Spin Fine Structure Reveals Biexciton Geometry in an Organic Semiconductor.

In organic semiconductors, biexcitons are key intermediates in carrier multiplication and exciton annihilation. Their local geometry governs their electronic properties and yet has been challenging to determine. Here, we access the structure of the recently discovered S=2 quintet biexciton state in an organic semiconductor using broadband optically detected magnetic resonance. We correlate the experimentally extracted spin structure with the molecular crystal geometry to identify the specific molecular pairings on which biexciton states reside.

Coupling between Rydberg States and Landau Levels of Electrons Trapped on Liquid Helium.

We investigate the coupling between Rydberg states of electrons trapped on a liquid helium surface and Landau levels induced by a perpendicular magnetic field. We show that this realizes a prototype quantum system equivalent to an atom in a cavity, where their coupling strength can be tuned by a parallel magnetic field. We determine experimentally the renormalization of the atomic transition energies induced by the coupling to the cavity, which can be seen as an analog of the Lamb shift. When the coupling is sufficiently strong, the transition between the ground and first excited Rydberg states splits into two resonances corresponding to dressed states with vacuum and one photon in the cavity. Our results are in quantitative agreement with the energy shifts predicted by the effective atom in a cavity model where all parameters are known with high accuracy.

[The role of structural changes of the urinary bladder extracellular matrix in the occurrence of different grades of adverse events after radiation therapy].

AIM: To investigate the role of structural changes of the urinary bladder extracellular matrix in the occurrence of different grades of adverse events after radiation therapy. MATERIALS AND METHODS: The connective tissue matrix was studied using 126 images obtained from the histological sections of the bladder biopsy specimens of 12 patients classified according to the clinical presentation and the grades of late bladder toxicity according to RTOG/EORTC Late Radiation Morbidity Scoring Scheme. Control images of the normal bladder (n=23) were collected from the autopsy samples. We used nonlinear microscopy imaging method capturing the second harmonic generation (SHG) signal and two-photon excitation auto-fluorescence (TPEA). RESULTS: The findings of nonlinear microscopy of urinary bladder histological sections showed that the structural changes in the connective tissue differed depending on the grade of adverse events: grade II adverse events were associated with the preservation of the structure of collagen fibers and their compression, grade III adverse events caused pronounced disorganization of collagen fibers, blurring without a definite fiber direction. At the same time, in a normal bladder, the structure of collagen fibers was visualized; they had a spiral shape and in some areas were collected in bundles. Collagen fibers and bundles were loosely arranged and accompanied by elastic fibers. The findings suggest that the grade of urinary bladder radiation injury correlates with the data detected by nonlinear microscopy. DISCUSSION: The mosaic structure of radiation-induced alterations of the bladder tissue, even in the areas most affected by radiation (posterior bladder wall, bladder trigone, and bladder neck) indicates that patients with radiation-induced high-grade toxicity need comprehensive care designed to preserve the bladder functional reserves and capacity. The prevention of radiation-related adverse events before radiation therapy should be based on urologic care aimed to detect and treat chronic inflammatory diseases of the bladder and preserve its functional reserves. Another way to improve outcomes is to optimize the management of adverse events. CONCLUSION: The examination of bladder tissue specimens taken from different parts of the bladder carried out using nonlinear microscopy in the SHG and TPEA modes revealed that the degree of structural changes in the connective tissue matrix in the post-radiation period varies and correlates with the grades of the radiation bladder toxicity. The results of this study can be used to substantiate measures to prevent the onset of high-grade toxicity after radiation therapy of pelvic malignancies.

Site-selective measurement of coupled spin pairs in an organic semiconductor.

From organic electronics to biological systems, understanding the role of intermolecular interactions between spin pairs is a key challenge. Here we show how such pairs can be selectively addressed with combined spin and optical sensitivity. We demonstrate this for bound pairs of spin-triplet excitations formed by singlet fission, with direct applicability across a wide range of synthetic and biological systems. We show that the site sensitivity of exchange coupling allows distinct triplet pairs to be resonantly addressed at different magnetic fields, tuning them between optically bright singlet ([Formula: see text]) and dark triplet quintet ([Formula: see text]) configurations: This induces narrow holes in a broad optical emission spectrum, uncovering exchange-specific luminescence. Using fields up to 60 T, we identify three distinct triplet-pair sites, with exchange couplings varying over an order of magnitude (0.3-5 meV), each with its own luminescence spectrum, coexisting in a single material. Our results reveal how site selectivity can be achieved for organic spin pairs in a broad range of systems.

[Urethral leiomyoma].

In urology practice, leiomyoma of the urinary bladder is considered a rare tumor. Urethral leiomyoma is even more unusual. This article is a case report of a very rare benign tumor originating from the smooth muscles of the urethra causing obstructive voiding in a woman.

[Tuberculosis of the prostate].

Genitourinary tract is the second most common site where extrapulmonary tuberculosis (TB) occurs. Genitourinary TB is notable for a latent clinical course and difficult diagnosis. The paper presents clinical observations of two patients treated in a urology department of a general public hospital. One of them was diagnosed with tuberculosis of the prostate, MTB+. In the other, TB of the prostate was suspected based on pathologic assessment of the surgical specimen after surgery for prostate cancer.