Four-Body Charge Transfer Processes in Heavy Particle Collisions

Fully differential cross sections (FDCS) for proton + helium single capture and transfer-excitation collisions are presented using the Four-Body Transfer-Excitation (4BTE) model. This is a first order perturbative model that allows for any two-particle interaction to be studied. For single capture, the effect of the projectile-nuclear term in the perturbation is examined. It is shown that inclusion of this term results in an unphysical minimum in the FDCS, but is required to correctly predict the magnitude of the experimental results. For transfer-excitation, the role of electron correlation in the target helium atom is studied, and shown to be unimportant in the calculation of the FDCS

Effects of Neonatal Supplemental Oxygen and High Fat Diet on Weight Gain, Ventricular Hypertrophy and Contractility

Premature birth represents about 13% of live births each year. Since lungs of these infants are underdeveloped, they receive supplemental oxygen right after birth, but little is known about its effects on the development of normal physiological responses and whether it impacts long-term cardio-metabolic function. Based on previous studies from our lab that showed increased pulse wave velocity in 12 month old rats exposed to neonatal supplemental oxygen, we hypothesized that neonatal exposure to supplemental oxygen causes cardiac hypertrophy and decreased left ventricular contractility. We also hypothesized that these effects to supplemental oxygen would be enhanced by 10 weeks on a high fat diet. To test the hypothesis, we used our rat model of 80% and 21% O2 exposed rats to FlO2=0.80 and 0.21 respectively, for 8 days post-birth. Two months after birth, these 80% and 21% rats were randomly assigned to either a high fat diet (60% of calories from animal fat) or low fat diet (CON) for 10 weeks during which their weights and caloric consumption were monitored. After 10 weeks, a Miller conductance catheter was inserted into the left ventricle to obtain pressure-volume loops and end-systolic pressure volume relationship, which was used to evaluate contractility. 80% rats exposed to CON diet showed higher cumulative weight gain than 21% rats on the same diet. No significant difference was observed between the weights of the left ventricles due to exposure to supplemental oxygen or high fat diet. Neonatal supplemental oxygen exposure decreased contractility whereas the combination of high fat diet and supplemental oxygen exposure reversed this effect. These data suggest that neonatal exposure to supplemental oxygen promotes weight gain and decreased ventricular contractility

Neonatal Supplemental Oxygen Exposure Promotes the Development of Metabolic Disease in Adult Rats

Premature infants frequently require supplemental oxygen to sustain life, but little is known about how supplemental oxygen administered during the critical developmental window after birth increases the risk of age-related disease, including obesity and diabetes. We hypothesized that neonatal rats exposed to supplemental oxygen (OXY) would have impaired glucose tolerance and that they would develop a diabetes phenotype earlier than controls (CON), when offered a high fat diet. We used an established rat model of neonatal oxygen exposure (80% O2 for 8-14 days) and glucose tolerance was evaluated 14 days and 12 months post-natally. To evaluate glucose tolerance, baseline blood glucose was measured after an overnight fast, followed by an intraperitoneal injection of concentrated glucose. Blood glucose was then measured 15, 30, 60 and 120 minutes post-injection. In a second experiment, two month old OXY and CON rats were randomly assigned to an animal-based fat diet (60% of calories from fat), or standard, low fat diet for ten weeks. At the beginning of the study and each subsequent week, glucose tolerance was measured. At 14 days and 12 months, OXY rats had higher blood glucose at 15 and 30 minutes compared to CON rats. OXY rats fed a high fat diet developed frank glucose intolerance after 4 weeks. Ten weeks of high fat diet had minimal effect on glucose tolerance in CON rats. Taken together, these data suggest that supplemental oxygen during the neonatal period may predispose the premature infant to the development of metabolic disease later in life

