Wide range linear magnetometer based on a sub-microsized K vapor cell.

39K atoms have the smallest ground state (2S1/2) hyperfine splitting of all the most naturally abundant alkali isotopes and, consequently, the smallest characteristic magnetic field value B0=A2S1/2/µB≈170G, where A2S1/2 is the ground state's magnetic dipole interaction constant. In the hyperfine Paschen-Back regime (B≫B0, where B is the magnitude of the external magnetic field applied on the atoms), only eight Zeeman transitions are visible in the absorption spectrum of the D1 line of 39K, while the probabilities of the remaining 16 Zeeman transitions tend to zero. In the case of 39K, this behavior is reached already at relatively low magnetic field B>B0. For each circular polarization (σ-,σ+), four spectrally resolved atomic transitions having sub-Doppler widths are recorded using a sub-microsized vapor cell of thickness L=120-390nm. We present a method that allows to measure the magnetic field in the range of 0.1-10kG with micrometer spatial resolution, which is relevant in particular for the determination of magnetic fields with large gradients (up to 3 G/µm). The theoretical model describes well the experimental results.

Increased Yield of Residual γH2AX Foci in p53-Deficient Human Lung Carcinoma Cells Exposed to Subpicosecond Beams of Accelerated Electrons.

We studied quantitative yield of residual (24 h post-irradiation) phosphorylated histone (γH2AX) foci as a marker of DNA double strand breaks in wild-type A549 and p53-deficient H1299 human lung carcinoma cells after exposure to subpicosecond (energy 4 MeV, pulse duration 400 fsec, peak dose rate during the pulse 16 GGy/s) and quasi-continuous (energy 3.6 MeV) beams of accelerated electrons in a dose range of 0.5-10.0 Gy. The efficiency of pulse irradiation in A549 and H1299 cells assessed by the yield of residual foci was higher than the efficiency of quasi-continuous exposure by 1.8 and 5.3 times, respectively. Significant differences in quantitative yield of residual γH2AX foci between wild-type and p53-deficient cell lines were observed only after exposure to subpicosecond, but not quasi-continuous beams of accelerated electrons.

[Ocular microcirculation after revascularization of the internal carotid artery in the early postoperative period]. / Mikrotsirkulyatsiya glaza posle rekonstruktivnykh operatsii na sonnykh arteriyakh v rannem posleoperatsionnom periode.

Carotid artery stenosis is the most common cause of ischemic stroke and transient ischemic attacks in the population of developed countries. Carotid endarterectomy (CEA) and carotid stenting (CAS) are effective treatments for carotid stenosis. In view of the need to improve the diagnosis of this condition and the anatomical relationship of the internal carotid arteries and vessels of the eye, studying retinal microvasculature has become an urgent problem. The theory suggesting that changes in ocular blood flow parameters may reflect disease status in patients with internal carotid artery (ICA) stenosis requires further investigation. PURPOSE: To study the impact of CEA and CAS interventions on ocular blood flow in patients with clinically significant ICA stenosis in the early postoperative period. MATERIAL AND METHODS: Thirty-two patients with hemodynamically significant stenosis (≥75%) of the left or right ICA were examined using optical coherence tomography angiography (OCT-A) and flowmetry before and after CEA or CAS in order to assess the changes in ocular blood flow parameters. RESULTS: There were no significant differences in hemodynamic parameters in the eyes on the side of the stenotic and non-stenotic ICA before revascularization. In the early postoperative period (3-7 days) in the ipsilateral eyes, there was an increase in blood flow density and vascular density at the level of the superficial and deep plexuses in the macular area (p≤0.05), as well as an increase in the ocular blood flow volume, the level of tolerated intraocular pressure (p≤0.05) and a decrease in intraocular pressure (p≤0.05) bilaterally. In the contralateral eyes, after ICA revascularization there was a partial improvement in microcirculation parameters according to OCT-A (p≤0.05). Peripapillary blood flow density and peripapillary vessel density did not change significantly either on the ipsilateral or the contralateral side. CONCLUSION: In patients with clinically significant ICA stenosis, ICA revascularization by stenting or endarterectomy contributed to an improvement in retinal microcirculation and retrobulbar blood flow in both eyes. OCT-A and flowmetry allow non-invasive assessment of retinal microvessels and retrobulbar blood flow, and the measurements provided by these methods can serve as valuable biomarkers for predicting and monitoring hemodynamic changes in patients who undergo CEA and CAS surgeries.

