The COSPAR planetary protection policy for missions to Icy Worlds: A review of history, current scientific knowledge, and future directions.

Recent discoveries related to the habitability and astrobiological relevance of the outer Solar System have expanded our understanding of where and how life may have originated. As a result, the Icy Worlds of the outer Solar System have become among the highest priority targets for future spacecraft missions dedicated to astrobiology-focused and/or direct life detection objectives. This, in turn, has led to a renewed interest in planetary protection concerns and policies for the exploration of these worlds and has been a topic of discussion within the COSPAR (Committee on Space Research) Panel on Planetary Protection. This paper summarizes the results of those discussions, reviewing the current knowledge and the history of planetary protection considerations for Icy Worlds as well as suggesting ways forward. Based on those discussions, we therefore suggest to (1) Establish a new definition for Icy Worlds for Planetary Protection that captures the outer Solar System moons and dwarf planets like Pluto, but excludes more primitive bodies such as comets, centaurs, and asteroids: Icy Worlds in our Solar System are defined as all bodies with an outermost layer that is believed to be greater than 50 % water ice by volume and have enough mass to assume a nearly round shape. (2) Establish indices for the lower limits of Earth life with regards to water activity (LLAw) and temperature (LLT) and apply them into all areas of the COSPAR Planetary Protection Policy. These values are currently set at 0.5 and -28 °C and were originally established for defining Mars Special Regions; (3) Establish LLT as a parameter to assign categorization for Icy Worlds missions. The suggested categorization will have a 1000-year period of biological exploration, to be applied to all Icy Worlds and not just Europa and Enceladus as is currently the case. (4) Have all missions consider the possibility of impact. Transient thermal anomalies caused by impact would be acceptable so long as there is less than 10-4 probability of a single microbe reaching deeper environments where temperature is >LLT in the period of biological exploration. (5) Restructure or remove Category II* from the policy as it becomes largely redundant with this new approach, (6) Establish that any sample return from an Icy World should be Category V restricted Earth return.

[Possibilities of ultrasound methods in diagnostics of eyelid tumors]. / Vozmozhnosti ul'trazvukovykh metodov issledovaniya v diagnostike novoobrazovanii vek.

PURPOSE: To determine the informative value of ultrasound biomicroscopy (UBM) with A-scan for assessment of qualitative and quantitative characteristics of eyelid tumors less than 5 mm in size. MATERIAL AND METHODS: The study included 25 patients (25 eyes) with eyelid tumors less than 5 mm in size. In addition to standard ophthalmic examination, complex ultrasound diagnostics including B-scan, Color Doppler imaging and UBM with A-scan were performed. The localization, size, structure of eyelid tumors and the state of perifocal tissues were evaluated. All patients underwent surgical treatment with following histological examinations of dissected tissues. Due to qualitative analysis of the studied formations and small number of included patients, there was no need in statistical analysis of the data. RESULTS: Complex application of UBM and A-scan allowed specifying the localization, size, structure of the small-sized tumors and detecting typical echographic signs of benign or malignant properties of the pathological process. Ultrasound data (UBM and A-scan) of eyelid tumors was highly correlated to histological features. CONCLUSION: UBM with A-scan can be recommended for differential diagnostics of small-sized tumors and optimizing their management.

Morphological Changes in the Retina Under Conditions of Experimental In Vivo Regional Ischemia/Reperfusion.

Two models of retinal ischemia/reperfusion were developed in an experiment on rats and structural changes in eye tissues in the early and late postischemic periods were studied. Ischemia/reperfusion was modeled by elevation of intraocular pressure to 110 mm Hg for 30 min with air injection into the anterior chamber of the eye with a special device or subconjunctival administration of 0.2 ml 4×10-6 M endothelin-1. Morphological studies of the retina of enucleated eyes were performed in 3, 7, and 30 days after ischemia/reperfusion. In 3 days, signs of retinal ischemia were seen (retinal edema and ganglion cell damage). In the late post-ischemic period (30 days), atrophy of the outer nuclear and outer plexiform layer of the retina was observed in animals with retinal ischemia/reperfusion caused by intraocular pressure elevation and complete destruction of neuronal cells was found after administration of endothelin-1.

On the limitations of some popular numerical models of flagellated microswimmers: importance of long-range forces and flagellum waveform.

