Pulse Energy and Pulse Duration Effects in the Ionization and Fragmentation of Iodomethane by Ultraintense Hard X Rays.

The interaction of intense femtosecond x-ray pulses with molecules sensitively depends on the interplay between multiple photoabsorptions, Auger decay, charge rearrangement, and nuclear motion. Here, we report on a combined experimental and theoretical study of the ionization and fragmentation of iodomethane (CH_{3}I) by ultraintense (∼10^{19} W/cm^{2}) x-ray pulses at 8.3 keV, demonstrating how these dynamics depend on the x-ray pulse energy and duration. We show that the timing of multiple ionization steps leading to a particular reaction product and, thus, the product's final kinetic energy, is determined by the pulse duration rather than the pulse energy or intensity. While the overall degree of ionization is mainly defined by the pulse energy, our measurement reveals that the yield of the fragments with the highest charge states is enhanced for short pulse durations, in contrast to earlier observations for atoms and small molecules in the soft x-ray domain. We attribute this effect to a decreased charge transfer efficiency at larger internuclear separations, which are reached during longer pulses.

Erratum: Delayed Onset of Nonthermal Melting in Single-Crystal Silicon Pumped with Hard X Rays [Phys. Rev. Lett. 120, 265701 (2018)].

This corrects the article DOI: 10.1103/PhysRevLett.120.265701.

Blastulation of a zygote to a hatched blastocyst without any clear cell division: an observational finding in a time-lapse system after in vitro fertilization.

PURPOSE: To describe an interesting not previously described morphokinetic finding. METHODS: Retrospective case report of a couple undergoing controlled ovarian stimulation (COS) followed by in vitro fertilization and blastocyst transfer. RESULTS: We identified a unique finding of blastulation of a fertilized human zygote after conventional in vitro fertilization. The fertilized zygote did not show any clear cytokinesis until approximately 107 h post insemination, when it started dividing into a blastocyst. By 113 h post insemination, inner cell mass and trophectoderm cells could be clearly distinguished and the blastocyst was completely hatched by 136 h post insemination. CONCLUSION: Time-lapse systems offer more detailed observations of embryonic development. Here, we report an atypical development of an embryo that was not described previously. We hope to become an insightful discussion among peers and incentive the publication of such findings in the future.

Delayed Onset of Nonthermal Melting in Single-Crystal Silicon Pumped with Hard X Rays.

In this work, we monitor the onset of nonthermal melting in single-crystal silicon by implementing an x-ray pump-x-ray probe scheme. Using the ultrashort pulses provided by the Linac Coherent Light Source (SLAC) and a custom-built split-and-delay line for hard x rays, we achieve the temporal resolution needed to detect the onset of the transition. Our data show no loss of long-range order up to 150±40 fs from photoabsorption, which we interpret as the time needed for the electronic system to equilibrate at or above the critical nonthermal melting temperature. Once such equilibration is reached, the loss of long-range atomic order proceeds inertially and is completed within 315±40 fs from photoabsorption.

Femtosecond response of polyatomic molecules to ultra-intense hard X-rays.

X-ray free-electron lasers enable the investigation of the structure and dynamics of diverse systems, including atoms, molecules, nanocrystals and single bioparticles, under extreme conditions. Many imaging applications that target biological systems and complex materials use hard X-ray pulses with extremely high peak intensities (exceeding 1020 watts per square centimetre). However, fundamental investigations have focused mainly on the individual response of atoms and small molecules using soft X-rays with much lower intensities. Studies with intense X-ray pulses have shown that irradiated atoms reach a very high degree of ionization, owing to multiphoton absorption, which in a heteronuclear molecular system occurs predominantly locally on a heavy atom (provided that the absorption cross-section of the heavy atom is considerably larger than those of its neighbours) and is followed by efficient redistribution of the induced charge. In serial femtosecond crystallography of biological objects-an application of X-ray free-electron lasers that greatly enhances our ability to determine protein structure-the ionization of heavy atoms increases the local radiation damage that is seen in the diffraction patterns of these objects and has been suggested as a way of phasing the diffraction data. On the basis of experiments using either soft or less-intense hard X-rays, it is thought that the induced charge and associated radiation damage of atoms in polyatomic molecules can be inferred from the charge that is induced in an isolated atom under otherwise comparable irradiation conditions. Here we show that the femtosecond response of small polyatomic molecules that contain one heavy atom to ultra-intense (with intensities approaching 1020 watts per square centimetre), hard (with photon energies of 8.3 kiloelectronvolts) X-ray pulses is qualitatively different: our experimental and modelling results establish that, under these conditions, the ionization of a molecule is considerably enhanced compared to that of an individual heavy atom with the same absorption cross-section. This enhancement is driven by ultrafast charge transfer within the molecule, which refills the core holes that are created in the heavy atom, providing further targets for inner-shell ionization and resulting in the emission of more than 50 electrons during the X-ray pulse. Our results demonstrate that efficient modelling of X-ray-driven processes in complex systems at ultrahigh intensities is feasible.