Approach to quantitative spectroscopy of atomic vapor in optical nanocells.

We present a method for recovery of narrow homogeneous spectral features out of a broad inhomogeneous overlapped profile based on second-derivative processing of the absorption spectra of alkali metal atomic vapor nanocells. The method is shown to preserve the frequency positions and amplitudes of spectral transitions, thus being applicable for quantitative spectroscopy. The proposed technique was successfully applied and tested for measurements of hyperfine splitting and atomic transition probabilities, development of an atomic frequency reference, determination of isotopic abundance, study of atom-surface interaction, and determination of magnetic-field-induced modification of atomic transition frequency and probability. The obtained experimental results are fully consistent with theoretical modeling.

Optical Transmission of an Atomic Vapor in the Mesoscopic Regime.

By measuring the transmission of near-resonant light through an atomic vapor confined in a nanocell we demonstrate a mesoscopic optical response arising from the nonlocality induced by the motion of atoms with a phase coherence length larger than the cell thickness. Whereas conventional dispersion theory-where the local atomic response is simply convolved by the Maxwell-Boltzmann velocity distribution-is unable to reproduce the measured spectra, a model including a nonlocal, size-dependent susceptibility is found to be in excellent agreement with the measurements. This result improves our understanding of light-matter interaction in the mesoscopic regime and has implications for applications where mesoscopic effects may degrade or enhance the performance of miniaturized atomic sensors.

Collective Lamb Shift of a Nanoscale Atomic Vapor Layer within a Sapphire Cavity.

We measure the near-resonant transmission of light through a dense medium of potassium vapor confined in a cell with nanometer thickness in order to investigate the origin and validity of the collective Lamb shift. A complete model including the multiple reflections in the nanocell reproduces accurately the observed line shape. It allows the extraction of a density-dependent shift and width of the bulk atomic medium resonance, deconvolved from the cavity effect. We observe an additional, unexpected dependence of the shift with the thickness of the medium. This extra dependence demands further experimental and theoretical investigations.

Saturated-absorption spectroscopy revisited: atomic transitions in strong magnetic fields (>20 mT) with a micrometer-thin cell.

The existence of crossover resonances makes saturated-absorption (SA) spectra very complicated when external magnetic field B is applied. It is demonstrated for the first time, to the best of our knowledge, that the use of micrometric-thin cells (MTCs, L≈40 µm) allows application of SA for quantitative studies of frequency splitting and shifts of the Rb atomic transitions in a wide range of external magnetic fields, from 0.2 up to 6 kG (20-600 mT). We compare the SA spectra obtained with the MTC with those obtained with other techniques and present applications for optical magnetometry with micrometer spatial resolution and a broadly tunable optical frequency lock.

Optical response of gas-phase atoms at less than λ/80 from a dielectric surface.

We present experimental observations of atom-light interactions within tens of nanometers (down to 11 nm) of a sapphire surface. Using photon counting we detect the fluorescence from of order one thousand Rb or Cs atoms, confined in a vapor with thickness much less than the optical excitation wavelength. The asymmetry in the spectral line shape provides a direct readout of the atom-surface potential. A numerical fit indicates a power law -C(α)/r(α) with α = 3.02 ± 0.06 confirming that the van der Waals interaction dominates over other effects. The extreme sensitivity of our photon-counting technique may allow the search for atom-surface bound states.

Maximal refraction and superluminal propagation in a gaseous nanolayer.

We present an experimental measurement of the refractive index of high density Rb vapor in a gaseous atomic nanolayer. We use heterodyne interferometry to measure the relative phase shift between two copropagating laser beams as a function of the laser detuning and infer a peak index n=1.26±0.02, close to the theoretical maximum of 1.31. The large index has a concomitant large index gradient creating a region with steep anomalous dispersion where a subnanosecond optical pulse is advanced by >100 ps over a propagation distance of 390 nm, corresponding to a group index n(g)=-(1.0±0.1)×10(5), the largest negative group index measured to date.

