Constraints on axion-like polarization oscillations in the cosmic microwave background with POLARBEAR

Very light pseudoscalar fields, often referred to as axions, are compelling dark matter candidates and can potentially be detected through their coupling to the electromagnetic field. Recently a novel detection technique using the cosmic microwave background (CMB) was proposed, which relies on the fact that the axion field oscillates at a frequency equal to its mass in appropriate units, leading to a time-dependent birefringence. For appropriate oscillation periods this allows the axion field at the telescope to be detected via the induced sinusoidal oscillation of the CMB linear polarization. We search for this effect in two years of POLARBEAR data. We do not detect a signal, and place a median $95 \%$ upper limit of $0.65 ^\circ$ on the sinusoid amplitude for oscillation frequencies between $0.02\,\text{days}^{-1}$ and $0.45\,\text{days}^{-1}$, which corresponds to axion masses between $9.6 \times 10^{-22} \, \text{eV}$ and $2.2\times 10^{-20} \,\text{eV}$. Under the assumptions that 1) the axion constitutes all the dark matter and 2) the axion field amplitude is a Rayleigh-distributed stochastic variable, this translates to a limit on the axion-photon coupling $g_{\phi \gamma} < 2.4 \times 10^{-11} \,\text{GeV}^{-1} \times ({m_\phi}/{10^{-21} \, \text{eV}})$.Comment: 17 pages, 5 figures, 2 tables. Published in Physical Review

Analysis of the triplet-state kinetics of a photosensitizer for photoimmunotherapy by fluorescence correlation spectroscopy

Herein, we evaluated the intersystem crossing quantum yield (Phi(ISC)) of a silicon phthalocyanine derivatized from IRDye700DX (IR700) which is used as a photosensitizer for photoimmunotherapy (PIT), using fluorescence correlation spectroscopy (FCS). The calculated Phi(ISC) was 0.019 +/- 0.002. The FCS measurement was validated by experiment in the presence of potassium iodide, which can change the kinetics of the relaxation process in the excited state

Theoretical and Experimental Studies on the Near-Infrared Photoreaction Mechanism of a Silicon Phthalocyanine Photoimmunotherapy Dye : Photoinduced Hydrolysis by Radical Anion Generation

Ligand release from IR700, a silicon phthalocyanine dye used in near-infrared (NIR) photoimmunotherapy, initiates cancer cell death after NIR absorption, although its photochemical mechanism has remained unclear. This theoretical study reveals that the direct Si-ligand dissociation by NIR light is difficult to activate because of the high dissociation energy even in excited states, i. e., >1.30 eV. Instead, irradiation generates the IR700 radical anion, leading to acid-base reactions with nearby water molecules (i. e., calculated pK(b) for the radical anion is 7.7) to produce hydrophobic ligand-released dyes. This suggests two possibilities: (1) water molecules participate in ligand release and (2) light is not required for Si-ligand dissociation as formation of the IR700 radical anion is sufficient. Experimental evidence confirmed possibility (1) by using O-18-labeled water as the solvent, while (2) is supported by the pH dependence of ligand exchange, providing a complete description of the Si-ligand bond dissociation mechanism

Theoretical and Experimental Studies on the Near‐Infrared Photoreaction Mechanism of a Silicon Phthalocyanine Photoimmunotherapy Dye: Photoinduced Hydrolysis by Radical Anion Generation

Ligand release from IR700, a silicon phthalocyanine dye used in near-infrared (NIR) photoimmunotherapy, initiates cancer cell death after NIR absorption, although its photochemical mechanism has remained unclear. This theoretical study reveals that the direct Si-ligand dissociation by NIR light is difficult to activate because of the high dissociation energy even in excited states, i. e., >1.30 eV. Instead, irradiation generates the IR700 radical anion, leading to acid-base reactions with nearby water molecules (i. e., calculated pK(b) for the radical anion is 7.7) to produce hydrophobic ligand-released dyes. This suggests two possibilities: (1) water molecules participate in ligand release and (2) light is not required for Si-ligand dissociation as formation of the IR700 radical anion is sufficient. Experimental evidence confirmed possibility (1) by using O-18-labeled water as the solvent, while (2) is supported by the pH dependence of ligand exchange, providing a complete description of the Si-ligand bond dissociation mechanism

Development of a red-shifted photosensitizer for near-infrared photoimmunotherapy of cancer