Similar ultrafast dynamics of several dissimilar Dirac and Weyl semimetals

Recent years have seen the rapid discovery of solids whose low-energy electrons have a massless, linear dispersion, such as Weyl, line-node, and Dirac semimetals. The remarkable optical properties predicted in these materials show their versatile potential for optoelectronic uses. However, little is known of their response in the picoseconds after absorbing a photon. Here we measure the ultrafast dynamics of four materials that share non-trivial band structure topology but that differ chemically, structurally, and in their low-energy band structures: ZrSiS, which hosts a Dirac line node and Dirac points; TaAs and NbP, which are Weyl semimetals; and Sr$_{1-y}$Mn$_{1-z}$Sb$_2$, in which Dirac fermions coexist with broken time-reversal symmetry. After photoexcitation by a short pulse, all four relax in two stages, first sub-picosecond, and then few-picosecond. Their rapid relaxation suggests that these and related materials may be suited for optical switches and fast infrared detectors. The complex change of refractive index shows that photoexcited carrier populations persist for a few picoseconds

Using coherent phonons for ultrafast control of the Dirac node of SrMnSb\u3csub\u3e2\u3c/sub\u3e

SrMnSb2 is a candidate Dirac semimetal whose electrons near the Y point have the linear dispersion and low mass of a Dirac cone. Here we demonstrate that ultrafast, 800-nm optical pulses can launch coherent phonon oscillations in Sr0.94Mn0.92Sb2, particularly an Ag mode at 4.4 THz. Through first-principles calculations of the electronic and phononic structure of SrMnSb2, we show that high-amplitude oscillations of this mode would displace the atoms in a way that transiently opens and closes a gap at the node of the Dirac cone. The ability to control the nodal gap on a subpicosecond timescale could create opportunities for the design and manipulation of Dirac fermions

Resistance training in humans and mechanical overload in rodents do not elevate muscle protein lactylation

Although several reports have hypothesized that exercise may increase skeletal muscle protein lactylation, empirical evidence in humans is lacking. Thus, we adopted a multifaceted approach to examine if acute and subchronic resistance training (RT) altered skeletal muscle protein lactylation levels. In mice, we also sought to examine if surgical ablation-induced plantaris hypertrophy coincided with increases in muscle protein lactylation. To examine acute responses, participants’ blood lactate concentrations were assessed before, during, and after eight sets of an exhaustive lower body RT bout (n = 10 trained college-aged men). Vastus lateralis biopsies were also taken before, 3-h post, and 6-h post-exercise to assess muscle protein lactylation. To identify training responses, another cohort of trained college-aged men (n = 14) partook in 6 weeks of lower-body RT (3x/week) and biopsies were obtained before and following the intervention. Five-month-old C57BL/6 mice were subjected to 10 days of plantaris overload (OV, n = 8) or served as age-matched sham surgery controls (Sham, n = 8). Although acute resistance training significantly increased blood lactate responses ~7.2- fold (p \u3c 0.001), cytoplasmic and nuclear protein lactylation levels were not significantly altered at the post-exercise time points, and no putative lactylation-dependent mRNA was altered following exercise. Six weeks of RT did not alter cytoplasmic protein lactylation (p = 0.800) despite significantly increasing VL muscle size (+3.5%, p=0.037), and again, no putative lactylation-dependent mRNA was significantly affected by training. Plantaris muscles were larger in OV versus Sham mice (+43.7%, p \u3c 0.001). However, cytoplasmic protein lactylation was similar between groups (p = 0.369), and nuclear protein lactylation was significantly lower in OV versus Sham mice (p \u3c 0.001). The current null findings, along with other recent null findings in the literature, challenge the thesis that lactate has an appreciable role in promoting skeletal muscle hypertrophy

Cluster M Mycobacteriophages Bongo, PegLeg, and Rey with Unusually Large Repertoires of tRNA Isotopes