Cooperative Lamb shift in an atomic vapor layer of nanometer thickness.

We present an experimental measurement of the cooperative Lamb shift and the Lorentz shift using a nanothickness atomic vapor layer with tunable thickness and atomic density. The cooperative Lamb shift arises due to the exchange of virtual photons between identical atoms. The interference between the forward and backward propagating virtual fields is confirmed by the thickness dependence of the shift, which has a spatial frequency equal to twice that of the optical field. The demonstration of cooperative interactions in an easily scalable system opens the door to a new domain for nonlinear optics.

Lower body negative pressure reduces jugular and portal vein volumes and counteracts the elevation of middle cerebral vein velocity during long-duration spaceflight.

Cephalad fluid shifts in space have been hypothesized to cause the spaceflight-associated neuro-ocular syndrome (SANS) by increasing the intracranial-ocular translaminal pressure gradient. Lower body negative pressure (LBNP) can be used to shift upper-body blood and other fluids toward the legs during spaceflight. We hypothesized that microgravity would increase jugular vein volume (JVvol), portal vein cross-sectional area (PV), and intracranial venous blood velocity (MCV) and that LBNP application would return these variables toward preflight levels. Data were collected from 14 subjects (11 males) before and during long-duration International Space Station (ISS) spaceflights. Ultrasound measures of JVvol, PV, and MCV were acquired while seated and supine before flight and early during spaceflight at day 45 (FD45) and late at day 150 (FD150) with and without LBNP. JVvol increased from preflight supine and seated postures (46 ± 48% and 646 ± 595% on FD45 and 43 ± 43% and 702 ± 631% on FD150, P < 0.05), MCV increased from preflight supine (44 ± 31% on FD45 and 115 ± 116% on FD150, P < 0.05), and PV increased from preflight supine and seated (51 ± 56% on FD45 and 100 ± 74% on FD150, P < 0.05). Inflight LBNP of -25 mmHg restored JVvol and MCV to preflight supine level and PV to preflight seated level. Elevated JVvol confirms the sustained neck-head blood engorgement inflight, whereas increased PV area supports the fluid shift at the splanchnic level. Also, MCV increased potentially due to reduced lumen diameter. LBNP, returning variables to preflight levels, may be an effective countermeasure.NEW & NOTEWORTHY Microgravity-induced fluid shifts markedly enlarge jugular and portal veins and increase cerebral vein velocity. These findings demonstrate a marked flow engorgement at neck and splanchnic levels and may suggest compression of the cerebral veins by the brain tissue in space. LBNP (-25 mmHg for 30 min) returns these changes to preflight levels and, thus, reduces the associated flow and tissue disturbances.

Hybrid PCL/CaCO3 scaffolds with capabilities of carrying biologically active molecules: Synthesis, loading and in vivo applications.

Designing advanced biomaterials for tissue regeneration with drug delivery and release functionalities remains a challenge in regenerative medicine. In this research, we have developed novel composite scaffolds based on polymeric polycaprolactone fibers coated with porous calcium carbonate structures (PCL/CaCO3) for tissue engineering and have shown their drug delivery and release in rats. In vivo biocompatibility tests of PCL/CaCO3 scaffolds were complemented with in vivo drug release study, where tannic acid (TA) was used as a model drug. Release of TA from the scaffolds was realized by recrystallization of the porous vaterite phase of calcium carbonate into the crystalline calcite. Cell colonization and tissue vascularization as well as transplantability of developed PCL/CaCO3+TA scaffolds were observed. Detailed study of scaffold transformations during 21-day implantation period was followed by scanning electron microscopy and X-ray diffraction studies before and after in vivo implantation. The presented results demonstrate that PCL/CaCO3 scaffolds are attractive candidates for implants in bone regeneration and tissue engineering with a possibility of loading biologically active molecules and controlled release.