Supernovae. 44Ti gamma-ray emission lines from SN1987A reveal an asymmetric explosion.

In core-collapse supernovae, titanium-44 ((44)Ti) is produced in the innermost ejecta, in the layer of material directly on top of the newly formed compact object. As such, it provides a direct probe of the supernova engine. Observations of supernova 1987A (SN1987A) have resolved the 67.87- and 78.32-kilo-electron volt emission lines from decay of (44)Ti produced in the supernova explosion. These lines are narrow and redshifted with a Doppler velocity of ~700 kilometers per second, direct evidence of large-scale asymmetry in the explosion.

Demonstration of simultaneous experiments using thin crystal multiplexing at the Linac Coherent Light Source.

Multiplexing of the Linac Coherent Light Source beam was demonstrated for hard X-rays by spectral division using a near-perfect diamond thin-crystal monochromator operating in the Bragg geometry. The wavefront and coherence properties of both the reflected and transmitted beams were well preserved, thus allowing simultaneous measurements at two separate instruments. In this report, the structure determination of a prototypical protein was performed using serial femtosecond crystallography simultaneously with a femtosecond time-resolved XANES studies of photoexcited spin transition dynamics in an iron spin-crossover system. The results of both experiments using the multiplexed beams are similar to those obtained separately, using a dedicated beam, with no significant differences in quality.

Effect of sitagliptin on cardiovascular outcomes in type 2 diabetes

BACKGROUND:Data are lacking on the long-term effect on cardiovascular events of adding sitagliptin, a dipeptidyl peptidase 4 inhibitor, to usual care in patients with type 2 diabetes and cardiovascular disease. METHODS: In this randomized, double-blind study, we assigned 14,671 patients to add either sitagliptin or placebo to their existing therapy. Open-label use of antihyperglycemic therapy was encouraged as required, aimed at reaching individually appropriate glycemic targets in all patients. To determine whether sitagliptin was noninferior to placebo, we used a relative risk of 1.3 as the marginal upper boundary. The primary cardiovascular outcome was a composite of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for unstable angina.RESULTS:During a median follow-up of 3.0 years, there was a small difference in glycated hemoglobin levels (least-squares mean difference for sitagliptin vs. placebo, -0.29 percentage points; 95% confidence interval [CI], -0.32 to -0.27). Overall, the primary outcome occurred in 839 patients in the sitagliptin group (11.4%; 4.06 per 100 person-years) and 851 patients in the placebo group (11.6%; 4.17 per 100 person-years). Sitagliptin was noninferior to placebo for the primary composite cardiovascular outcome (hazard ratio, 0.98; 95% CI, 0.88 to 1.09; P<0.001). Rates of hospitalization for heart failure did not differ between the two groups (hazard ratio, 1.00; 95% CI, 0.83 to 1.20; P=0.98). There were no significant between-group differences in rates of acute pancreatitis (P=0.07) or pancreatic cancer (P=0.32).

Asymmetries in core-collapse supernovae from maps of radioactive 44Ti in Cassiopeia A.

Asymmetry is required by most numerical simulations of stellar core-collapse explosions, but the form it takes differs significantly among models. The spatial distribution of radioactive (44)Ti, synthesized in an exploding star near the boundary between material falling back onto the collapsing core and that ejected into the surrounding medium, directly probes the explosion asymmetries. Cassiopeia A is a young, nearby, core-collapse remnant from which (44)Ti emission has previously been detected but not imaged. Asymmetries in the explosion have been indirectly inferred from a high ratio of observed (44)Ti emission to estimated (56)Ni emission, from optical light echoes, and from jet-like features seen in the X-ray and optical ejecta. Here we report spatial maps and spectral properties of the (44)Ti in Cassiopeia A. This may explain the unexpected lack of correlation between the (44)Ti and iron X-ray emission, the latter being visible only in shock-heated material. The observed spatial distribution rules out symmetric explosions even with a high level of convective mixing, as well as highly asymmetric bipolar explosions resulting from a fast-rotating progenitor. Instead, these observations provide strong evidence for the development of low-mode convective instabilities in core-collapse supernovae.

