Radiation Enhancement Research Articles

Unsteady hybrid nanofluid flow over a convectively heated cylinder with inclined magnetic field and viscous dissipation: A multiple regression analysis

The current study explores the aspects of unsteady stagnation point flow of hybrid nanofluid (Cu-Al2O3/H2O) over a continuously moving and convectively heated stretching cylinder under the influence of oblique Lorentz force. The impacts of velocity slip, Joule dissipation, thermal radiation, viscous dissipation and internal heat generation are also incorporated into this study. Appropriate thermo-physical relations for the hybrid nanofluid are accomplished by following the Xue model. With the use of suitable similarity transformations, the governing dimensional mathematical equations are converted into dimensionless forms. Numerical solutions are obtained for the velocity and energy fields with the help of a shooting technique based on the Runge–Kutta–Fehlberg method of 5-th order and secant iteration. Graphical and tabular representations of numerical data are used to explore the physical impacts of various pertinent parameters on the hybrid nanofluid velocity and temperature. The stability of this approach and the validity of the obtained results are illustrated by comparing the current findings to previously reported data for a specific case. Further, the multiple (quadratic) regression analysis is performed to show the dominance of physical parameters on local skin-friction coefficient and Nusselt number. The thermal buoyancy force boosts the fluid flow while a reverse trend is observed for the magnetic and the velocity slip parameters. Heat transfer rate at the surface is improved with the enhancement in Biot number, thermal radiation and unsteadiness parameters.

Tunable enhancement of harmonic radiation in coupled quantum wells

Tunable enhancement of harmonic radiation in coupled quantum wells

Detection of Flare-induced Plasma Flows in the Corona of EV Lac with X-Ray Spectroscopy

Stellar flares are characterized by sudden enhancement of electromagnetic radiation from the atmospheres of stars. Compared to their solar counterparts, our knowledge on the coronal plasma dynamics of stellar flares and their connection to coronal mass ejections remains very limited. With time-resolved high-resolution spectroscopic observations from the Chandra X-ray Observatory, we detected noticeable coronal plasma flows during several stellar flares on a nearby dMe star EV Lac. In the observed spectra of O viii (3 MK), Fe xvii (6 MK), Mg xii (10 MK), and Si xiv (16 MK) lines, these flare-induced upflows/downflows appear as significant Doppler shifts of several tens to 130 km s−1 , and the upflow velocity generally increases with temperature. Variable line ratios of the Si xiii triplet reveal that this plasma flows in most flares are accompanied by an increase in the coronal plasma density and temperature. We interpret these results as X-ray evidence of chromospheric evaporation on EV Lac. In two successive flares, the plasma flow pattern and a sharp increase of the measured coronal density are highly suggestive of explosive evaporation. The transition from redshifts to blueshifts in such an explosive evaporation occurs at a temperature of at least 10 MK, much higher than that observed in solar flares (∼1 MK). However, in one flare the cool and warm upflows appear to be accompanied by a decreasing plasma density, which might be explained by a stellar filament/prominence eruption coupled to this flare. These results provide important clues to understanding the coronal plasma dynamics during flares on M dwarfs.

Dual PI3K/mTOR Inhibitor NVP-BEZ235 Leads to a Synergistic Enhancement of Cisplatin and Radiation in Both HPV-Negative and -Positive HNSCC Cell Lines.