Rapid parallel measurements of macroautophagy and mitophagy in mammalian cells using a single fluorescent biosensor.

Mitochondrial dysfunction is implicated in many human diseases and occurs in normal aging. Mitochondrial health is maintained through organelle biogenesis and repair or turnover of existing mitochondria. Mitochondrial turnover is principally mediated by mitophagy, the trafficking of damaged mitochondria to lysosomes via macroautophagy (autophagy). Mitophagy requires autophagy, but is itself a selective process that relies on specific autophagy-targeting mechanisms, and thus can be dissociated from autophagy under certain circumstances. Therefore, it is important to assess autophagy and mitophagy together and separately. We sought to develop a robust, high-throughput, quantitative method for monitoring both processes in parallel. Here we report a flow cytometry-based assay capable of rapid parallel measurements of mitophagy and autophagy in mammalian cells using a single fluorescent protein biosensor. We demonstrate the ability of the assay to quantify Parkin-dependent selective mitophagy in CCCP-treated HeLa cells. In addition, we show the utility of the assay for measuring mitophagy in other cell lines, as well as for Parkin-independent mitophagy stimulated by deferiprone. The assay makes rapid measurements (10,000 cells per 6 seconds) and can be combined with other fluorescent indicators to monitor distinct cell populations, enabling design of high-throughput screening experiments to identify novel regulators of mitophagy in mammalian cells.

Modeling of evoked field potentials in hippocampal CA1 area describes their dependence on NMDA and GABA receptors.

A computer model of the hippocampal CA1 area, which receives synaptic inputs from CA3 neurons via the Schaffer collaterals, was constructed. Pyramidal cells (PC) and two types of interneurons were represented by compartmental models, and mechanisms of feed-forward inhibition (FFI) and recurrent inhibition were incorporated. Four types of receptor mediated synaptic conductances were used in the model: those of AMPA, GABA(A), GABA(B) and N-methyl-D-aspartate (NMDA). The output of the model, i.e. the field potential calculated at various points in space, was able to qualitatively reproduce the main features of field potentials, which were recorded in hippocampal slices maintained in vitro for both subthreshold and suprathreshold stimulation. In both the experiments and the model, the influence of NMDA and GABA synaptic currents affected mostly the late, decaying phase of evoked field potentials. The modeled interaction of NMDA and GABA components could explain the enhancement of the field potential late phase, which was observed experimentally during paired-pulse stimulation.

Ultrasound evaluation of the magnitude of pneumothorax: a new concept.

Pneumothorax is commonly seen in trauma patients; the diagnosis is confirmed by radiography. The use of ultrasound where radiographic capabilities are absent, is being investigated by the National Aeronautics and Space Administration. We investigated the ability of ultrasound to assess the magnitude of pneumothorax in a porcine model. Sonography was performed on anesthetized pigs in both ground-based laboratory (n = 5) and microgravity conditions (0 x g) aboard the KC-135 aircraft during parabolic flight (n = 4). Aliquots of air (50-100 cm3) were introduced into the chest to simulate pneumothorax. Results were videorecorded and digitized for later interpretation. Several distinct sonographic patterns of partial lung sliding were noted including the combination of a sliding zone with a still zone and a "segmented" sliding zone. These "partial lung sliding" patterns exclude massive pneumothorax manifested by a complete separation of the lung from the parietal pleura. In 0 x g, the sonographic picture is more diverse; one x g differences between posterior and anterior aspects are diminished. Modest pneumothorax can be inferred by the ultrasound sign of "partial lung sliding." This finding, which increases the negative predictive value of thoracic ultrasound, may be attributed to intermittent pleural contact, small air spaces, or alterations in pleural lubricant. Further studies of these phenomena are warranted.

Percutaneous aspiration of fluid for management of peritonitis in space.