CD36 mRNA expression is increased in CD14+ monocytes of patients with coronary heart disease.

1. Blood-derived monocytes/macrophages within the intima of the arterial wall are the main source of inflammatory cytokines and factors contributing to lesion growth, plaque instability and thrombotic events. In the present study, we assessed the hypothesis that mRNA expression levels of candidate genes of atherosclerosis in circulating CD14(+) blood monocytes are associated with coronary heart disease (CHD). 2. We investigated mRNA expression levels using reverse transcription-polymerase chain reaction of genes involved in cholesterol uptake (macrophage scavenger receptor (MSR1), scavenger receptor class B member 1 (SRB1), lectin-like oxidized low-density lipoprotein (LDL) receptor 1 (LOX1), CD36, LDL receptor (LDLR)), reverse cholesterol transport (apolipoprotein E (ApoE), ATP-binding cassette sub-family A member 1 (ABCA1)) and inflammation (tumour necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-1alpha (MIP-1alpha), interleukin-6 (IL-6), tissue factor) in CD14(+) monocytes from 119 consecutively recruited patients and found that median CD36 mRNA expression levels were significantly increased in patients with CHD compared with controls (111 x 10(3) vs 96 x 10(3) copies/10(6) copies beta-actin, respectively; n = 79 and 40, respectively; P < 0.05), despite a high interindividual variability in gene expression. 3. A common T --> C polymorphism (rs2151916) located only 14 bp upstream of the upstream transcriptional start site did not influence CD36 expression. 4. Expression levels of the other candidate genes investigated in the present study did not show any statistically significant differences between patients with CHD and controls. 5. We conclude that CD36 mRNA expression is significantly increased in patients with CHD and may serve as an indicator of CHD burden.

Role of brain natriuretic peptide in risk stratification of patients with congestive heart failure.

OBJECTIVES: Using a prospective study design, we assessed the value of brain natriuretic peptide (BNP) to identify patients with heart failure who have an increased risk of deterioration of their functional status. Furthermore, we examined the relationship between BNP and various clinical characteristics incorporated into an established survival model used for risk stratification. BACKGROUND: Prediction of the clinical course is a crucial part of the decision-making process about the adequate treatment strategy for patients with advanced congestive heart failure (CHF). Although laborious, multivariable indexes have been established for risk stratification, simple plasma BNP measurements may be as useful as prognostic indicators. METHODS: In 78 patients referred to our heart failure clinic, plasma BNP levels were compared with the results of a multivariable prognostic model. To assess the prognostic power of BNP, the clinical course of this cohort was monitored for a median follow-up period of 398 days. RESULTS: At study entry, plasma BNP and the heart failure survival score (HFSS) showed a significant correlation (r = -0.706). During follow-up, Kaplan-Meier estimates of freedom from clinical events differed significantly for patients above and below the 75th percentile concentrations of plasma BNP (p < 0.0001). Changes in plasma BNP were significantly related to changes in limitations of physical activity, as demonstrated by logistic regression analysis (chi-square statistic = 24.9, p < 0.0001). Proportional hazards analysis confirmed BNP as a powerful predictor of functional status deterioration (p < 0.0001). This prognostic information was as powerful as that derived from the multivariable HFSS. CONCLUSIONS: Measurement of plasma BNP concentrations might provide a useful and cost-effective screening tool that helps reduce the need and frequency for more expensive cardiac tests.

KARMEN time anomaly: search for a neutral particle of mass 33.9 MeV in pion decay

We have searched for the pion decay pi(+)-->&mgr;+X, where X is a neutral particle of mass 33.905 MeV. This process was suggested by the KARMEN Collaboration to explain an anomaly in their observed time distribution of neutrino induced reactions. Having measured the muon momentum spectrum of charged pions decaying in flight, we find no evidence for this process and place an upper limit on the branching fraction eta

Attenuated cardiac allograft vasculopathy in mice with targeted deletion of the transcription factor STAT4.