Near-infrared photoimmunotherapy (NIR-PIT) is a recently described method for cancer treatment that utilizes an antibody-conjugated phthalocyanine photosensitizer and NIR light. In NIR-PIT, light of 690 nm wavelength is used to activate a photosensitizer, IR700, while longer-wavelength light penetrates deeper into tissues. Thus, more effective NIR-PIT would be achieved by using photosensitizers that are activated by longer-wavelength light. The absorption wavelength would be red-shifted by destabilizing the highest occupied molecular orbital (HOMO) energy level by introducing electron donating groups at the α positions of a phthalocyanine ring. In this study, we developed a red-shifted photosensitizer for NIR-PIT, KA800, whose absorption wavelength was red-shifted by the introduction of ethoxy groups to IR700. As intended, the absorption maximum of KA800 was red-shifted compared to IR700 by 84 nm. Although phototoxicity of the antibody-KA800 (Ab-KA800) conjugate was observed in cultured cancer cells, no therapeutic effect was observed in mice. This is because the cytotoxicity of Ab-KA800 was mainly due to singlet oxygen, which can be quenched by abundant antioxidants in vivo. KA800 had low reactivity with respect to axial ligand cleavage required for inducing cell death via aggregate formation, a unique cytotoxic mechanism in NIR-PIT. The axial ligand cleavage proceeds via the anion radical formation of the photosensitizer, and KA800 was found to be less likely to receive an electron than IR700. This may be due to the destabilization of the HOMO energy level of KA800. Therefore, our findings suggest that stabilizing the lowest unoccupied molecular orbital (LUMO) energy level would be better than destabilizing the HOMO energy level for developing a red-shifted photosensitizer for NIR-PIT

Exploration of the polarization angle variability of the Crab Nebula with POLARBEAR and its application to the search for axion-like particles

International audienceThe Crab Nebula, also known as Tau A, is a polarized astronomical source at millimeter wavelengths. It has been used as a stable light source for polarization angle calibration in millimeter-wave astronomy. However, it is known that its intensity and polarization vary as a function of time at a variety of wavelengths. Thus, it is of interest to verify the stability of the millimeter-wave polarization. If detected, polarization variability may be used to better understand the dynamics of Tau A, and for understanding the validity of Tau~A as a calibrator. One intriguing application of such observation is to use it for the search of axion-light particles (ALPs). Ultralight ALPs couple to photons through a Chern-Simons term, and induce a temporal oscillation in the polarization angle of linearly polarized sources. After assessing a number of systematic errors and testing for internal consistency, we evaluate the variability of the polarization angle of the Crab Nebula using 2015 and 2016 observations with the 150 GHz POLARBEAR instrument. We place a median 95% upper bound of polarization oscillation amplitude $A < 0.065^\circ$ over the oscillation frequencies from $0.75~\mathrm{year}^{-1}$ to $0.66~\mathrm{hour}^{-1}$. Assuming that no sources other than ALP are causing Tau A's polarization angle variation, that the ALP constitutes all the dark matter, and that the ALP field is a stochastic Gaussian field, this bound translates into a median 95% upper bound of ALP-photon coupling $g_{a\gamma\gamma} < 2.16\times10^{-12}\,\mathrm{GeV}^{-1}\times(m_a/10^{-21} \mathrm{eV})$ in the mass range from $9.9\times10^{-23} \mathrm{eV}$ to $7.7\times10^{-19} \mathrm{eV}$. This demonstrates that this type of analysis using bright polarized sources is as competitive as those using the polarization of cosmic microwave background in constraining ALPs

Exploration of the polarization angle variability of the Crab Nebula with POLARBEAR and its application to the search for axion-like particles

International audienceThe Crab Nebula, also known as Tau A, is a polarized astronomical source at millimeter wavelengths. It has been used as a stable light source for polarization angle calibration in millimeter-wave astronomy. However, it is known that its intensity and polarization vary as a function of time at a variety of wavelengths. Thus, it is of interest to verify the stability of the millimeter-wave polarization. If detected, polarization variability may be used to better understand the dynamics of Tau A, and for understanding the validity of Tau~A as a calibrator. One intriguing application of such observation is to use it for the search of axion-light particles (ALPs). Ultralight ALPs couple to photons through a Chern-Simons term, and induce a temporal oscillation in the polarization angle of linearly polarized sources. After assessing a number of systematic errors and testing for internal consistency, we evaluate the variability of the polarization angle of the Crab Nebula using 2015 and 2016 observations with the 150 GHz POLARBEAR instrument. We place a median 95% upper bound of polarization oscillation amplitude $A < 0.065^\circ$ over the oscillation frequencies from $0.75~\mathrm{year}^{-1}$ to $0.66~\mathrm{hour}^{-1}$. Assuming that no sources other than ALP are causing Tau A's polarization angle variation, that the ALP constitutes all the dark matter, and that the ALP field is a stochastic Gaussian field, this bound translates into a median 95% upper bound of ALP-photon coupling $g_{a\gamma\gamma} < 2.16\times10^{-12}\,\mathrm{GeV}^{-1}\times(m_a/10^{-21} \mathrm{eV})$ in the mass range from $9.9\times10^{-23} \mathrm{eV}$ to $7.7\times10^{-19} \mathrm{eV}$. This demonstrates that this type of analysis using bright polarized sources is as competitive as those using the polarization of cosmic microwave background in constraining ALPs