Interaction of positronium with dissolved oxygen in liquids.

The interaction of positronium (Ps) with molecular oxygen dissolved in liquids is experimentally investigated. Computer software has been developed for fitting the positron annihilation lifetime spectra in liquids using parameters with clear physical meaning: rate constants of the Ps chemical reactions, annihilation rate constants of the different positron states, probability of Ps formation in a quasi-free state, typical formation time of a Ps nanobubble. Such processing of the spectra allowed identification of the dominant interaction of the Ps atom with dissolved oxygen. It turns out to be mainly ortho-para-conversion (Ps → 1/4 p-Ps + 3/4 o-Ps), but not oxidation (Ps + O2→ e+ + O2-). Values of the reaction rate constants are obtained.

18 F-sodium fluoride positron emission tomography of the racing Thoroughbred fetlock: Validation and comparison with other imaging modalities in nine horses.

BACKGROUND: Early and accurate detection of stress remodelling in racehorses is of utmost importance to prevent catastrophic injuries. Current imaging techniques have limitations in assessing early changes predisposing to catastrophic breakdowns. Positron emission tomography (PET) using 18 F-sodium fluoride (18 F-NaF) is a sensitive method for the detection of early bone turnover and may improve early recognition of subtle injuries. OBJECTIVES: To validate the clinical use of 18 F-NaF PET in Thoroughbred racehorses, to assess the value of PET in the detection of bone lesions and to compare PET results with findings of other advanced imaging modalities, clinical examination and pathology. STUDY DESIGN: Experimental exploratory study. METHODS: Twenty fetlocks from nine Thoroughbred racehorses were imaged using 18 F-NaF PET, computed tomography (CT) and scintigraphy. Five fetlocks were also imaged with magnetic resonance imaging and four fetlocks were also examined histologically. Imaging findings were independently reviewed by three board certified radiologists. Imaging, clinical and histopathological findings were correlated. RESULTS: PET imaging was well-tolerated by all horses. PET detected focal areas of 18 F-NaF uptake in instances where other imaging modalities did not identify abnormalities, in particular in the proximal sesamoid bones. Maximal standardised uptake values could be measured to quantify the activity of lesions. Areas of 18 F-NaF uptake corresponded to regions of increased vascularity and increased osteoblastic activity. MAIN LIMITATIONS: Limited number of cases. CONCLUSIONS: 18 F-NaF PET imaging of the Thoroughbred fetlock is feasible and compares favourably with other imaging modalities in detecting stress remodelling in Thoroughbred racehorses. PET appears to be a beneficial imaging modality when used for early detection of stress remodelling in an effort to prevent catastrophic musculoskeletal injuries in this population of horses.

18 F-sodium fluoride positron emission tomography of the equine distal limb: Exploratory study in three horses.

BACKGROUND: Positron emission tomography (PET) is a cross-sectional, functional imaging modality that has recently become available to the horse. The use of 18 F-sodium fluoride (18 F-NaF), a PET bone tracer, has not previously been reported in this species. OBJECTIVES: To assess the feasibility of 18 F-NaF PET in the equine distal limb and explore possible applications in the horse in comparison with other imaging modalities. STUDY DESIGN: Exploratory descriptive study involving three research horses. METHODS: Horses were placed under general anaesthesia prior to intravenous (i.v.) administration of 1.5 MBq/kg of 18 F-NaF. Positron emission tomography imaging of both front feet and fetlocks was performed using a portable scanner. Computed tomography (CT) of the distal limb was performed under a separate anaesthetic episode. Bone scintigraphy and magnetic resonance imaging (MRI) were subsequently performed under standing sedation. Images obtained from PET and other imaging modalities were independently assessed and the results correlated. RESULTS: Positron emission tomography images were obtained without complication. The radiation exposure rate was similar to equine bone scintigraphy. Positron emission tomography detected focal 18 F-NaF uptake in areas where other imaging modalities did not identify any abnormalities. This included sites of ligamentous attachment, subchondral compact bone plate and the flexor cortex of the navicular bone. 18 F-NaF uptake was identified in some, but not all, osseous fragments and areas of osseous formation, suggesting a distinction between active and inactive lesions. MAIN LIMITATIONS: A small number of horses were included and histopathology was not available. CONCLUSIONS: 18 F-NaF PET imaging of the equine distal limb provides useful additional information when compared with CT, MRI and scintigraphy and has the potential for both research and clinical applications in the horse. The Summary is available in Chinese - see Supporting information.

