Ultrafast Loss of Lattice Coherence in the Light-Induced Structural Phase Transition of V_{2}O_{3}.

In solids, the response of the lattice to photoexcitation is often described by the inertial evolution on an impulsively modified potential energy surface which leads to coherent motion. However, it remains unknown if vibrational coherence is sustained through a phase transition, during which coupling between modes can be strong and may lead to rapid loss of coherence. Here we use coherent phonon spectroscopy to track lattice coherence in the structural phase transition of V_{2}O_{3}. In both the low and high symmetry phases unique coherent phonon modes are generated at low fluence. However, coherence is lost when driving between the low and high symmetry phases. Our results suggest strongly damped noninertial dynamics dominate during the phase transition due to disorder and multimode coupling.

Forces generated during stretch in the heart of the lobster Homarus americanus are anisotropic and are altered by neuromodulators.

Mechanical and neurophysiological anisotropies mediate three-dimensional responses of the heart of ITALIC! Homarus americanus Although hearts ITALIC! in vivoare loaded multi-axially by pressure, studies of invertebrate cardiac function typically use uniaxial tests. To generate whole-heart length-tension curves, stretch pyramids at constant lengthening and shortening rates were imposed uniaxially and biaxially along longitudinal and transverse axes of the beating whole heart. To determine whether neuropeptides that are known to modulate cardiac activity in ITALIC! H. americanusaffect the active or passive components of these length-tension curves, we also performed these tests in the presence of SGRNFLRFamide (SGRN) and GYSNRNYLRFamide (GYS). In uniaxial and biaxial tests, both passive and active forces increased with stretch along both measurement axes. The increase in passive forces was anisotropic, with greater increases along the longitudinal axis. Passive forces showed hysteresis and active forces were higher during lengthening than shortening phases of the stretch pyramid. Active forces at a given length were increased by both neuropeptides. To exert these effects, neuropeptides might have acted indirectly on the muscle via their effects on the cardiac ganglion, directly on the neuromuscular junction, or directly on the muscles. Because increases in response to stretch were also seen in stimulated motor nerve-muscle preparations, at least some of the effects of the peptides are likely peripheral. Taken together, these findings suggest that flexibility in rhythmic cardiac contractions results from the amplified effects of neuropeptides interacting with the length-tension characteristics of the heart.

Trajectory-resolved Coulomb focusing in tunnel ionization of atoms with intense, elliptically polarized laser pulses.

In strong-field light-matter interactions, the strong laser field dominates the dynamics. However, recent experiments indicate that the Coulomb force can play an important role as well. In this Letter, we have studied the photoelectron momentum distributions produced from noble gases in elliptically polarized, 800 nm laser light. By performing a complete mapping of the three-dimensional electron momentum, we find that Coulomb focusing significantly narrows the lateral momentum spread. We find a surprisingly sensitive dependence of Coulomb focusing on the initial transverse momentum distribution, i.e., the momentum at the moment of birth of the photoelectron. We also observe a strong signature of the low-energy structure in the above threshold ionization spectrum.

Results from the Radiation Assessment Detector on the International Space Station: Part 1, the Charged Particle Detector.

We report the results of the first six years of measurements of the energetic particle radiation environment on the International Space Station (ISS) with the Radiation Assessment Detector (ISS-RAD), spanning the period from February 2016 to February 2022. The first RAD was designed and built for MSL, the Mars Science Laboratory rover, also known as Curiosity; it has been operating on Mars since 2012 and is referred to here as MSL-RAD. ISS-RAD combines two sensor heads, one nearly identical to the single MSL-RAD sensor head, the other with greatly enhanced sensitivity to fast neutrons. These two sensor heads are referred to as the Charged Particle Detector (CPD) and Fast Neutron Detector (FND), respectively. Despite its name, the CPD is also capable of measuring high-energy neutrons and γ-rays, as is MSL-RAD. ISS-RAD was flown to the ISS in December 2015 and was deployed in February 2016, initially in the USLab module. RAD was used as a survey instrument from January 2017 through May 2020, when the instrument was positioned in the USLab and set to a zenith-pointing orientation. The energetic particle environment on the ISS is complex and varies on short time scales owing to the orbit, which has a 51.6∘ inclination with respect to the equator and has had an altitude in the 400-440 km range in this time period. The ISS moves continuously through the geomagnetic field, the strength of which varies with latitude, longitude, and altitude. The orbit passes through the South Atlantic Anomaly (SAA) several times a day, where magnetically trapped protons and electrons produce large but transient increases in observed fluxes and absorbed dose rates. The environment inside the ISS is affected by the solar cycle, altitude, and the local shielding, which varies between different ISS modules. We report results for charged particle absorbed dose and dose equivalent rates in various positions in the ISS. In an accompanying paper, we report similar results for neutron dose equivalent rates obtained with the ISS-RAD Fast Neutron Detector.

