Performance of Hamamatsu 64-anode photomultipliers for use with wavelength--shifting optical fibres

Hamamatsu R5900-00-M64 and R7600-00-M64 photomultiplier tubes will be used with wavelength--shifting optical fibres to read out scintillator strips in the MINOS near detector. We report on measurements of the gain, efficiency, linearity, crosstalk, and dark noise of 232 of these PMTs, of which 219 met MINOS requirements.Comment: 15 pages, 12 figures. Accepted by Nucl. Inst. Meth.

Semi-Analytic Stellar Structure in Scalar-Tensor Gravity

Precision tests of gravity can be used to constrain the properties of hypothetical very light scalar fields, but these tests depend crucially on how macroscopic astrophysical objects couple to the new scalar field. We develop quasi-analytic methods for solving the equations of stellar structure using scalar-tensor gravity, with the goal of seeing how stellar properties depend on assumptions made about the scalar coupling at a microscopic level. We illustrate these methods by applying them to Brans-Dicke scalars, and their generalization in which the scalar-matter coupling is a weak function of the scalar field. The four observable parameters that characterize the fields external to a spherically symmetric star (the stellar radius, R, mass, M, scalar `charge', Q, and the scalar's asymptotic value, phi_infty) are subject to two relations because of the matching to the interior solution, generalizing the usual mass-radius, M(R), relation of General Relativity. We identify how these relations depend on the microscopic scalar couplings, agreeing with earlier workers when comparisons are possible. Explicit analytical solutions are obtained for the instructive toy model of constant-density stars, whose properties we compare to more realistic equations of state for neutron star models.Comment: 39 pages, 9 figure

Performance of different photocathode materials in a liquid argon purity monitor

Purity monitor devices are increasingly used in liquid noble gas time projection chambers to measure the lifetime of drifting electrons. Purity monitors work by emitting electrons from a photocathode material via the photoelectric effect. The electrons are then drifted towards an anode by means of an applied electric drift field. By measuring the difference in charge between the cathode and the anode, one can extract the lifetime of the drifting electrons in the medium. For the first time, we test the performance of different photocathode materials—silver, titanium, and aluminium—and compare them to gold, which is the standard photocathode material used for purity monitors. Titanium and aluminium were found to have a worse performance than gold in vacuum, whereas silver showed a signal of the same order of magnitude as gold. Further tests in liquid argon were carried out on silver and gold with the conclusion that the signal produced by silver is about three times stronger than that of gold

Complex temperatures zeroes of partition function in spin-glass models

An approximate method is proposed for investigating complex-temperature properties of real-dimensional spin-glass models. The method uses the complex-temperature data of the ferromagnetic model on the same lattice. The universality line in the complex-temperature space is obtained.Comment: latex, corrected some misprint

Selective Phosphorylation of Conjugated α-Enones at the Carbonyl Group, Catalyzed by Cyclohexylamine

Reaction of dialkyl phosphites with benzalacetophenone (chalcone) and benzalacetone in the presence of cyclohexylamine as a catalyst is a convenient preparative method for selective phosphorylation of conjugated α, β-unsaturated carbonyl compounds at the carbonyl group. The kinetics of cyclohexylamine-catalyzed addition of dialkyl phosphites to cis- and trans-chalcones is studied, and factors are revealed that influence the reactivity of addends in this reaction

Phase diagram of the pp-spin-interacting spin glass with ferromagnetic bias and a transverse field in the infinite-pp limit

The phase diagram of the $p$-spin-interacting spin glass model in a transverse field is investigated in the limit $p \to \infty$ under the presence of ferromagnetic bias. Using the replica method and the static approximation, we show that the phase diagram consists of four phases: Quantum paramagnetic, classical paramagnetic, ferromagnetic, and spin-glass phases. We also show that the static approximation is valid in the ferromagnetic phase in the limit $p \to \infty$ by using the large-$p$ expansion. Since the same approximation is already known to be valid in other phases, we conclude that the obtained phase diagram is exact.Comment: 16 pages, 4 figures. another additional author, some amendment

RADIOSURGICAL TREATMENT OF BENIGN SMALL EYELID TUMORS

Aim of the study – to evaluate the long-term results of the radiosurgical method using microsurgical techniques for the treatment of small benign eyelid tumors. Material and methods. In Ocular Oncology Centre of Helmholtz Moscow Research Institute of Eye Diseases for the period from 2012 to 2018 year 248 patients were examined and treated (108 children aged 12 ± 1.2 years and 140 adults aged 46 ± 8.1 years) with benign eyelid tumors: pigmented (nevus), vascular (capillary hemangiomas), epithelial (follicular keratosis, keratopapilloma). The Surgitron EMC radiosurgery device was used as surgical aids. All patients used microsurgical technique. The longitudinal size of the tumors was 3.4 ± 0.5 mm, transverse – 6 ± 0.8 mm. All patients after surgical treatment underwent histopathological study. The observation period is on average 6 ± 1.4 years. Results. In 133 (53.6 %) of 248 patients, nevi were detected, in 76 (30.7 %) – keratopapilloma and inverted follicular keratosis, in 39 (15.7 %) – capillary hemangioma. Various modifications of radiosurgical treatment were used depending on the location of the tumor, its size, the degree of activity using different modes and powers from 1 to 4 Wt. Intraoperative complications were not noted. The early postoperative period was accompanied by the presence of signs of mild inflammation, which was stopped by local therapy. The formation of a tender scar was observed on average after 7 ± 2 days. Two cases (0.8 %) of recurrence of keratopapilloma were noted 2 years after the first operation. Tumors were removed by radio excision. Conclusion. Benign eyelid tumors, especially of melanocytic origin, are subject to obligatory dynamic observation, and if minimal signs of their progression are detected, their surgical removal is indicated. Radiosurgical treatment using microsurgical techniques is the method of choice in the treatment of small benign eyelid tumors and depends on the size of the tumor, its localization and the nature of the tumor process. The use of the radiosurgical method with obligatory microsurgical technique for treating benign tumors of small sizes with the observance of the rules of radicalness and antiblasticity allows maintaining visual functions with simultaneous surgical treatment, providing normal anatomical and topographic correlations of the anterior segment of the eye and high quality of life of the patient