Simple SummaryHead and neck cancers (HNSCCs), especially in the advanced stages, are predominantly treated by radiochemotherapy, including cisplatin. The cure rates are clearly higher for HPV-positive HNSCCs when compared to HPV-negative HNSCCs. For both entities, this treatment is accompanied by serious adverse reactions, mainly due to cisplatin administration. We reported earlier that for both HPV-positive and negative HNSCC cells, the effect of radiotherapy was strongly enhanced when pretreated using the dual PI3K/mTOR inhibitor NVP-BEZ235 (BEZ235). The current study shows that for HPV-positive cells, BEZ235 will strongly enhance the effect of cisplatin alone. More important, preincubation with BEZ235 was found to alter the purely additive effect normally seen when cisplatin is combined with radiation into a strong synergistic enhancement. This tri-modal combination might allow for the enhancement of the effect of radiochemotherapy, even with reduced cisplatin.The standard of care for advanced head and neck cancers (HNSCCs) is radiochemotherapy, including cisplatin. This treatment results in a cure rate of approximately 85% for oropharyngeal HPV-positive HNSCCs, in contrast to only 50% for HPV-negative HNSCCs, and is accompanied by severe side effects for both entities. Therefore, innovative treatment modalities are required, resulting in a better outcome for HPV-negative HNSCCs, and lowering the adverse effects for both entities. The effect of the dual PI3K/mTOR inhibitor NVP-BEZ235 on a combined treatment with cisplatin and radiation was studied in six HPV-negative and six HPV-positive HNSCC cell lines. Cisplatin alone was slightly more effective in HPV-positive cells. This could be attributed to a defect in homologous recombination, as demonstrated by depleting RAD51. Solely for HPV-positive cells, pretreatment with BEZ235 resulted in enhanced cisplatin sensitivity. For the combination of cisplatin and radiation, additive effects were observed. However, when pretreated with BEZ235, this combination changed into a synergistic interaction, with a slightly stronger enhancement for HPV-positive cells. This increase could be attributed to a diminished degree of DSB repair in G1, as visualized via the detection of γH2AX/53BP1 foci. BEZ235 can be used to enhance the effect of combined treatment with cisplatin and radiation in both HPV-negative and -positive HNSCCs.

A study on radiation interactions, dose enhancement, and hydrolysis with metallic nanoparticles irradiated by 6 megavoltage X-rays: Geant4 Monte Carlo simulation

Nanoparticles (NPs) have been suggested to increase cancer radiotherapy efficiency. However, a fulfillment of knowledge on mechanisms of radiation dose enhancement by NPs is needed. The aim of present study was to evaluate the enhancement of radiation effects by metal NPs at physical and chemical levels. Geant4-DNA Monte Carlo simulation was used for assessment of radiation interaction processes, radiation dose effect and the produced hydrolysis byproducts following 6 MV X-rays. According to the results NPs of this study may be divided in three categories: low dose enhancers (TiO2NP, Fe3O4NP, GeNP), medium dose enhancers (BiNP, AgNP) and high dose enhancers (GNP, PtNP). It found that mass density of NPs may be the most effective feature on DER. Higher radiation enhancement efficiencies by GNP, PtNP may be produced due to the induced high energetic photoelectrons and Compton electrons and also the produced free radicals.

Abstract 216: Expression of DNA damage response proteins modifies the efficacy of CDK4/6 inhibitor-mediated radiosensitization in breast cancer models