BACKGROUND: To study transcription factor signaling pathways that mediate cardiac allograft vasculopathy, we used mice with targeted gene deletion of signal transducer and activator of transcription (STAT)4 and STAT6 as recipients in our mouse cardiac transplant model of chronic rejection. METHODS AND RESULTS: At day 55 after transplantation, cardiac grafts placed into STAT4 -/- (n=10) had reduced frequency (24+/-2%) and severity (9+/-4%) of vascular occlusion compared with wild-type controls (n=7, frequency 70+/-12% [P<0.001], severity 25+/-6% [P<0.05]). This decrease was associated with reduced intragraft expression ((32)P RT-PCR and immunohistochemistry) of the Th1 signature cytokines interferon-gamma (P<0.001) and interleukin (IL)-2 (P<0.001). Furthermore, cardiac grafts in STAT4 -/- had fewer infiltrating CD45(+) mononuclear cells (99+/-27 cells/mm(3) compared with 551+/-168 cells/mm(3) in wild-type controls [P<0.05]) and reduced expression of P-selectin (P<0.001) and E-selectin (P<0.01) ligand, recently shown to regulate Th1 cell recruitment. In contrast, in grafts placed into STAT6 -/- (n=11), the development of cardiac allograft vasculopathy (frequency 62+/-8%, severity 28+/-6%) and Th2 cytokine profiles (IL-4, IL-10) were comparable to those in wild-type controls. CONCLUSIONS: Hence, we show that immune responses mediated by STAT4, but not STAT6, contribute to the development of cardiac allograft vasculopathy. We speculate that when present, STAT4-mediated signaling pathways may promote cardiac allograft vasculopathy by directing Th1-specific lymphocyte recruitment, activation, and effector functions.

Pathogenetic mechanisms of cardiac allograft vasculopathy--impact of nitric oxide.

In the cytokine-enriched environment of the chronically rejecting allograft, nitric oxide (NO) is predominantly produced by the inducible isoform of NOS synthase (NOS2) expressed by recipient-derived infiltrating immune cells as well as donor-derived vascular smooth muscle cells and endothelial cells. Early and persistent upregulation of NOS2 in allografts with cardiac allograft vasculopathy and downregulation of NOS2 coinciding with immunosuppressive attenuation of cardiac allograft vasculopathy have suggested NO as a regulator of cardiac allograft vasculopathy, the hallmark of chronic rejection. Pathogenetically, the development of cardiac allograft vasculopathy can be divided into an early phase, characterized by endothelial dysfunction, and a later phase, characterized by structural changes of vessel wall morphology. Several lines of evidence have shown that NO might play an essential role in both phases. Endothelial dysfunction due to immune-mediated injury of endothelial cells has been suggested as an early response-to-injury event in the pathogenesis of cardiac allograft vasculopathy. Functional studies in human transplant recipients have documented endothelial dysfunction of coronary artery vessels. Administration of L-arginine, the precursor of NO, improved endothelial function of both epicardial coronary arteries and coronary microvasculature indicating a protective effect of NO. To assess the impact of NO on the development of late structural changes, the severity of cardiac allograft vasculopathy was assessed in mice with targeted deletion of NOS2. A significant increase of vascular occlusion in NOS2-knockout mice demonstrated an antiarteriosclerotic effect of NOS2. In part, this effect could be explained by reduced neointimal smooth muscle cell accumulation after alloimmune injury. Taken together, NO plays an important role in maintaining vessel integrity after transplantation. Disruptions in NO pathways seem to play a key role in the progression from endothelial dysfunction to structural changes.

Alloimmune-mediated apoptosis: comparison in mouse models of acute and chronic cardiac rejection.

BACKGROUND: The purpose of the present study was (1) to compare apoptotic activity in models of acute and chronic rejection and (2) to study the cellular distribution of parenchymal versus inflammatory cell apoptosis. METHODS: Heterotopic cardiac mouse transplantation (CBA into C57BL/6) was used to produce allografts undergoing acute (day 7, untreated recipients, n=6) or chronic (day 55, anti-CD4/8 for 28 days, n=6) rejection. As references, we used 55-day isograft controls (n=5) and native hearts (n=6). To assess apoptotic activity, we quantified DNA laddering (32P incorporation), DNA fragmentation (antinucleosome ELISA), and caspase-1 transcript levels (32P-reverse transcriptase-polymerase chain reaction). To localize apoptosis, we performed terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. RESULTS: DNA laddering and nucleosome levels were increased in allografts undergoing acute or chronic rejection when compared with both controls. Both parameters were twofold higher in acutely compared with chronically rejecting hearts. Caspase-1 transcript levels were increased in acutely (P<0.0001) and chronically rejecting hearts (P=0.004). Acutely rejecting grafts had more terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive nuclei (53+/-3 nuclei/high-powered field) than chronically rejecting grafts (9+/-1 nuclei/high-powered field, P<0.0001), but the distribution between graft-infiltrating inflammatory cells and myocytes was similar. Vascular cells undergoing apoptosis were infrequent in both forms. CONCLUSION: Using four separate indices, apoptotic activity is more pronounced in cardiac allografts undergoing acute compared with chronic rejection. This reflects, in part, the degree of alloimmune response. However, we speculate that the contributions of apoptosis to various forms of rejection are multifactorial. The long-term outcome to the graft may depend upon the magnitude, timing, and target of programmed cell death.