For a sperm-cell-like flagellated swimmer in an unbounded domain, several numerical models of different fidelity are considered based on the Stokes flow approximation. The models include a regularized Stokeslet method and a three-dimensional finite-element method, which serve as the benchmark solutions for several approximate models considered. The latter include the resistive force theory versions of Lighthill, and Gray and Hancock, as well as a simplified approximation based on computing the hydrodynamic forces exerted on the head and the flagellum separately. It is shown how none of the simplified models is robust enough with regards to predicting the effect of the swimmer head shape change on the swimmer dynamics. For a range of swimmer motions considered, the resulting solutions for the swimmer force and velocities are analysed and the applicability of the Stokes model for the swimmers in question is probed.

[Possibilities of hybrid surgery in treatment of thoracoabdominal aneurysms].

The authors present a clinical case report and review of literature concerning treatment of extremely complicated pathology - thoracoabdominal aortic aneurysm, also reflecting the most difficult problems and complications of classical surgical treatment. A successful clinical example showed advantages of a new, less invasive approach, i.e., hybrid surgery. Based on analysing literature sources, the authors describe controversial points of carrying out a hybrid operation and its results. Accumulating experience in and improving technology of the hybrid operation would make it possible to further improve therapeutic outcomes.

Prospective slice-by-slice motion correction reduces false positive activations in fMRI with task-correlated motion.

OBJECTIVE: We aimed to test the hypothesis that slice-by-slice prospective motion correction at 7T using an optical tracking system reduces the rate of false positive activations in an fMRI group study with a paradigm that involves task-correlated motion. MATERIALS AND METHODS: Brain activation during right leg movement was measured using a block design on 15 volunteers, with and without prospective motion correction. Clearly erroneous activations were compared between both cases, at the individual level. Additionally, conventional group analysis was performed. RESULTS: The number of falsely activated voxels with T-values higher than 5 was reduced by 48% using prospective motion correction alone, without additional retrospective realignment. In the group analysis, the statistical power was increased - the peak T-value was 26% greater, and the number of voxels in the cluster representing the right leg was increased by a factor of 9.3. CONCLUSION: Slice-by-slice prospective motion correction in fMRI studies with task-correlated motion can substantially reduce false positive activations and increase statistical power.

PexLoc-Parallel excitation using local encoding magnetic fields with nonlinear and nonbijective spatial profiles.

With the recent proposal of using magnetic fields that are nonlinear by design for spatial encoding, new flexibility has been introduced to MR imaging. The new degrees of freedom in shaping the spatially encoding magnetic fields (SEMs) can be used to locally adapt the imaging resolution to features of the imaged object, e.g., anatomical structures, to reduce peripheral nerve stimulation during in vivo experiments or to increase the gradient switching speed by reducing the inductance of the coils producing the SEMs and thus accelerate the imaging process. In this work, the potential of nonlinear and nonbijective SEMs for spatial encoding during transmission in multidimensional spatially selective excitation is explored. Methods for multidimensional spatially selective excitation radiofrequency pulse design based on nonlinear encoding fields are introduced, and it is shown how encoding ambiguities can be resolved using parallel transmission. In simulations and phantom experiments, the feasibility of selective excitation using nonlinear, nonbijective SEMs is demonstrated, and it is shown that the spatial resolution with which the target distribution of the transverse magnetization can be realized varies locally. Thus, the resolution of the target pattern can be increased in some regions compared with conventional linear encoding. Furthermore, experimental proof of principle of accelerated two-dimensional spatially selective excitation using nonlinear SEMs is provided in this study.

[Receptor elements for biosensors in two ways of methylotrophic yeast immobilization].

Receptor elements for biosensors based on Hansenula polymorpha NCYC 495 In yeast cells for ethanol assay were developed using two ways of cell immobilization, i.e., physical adsorption on a glass fiber membrane and covalent binding on a modified nitrocellulose membrane. The linear diapason of ethanol assays for a biosensor based on yeast cells adsorbed on glass fiber was 0.05-1.18; for a biosensor based on yeasts immobilized on a nitrocellulose membrane, 0.2-1.53 mM. Receptor elements based on sorbed cells possessed 2.5 times higher long-term stability. The time response was 1.5 times less for cells immobilized using DEAE-dextran and benzochinone. The results of ethyl alcohol assays using biosensors based on cells immobilized via adsorption and covalent binding, as well as using the standard areometric method, had high correlation coefficients (0.998 and 0.997, respectively, for the two ways of immobilization). The results indicate the possibility to consider the described models of receptor elements for biosensors as prototypes for experimental samples for practical use.

