Blazar spectral variability as explained by a twisted inhomogeneous jet.

Blazars are active galactic nuclei, which are powerful sources of radiation whose central engine is located in the core of the host galaxy. Blazar emission is dominated by non-thermal radiation from a jet that moves relativistically towards us, and therefore undergoes Doppler beaming. This beaming causes flux enhancement and contraction of the variability timescales, so that most blazars appear as luminous sources characterized by noticeable and fast changes in brightness at all frequencies. The mechanism that produces this unpredictable variability is under debate, but proposed mechanisms include injection, acceleration and cooling of particles, with possible intervention of shock waves or turbulence. Changes in the viewing angle of the observed emitting knots or jet regions have also been suggested as an explanation of flaring events and can also explain specific properties of blazar emission, such as intra-day variability, quasi-periodicity and the delay of radio flux variations relative to optical changes. Such a geometric interpretation, however, is not universally accepted because alternative explanations based on changes in physical conditions-such as the size and speed of the emitting zone, the magnetic field, the number of emitting particles and their energy distribution-can explain snapshots of the spectral behaviour of blazars in many cases. Here we report the results of optical-to-radio-wavelength monitoring of the blazar CTA 102 and show that the observed long-term trends of the flux and spectral variability are best explained by an inhomogeneous, curved jet that undergoes changes in orientation over time. We propose that magnetohydrodynamic instabilities or rotation of the twisted jet cause different jet regions to change their orientation and hence their relative Doppler factors. In particular, the extreme optical outburst of 2016-2017 (brightness increase of six magnitudes) occurred when the corresponding emitting region had a small viewing angle. The agreement between observations and theoretical predictions can be seen as further validation of the relativistic beaming theory.

Symmetric dimethylarginine concentrations in dogs with hypothyroidism before and after treatement with levothyroxine.

OBJECTIVES: To evaluate the serum symmetric dimethylarginine (SDMA) and serum creatinine concentrations in a population of hypothyroid dogs at the time of diagnosis and after treatment. MATERIALS AND METHODS: Serum SDMA and serum creatinine were measured in serum samples of 24 healthy dogs and 24 hypothyroid dogs, at the time of diagnosis (T0) and after supplementation with levothyroxine (T1). RESULTS: The mean SDMA concentrations (reference intervals [RI] <18 µg/dL and <14 µg/dL depending on the source) were 11.7 ± 3.5 µg/dL, 13.8 ± 3.1 µg/dL and 11.83 ± 2.87 µg/dL in healthy dogs, and in the hypothyroid dogs at T0 and T1, respectively. The SDMA concentrations were higher in the hypothyroid dogs at T0 in comparison with the healthy dogs. Of the hypothyroid dogs, 1 out of 24 had an SDMA concentration above 18 µg/dL and 12 out of 24 above 14 µg/dL at T0. At T1, none of the hypothyroid dogs had SDMA concentrations above 18 µg/dL and two of them had SDMA concentrations above 14 µg/dL. The serum creatinine concentration was higher in the hypothyroid dogs at T0 as compared to the healthy dogs. At T0, 8 out of 24 hypothyroid dogs had serum creatinine concentrations above the RI (>1.4 mg/dL). In all but one dog, serum creatinine normalised after treatment. CLINICAL SIGNIFICANCE: The SDMA and serum creatinine concentrations were higher in hypothyroid dogs at diagnosis as compared to healthy dogs. Serum creatinine concentrations were increased in one-third of the hypothyroid dogs and in the majority of cases normalised after levothyroxine supplementation. SDMA concentrations were rarely above the upper limit of the RI when the higest (<18 µg/dL) cut-off was employed. The diagnostic accuracy of SDMA in dogs with thyroid dysfunction requires additional evaluation.

[The Ogilvie syndrome. Review of literature and report of 2 cases]. / La sindrome di Ogilvie. Revisione della letteratura e presentazione di due casi.

Two cases of pseudo-obstruction of the colon (Ogilvie's syndrome) are presented. Increasing abdominal distension and the pain suggested surgical treatment for both patients. The operation showed in the first case a marked dilatation of the transverse colon and sigmoid, in the second the dilatation of the ascending and transverse colon, without any distal obstruction. Enterotomy was performed only in the first case, as the diameter of the colon was more then 10 cm. The authors, by review of the literature and their own experience, propose a critical revision of the syndrome, discussing the physiopathology of the rising disease.

Photocatalytic activity of TiO2/SiO2 systems.