Magnetic microkayaks: propulsion of microrods precessing near a surface by kilohertz frequency, rotating magnetic fields.

Surface-swimming nano- and micromotors hold significant potential for on-chip mixing, flow generation, sample manipulation, and microrobotics. Here we describe rotating microrods magnetized nearly orthogonally to their long axes. When actuated near a solid surface, these microrods demonstrate precessing motion, with rods describing a double cone similar to the motion of a kayaker's paddle. The precessing motion induces translation. At 1 kHz, these "microkayaks" move at translational velocities of ≈14 µm s-1 and generate advective flows up to 10 µm s-1.

ZnO Luminescence and scintillation studied via photoexcitation, X-ray excitation, and gamma-induced positron spectroscopy.

The luminescence and scintillation properties of ZnO single crystals were studied by photoluminescence and X-ray-induced luminescence (XRIL) techniques. XRIL allowed a direct comparison to be made between the near-band emission (NBE) and trap emissions providing insight into the carrier recombination efficiency in the ZnO crystals. It also provided bulk luminescence measurements that were not affected by surface states. The origin of a green emission, the dominant trap emission in ZnO, was then investigated by gamma-induced positron spectroscopy (GIPS) - a unique defect spectroscopy method that enables positron lifetime measurements to be made for a sample without contributions from positron annihilation in the source materials. The measurements showed a single positron decay curve with a 175 ps lifetime component that was attributed to Zn vacancies passivated by hydrogen. Both oxygen vacancies and hydrogen-decorated Zn vacancies were suggested to contribute to the green emission. By combining scintillation measurements with XRIL, the fast scintillation in ZnO crystals was found to be strongly correlated with the ratio between the defect luminescence and NBE. This study reports the first application of GIPS to semiconductors, and it reveals the great benefits of the XRIL technique for the study of emission and scintillation properties of materials.

Dynamic inversion enables external magnets to concentrate ferromagnetic rods to a central target.

The ability to use magnets external to the body to focus therapy to deep tissue targets has remained an elusive goal in magnetic drug targeting. Researchers have hitherto been able to manipulate magnetic nanotherapeutics in vivo with nearby magnets but have remained unable to focus these therapies to targets deep within the body using magnets external to the body. One of the factors that has made focusing of therapy to central targets between magnets challenging is Samuel Earnshaw's theorem as applied to Maxwell's equations. These mathematical formulations imply that external static magnets cannot create a stable potential energy well between them. We posited that fast magnetic pulses could act on ferromagnetic rods before they could realign with the magnetic field. Mathematically, this is equivalent to reversing the sign of the potential energy term in Earnshaw's theorem, thus enabling a quasi-static stable trap between magnets. With in vitro experiments, we demonstrated that quick, shaped magnetic pulses can be successfully used to create inward pointing magnetic forces that, on average, enable external magnets to concentrate ferromagnetic rods to a central location.

[Actual issues of pathogenesis of tuberculosis of male genital organs].

Based on a survey of 467 men with genital tuberculosis, following conclusions were made. The presence of morphological signs of nonspecific prostatitis of toxic-allergic genesis in patients with newly diagnosed tuberculosis of the urinary and genital organs proves the possibility of primary infection of the epididymis with Mycobacterium tuberculosis. Primarily isolated epididymal tuberculosis was diagnosed in 21 (4,5%) patients. Tuberculous of testicles is in direct relationship to the duration of the existence of tuberculous infection in the epididymis. Bilateral tuberculous of the epididymis is always combined with tuberculosis of the prostate. Opportunity of both primary and secondary infection of the prostate gland with Mycobacterium tuberculosis can be considered as proved. 15 (3,2%) patients had initially isolated prostatic tuberculosis. Based on clinical observations, exogenous way of introduction of infection in tuberculosis of genital organs in men was not confirmed. The lymphogenous and hematogenous pathways are leading and most common pathways of Mycobacterium tuberculosis in the male genitals. In patients with tuberculosis of the prostate, which is combined with a lesion of urinary organs, without involvement of scrotum in the pathological process, infection of prostate occurs by urinogenous way. Tuberculosis of the seminal vesicles is always secondary; none of the patients were initially diagnosed with isolated process. Based on the clinical manifestations of the disease and a detailed examination of the patient, it is virtually impossible to establish a particular way of infection in the male genitals. The main value of the information about the possible ways of tuberculosis infection consists of fully examination of reproductive system with histological and bacteriological verification of the diagnosis of each genital organs in each man with suspected tuberculosis.