[Endovascular balloon angioplasty of a stenotic lesion of autovenous bypass grafts in the infrainguinal position].

Analysed in the article are the results of dynamic follow up of autovenous bypass grafts in the infrainguinal position. About 80% of patients were operated on for lower limb critical ischaemia. Remote patency of the bypass grafts amounted to 68%. Also presented herein are the outcomes of balloon angioplasty of the bypass grafts (30 interventions) in both immediate and remote periods. Primary success was achieved in 94% of cases. The early stage (30 days) was characterized by two thromboses of the bypass graft, and the remote period showed eleven restenoses. Two limb amputations were performed. The role of endovascular correction of bypass graft stenoses in order to save the limb is determined.

[Own experience endovascular prosthetic repair of abdominal aortic aneurysms].

Endovascular prosthetic repair has increasingly been used over the last several decades. This type of intervention is indicated for patients running a high surgical and anaesthesiological risk of an open surgical procedure. The experience gained in endovascular prosthetic repair of abdominal aortic aneurysms makes it possible to extend the indications for its practical application. The authors describe herein their experience gained in a total of 20 procedures of endovascular prosthetic repair of abdominal aortic aneurysms using the Gore Excluder endograft device in patients running a high risk of an open surgical intervention. There were neither short -nor long-term lethal outcomes. Three patients after endovascular prosthetic repair were found to have type 1 endoleak and two appeared to have type 2 endoleak. Type 1 endoleaks were coped with intraoperationally. Dynamic follow-up (at 1, 6, 12 months after surgery) of patients including computed tomography showed no complications whatsoever (i. e., no endoleaks, endograft migration, nor increase in the aneurysm's diameter). After endografting of abdominal aortic aneurysms there were neither cardiac nor respiratory complications in the immediate postoperative period. Hence, endografting of an abdominal aortic aneurysm is a method of choice for high-risk patients.

Single-voxel MRS with prospective motion correction and retrospective frequency correction.

Subject motion during MRS investigations is a factor limiting the quality and the diagnostic value of the spectra. The possibility of using external motion tracking data to correct for artefacts in MR imaging has been demonstrated previously. In this paper the utility of prospective motion correction for single-voxel proton MRS is investigated. The object motion data are used in real time to update the position of the spectroscopy voxel during the acquisition prior to every sequence repetition cycle. It is not, however, sufficient to update the voxel position alone due to shim changes accompanying subject motion. Adverse effects of frequency shifts induced by subject motion are effectively suppressed by the interleaved reference scan method.

SENSE shimming (SSH): A fast approach for determining B(0) field inhomogeneities using sensitivity coding.

The pursuit of ever higher field strengths and faster data acquisitions has led to the construction of coil arrays with high numbers of elements. With the sensitivity encoding (SENSE) technique, it has been shown that the sensitivity of those elements can be used for spatial image encoding. Here, a proof-of-principle is presented of a method that can be considered an extreme case of the SENSE approach, completely abstaining from using encoding gradients. The resulting sensitivity encoded free-induction decay (FID) data are then not used for imaging, but for determining B(0) field inhomogeneity distribution. The method has therefore been termed "SENSE shimming" (SSH). In phantom experiments the method's ability to detect inhomogeneities of up to the second order is demonstrated.

[Enteral nutrition as a method of correction of protein energetic insufficiency in patients with perforating gastric and duodenal ulcer].

The results of examinations and treatment of 338 patients operated by reason of perforated gastric and duodenal ulcer (PGDU). It was established, that parenteral and oral nutrition in PGDU patients after traditional surgical operation did not improve patients' trophic state. Performance of early enteral nutrition with Pevzner's diet and nutritive maintenance during all postoperative period in patients, operated by low-invasive methods, has favorable influence on patients' trophic state.

High resolution single-shot EPI at 7T.

OBJECTIVE: Single-shot echo planar imaging (EPI) acquisitions at 7T are challenging due to increased distortions, signal dropouts, RF-power requirements, and reduced T2*. This study developed and tested pulse sequence and protocol modifications required to allow high resolution EPI for whole brain functional neuroimaging. MATERIALS AND METHODS: Using geometric distortion correction methods, modified fat saturation, and parallel imaging, we acquired high resolution single-shot gradient-echo EPI data at 7T with different spatial resolution. The BOLD sensitivity was evaluated and quantified in a breath hold experiment. RESULTS: Single-shot EPI data with isotropic resolution from 3 to 1.1 mm were acquired in human subjects. The RF-power deposition has been reduced to allow up to 22 slices per second. In addition, acoustic noise and helium boil-off have been reduced. A reduction of the fat saturation flip angle resulted in up to 20% signal gain without compromising the fat suppression quality. For the coil used, the BOLD sensitivity is highest for 2 or 1.4 mm isotropic resolution. CONCLUSION: High resolution single-shot EPI in the whole brain can be performed at 7T with high efficiency, low signal dropout, and without major geometric distortions.