Abstract Purpose: CDK4/6 inhibitors (CDK4/6i) are standard of care for the treatment of locally advanced and metastatic estrogen receptor-positive (ER+), HER2-negative metastatic breast cancer (BC). CDK4/6 inhibition + radiation therapy (RT) is synergistic in both ER+ and triple negative breast cancers (TNBC), but the underlying mechanism is not entirely understood. In this study, we evaluated how pre-existing or genetically engineered deficits in DNA damage response genes (BRCA1/2, RAD51, RB1, XRCC6, TP53) influence radiosensitization. We hypothesized that inhibition of homologous recombination (HR) would prevent CDK4/6i-mediated radiosensitization and blocking non-homologous end joining (NHEJ) would be synergistic. Methods: Cellular proliferation assays determined the half-maximal inhibitory concentrations (IC50) of the 3 approved CDK4/6i palbociclib, ribociclib, and abemaciclib. Clonogenic survival assays determined the radiation enhancement ratios (rERs) and evaluated the efficacy of CDK4/6i + RT. Immunofluorescence assays measured RAD51 foci formation and quantified micronuclei formation following RT and/or CDK4/6 inhibition. Immunoprecipitation with myc-RAD51 and GFP-RB assessed potential protein-protein interactions. Results: While ER+ and TNBC cell lines with wild type BRCA1 expression are radiosensitized by CDK4/6i, BRCA1-deficient SUM-149 cells are not radiosensitized by CDK4/6i at concentrations up to 1µM (rER: 0.92-1.01). In an MCF-7 isogenic model of BRCA2 knockout, CDK4/6i-mediated radiosensitization was abolished compared to Cas9 control or parental cell lines. In ER+ BC cell lines (MCF-7-p53 wt, T47D-p53 mutant), transient or genetic knockdown of RAD51 prevented CDK4/6i-induced radiosensitization. The total quantity of RT-induced RAD51 foci increased in vitro following overexpression of RB-a tumor suppressor and downstream target of CDK4/6. RB overexpression also rescued CDK4/6i-mediated radiosensitization in RB-deficient cell lines through changes in HR efficiency but not via NHEJ or altered micronuclei formation. Moreover, immunoprecipitation of RAD51 in ER+ (MCF-7) and TNBC (MDA-MB-231) cells exhibited an interaction with RB. Conversely, loss of the NHEJ-associated protein Ku70 (XRCC6) was synergistic with palbociclib + RT in MCF7 (rER: 1.76-2.44) and T47D (rER: 1.61-3.88) cells. Finally, CRISPR Cas9-mediated loss of the tumor suppressor p53 (TP53) did not affect radiosensitization induced by CDK4/6i in isogenic p53 wt ER+ (MCF-7, rER: 1.19-1.33) and p53 wt TNBC (CAL-51, rER: 1.23-1.52) cell lines with TP53 loss. Conclusions: Taken together, our results in multiple non-overlapping isogenic models of ER+ and TNBC suggest that CDK4/6i-mediated radiosensitization of BC cell lines occurs through impaired HR activity and RB signaling, and not through the actions of p53 or NHEJ-mediated DNA repair. Citation Format: Kassidy M. Jungles, Andrea M. Pesch, Nicole Hirsh, Anna R. Michmerhuizen, Kari Wilder-Romans, Benjamin C. Chandler, Meilan Liu, Lynn Lerner, Lori J. Pierce, James M. Rae, Corey W. Speers. Expression of DNA damage response proteins modifies the efficacy of CDK4/6 inhibitor-mediated radiosensitization in breast cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 216.

Enhancement and Manipulation of Near-Field Thermal Radiation Using Hybrid Hyperbolic Polaritons

Owing to a high electromagnetic confinement and a strong photonic density of states, hyperbolic surface plasmon polaritons (HSPPs) provide a fascinating promise for applications in thermal photonics. In this work, we theoretically predict a possibility for the improvement of the near-field radiative heat transfer on the basis of tailoring the electromagnetic state of hyperbolic metasurfaces by the uniaxial hyperbolic substrate. By using the photonic tunneling coefficient and the polaritons dispersion, we present a comprehensive study of the hybrid effect of the hyperbolic substrate on HSPPs. We find that due to the hybrid effect of the hyperbolic substrate, the anisotropy surface state of hyperbolic metasurfaces would undergo significant deformations and even topological transition. Moreover, we systematically exhibit the evolution of such hybrid hyperbolic mode with different thicknesses of the hyperbolic substrate and analyze the thickness effect on radiative properties of the hybrid system. It is shown that the resulting heat transfer with the assistance of the hybrid hyperbolic mode by optimizing the substrate parameters is many times stronger than that of monolayer hyperbolic metasurface at the same vacuum gap. Taken together, our results provide a platform to tailor 2D hyperbolic plasmons as a potential strategy toward passive or active control of the near-field heat transfer, and the hybrid hyperbolic mode presented here may facilitate the system design for near-field energy harvesting, thermal imaging, and radiative cooling applications.