Structure and morphology in diffusion-driven growth of nanowires: the case of ZnTe.

Gold-catalyzed ZnTe nanowires were grown at low temperature by molecular beam epitaxy on a ZnTe(111) B buffer layer, under different II/VI flux ratios, including with CdTe insertions. High-resolution electron microscopy and energy-dispersive X-ray spectroscopy (EDX) gave information about the crystal structure, polarity, and growth mechanisms. We observe, under stoichiometric conditions, the simultaneous presence of zinc-blende and wurtzite nanowires spread homogeneously on the same sample. Wurtzite nanowires are cylinder-shaped with a pyramidal-structured base. Zinc-blende nanowires are cone-shaped with a crater at their base. Both nanowires and substrate show a Te-ended polarity. Te-rich conditions favor zinc-blende nanowires, while Zn-rich suppress nanowire growth. Using a diffusion-driven growth model, we present a criterion for the existence of a crater or a pyramid at the base of the nanowires. The difference in nanowire morphology indicates lateral growth only for zinc-blende nanowires. The role of the direct impinging flux on the nanowire's sidewall is discussed.

Porous Silicon-Based Quantum Dot Broad Spectrum Radiation Detector.

Silicon is a convenient and inexpensive platform for radiation detection, but has low stopping power for x-rays and gamma-rays with high energy (e.g., 100 keV, as used in computed tomography and digital radiography, or 1 MeV, as desired for detection of nuclear materials). We have effectively increased the stopping power of silicon detectors by producing a layer of porous or micro-machined silicon, and infusing this layer with semiconductor quantum dots made of electron-dense materials. Results of prototype detectors show sensitivity to infrared, visible light, and x-rays, with dark current of less than 1 nA/mm2.

[Capacities of rapid diagnostic methods in renal tuberculosis].

The paper comparatively assesses routine and new medical technologies (metachromatic urine test, polymerase chain reaction, chromatographic mass spectrometry, and enzyme immunoassay) for detection of Mycobacterium tuberculosis and tuberculosis antibodies. It is shown that molecular biological and immune assays may be used only for rapid diagnosis and screening, followed by a full-scale phthisiourological study as the detection of markers of Mycobacterium tuberculosis and tuberculosis antibodies cannot be a criterion for establishing renal tuberculosis. The authors consider that the conventional microbiological tests whose validity is beyond question in case of positive results are the most established and practice-tested canons of phthisiourological diagnosis.

[Comparative evaluation of therapeutic effects of 3 and 4 antitubercular agents at the initial stage of the treatment of renal tuberculosis]. / Sravnitel'naia otsenka terapevticheskogo vozdeistviia 3 i 4 protivotuberkuleznykh preparatov na initsial'nom étape lecheniia tuberkuleza pochek.

Three groups of the parameters of the therapeutic effects of 3 and 4 antituberculous drugs on renal tuberculous inflammation were identified. The primary effect of 4 drugs was much frequently manifested itself by the normalization of urinalysis and the transfer of cultured to uncultured Mycobacterium tuberculosis (MBT). The equivalent effect of 3 and 4 drugs was characterized by the similar rate of continuation of specific mycobacteriuria, by the detection of MBT in the cavernous contents from the removed tuberculosis-afflicted kidney and by the equivalent morphological characteristics of tuberculous inflammation involution. The negative impact of the therapeutic action of 4-component chemotherapy appeared as a much larger number of cases of intolerance of antituberculous drugs, hepatic and renal failures, and toxic-and-allergic reactions.

[Role of polymerase chain reaction in diagnosing tuberculosis of the bladder and male sex organs]. / Rol' polimeraznoi tseppnoi reaktsii v diagnostike tuberkuleza mochevykh i muzhskikh polovykh organov.

