Raman Interferometry between Autoionizing States to Probe Ultrafast Wave-Packet Dynamics with High Spectral Resolution.

Photoelectron interferometry with femtosecond and attosecond light pulses is a powerful probe of the fast electron wave-packet dynamics, albeit it has practical limitations on the energy resolution. We show that one can simultaneously obtain both high temporal and spectral resolution by stimulating Raman interferences with one light pulse and monitoring the modification of the electron yield in a separate step. Applying this spectroscopic approach to the autoionizing states of argon, we experimentally resolved its electronic composition and time evolution in exquisite detail. Theoretical calculations show remarkable agreement with the observations and shed light on the light-matter interaction parameters. Using appropriate Raman probing and delayed detection steps, this technique enables highly sensitive probing and control of electron dynamics in complex systems.

Underwater, low-frequency noise in a coastal sea turtle habitat.

Underwater sound was recorded in one of the major coastal foraging areas for juvenile sea turtles in the Peconic Bay Estuary system in Long Island, New York. The recording season of the underwater environment coincided with the sea turtle activity season in an inshore area where there is considerable boating and recreational activity, especially during the summer between Independence Day and Labor Day. Within the range of sea turtle hearing, average noise pressure reached 110 dB during periods of high human activity and diminished proportionally, down to 80 dB, with decreasing human presence. Therefore, during much of the season when sea turtles are actively foraging in New York waters, their coastal habitats are flooded with underwater noise. During the period of highest human activity, average noise pressures within the range of frequencies heard by sea turtles were greater by over two orders of magnitude (26 dB) than during the lowest period of human activity. Sea turtles undoubtedly are exposed to high levels of noise, most of which is anthropogenic. Results suggest that continued exposure to existing high levels of pervasive anthropogenic noise in vital sea turtle habitats and any increase in noise could affect sea turtle behavior and ecology.

Ureteral segment replacement using a circumferential small-intestinal submucosa xenogenic graft.

We wished to determine whether small-intestinal submucosa (SIS) will epithelialize when used as a ureteral replacement material. An 11-mm segment of native ureter was excised from eight New Zealand White rabbits and replaced with an 11-mm porcine SIS graft, which was circumferentially wrapped around a ureteral stent. The SIS ureteral grafts were harvested at 11 days or 35 days postimplantation and examined grossly and by standard light microscopy techniques. Partial epithelialization with the ingrowth of urothelium, smooth muscle cells, and blood vessels was observed in the grafts harvested at 11 days postimplantation. The SIS ureteral grafts examined at 35 days postimplantation showed additional restructuring of the smooth muscle cell layer and more organized epithelialization in comparison to the SIS graft examined at 11 days. After 35 days of regenerative healing, elements of all three layers of the native ureter were observed within the collagen matrix of the SIS graft. No significant complications were observed, but all subjects (8/8) demonstrated mild intra-abdominal adhesions. Mild collecting system dilatations were observed in 4/4 (100%) of the animals harvested at 35 days and in 0/4 (0%) of the animals harvested at 11 days. We have this demonstrated in this preliminary study that SIS xenografts will epithelialize when used as a ureteral replacement material. The repair mechanism of these ureteral grafts occurred through a regenerative healing process rather than by scar formation. With further studies, this material may prove to be a useful treatment option in patients with ureteral injuries.

Mechanism for the destruction of H+3 ions by electron impact.

The rate at which the simplest triatomic ion (H+3) dissociates following recombination with a low-energy electron has been measured in numerous experiments. This process is particularly important for understanding observations of H+3 in diffuse interstellar clouds. But, despite extensive efforts, no theoretical treatment has yet proved capable of predicting the measured dissociative recombination rates at low energy, even to within an order of magnitude. Here we show that the Jahn-Teller symmetry-distortion effect-almost universally neglected in the theoretical description of electron-molecule collisions-generates recombination at a much faster rate than any other known mechanism. Our estimated rate constant overlaps the range of values spanned by experiments. We treat the low-energy collision process as a curve-crossing problem, which was previously thought inapplicable to low-energy recombination in H+3. Our calculation reproduces the measured propensity for three-body versus two-body breakup of the neutral fragments, as well as the vibrational distribution of the H2 product molecules.

An alternative to synthetic aortic grafts using jejunum.