Implications for Additional Plasma Heating Driving the Extreme-ultraviolet Late Phase of a Solar Flare with Microwave Imaging Spectroscopy

Extreme-ultraviolet late phase (ELP) refers to the second extreme-ultraviolet (EUV) radiation enhancement observed in certain solar flares, which usually occurs tens of minutes to several hours after the peak of soft X-ray emission. The coronal loop system that hosts the ELP emission is often different from the main flaring arcade, and the enhanced EUV emission therein may imply an additional heating process. However, the origin of the ELP remains rather unclear. Here we present the analysis of a C1.4 flare that features such an ELP, which is also observed in microwave wavelengths by the Expanded Owens Valley Solar Array. Similar to the case of the ELP, we find a gradual microwave enhancement that occurs about 3 minutes after the main impulsive phase microwave peaks. Radio sources coincide with both foot points of the ELP loops and spectral fits on the time-varying microwave spectra demonstrate a clear deviation of the electron distribution from the Maxwellian case, which could result from injected nonthermal electrons or nonuniform heating to the footpoint plasma. We further point out that the delayed microwave enhancement suggests the presence of an additional heating process, which could be responsible for the evaporation of heated plasma that fills the ELP loops, producing the prolonged ELP emission.

The impact of forest‐controlled snow variability on late‐season streamflow varies by climatic region and forest structure

AbstractPrevious studies have documented how forests influence snow at fine spatial scales, but none have documented the influence that existing forest‐snow variability has on streamflow. To test how much forest‐controlled snow variability influences streamflow, a tiling parameterization based on classifications from high‐resolution (1–3 m) vegetation maps was incorporated into the Distributed Hydrology and Soil Vegetation Model (DHSVM). Within each grid cell (90–150 m), the tiling parameterization simulated forest‐snow variability with four independently evolving snowpacks. Each tile had unique radiation conditions to represent conditions underneath the canopy, in exposed areas, and along north‐ and south‐facing forest edges. This tiled parameterization was used to test where and when detailed forest‐snow modelling should be considered further and where and when the impacts are too small to be worth the effort. To test this, tiled model simulations of streamflow were compared to non‐tiled model simulations in the Sierra Nevada, CA, the Jemez Mountains, NM, and the Eastern Cascades, WA. In Tuolumne, CA, the tiled model simulated little difference in grid cell average SWE, and late‐season streamflow decreased by only 3%–4% compared to the non‐tiled model. In Jemez, NM, the tiled model decreased late‐season streamflow by 18% due to increased sublimation. In Chiwawa, WA, the tiled model increased late‐season streamflow by 15% due to high shortwave radiation attenuation and less longwave radiation enhancement from the forest. Furthermore, within the Chiwawa, a substantial silvicultural practice was synthetically implemented to increase the north‐facing edge's fractional area. This silvicultural experiment, which used the same fractional forest area in all simulations increased late‐season streamflow by 35% compared to tiled model simulations that did not represent forest edges. In conclusion, representing forest‐SWE variability had an effect on late‐season streamflow in some watersheds but not in others based on the fractional area of the forest edges, forest characteristics, and climate conditions.

Androgen and oestrogen receptor co-expression determines the efficacy of hormone receptor-mediated radiosensitisation in breast cancer

PurposeRadiation therapy (RT) and hormone receptor (HR) inhibition are used for the treatment of HR-positive breast cancers; however, little is known about the interaction of the androgen receptor (AR) and estrogen receptor (ER) in response to RT in AR-positive, ER-positive (AR+/ER+) breast cancers. Here we assessed radiosensitisation of AR+/ER+ cell lines using pharmacologic or genetic inhibition/degradation of AR and/or ER.MethodsRadiosensitisation was assessed with AR antagonists (enzalutamide, apalutamide, darolutamide, seviteronel, ARD-61), ER antagonists (tamoxifen, fulvestrant) or using knockout of AR.ResultsTreatment with AR antagonists or ER antagonists in combination with RT did not result in radiosensitisation changes (radiation enhancement ratios [rER]: 0.76–1.21). Fulvestrant treatment provided significant radiosensitisation of CAMA-1 and BT-474 cells (rER: 1.06–2.0) but not ZR-75-1 cells (rER: 0.9–1.11). Combining tamoxifen with enzalutamide did not alter radiosensitivity using a 1 h or 1-week pretreatment (rER: 0.95–1.14). Radiosensitivity was unchanged in AR knockout compared to Cas9 cells (rER: 1.07 ± 0.11), and no additional radiosensitisation was achieved with tamoxifen or fulvestrant compared to Cas9 cells (rER: 0.84–1.19).ConclusionWhile radiosensitising in AR + TNBC, AR inhibition does not modulate radiation sensitivity in AR+/ER+ breast cancer. The efficacy of ER antagonists in combination with RT may also be dependent on AR expression.

