We theoretically demonstrate for the first time that a single free electron in circular or spiral motion emits twisted photons carrying well-defined orbital angular momentum along the axis of the ...electron circulation, in adding to spin angular momentum. We show that, when the electron velocity is relativistic, the radiation field contains harmonic components and the photons of lth harmonic carry lℏ total angular momentum for each. This work indicates that twisted photons are naturally emitted by free electrons and are more ubiquitous in laboratories and in nature than ever thought.
Abstract The potential for RNA-based agents to serve as effective therapeutics for central nerve systems (CNS) disorders has been successfully demonstrated in vitro . However, the blood–brain barrier ...limits the distribution of systemically administered therapeutics to the CNS, posing a major challenge for drug development aimed at combatting CNS disorders. Therefore, the development of effective strategies to enhance siRNA delivery to the brain is of great interest in clinical and pharmaceutical fields. To improve the efficiency of small interfering RNA (siRNA) delivery to the brain, we developed a nose-to-brain delivery system combined with cell-penetrating peptide (CPP) modified nano-micelles comprising polyethylene glycol–polycaprolactone (PEG–PCL) copolymers conjugated with the CPP, Tat (MPEG–PCL–Tat). In this study, we describe intranasal brain delivery of siRNA or dextran (Mw: 10,000 Da) as a model siRNA, by using MPEG–PCL–Tat. Intranasal delivery of dextran with MPEG–PCL–Tat improved brain delivery compared to intravenous delivery of dextran either with or without MPEG–PCL–Tat. We also studied the intranasal transfer of MPEG–PCL–Tat to the brain via the olfactory and trigeminal nerves, the putative pathways to the brain from the nasal cavity. We found that MPEG–PCL–Tat accelerated transport along the olfactory and trigeminal nerve pathway because of its high permeation across the nasal mucosa.
We theoretically show that a single free electron in circular motion radiates an electromagnetic wave possessing helical phase structure, which is closely related to orbital angular momentum carried ...by it. We experimentally demonstrate it by interference and double-slit diffraction experiments on radiation from relativistic electrons in spiral motion. Our results indicate that photons carrying orbital angular momentum should be created naturally by cyclotron/synchrotron radiations or Compton scatterings in various situations in cosmic space. We propose promising laboratory vortex photon sources in various wavelengths ranging from radio wave to gamma-rays.
We verify that each wave packet of spontaneous radiation from two undulators placed in series has a double-pulsed temporal profile with pulse spacing which can be controlled at the attosecond level. ...Using a Mach-Zehnder interferometer operating at ultraviolet wavelengths, we obtain the autocorrelation trace for the spontaneous radiation from the tandem undulator. The results clearly show that the wave packet has a double-pulsed structure, consisting of a pair of 10-cycle oscillations with a variable separation. We also report the characterization of the time delay between the double-pulsed components in different wavelength regimes. The excellent agreement between the independent measurements confirms that a tandem undulator can be used to produce double-pulsed wave packets at arbitrary wavelength.
Abstract
As accelerators and electron microscopes become more advanced, high-performance photocathodes are required. In particular, Cesium potassium antimonide (CsK
2
Sb) photocathode is of interest ...because of its low emittance, excitability in visible light, and high quantum efficiency (QE). The challenge is its high susceptibility to environment that lead to low operating vacuum pressure and short lifetime/low extraction charge. To resolve these issues, it is necessary to understand the molecular structure of the cathode and its degradation mechanism. In this study, we transported CsK
2
Sb photocathode to a beamline of synchrotron radiation facility using a vacuum transport system for molecular structure analysis. Specifically, the cathode was deposited in an evaporation system at Nagoya University. We transported it to Aichi Synchrotron Radiation Center (Aichi SR) located 15 km away, and analyzed it in the depth direction by X-ray photoelectron spectroscopy (XPS) at BL7U. Based on the results, we quantitatively evaluated the composition ratios and stoichiometry of the cathode elements (Sb, K, Cs). A Cs ex-cess state of surface was observed at the surface, and it is consistent with previous studies. The intended atomic structure of CsK
2
Sb was formed only at a few nanometres of the surface on the Mo substrate. On the other hand, the CsK
2
Sb cathode structure on the graphene substrate was preserved further in the depth direction.
Abstract
The synchrotron light source with the electron energy of 1.2 GeV is operated by Aichi Synchrotron Radiation Centre (AichiSR) in Aichi prefecture, Japan. The light has been offered to ...industrial and academic users since March 2013 in the top-up operation mode to maintain a constant current of 300 mA. This facility was established by Aichi prefecture, universities, and industries with support of government. Major purpose of the light source is to support research and development activities of industries and academia mostly in the area, which is the heart land of manufacturing of Japan. This paper describes evolution of the beamlines and recent research results and their impact to the society.
Display omitted
Drug delivery from topically instilled eye drops to the posterior segment of the eye has long been one of the greatest challenges of ocular drug development. We developed methods of ...liposome preparation utilizing a microfluidizer to achieve adjustable nanoparticle size (even less than 80nm) and high loading capacity of plasmid DNA. The microfluidizing process parameters were shown to affect the size of the liposomes. Higher operating pressures and passage for at least 10 times through the microfluidizer produced small liposomes with narrow size distribution. The liposomes were physically stable for several months at +4°C. In vivo distribution of the optimized liposome formulations in the rat eyes was investigated with confocal microscopy of the histological specimens. Transferrin was used as a targeting ligand directed to retinal pigment epithelium. Size dependent distribution of liposomes to different posterior segment tissues was seen. Liposomes with the diameter less than 80nm permeated to the retinal pigment epithelium whereas liposomes with the diameter of 100nm or more were distributed to the choroidal endothelium. Active targeting was shown to be necessary for liposome retention to the target tissue. In conclusion, these microfluidizer produced small liposomes in eye drops are an attractive option for drug delivery to the posterior segment tissues of the eye.
A high-performance photocathode is required to advanced accelerators and electron microscopes. In particular, the CsK2Sb photocathode is of interest because it has features such as low emittance, ...excitability with visible light, and high quantum efficiency (QE). Generally, the CsK2Sb photocathode is produced by depositing a cathode element on a substrate, so that the cathode performance strongly depends on the surface condition of the substrate. We have found graphene as reusable substrate, which has the property of being chemically inactive. In this study, graphene film quality dependence of CsK2Sb photocathode performance was evaluated. Specifically, CsK2Sb photocathode was deposited using different quality graphene film substrates and their QE values and uniformity were compared. The quality of graphene films was analyzed using X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). We found that the graphene film can be cleaned by heating at 500 deg. The QE of the cathode on a good quality graphene film was higher and more uniform than that on a poor quality graphene film.
Abstract
Skin surface contamination by alpha-emitters is in itself not hazardous, but it would cause significant internal exposure in the case of injured skin as well as misjudgment in direct in vivo ...measurements (e.g. lung counting). The present study determined the source efficiency of alpha-emitters (241Am) applied to swine skin samples by analysing the observed alpha-particle energy spectra using advanced alpha-spectrometric simulation. Based on our results, the source efficiency was determined to be 0.365 (alpha-particle s−1 per Bq) on average (c.f. 0.5 in the case of no self-absorption in the source). The decrease in source efficiency would be attributed primarily to the radionuclide entering hair follicles or deep wrinkles. The degradation of the measured spectra from the skin samples indicates the penetration of some radionuclides into the upper layers of the stratum corneum. Although this study was limited to results obtained from swine skin samples, it suggests that irregularities in the skin surface may affect direct alpha measurements.
PDF
