array (HERA) has produced the experiment’s first upper limits on the power spectrum of 21 cm fluctuations at z ∼ 8 and 10. Here, we use several independent theoretical models to infer constraints on the intergalactic medium (IGM) and galaxies during the epoch of reionization from these limits. We find that the IGM must have been heated above the adiabatic-cooling threshold by z ∼ 8, independent of uncertainties about IGM ionization and the radio background. Combining HERA limits with complementary observations constrains the spin temperature of the z ∼ 8 neutral IGM to 27 K 〈 T ¯ S 〉 630 K (2.3 K 〈 T ¯ S 〉 640 K) at 68% (95%) confidence. They therefore also place a lower bound on X-ray heating, a previously unconstrained aspects of early galaxies. For example, if the cosmic microwave background dominates the z ∼ 8 radio background, the new HERA limits imply that the first galaxies produced X-rays more efficiently than local ones. The z ∼ 10 limits require even earlier heating if dark-matter interactions cool the hydrogen gas. If an extra radio background is produced by galaxies, we rule out (at 95% confidence) the combination of high radio and low X-ray luminosities of L r,ν /SFR > 4 × 1024 W Hz−1 M ⊙ − 1 yr and L X /SFR < 7.6 × 1039 erg s−1 M ⊙ − 1 yr. The new HERA upper limits neither support nor disfavor a cosmological interpretation of the recent Experiment to Detect the Global EOR Signature (EDGES) measurement. The framework described here provides a foundation for the interpretation of future HERA results.

Development, Characterization and Valuable Use of Novel Dosimeter Film Based on PVA Polymer Doped Nitro Blue Tetrazolium Dye and AgNO3 for the Accurate Detection of Low X-ray Doses

Currently, the uncontrolled exposure of individuals to X-rays during medical examinations represents a substantial danger that threatens both medical professionals and patients. Therefore, radiation dosimetry for low X-ray doses is a very important control of radiation practice in medical diagnostic radiology. In line with this, the current study proposes a valuable dosimeter-based PVA thin film doubly doped with silver nitrate salt and nitro blue tetrazolium dye. The nanocomposite film was prepared via a simple casting method and the different processing parameters were optimized. The performance of radiation detection was evaluated according to optical, chromic, chemical and structural changes after exposure to variable low X-ray doses (0, 2, 4, 10 and 20 mGy). The different film labels exhibited an excellent stability behavior in dark and light upon 30 days of storage. The UV-Vis spectrophotometric study showed a gradual increase in the maximum absorbance as a function of the dose and the corresponding response curve confirmed this linear variation (R = 0.998). A clear structural modification was recorded via X-ray diffraction (XRD) analysis revealing the increase in crystallinity with the level of the dose received by the nanocomposite films. Microscopic surface analysis via SEM assessments revealed a significant morphological change in PVA/Ag+/NBT films exposed to increased radiation doses and typical dendrites growing in needle- or tree-like microstructures appeared with a high X-ray dose. Finally, the nanocomposite films before and after irradiation were evaluated via a spectrocolorimetric study and the different CIELab coordinates, the color difference, as well as the color strength, showed a linear correlation with the intensity of the applied dose. This new dosimeter design could, therefore, provide a promising and efficient alternative for prompt and accurate detection of low X-rays doses in diagnostic radiology.

Low-x improved TMD approach to the lepto- and hadroproduction of a heavy-quark pair

We study the lepto- and hadroproduction of a heavy-quark pair in the ITMD factorization framework for dilute-dense collisions. Due to the presence of a nonzero quark mass and/or nonzero photon virtuality, new contributions appear compared to the cases of photo- and hadroproduction of dijets, for which the ITMD framework was originally derived. These extra terms are sensitive to gluons that are not fully linearly polarized. At small x, those gluons emerge only when all saturation effects are carefully taken into account. Therefore, the resulting contributions are absent in linear small-x frameworks, where gluons are fully linearly polarized. We show, however, that even for large gluon transverse momentum, these contributions are not always negligible, due to the behavior of the off-shell hard factors.

Square DRA feed for parabolic reflector antenna for satellite communication application

A square dielectric resonator antenna (SDRA) offering high polarization purity as a feed for parabolic reflector antenna is presented in this paper. Three sequences of holes are strategically integrated into the SDRA to enhance the polarization purity of the desired mode by suppressing the cross-polarization (X-pol) generating higher order mode. A detailed study on the performance of the parabolic reflector antenna with the proposed SDRA feed is also performed. The composite structure provides low X-pol levels of −33 dB at the half-power beamwidth (HPBW) points and −35 dB at the 1 dB co-polarization region in the H-plane. The composite structure radiates in the broadside direction with a high gain of 26 dBi and radiation efficiency of 95%. The proposed SDRA is designed to operate at 3 GHz of the S-band. A prototype of the proposed design is fabricated and experimentally verified. A measured X-pol isolation of 39 dB at ±15% of HPBW (European Telecommunication Standards Institute [ETSI] standard for satellite communication) and 50 dB at boresight is obtained in the H-plane. The small size, light weight, stable radiation performance and high polarization purity offered by the proposed SDRA make it a suitable candidate for satellite communication application.

Stabilization of Superionic-Conducting High-Temperature Phase of Li(Cb9h10) via Solid Solution Formation with Li2(B12H12)

We report the stabilization of the high-temperature (high-T) phase of lithium carba-closo-decaborate, Li(CB9H10), via the formation of solid solutions in a Li(CB9H10)-Li2(B12H12) quasi-binary system. Li(CB9H10)-based solid solutions in which [CB9H10]− is replaced by [B12H12]2− were obtained at compositions with low x values in the (1−x)Li(CB9H10)−xLi2(B12H12) system. An increase in the extent of [B12H12]2− substitution promoted stabilization of the high-T phase of Li(CB9H10), resulting in an increase in the lithium-ion conductivity. Superionic conductivities of over 10−3 S cm−1 were achieved for the compounds with 0.2 ≤ x ≤ 0.4. In addition, a comparison of the Li(CB9H10)−Li2(B12H12) system and the Li(CB9H10)−Li(CB11H12) system suggests that the valence of the complex anions plays an important role in the ionic conduction. In battery tests, an all-solid-state Li–TiS2 cell employing 0.6Li(CB9H10)−0.4Li2(B12H12) (x = 0.4) as a solid electrolyte presented reversible battery reactions during repeated discharge–charge cycles. The current study offers an insight into strategies to develop complex hydride solid electrolytes.