Attenuated acute cardiac rejection in NOS2 -/- recipients correlates with reduced apoptosis.

BACKGROUND: The mechanisms through which NOS2-mediated pathways regulate graft failure in acute cardiac rejection are ill defined. To determine whether apoptosis promoted by NOS2 may contribute, we used a heterotopic transplant model to study mouse cardiac allografts placed in recipients with targeted gene deletion of NOS2. METHODS AND RESULTS: Using 5 different indexes of apoptosis, we showed that mouse cardiac allografts placed in NOS2 -/- recipients (n=7) had reduced apoptotic activity compared with those in NOS2 +/+ controls (n=8). There were significantly fewer TUNEL-positive nuclei per high-powered field (P<0.01), less DNA fragmentation (antinucleosome ELISA; P<0.05), lower corrected transcript levels for caspase-1 and -3 (32P reverse transcriptase-polymerase chain reaction; P<0.01), and reduced caspase-3 activity (cleavage of DEVD-pNA [P<0.001] and poly [ADP-ribose] polymerase) in grafts from NOS2 -/- recipients. This concordant reduction in apoptotic indexes paralleled the improved histological outcome of grafts transplanted into NOS2 -/- recipients (assessed as rejection scores; P=0.012). To identify pathways controlled by NOS2, we compared intragraft transcript levels of potential triggers and regulators. Whereas Fas ligand/Fas and tumor necrosis factor (TNF)-alpha/TNF receptor-1 levels were not altered by NOS2 deficiency, transcript levels for p53 were significantly lower in grafts from NOS2 -/- recipients, coinciding with a significant increase in the antiapoptotic Bcl-2/Bax balance and decrease in Bcl-Xl levels. CONCLUSIONS: Using NOS2 knockout mice, we demonstrated that NOS2-mediated pathways can promote acute rejection, at least in part, by inducing apoptotic cell death. When NOS2 is present, p53 might control NOS2-mediated apoptosis by stimulating Bax and repressing Bcl-2 and Bcl-Xl expression, which may activate the cell death program in the rejecting heart.

NOS2 mediates opposing effects in models of acute and chronic cardiac rejection: insights from NOS2-knockout mice.

To compare regulatory effects of NOS2 in acute and chronic cardiac allograft rejection, we used NOS2 knockout mice as recipients in a cardiac transplant model. To study acute and chronic rejection separately but within the same genetic strain combination, we compared allografts placed into recipients without or with immunosuppression (anti-CD4/8 for 28 days). NOS2 mRNA and protein expression were compared using 32P-RT-PCR and immunohistochemistry. In our acute rejection model, NOS2 was predominately localized to graft-infiltrating immune cells. At day 7, grafts in NOS2-deficient recipients (n = 7) showed reduced inflammatory infiltrates and myocyte damage resulting in significantly lower rejection scores (1.6 +/- 0.4) compared to wild-type controls (n = 18; 2.8 +/- 0.2, P = 0.002). In contrast, in our chronic rejection model, additional NOS2 expression was localized to graft-parenchymal cells. At day 55, grafts in NOS2-deficient recipients (n = 12) showed more parenchymal infiltration and parenchymal destruction (rejection score 3.8 +/- 0.1) than wild-type controls (n = 15; 1.6 +/- 0.2, P < 0.0001). This was associated with a significant decrease in ventricular contractility (palpation score 0.3 +/- 0.1 compared to 2.3 +/- 0.3 in wild-type, P < 0.0001). Hence, NOS2 promotes acute but prevents chronic rejection. These opposing effects during acute and chronic cardiac allograft rejection are dependent on the temporal and spatial expression pattern of NOS2 during both forms of rejection.