Nonlocal composite metamaterial in calculation of near-field thermal rectification.

We consider the near-field radiative heat transfer (NFRHT) between a semi-infinite polar dielectric plate and a composite metamaterial containing semiconductor nanoparticles with spatial dispersion or nonlocality. We show that the enhancement of near-field heat radiation is found owing to the strong coupling of surface phonon polaritons (SPhPs) excited between polar dielectric plate and air, and localized surface plasmon polaritons (LSPPs) in the composite metamaterials. The introduction of nonlocality is helpful to enhance the NFRHT and even the rectification efficiency significantly when the temperature difference is small. For a large volume fraction of semiconductor nanoparticles, the thermal rectification efficiency can be larger than 90% at a small temperature difference within 150 K. Our findings may pave a way for thermal devices based on composite metamaterial containing semiconductor nanoparticles.

SYNTHESIS OF Mg-DOPED n(ZnO) THIN FILMS USING SOL-GEL 6 DIP-COATING METHOD AND CHARACTERIZATION OF ITS STRUCTURAL AND OPTICAL PROPERTIES

Mg-doped ZnO alloy thin films having hexagonal Wurtzite structures were prepared using the Sol-Gel method. The doping results into, increased surface roughness and reduced grain size. Photonic applications are made easier by altering the optical bandgap of ZnO nano-structured thin films doped with various components. Mg metal atom doped ZnO films are an excellent example for study. In this work, the thin film of Mg-doped ZnO is formed on glass substrate via dip coating method with varied concentration of dopant. Dip-coating method is one of the cheapest methods. SEM, Raman spectroscopy and UV-vis spectroscopy are used to characterize the thin films. The spectroscopic analysis revealed a more uniformed crystalline nano-structured surface with fewer structural deffects. As the Mg atom concentration is increased, the results show a linear increment in the band gap of Mg-doped ZnO thin film in comparsion to the pure ZnO nanostructured thin film, as well as there occurs an improvement in crystalline character. The reduction in intensity of visible radiation (enhancement in radiation in UV region) with increase in Mg concentration indicates for a decrease in intrinsic defects. The changing trends in optical and structural parameters as with increased Mg content reveal a nonlinear and non-monotonic relations. The work provides insights to analyse the dependence of optical bandgap on crystal structure and defects.

Experimental investigation of a novel split type vacuum tube solar air thermal collection-stepped storage system (ST-VTSATC-SSS)

A novel split type vacuum tube (VT) solar air thermal collection-stepped storage system (ST-VTSATC-SSS) is proposed in this study to address the problem of carbon and pollution emissions from coal-fired heating in rural areas. A VT air collector is used to decrease heat loss. Paraffin and lauric acid are used to conduct thermal stepped storage. The performance of ST-VTSATC-SSS is experimentally investigated. On the coldest day in winter in 2021(Ta = −2.1 °C), the collector efficiency is 61.7%, the collection-storage efficiency is 40.7%, and the heat storage is 13.7 MJ. During the thermal collection process, the thermal collection-storage efficiency can be improved by enhancing the air volume flow rate, it decreases with the enhancement of solar radiation, and it can reach 55.3%. During the thermal discharge process, increasing the air volume flow rate can enlarge the discharge power. The average discharge power can reach 904 W. The result reveals that ST-VTSATC-SSS can rapidly release heat. Besides, a heating application for the master bedroom is analyzed. In the heating season, this mechanism can save coal of 373.0 kg and reduce CO2 by 977.3 kg, and the heating cost is 14.6 ¥/GJ. The ST-VTSATC-SSS contributes a new, clean, and low cost heating method in rural building heating.