Results from the Radiation Assessment Detector on the International Space Station, Part 2: The fast neutron detector.

We report the results of the first six years of measurements of so-called fast neutrons on the International Space Station (ISS) with the Radiation Assessment Detector (ISS-RAD), spanning the period from February 2016 to February 2022. ISS-RAD combines two sensor heads, one nearly identical to the single sensor head in the Mars Science Laboratory RAD (MSL-RAD). The latter is described in a companion article to this one. The novel sensor is the FND, or fast neutron detector, designed to measure neutrons with energies in the range from 200 keV to about 8 MeV. ISS-RAD was deployed in February 2016 in the USLAB module, and then served as a survey instrument from March 2017 until May 2020. Data were acquired in Node3, the Japanese Pressurized Module, Columbus, and Node2. At the conclusion of the survey portion of RAD's planned 10-year campaign on ISS, the instrument was stationed in the USLAB; current plans call for it to remain there indefinitely. The radiation environment on the ISS consists of a complex mix of charged and neutral particles that varies on short time scales owing to the Station's orbit. Neutral particles, and neutrons in particular, are of concern from a radiation protection viewpoint, because they are both highly penetrating (since they do not lose energy via direct ionization) and, at some energies, have high biological effectiveness. Neutrons are copiously produced by GCRs and other incident energetic particles when they undergo nuclear interactions in shielding. As different ISS modules have varying amounts of shielding, they also have varying neutron environments. We report results for neutron fluences and dose equivalent rates in various positions in the ISS.

Results from the Radiation Assessment Detector on the International Space Station: Part 3, combined results from the CPD and FND.

The energetic particle radiation environment on the International Space Station (ISS) includes both charged and neutral particles. Here, we make use of the unique capabilities of the Radiation Assessment Detector (ISS-RAD) to measure both of these components simultaneously. The Charged Particle Detector (CPD) is, despite its name, capable of measuring neutrons in the energy range from about 4 MeV to a few hundred MeV. Combined with data from the Fast Neutron Detector (FND) in the 0.2 to 8 MeV range, we present the first broad-spectrum measurements of the neutron environments in various locations within the ISS since an early Bonner-Ball experiment that was conducted before the Station was fully constructed. The data presented here span the time period from February 2016 to February 2022. In addition to presenting broad-spectrum neutron fluence measurements, we show correlations of the measured neutron dose equivalent with charged-particle dose rates. The ratio of charged-particle dose to neutron dose equivalent is found to be relatively stable within the ISS.

Direct observation of ultrafast exciton localization in an organic semiconductor with soft X-ray transient absorption spectroscopy.

The localization dynamics of excitons in organic semiconductors influence the efficiency of charge transfer and separation in these materials. Here we apply time-resolved X-ray absorption spectroscopy to track photoinduced dynamics of a paradigmatic crystalline conjugated polymer: poly(3-hexylthiophene) (P3HT) commonly used in solar cell devices. The π→π* transition, the first step of solar energy conversion, is pumped with a 15 fs optical pulse and the dynamics are probed by an attosecond soft X-ray pulse at the carbon K-edge. We observe X-ray spectroscopic signatures of the initially hot excitonic state, indicating that it is delocalized over multiple polymer chains. This undergoes a rapid evolution on a sub 50 fs timescale which can be directly associated with cooling and localization to form either a localized exciton or polaron pair.

First observation of the exchange of transverse and longitudinal emittances.

An experimental program to demonstrate a novel phase-space manipulation in which the horizontal and longitudinal emittances of a particle beam are exchanged has been completed at the Fermilab A0 Photoinjector. A new beam line, consisting of a TM(110) deflecting mode cavity flanked by two horizontally dispersive doglegs has been installed. We report on the first direct observation of transverse and longitudinal emittance exchange.