Detection of M. tuberculosis DNA by polymerase chain reaction (PCR) and standard technique was compared in 76 new cases of urogenital tuberculosis. In the urinary test PCR confirmed tuberculous etiology of the disease and corresponded to M. tuberculosis detection in 27 (60%) of 45 patients with urinary tuberculosis. M. tuberculosis DNA detection rose significantly in patients with mycobacteriuria (71%) and in examination of aspirates from isolated renal cavern, blocked kidney, epididymis, prostate and seminal vesicles. Treatment for 1 month and longer transforms the positive result into the negative one. Of 16 patients with tuberculosis of male sexual organs M. tuberculosis DNA were detected by PCR in prostatic secretion in 43.7%, in ejaculate in 93%. This did not correlate with detection of M. tuberculosis. Thus, PCR is recommended for instant diagnosis and screening before further examination and cannot be the only method in identification of urogenital tuberculosis.

[Dialysis amyloidosis syndrome in patients aged over 55 years and undergoing a hemodialysis program]. / Sindrom dializnogo amiloidoza u patsientov starshe 55 let, nakhodiashchikhsia na programmnom gemodialize.

The clinical-and-biochemical signs of the dialysis amyloidosis syndrome were studied in two groups of patients with chronic renal insufficiency (CRI), who have been undergoing a multi-year renal-substitutive therapy (program-type hemodialysis). The first group comprised 77 adult patients (aged 18-40), the second group comprised 49 "elderly" patients (aged 55-73). Apart from the standard analyses, the dynamics of beta 2-microglobulin (beta 2-M) was studied in the blood of patients. Specific features in the development of the syndrome of dialysis amyloidosis were described; they correlated with the level of beta 2-M, with a duration of program-type hemodialysis, with the elderly age of patients, with variants of renal pathologies, and with an concomitant diabetes mellitus.

[Age-related changes in large joints and long tubular bones of the upper extremity in children (echographic data)]. / Vozrastnye izmeneniia krupnykh sustavov i dlinnykh trubchatykh kostei verkhnikh konechnostei u detei (po dannym ékhografii).

Two hundred and ten children at the age of 17 days up to 15 years have been examined. Echocameras, working in the grey scale regime have been used. At examination of the arm, forearm, brachial, elbow and radiocarpal joints in the children the most informative are longitudinal echographic approaches. At examination of the brachial bone head in the children older than 10 years only the anterior longitudinal approach is informative. To perform the echographic investigation of various elements of the locomotor apparatus of the upper extremities in children older than 9-10 years is difficult. The echographic reveal of additional nuclei of ossification and synostosis stages of the long tubular bones of the upper extremities in children often coincide in time with roentgenological data.

[Ways of increasing the effectiveness of the treatment of male patients with genital tuberculosis]. / Puti povysheniia éffektivnosti lecheniia bol'nykh tuberkulezom muzhskikh polovykh organov.

Endolymphic therapy proved to be a considerable resource for the rise in the treatment efficacy of specific inflammatory diseases of the male genital organs without adding to the antituberculous drug dosage. Indirect endolymphic chemotherapy appears to be more accessible and not labour-intensive, instead it can increase the efficacy of a conservative therapy of men with genital tuberculosis. Besides, it seems to be promising in relation to the preservation of fertility after tuberculous epididymitis.

[Age-related characteristics of the stromal-parenchymal relations of the human thymus]. / Vozrastnaia kharakteristika stromal'no-parenkhimatoznykh otnoshenii timusa cheloveka.

In 155 thymuses and in 57 capsules of the organ, distributed according to 12 age groups, beginning from fetuses of 5 months up to 90 years, age transformations of stromal-parenchymatous relations of the human thymus have been studied and quantitatively estimated. During the postnatal ontogenesis the thymic capsule and its intraorganic connective, tissue frame together with the parenchyma undergo certain phase reorganizations, specific for each age period. The greatest development of the thymic connective tissue frame reaches at the age of 1-3 years and during sex maturation period. The thymic lymphoepithelial tissue exists during all age periods. In the thymic adipose body foci of extramedullary lymphopoesis are revealed, beginning from the first mature up to the elderly age.