The giant enhancement of nonreciprocal radiation in Thue-morse aperiodic structures

Nonreciprocal radiation has potential applications in the fields of aerospace, energy conversion, and communications. In this paper, the strong nonreciprocal radiation effect in Thue-morse aperiodic structure is systematically investigated. It is achieved by placing a Thue-morse aperiodic magnetophotonic crystal atop a metallic mirror backed with a dielectric substrate. The giant enhancement of nonreciprocal radiation is achieved at the wavelength of 16 μm when the applied magnetic field is 3 T and the incident angle is 60°. This giant enhancement of nonreciprocity is attributed to the Tamm plasmon polaritons (TPPs) excited at the interface between the Thue-morse aperiodic magnetophotonic crystal and the metal mirror, and is confirmed by investigating the distribution of the normalized magnetic field amplitude. Besides, the performance of the enhanced nonreciprocal radiation could be expanded to the waveband smaller than 16 μm. The novelty of this work is that a new scheme is proposed to achieve giant enhancement of nonreciprocal radiation with lamellar structure. It is believed such structure can be employed to verify the Kirchhoff’s law with nonreciprocal mediums and will prompt the development of light harvesting devices and thermal emitters.

Broadening and Redward Asymmetry of Hα Line Profiles Observed by LAMOST during a Stellar Flare on an M-type Star

Abstract Stellar flares are characterized by sudden enhancement of electromagnetic radiation in stellar atmospheres. So far, much of our understanding of stellar flares has come from photometric observations, from which plasma motions in flare regions could not be detected. From the spectroscopic data of LAMOST DR7, we have found one stellar flare that is characterized by an impulsive increase followed by a gradual decrease in the Hα line intensity on an M4-type star, and the total energy radiated through Hα is estimated to be of the order of 1033 erg. The Hα line appears to have a Voigt profile during the flare, which is likely caused by Stark pressure broadening due to the dramatic increase in electron density and/or opacity broadening due to the occurrence of strong nonthermal heating. Obvious enhancement has been identified in the red wing of the Hα line profile after the impulsive increase in the Hα line intensity. The red-wing enhancement corresponds to plasma moving away from the Earth at a velocity of 100–200 km s−1. According to our current knowledge of solar flares, this red-wing enhancement may originate from: (1) flare-driven coronal rain, (2) chromospheric condensation, or (3) a filament/prominence eruption either with nonradial backward propagation or with strong magnetic suppression. The total mass of the moving plasma is estimated to be of the order of 1015 kg.

Experimental study on the effect of fan-shaped water mist on horizontal under-expanded hydrogen jet flames

A series of experiments were performed on the fan-shaped water mist interaction with the horizontal under-expanded hydrogen jet flames. The effects of various water mist pressures and horizontal release positions were focused on flame length, temperature, and radiant heat flux. The results show that, water mist causes the flame to be tilted and the tilt angle of the flame increases with the water mist pressure, and the horizontal length of the flame is shortened. It is also found that water mist may lead to the radiation and temperature enhancement on the axis and downstream of the action position of water mist and flame, which is closely related to the configuration of water mist. However, this situation disappears and the temperature and radiation decrease with the increase of water mist pressure.

Insights into Nanomedicine for Head and Neck Cancer Diagnosis and Treatment.

Head and neck cancers rank sixth among the most common cancers today, and the survival rate has remained virtually unchanged over the past 25 years, due to late diagnosis and ineffective treatments. They have two main risk factors, tobacco and alcohol, and human papillomavirus infection is a secondary risk factor. These cancers affect areas of the body that are fundamental for the five senses. Therefore, it is necessary to treat them effectively and non-invasively as early as possible, in order to do not compromise vital functions, which is not always possible with conventional treatments (chemotherapy or radiotherapy). In this sense, nanomedicine plays a key role in the treatment and diagnosis of head and neck cancers. Nanomedicine involves using nanocarriers to deliver drugs to sites of action and reducing the necessary doses and possible side effects. The main purpose of this review is to give an overview of the applications of nanocarrier systems to the diagnosis and treatment of head and neck cancer. Herein, several types of delivery strategies, radiation enhancement, inside-out hyperthermia, and theragnostic approaches are addressed.