3,5-Diamino-4H-1,2,4-triazol-1-ium (6-carb-oxy-pyridine-2-carboxyl-ato)(pyridine-2,6-dicarboxyl-ato)cuprate(II) trihydrate.

In the complex anion of the title compound, (C(2)H(6)N(5))[Cu(C(7)H(4)NO(4))(C(7)H(3)NO(4))]·3H(2)O, the Cu(II) atom is coordinated by tridentate 6-carb-oxy-pyridine-2-carboxyl-ate and pyridine-2,6-dicarboxyl-ate ligands and is surrounded by four O atoms in the equatorial plane and two N atoms in axial positions in a distorted octa-hedral geometry. In the crystal, the components are linked into a three dimensional network by O-H⋯O, N-H⋯O, N-H⋯N and C-H⋯O hydrogen bonds and a π-π inter-action with a centroid-centroid distance of 3.6080 (8) Å.

3,5-Diamino-4H-1,2,4-triazol-1-ium hydroxonium bis-(pyridine-2,6-di-carboxyl-ato)cobaltate(II) pyridine-2,6-dicarb-oxy-lic acid monohydrate.

The asymmetric unit of the title complex, (C(2)H(6)N(5))(H(3)O)[Co(C(7)H(3)NO(4))(2)]·C(7)H(5)NO(4)·H(2)O, contains a Co(II) ion coordin-ated by four O atoms and two N atoms from two dipicolinate ligands in a disorted octa-hedral environment, a protonated triazole mol-ecule, a neutral pyridine-2,6-dicarb-oxy-lic acid mol-ecule, a hydroxonium ion and a solvent water mol-ecule. In the crystal, the components are linked into a three-dimensional framework by inter-molecular O-H⋯O, N-H⋯O and N-H⋯N and weak C-H⋯O hydrogen bonds. In addition, π-π stacking inter-actions with centroid-centroid distances in the range 3.4809 (7)-3.8145 (6) Šare observed.

Rat islet cell aggregates are superior to islets for transplantation in microcapsules.

AIMS/HYPOTHESIS: Islet transplantation is a promising treatment for type 1 diabetes but is hampered by a shortage of donor human tissue and early failure. Research on islet cell transplantation includes finding new sources of cells and immunoisolation to protect from immune assault and tumourigenic potential. Small islet cell aggregates were studied to determine if their survival and function were superior to intact islets within microcapsules because of reduced oxygen transport limitation and inflammatory mediators. METHODS: Islet cell aggregates were generated by dispersing rat islets into single cells and allowing them to re-aggregate in culture. Rat islets and islet cell aggregates were encapsulated in barium alginate capsules and studied when cultured in low (0.5% or 2%) or normal (20%) oxygen, or transplanted into mice. RESULTS: Encapsulated islet cell aggregates were able to survive and function better than intact islets in terms of oxygen-consumption rate, nuclei counts, insulin-to-DNA ratio and glucose-stimulated insulin secretion. They also had reduced expression of pro-inflammatory genes. Islet cell aggregates showed reduced tissue necrosis in an immunodeficient transplant model and a much greater proportion of diabetic xenogeneic transplant recipients receiving islet cell aggregates (tissue volume of only 85 islet equivalents) had reversal of hyperglycaemia than recipients receiving intact islets. CONCLUSIONS/INTERPRETATION: These aggregates were superior to intact islets in terms of survival and function in low-oxygen culture and during transplantation and are likely to provide more efficient utilisation of islet tissue, a finding of importance for the future of cell therapy for diabetes.

Femtosecond Laser Mass Spectrometry and High Harmonic Spectroscopy of Xylene Isomers.

Structural isomers, molecules having the same chemical formula but with atoms bonded in different order, are hard to identify using conventional spectroscopy and mass spectrometry. They exhibit virtually indistinguishable mass spectra when ionized by electrons. Laser mass spectrometry based on photoionization of the isomers has emerged as a promising alternative but requires shaped ultrafast laser pulses. Here we use transform limited femtosecond pulses to distinguish the isomers using two methods. First, we probe doubly charged parent ions with circularly polarized light. We show that the yield of doubly charged ortho-xylene decreases while para-xylene increases over a range of laser intensities when the laser polarization is changed from linear to circular. Second, we probe high harmonic generation from randomly oriented isomer molecules subjected to an intense laser field. We show that the yield of high-order harmonics varies with the positioning of the methyl group in xylene isomers (ortho-, para- and meta-) and is due to differences in the strength of tunnel ionization and the overlap between the angular peaks of ionization and photo-recombination.