BACKGROUND: As a medical emergency that can affect even well-screened, healthy individuals, peritonitis developing during a long-duration space exploration mission may dictate deviation from traditional clinical practice due to the absence of otherwise indicated surgical capabilities. Medical management can treat many intra-abdominal processes, but treatment failures are inevitable. In these circumstances, percutaneous aspiration under sonographic guidance could provide a "rescue" strategy. HYPOTHESIS: Sonographically guided percutaneous aspiration of intra-peritoneal fluid can be performed in microgravity. METHODS: Investigations were conducted in the microgravity environment of NASA's KC-135 research aircraft (0 G). The subjects were anesthetized female Yorkshire pigs weighing 50 kg. The procedures were rehearsed in a terrestrial animal lab (1 G). Colored saline (500 mL) was introduced through an intra-peritoneal catheter during flight. A high-definition ultrasound system (HDI-5000, ATL, Bothell, WA) was used to guide a 16-gauge needle into the peritoneal cavity to aspirate fluid. RESULTS: Intra-peritoneal fluid collections were easily identified, distinct from surrounding viscera, and on occasion became more obvious during weightless conditions. Subjectively, with adequate restraint of the subject and operators, the procedure was no more demanding than during the 1-G rehearsals. CONCLUSIONS: Sonographically guided percutaneous aspiration of intra-peritoneal fluid collections is feasible in weightlessness. Treatment of intra-abdominal inflammatory conditions in spaceflight might rely on pharmacological options, backed by sonographically guided percutaneous aspiration for the "rescue" of treatment failures. While this risk mitigation strategy cannot guarantee success, it may be the most practical option given severe resource limitations.

Diagnostic ultrasound at MACH 20: retroperitoneal and pelvic imaging in space.

An operationally available diagnostic imaging capability augments spaceflight medical support by facilitating the diagnosis, monitoring and treatment of medical or surgical conditions, by improving medical outcomes and, thereby, by lowering medical mission impacts and the probability of crew evacuation due to medical causes. Microgravity-related physiological changes occurring during spaceflight can affect the genitourinary system and potentially cause conditions such as urinary retention or nephrolithiasis for which ultrasonography (U/S) would be a useful diagnostic tool. This study describes the first genitourinary ultrasound examination conducted in space, and evaluates image quality, frame rate, resolution requirements, real-time remote guidance of nonphysician crew medical officers and evaluation of on-orbit tools that can augment image acquisition. A nonphysician crew medical officer (CMO) astronaut, with minimal training in U/S, performed a self-examination of the genitourinary system onboard the International Space Station, using a Philips/ATL Model HDI-5000 ultrasound imaging unit located in the International Space Station Human Research Facility. The CMO was remotely guided by voice commands from experienced, earth-based sonographers stationed in Mission Control Center in Houston. The crewmember, with guidance, was able to acquire all of the target images. Real-time and still U/S images received at Mission Control Center in Houston were of sufficient quality for the images to be diagnostic for multiple potential genitourinary applications. Microgravity-based ultrasound imaging can provide diagnostic quality images of the retroperitoneum and pelvis, offering improved diagnosis and treatment for onboard medical contingencies. Successful completion of complex sonographic examinations can be obtained even with minimally trained nonphysician ultrasound operators, with the assistance of ground-based real-time guidance.

Use of the Internet for long-term clinical follow-up.

Use of the Internet for patient-specific consultation across international boundaries has been demonstrated. This report describes the efforts of Baylor College of Medicine and NASA to conduct a telemedicine consultation with Moscow, Russia. Consultation between Russian and American physicians was performed over the Internet with a combination of real-time and store-and-forward techniques. The clinical focus involved a 65-year old Russian scientist who had undergone mitral valve replacement in the United States 5 years earlier. Development of new activity-related chest pain, dyspnea, and intermittent atrial fibrillation led to a consultation with his American cardiologist and cardiac surgeon. Real-time video was supplemented with telephone voice communication to overcome bandwidth limitations. Prior to the video link, the patient's recent history and clinical data were made available via the Internet using file transfer protocol (FTP). The patient's medications, new electrocardiographic findings, and activity status were reviewed. Specific clinical recommendations were made as a result of this telemedicine consultation. This case illustrates the technical factors, clinical implications, and confidentiality issues related to using the Internet for telemedicine consultations and demonstrates that the Internet may provide an alternative means for long-term clinical follow-up of patients.