Genomic analysis of a large set of phages infecting the common hostMycobacterium smegmatis mc2155 shows that they span considerable genetic diversity. There are more than 20 distinct types that lack nucleotide similarity with each other, and there is considerable diversity within most of the groups. Three newly isolated temperate mycobacteriophages, Bongo, PegLeg, and Rey, constitute a new group (cluster M), with the closely related phages Bongo and PegLeg forming subcluster M1 and the more distantly related Rey forming subcluster M2. The cluster M mycobacteriophages have siphoviral morphologies with unusually long tails, are homoimmune, and have larger than average genomes (80.2 to 83.7 kbp). They exhibit a variety of features not previously described in other mycobacteriophages, including noncanonical genome architectures and several unusual sets of conserved repeated sequences suggesting novel regulatory systems for both transcription and translation. In addition to containing transfer-messenger RNA and RtcB-like RNA ligase genes, their genomes encode 21 to 24 tRNA genes encompassing complete or nearly complete sets of isotypes. We predict that these tRNAs are used in late lytic growth, likely compensating for the degradation or inadequacy of host tRNAs. They may represent a complete set of tRNAs necessary for late lytic growth, especially when taken together with the apparent lack of codons in the same late genes that correspond to tRNAs that the genomes of the phages do not obviously encode

Updated Planetary Mass Constraints of the Young V1298 Tau System Using MAROON-X

The early K-type T-Tauri star, V1298 Tau ($V=10\,{\rm mag}$, ${\rm age}\approx20-30\,{\rm Myr}$) hosts four transiting planets with radii ranging from $4.9-9.6\,R_\oplus$. The three inner planets have orbital periods of $\approx8-24\,{\rm d}$ while the outer planet's period is poorly constrained by single transits observed with \emph{K2} and \emph{TESS}. Planets b, c, and d are proto-sub-Neptunes that may be undergoing significant mass loss. Depending on the stellar activity and planet masses, they are expected to evolve into super-Earths/sub-Neptunes that bound the radius valley. Here we present results of a joint transit and radial velocity (RV) modelling analysis, which includes recently obtained \emph{TESS} photometry and MAROON-X RV measurements. Assuming circular orbits, we obtain a low-significance ($\approx2\sigma$) RV detection of planet c implying a mass of $19.8_{-8.9}^{+9.3}\,M_\oplus$ and a conservative $2\sigma$ upper limit of $<39\,M_\oplus$. For planets b and d, we derive $2\sigma$ upper limits of $M_{\rm b}<159\,M_\oplus$ and $M_{\rm d}<41\,M_\oplus$. For planet e, plausible discrete periods of $P_{\rm e}>55.4\,{\rm d}$ are ruled out at a $3\sigma$ level while seven solutions with $43.3<P_{\rm e}/{\rm d}<55.4$ are consistent with the most probable $46.768131\pm000076\,{\rm d}$ solution within $3\sigma$. Adopting the most probable solution yields a $2.6\sigma$ RV detection with mass a of $0.66\pm0.26\,M_{\rm Jup}$. Comparing the updated mass and radius constraints with planetary evolution and interior structure models shows that planets b, d, and e are consistent with predictions for young gas-rich planets and that planet c is consistent with having a water-rich core with a substantial ($\sim5\%$ by mass) H$_2$ envelope.Comment: 18 pages, 13 figures, accepted for publication in A

Coherent spinor dynamics in a spin-1 Bose condensate

Collisions in a thermal gas are perceived as random or incoherent as a consequence of the large numbers of initial and final quantum states accessible to the system. In a quantum gas, e.g. a Bose-Einstein condensate or a degenerate Fermi gas, the phase space accessible to low energy collisions is so restricted that collisions be-come coherent and reversible. Here, we report the observation of coherent spin-changing collisions in a gas of spin-1 bosons. Starting with condensates occupying two spin states, a condensate in the third spin state is coherently and reversibly created by atomic collisions. The observed dynamics are analogous to Josephson oscillations in weakly connected superconductors and represent a type of matter-wave four-wave mixing. The spin-dependent scattering length is determined from these oscillations to be -1.45(18) Bohr. Finally, we demonstrate coherent control of the evolution of the system by applying differential phase shifts to the spin states using magnetic fields.Comment: 19 pages, 3 figure