Author Correction: Femtosecond Laser Mass Spectrometry and High Harmonic Spectroscopy of Xylene Isomers.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Accurate prediction of X-ray pulse properties from a free-electron laser using machine learning.

Free-electron lasers providing ultra-short high-brightness pulses of X-ray radiation have great potential for a wide impact on science, and are a critical element for unravelling the structural dynamics of matter. To fully harness this potential, we must accurately know the X-ray properties: intensity, spectrum and temporal profile. Owing to the inherent fluctuations in free-electron lasers, this mandates a full characterization of the properties for each and every pulse. While diagnostics of these properties exist, they are often invasive and many cannot operate at a high-repetition rate. Here, we present a technique for circumventing this limitation. Employing a machine learning strategy, we can accurately predict X-ray properties for every shot using only parameters that are easily recorded at high-repetition rate, by training a model on a small set of fully diagnosed pulses. This opens the door to fully realizing the promise of next-generation high-repetition rate X-ray lasers.

Measurement of sulfur L2,3 and carbon K edge XANES in a polythiophene film using a high harmonic supercontinuum.

We use a high harmonic generated supercontinuum in the soft X-ray region to measure X-ray absorption near edge structure (XANES) spectra in polythiophene (poly(3-hexylthiophene)) films at multiple absorption edges. A few-cycle carrier-envelope phase-stable laser pulse centered at 1800 nm was used to generate a stable soft X-ray supercontinuum, with amplitude gating limiting the generated pulse duration to a single optical half-cycle. We report a quantitative transmission measurement of the sulfur L2,3 edge over the range 160-200 eV and the carbon K edge from 280 to 330 eV. These spectra show all the features previously reported in the XANES spectra of polythiophene, but for the first time they are measured with a source that has an approximately 1 fs pulse duration. This study opens the door to measurements that can fully time-resolve the photoexcited electronic dynamics in these systems.

Cardiovascular response to acute and chronic endotoxemia in an awake, volume-resuscitated, canine model.

The cardiovascular response to endotoxemia was evaluated in an awake, intravascular volume-resuscitated canine model. The animals were chronically instrumented for ultrasonic crystal dimension analysis and pressure measurements of the left ventricle (LV), aorta, right atrium (RA), and pulmonary artery (PA) and for cardiac output (CO) measurement. Lipopolysaccharide (Escherichia coli 011:B4) (LPS) was administered intravenously either as an acute, high dose bolus (5 mg/kg; n = 5), a high dose bolus after complete beta-blockade with propranolol (n = 3), or a chronic, low dose infusion (5 micrograms/kg/h; n = 7). Relative to baseline values, cardiac contractility was increased after acute high dose LPS bolus, however this effect was negated by beta-blockade. Chronic, low dose LPS infusion produced an increase in cardiac contractility at 1 h, a return to baseline by 4 h, and maximal contractile depression by 24 h. No change was seen in LV compliance after the high dose LPS bolus. The LV end diastolic volume was decreased by the high dose LPS bolus. This change was blocked by propranolol administration. Chronic LPS administration was accompanied by a decrease in LV compliance and an increase in LV end diastolic volume. Other cardiovascular indices (heart rate, CO, systemic vascular resistance) changed in a fashion similar to human sepsis. These findings confirm that endotoxemia in conscious canine subjects causes changes in cardiovascular function similar to that seen in human and animal models of sepsis. This study also allows us to explain some of the discrepancies between earlier studies of human sepsis and animal models in which the appropriate clinical conditions and an intact neuro-endocrine axis were not maintained.

Biodosimetry results from space flight Mir-18.