Combined surgical management of a subclavian artery aneurysm complicated by an embolism to arteries of an upper limb.

The authors report herein a successful therapeutic outcome in a patient presenting with a posttraumatic subclavian artery aneurysm complicated by an embolism to arteries of an upper extremity, treated by means of endovascular prosthetic repair combined with a bypass-grafting operation on the arteries of the upper limb involved. A detailed description of the methodology and the course of the operation is provided. In the postoperative period, the clinical manifestations of ischaemia of the upper limb were completely relieved. The outcome of the operation was confirmed by intraoperative angiography, as well as by postoperative duplex scanning.

[Stenting in vertebral artery dissection: an approach to management].

We describe a 56-years-old patient with spontaneous extracranial vertebral artery dissection, which was provoked by neck movements. Clinically dissection manifested with transient ischemic attacks in vertebrobasilar system which lasted during 3 months and often combined with occipital headache. Contrast angiography revealed subtotal stenosis of segment V1 of the right VA, extending from the ostium for a length of 1-1.5 cm with thread-like double lumen (true and false lumens). The rest part of V1 segment of the right VA was irregularly narrowed up to 40-50%. A good contrast filling of the rightVA beginning from segment V2 was carried out by the collateral circulation from thyreocervical trunk. No atherosclerotic plaques in extra- intracranial arteries were found. The patient was subjected to stenting of segment VI of right VA that resulted in a complete restoration of the arterial lumen. No postoperative complications were observed.

Prospective real-time slice-by-slice motion correction for fMRI in freely moving subjects.

Subject motion is still the major source of data quality degradation in functional magnetic resonance imaging (fMRI) studies. Established methods correct motion between successive repetitions based on the acquired imaging volumes either retrospectively or prospectively. A fast, highly accurate, and prospective real-time correction method for fMRI using external optical motion tracking has been implemented. The head position is determined by means of an optical stereoscopic tracking system. The method corrects motion during the acquisition of an fMRI time series on a slice-by-slice basis by continuously updating the imaging volume position to follow the motion of the head. This method allows the measurement of fMRI data in the presence of significant motion during the acquisition of a single volume. Even without intentional motion, fMRI signal stability is maintained and higher sensitivity to detect activation is achieved without reducing specificity. With significant motion, only the proposed approach allowed detection of brain activation. The results show that the new method is superior to image-based correction methods, which fail in the case of fast or excessive motion.

Magnetic resonance imaging of freely moving objects: prospective real-time motion correction using an external optical motion tracking system.

Subject motion and associated artefacts limit the applicability of MRI and the achievable quality of the images acquired. In this paper, a fully integrated method for prospective correction of arbitrary rigid body motion employing an external motion tracking device is demonstrated for the first time. The position of the imaging volume is updated prior to every excitation of the spin system. The performance of the available tracking hardware and its connection to the MR imager is analyzed in detail. With the introduction of a novel calibration procedure the accuracy of motion correction is improved compared to previous approaches. Together with the high geometry update rate even freely moving objects can be imaged without motion related artefacts. The high performance and image quality improvement in case of subject motion are demonstrated for various imaging techniques such as gradient and spin echo, as well as echo planar imaging.

Dual-contrast echo planar imaging with keyhole: application to dynamic contrast-enhanced perfusion studies.

A new EPI-based method is presented which features optimized sampling of k-space enabling the integrated acquisition of two gradient echo images. The first of these images is predominantly T1 weighted and the second is T*2 weighted. The new method combines echo sharing of sparsely acquired high spatial frequency components with the keyhole technique and half-Fourier image reconstruction. The feasibility of acquiring high spatial and temporal resolution in vivo images for perfusion mapping is demonstrated. In contrast to most current perfusion methods, which acquire the T1- and T*2-weighted images in separate acquisitions, the need for image co-registration here is obviated since both sets of images are EPI-based and are acquired within the same measurement.