Silica-supported TiO(2) powders were synthesized by a wet method under mild conditions. The aim of the work was the preparation of TiO(2)/SiO(2) additives for photocatalytic cements. Three types of commercial SiO(2) were used as supports: Cabot, Axim and Fly Ash. Cabot silica was ultra-pure whereas the other two silica contained different percentages of various oxides. The TiO(2)/SiO(2) samples, denoted TiO(2)/Cabot, TiO(2)/Axim and TiO(2)/Fly Ash, were prepared by boiling suspensions obtained by addition of silica to a solution of TiCl(4) in water (volume ratio 1:10). The photocatalytic activity was evaluated in a gas-solid system both in batch and in continuous reactors using 2-propanol as probe molecule. SEM-EDX analysis revealed that titanium dioxide was quantitatively deposited on silica. TiO(2)/Axim and TiO(2)/Fly Ash were scarcely active whereas a good photoactivity was exhibited by the TiO(2)/Cabot sample both in the batch and in the continuous system. Consequently only the last sample was tested for both NO(x) abatement and for 4-nitrophenol photodegradation in a liquid-solid system.

Preparation of N-doped TiO(2): characterization and photocatalytic performance under UV and visible light.

Nanocrystalline N-doped TiO(2) samples were prepared by using TiCl(4) or TiOSO(4) as precursors. The powders were characterized by X-ray diffraction, BET specific surface area measurements, scanning electron microscopy, diffuse reflectance spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The photocatalytic activity was tested using the photodegradation of 4-nitrophenol under UV and visible light.Some samples were more active than commercial Degussa P25. A shift of the absorption edge to a lower energy and a stronger absorption in the visible light region were observed in the samples obtained from TiCl(4). Two absorption edges were observed in the samples derived from TiOSO(4) and calcined at 400 degrees C: the main edge due to TiO(2) and the second one due to the presence of a localised midgap band that induces the visible light activity.

[Study of spondylodiscitis with magnetic resonance. Use of gadolinium-DTPA]. / Studio delle spondilodisciti con risonanza magnetica. Utilizzazione del gadolinio-DPTA.

Eighteen patients suffering from spondylodiscitis were examined with MRI and 22 pathologic levels were identified: 1 cervical, 6 thoracic and 15 lumbosacral. As for etiology, 4 cases were tubercular, 3 strepto-staphylococcal, 3 brucellar 1 strepto-bacteroides and 11 of unknown origin. Five patients underwent MR follow-up 4-9 months after the clinical onset. SE T1- and T2-weighed sequences were always performed and 11 patients, with 13 pathologic levels, also underwent SE T1-weighted sequences with i.v. Gd-DTPA administration. No correlation could be made between the signal intensity of the involved vertebral bodies and disks and etiology. On SE T1-weighted sequences 91% of the vertebral bodies were hypointense, whereas the intervertebral disks were hypointense in 55% of cases and isointense in 45%. On SE T2-weighted sequences, the vertebrae appeared hyperintense in 65% of the cases while the disks were hyperintense in 55% and isointense in 41%. After Gd-DTPA injection signal intensity increased in 100% of cases, both at the body and at the disk. In 6 cases an inflammatory infiltration of the intracanalar structures was found, whose identifications was possible, in 4 cases, only after contrast medium injection. In the follow-up of 5 cases at 4-9 months the vertebral bodies remained hypointense in 3 cases on T1-weighted sequences, while in 2 cases signal intensity tended to normalize. Signal normalized in 4 cases on T2-weighted sequences. In 2 follow-up examinations disk structures were never depicted, neither on T1- nor on T2-weighted sequences. To conclude, T1-weighted sequences appear to be more sensitive than T2-weighted sequences to demonstrate inflammatory processes in the vertebral bodies, while the two sequences are equivalent to evaluate the disks. Gadolinium-enhanced T1-weighted sequences were more sensitive than the T1- and T2-weighted ones, especially to assess the extent of inflammatory processes into the spinal canal and to evaluate their persistence. The authors suggest the use of unenhanced and enhanced SE T1-weighted sequences only at least in the follow-up of spondylodiscitis.

Some remarkable effects of thiopeptide and derived linkages on lysozyme release from neutrophils by esters of the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (f-Met-Leu-Phe-OR).

A variety of recently synthesized analogues of the chemotactic agent f-Met-Leu-Phe-OR modified in the backbone were tested for their ability to induce the release of lysozyme from human neutrophils. In sharp contrast to the effects of thiopeptide linkages on the biological activity of Leu5-enkephalin as previously reported, the presence of single thioamide bonds at either one of the endo-positions of the chemotactic peptide, abolished activity. Thioamide-derived linkages such as amidoximes and cyanamidines were generally also detrimental to activity, except in the cases of the cyanamidoformyl derivatives which showed enhanced activity and two amidoxime esters, one O-acetylated and the other O-esterified intramolecularly, which retained moderate activity. The mechanistic significance of these results is discussed in terms of conformational effects on receptor recognition.