Synthetic materials currently used for arterial grafts can provoke serious complications such as infection, rejection, and incomplete reendothelialization. Porcine small intestinal submucosa (SIS) allografts (homografts) may not share these disadvantages yet still may provide an effective graft alternative. This study was designed to provide additional information concerning the performance of this material when used as an allo-patch graft. A porcine model was selected to enable hemodynamic comparisons to the adult human physiology. Slaughterhouse small intestine was used to prepare the SIS graft material. A well-vascularized section ofjejunum was resected, rinsed, and maintained in 0.9% NaCl solution containing 10% gentamicin. The graft was prepared by removing the serosal layer, inverting the material, and discarding the mucosal surface in a similar manner. The remaining submucosa and stratum compactum constituted the graft material and was subdivided into sizes from 1.5 to 3.0 cm2 tacked to foil for manageability, and was returned to the gentamicin solution. The surgery was initiated with a femoral arterial line in the anesthetized swine, followed by isolation and preparation of the infrarenal aorta for grafting. Cross-clamps were applied and a 1.0 x 1.5-cm section of aortic wall was resected. Two sides of allograft were freed from the foil and sewn into the aorta. Then the remaining sides were removed from the foil and final graft placement was completed. The graft was harvested at postoperative day 28 and presented for microscopic examination. Results confirmed that reendothelialization with neovascularization had occurred during this interval.

Healing of incisions in the tongue: a comparison of results with milliwatt carbon dioxide laser tissue welding versus suture repair.

The healing of carbon dioxide laser weld closures produced by two commercial instruments of differing design were compared. Healing after laser welding was also compared to healing following conventional suture closure. Healing was evaluated histologically and by measurement of tensile strength over time. No histologic differences were found between closures produced by different lasers; however, in all cases suture closure resulted in slower healing times consistent with a foreign body reaction prolonging the healing process. Tensile strength measurements were performed at intervals over the first 21 days after the operation. Laser repair was found to be equivalent to or stronger than suture repair at every interval measured. The clinical use of the carbon dioxide laser for tissue welding of oral injuries should be investigated further, since it appears to be a good alternative to suture repair.

Acoustical Detection of High-Density Krill Demersal Layers in the Submarine Canyons off Georges Bank.

High-density demersal layers of krill have been detected in the submarine canyons off Georges Bank by means of a high-frequency, dual-beam bioacoustical technique. Krill densities in these demersal layers were observed to be two to three orders of magnitude greater than the highest densities observed in water-column scattering layers. Such abundances may help explain the unusually high squid and demersal fish production estimates attributed to the Georges Bank ecosystem.

A somatic component to myocardial infarction.

Sixty two patients were randomised to be seen by osteopathic physicians for palpation of the thoracic paravertebral soft tissue, T1-T8. Twenty five patients had clinically confirmed acute myocardial infarction. Of the remainder, 22 without known cardiovascular disease served as controls and 15 were placed in an excluded group because of diagnosed cardiovascular disease other than myocardial infarction. Observations were described in predetermined standard terminology. The control group was found to have a low incidence of palpable changes throughout the thoracic dorsum, and these changes were uniformly distributed from T1 to T8. Examination of the group with myocardial infarction disclosed a significantly higher incidence of soft tissue changes (increased firmness, warmth, ropiness, oedematous changes, heavy musculature), confined almost entirely to the upper four thoracic levels. The 15 patients who were excluded from the experimental group because they had various cardiovascular diseases other than myocardial infarction also showed significantly different changes on palpation compared with the group with myocardial infarction. These findings suggest that myocardial infarction is accompanied by characteristic paravertebral soft tissue changes which are readily detected by palpation.

Effects of carbon monoxide inhalation on ventricular fibrillation.

Since, in a previous study, inhalation of carbon monoxide resulted in demonstrable electrocardiographic effects on the myocardium, it was of interest to determine the effects of reduced hemoglobin oxygen content following carbon monoxide inhalation on the vulnerability of the heart to fibrillation. Normal monkeys and monkeys subjected to myocardial infarction were exposed to 100 ppm (115 mg/cu m) carbon monoxide for six hours, and the vulnerability of the heart to induced fibrillation was evaluated. The mean carboxyhemoglobin (COHb) concentration attained was 9.3%. The voltage required to induce fibrillation was highest for normal, air-breathing animals and lowest for infarcted animals inhaling carbon monoxide. Infarction alone and carbon monoxide alone each required significantly less voltage for fibrillation, and when the two were combined, the effects were additive.