Astronauts are classified as radiation workers due to the presence of ionizing radiation in space. For the assessment of health risks, physical dosimetry has been indispensable. However, the change of the location of dosimeters on the crew members, the variation in dose rate with location inside the spacecraft and the unknown biological effects of microgravity can introduce significant uncertainties in estimating exposure. To circumvent such uncertainty, a study on the cytogenetic effects of space radiation in human lymphocytes was proposed and conducted for Mir-18, a 115-day mission. This study used fluorescence in situ hybridization (FISH) with whole-chromosome painting probes to score chromosomal exchanges and the Giemsa staining method to determine the frequency of dicentrics. The growth kinetics of cells and sister chromatid exchanges (SCEs) were examined to ensure that chromosomal aberrations were scored in the first mitosis and were induced primarily by space radiation. Our results showed that the frequency of chromosomal aberrations increased significantly in postflight samples compared to samples drawn prior to flight, and that the frequency of SCEs was similar for both pre- and postflight samples. Based on a dose-response curve for preflight samples exposed to gamma rays, the absorbed dose received by crew members during the mission was estimated to be about 14.75 cSv. Because the absorbed dose measured by physical dosimeters is 5.2 cGy for the entire mission, the RBE is about 2.8.

Acipimox increases glucose disposal in normal man independent of changes in plasma nonesterified fatty acid concentration and whole-body lipid oxidation rate.

The short-term administration of a nicotinic acid analogue (acipimox) increases insulin sensitivity and consequently glucose disposal, both in patients with non-insulin-dependent diabetes mellitus (NIDDM) and in patients with cirrhosis. This effect has been attributed to a decrease in plasma nonesterified fatty acid (NEFA) levels and fatty acid oxidation rates, and a corresponding increase in carbohydrate oxidation. The aim of the present study was to determine whether acipimox influenced glucose disposal independent of changes in lipid metabolism. Seven normal men (age, 31 +/- 4 years; body mass index, 23.2 +/- 1.8 kg.m-2; fat-free mass [FFM], 66.8 +/- 4.2 kg) were studied on two separate occasions with hyperinsulinemic (0.06 U.kg FFM-1.h-1) euglycemic clamps (duration, 150 minutes). A primed (150 U), continuous (0.4 U.kg-1.min-1) infusion of heparin together with 10% intralipid (25 mL.h-1) was infused in both studies from -90 to 150 minutes to maintain comparable levels of plasma NEFA and lipid oxidation rates. Acipimox (500-mg capsules) or placebo were administered orally in a double-blind random fashion at t = -90 and t = 0 minutes. Whole-body lipid and carbohydrate oxidation were measured in the last 30 minutes of both the basal (preclamp) period (-30 to 0 minutes) and the clamp period (120 to 150 minutes).(ABSTRACT TRUNCATED AT 250 WORDS)

Four-day incubation for detection of bacteremia using the BACTEC 9240.

Records of 29,356 blood cultures performed between April 1994 and April 1997, using the BACTEC 9240 continuous monitoring blood culture system, were reviewed retrospectively. From these, 3,127 blood culture vials became positive. Of 95 blood culture isolates detected after three days of incubation, 63 were recovered on day four and 32 on day five. Twenty-six contaminants were recovered on day four, and 21 on day five. Chart review was performed for all day four and five isolates that did not meet our definition of a contaminant. Of the 40 isolates that were clinically insignificant, 31 were recovered on day four, and nine on day five. Of eight clinically significant isolates, six were recovered on day four, and two on day five. Our data support a four-day incubation protocol for the recovery of all clinically significant bacteria with overall sensitivity reduced by only 0.06% when compared with a five-day protocol.

Analysis of the human Ig isotype response to individual transferrin binding proteins A and B from Neisseria meningitidis.

Subcapsular antigens, including transferrin binding proteins, are being considered as potential vaccines against serogroup B meningococci. This study examined the human isotype antibody responses in cases of meningococcal disease to meningococcal TbpA (transferrin binding protein A) and TbpB (transferrin binding protein B) from two strains (SD and B16B6) expressing high and low molecular mass TbpB respectively. TbpA isolated from both strains were recognised more frequently and higher durable ELISA absorbance values were detected than those detected against TbpB from either strain. These antibody responses to Tbps were independent of the infecting meningococcal strain type. The antibody response to the four proteins was highly variable between individuals and differed significantly against all four antigens. The variability of immune responses to each Tbp from the two strains suggests that a successful vaccine would need to include TbpA and TbpB from a number of strains.