Estrogen receptor inhibition mediates radiosensitization of ER-positive breast cancer models

Endocrine therapy (ET) is an effective first-line therapy for women with estrogen receptor-positive (ER + ) breast cancers. While both ionizing radiation (RT) and ET are used for the treatment of women with ER+ breast cancer, the most effective sequencing of therapy and the effect of ET on tumor radiosensitization remains unclear. Here we sought to understand the effects of inhibiting estrogen receptor (ER) signaling in combination with RT in multiple preclinical ER+ breast cancer models. Clonogenic survival assays were performed using variable pre- and post-treatment conditions to assess radiosensitization with estradiol, estrogen deprivation, tamoxifen, fulvestrant, or AZD9496 in ER+ breast cancer cell lines. Estrogen stimulation was radioprotective (radiation enhancement ratios [rER]: 0.51–0.82). Conversely, when given one hour prior to RT, ER inhibition or estrogen depletion radiosensitized ER+ MCF-7 and T47D cells (tamoxifen rER: 1.50–1.60, fulvestrant rER: 1.76–2.81, AZD9496 rER: 1.33–1.48, estrogen depletion rER: 1.47–1.51). Combination treatment resulted in an increase in double-strand DNA (dsDNA) breaks as a result of inhibition of non-homologous end joining-mediated dsDNA break repair with no effect on homologous recombination. Treatment with tamoxifen or fulvestrant in combination with RT also increased the number of senescent cells but did not affect apoptosis or cell cycle distribution. Using an MCF-7 xenograft model, concurrent treatment with tamoxifen and RT was synergistic and resulted in a significant decrease in tumor volume and a delay in time to tumor doubling without significant toxicity. These findings provide preclinical evidence that concurrent treatment with ET and RT may be an effective radiosensitization strategy.

Estimation of Cosmic Effect on Background Nuclear Radiation

The effect of cosmos on background nuclear radiation has been estimated with altitude on Idanre hill using the rad scanner model 500VBR. Five readings were taken in order to ensure accuracy and reliability of the result. The mean absorbed dose rate in air for ground, middle and top of the hill were estimated to be 322.67±35.80, 353.72±37.79 and 457.88 ± 40.30 nGy h-1 respectively. The absorbed dose rate and the effective dose equivalent increases with height which is an indication of nuclear radiation enhancement by the cosmos. The mean outdoor annual effective dose equivalent was obtained as 0.40±0.05, 0.43±0.08 and 0.56±0.06 mSv y-1 respectively. The mean absorbed dose rate and the mean outdoor annual effective dose equivalent from different heights are higher than the world average of 59 nGy h-1 r and 0.07 mSv y-1 respectively and the World Health Organization recommendation of 0.1 mSv y-1, but lower than the International Commission on Radiological Protection recommendation of 1.0 mSv y-1. The estimated excess lifetime cancer risk 1.83 x10-3 is higher than the world average value of 2.9 x 10-4. This implies a highly significant radiation health risk in the area most predominantly as the height increases and the cosmic effect heightened up. Keywords: Cosmos; Background nuclear radiation; Rad scanner; Effective dose; Cancer risk.

Tunable radiation enhancement and suppression using a pair of photonically doped epsilon-near-zero (ENZ) slabs.

Manipulation of the radiation efficiency and pattern of quantum emitters by engineering the electromagnetic properties of the surrounding medium is crucial for designing various light sources. Here, we theoretically demonstrate the possibility of designing a compact and tunable resonator using a pair of photonically doped epsilon-near-zero (ENZ) slabs that are separated by a deeply subwavelength air gap. Such resonators are shown to be capable of switching between completely transparent and opaque states, for a TM-polarized normally incident plane wave, by slightly changing the permittivity of the dielectric dopants. We exploit this behavior for tunable radiation enhancement and suppression for a quantum emitter placed inside the air gap.