Attosecond nonlinear polarization and light-matter energy transfer in solids.

Electric-field-induced charge separation (polarization) is the most fundamental manifestation of the interaction of light with matter and a phenomenon of great technological relevance. Nonlinear optical polarization produces coherent radiation in spectral ranges inaccessible by lasers and constitutes the key to ultimate-speed signal manipulation. Terahertz techniques have provided experimental access to this important observable up to frequencies of several terahertz. Here we demonstrate that attosecond metrology extends the resolution to petahertz frequencies of visible light. Attosecond polarization spectroscopy allows measurement of the response of the electronic system of silica to strong (more than one volt per ångström) few-cycle optical (about 750 nanometres) fields. Our proof-of-concept study provides time-resolved insight into the attosecond nonlinear polarization and the light-matter energy transfer dynamics behind the optical Kerr effect and multi-photon absorption. Timing the nonlinear polarization relative to the driving laser electric field with sub-30-attosecond accuracy yields direct quantitative access to both the reversible and irreversible energy exchange between visible-infrared light and electrons. Quantitative determination of dissipation within a signal manipulation cycle of only a few femtoseconds duration (by measurement and ab initio calculation) reveals the feasibility of dielectric optical switching at clock rates above 100 terahertz. The observed sub-femtosecond rise of energy transfer from the field to the material (for a peak electric field strength exceeding 2.5 volts per ångström) in turn indicates the viability of petahertz-bandwidth metrology with a solid-state device.

Direct observation of electron propagation and dielectric screening on the atomic length scale.

The propagation and transport of electrons in crystals is a fundamental process pertaining to the functioning of most electronic devices. Microscopic theories describe this phenomenon as being based on the motion of Bloch wave packets. These wave packets are superpositions of individual Bloch states with the group velocity determined by the dispersion of the electronic band structure near the central wavevector in momentum space. This concept has been verified experimentally in artificial superlattices by the observation of Bloch oscillations--periodic oscillations of electrons in real and momentum space. Here we present a direct observation of electron wave packet motion in a real-space and real-time experiment, on length and time scales shorter than the Bloch oscillation amplitude and period. We show that attosecond metrology (1 as = 10(-18) seconds) now enables quantitative insight into weakly disturbed electron wave packet propagation on the atomic length scale without being hampered by scattering effects, which inevitably occur over macroscopic propagation length scales. We use sub-femtosecond (less than 10(-15) seconds) extreme-ultraviolet light pulses to launch photoelectron wave packets inside a tungsten crystal that is covered by magnesium films of varied, well-defined thicknesses of a few ångströms. Probing the moment of arrival of the wave packets at the surface with attosecond precision reveals free-electron-like, ballistic propagation behaviour inside the magnesium adlayer--constituting the semi-classical limit of Bloch wave packet motion. Real-time access to electron transport through atomic layers and interfaces promises unprecedented insight into phenomena that may enable the scaling of electronic and photonic circuits to atomic dimensions. In addition, this experiment allows us to determine the penetration depth of electrical fields at optical frequencies at solid interfaces on the atomic scale.

Molecular breakpoint analysis and relevance of variable mosaicism in a woman with short stature, primary amenorrhea, unilateral gonadoblastoma, and a 46,X,del(Y)(q11)/45,X karyotype.

We report on a 30-year-old woman with short stature, completely female external genitalia, primary amenorrhea, bilateral streak gonads, unilateral gonadoblastoma, and a 46,X,del(Y)(q11)/45,X karyotype. Variable levels of mosaicism were found in blood and cultivated fibroblasts from both the skin and ovaries, with the percentage of the 45,X lineage never exceeding 33%. Fluorescence in situ hybridization (FISH) was performed with alpha satellite centromere region probes of the X and Y chromosomes (DXZ1 and DXZ3) as well as with the unique-sequence, locus-specific, sex-determining region of the Y chromosome gene (SRY) and the DXZ1 probes. Each signal was noted for DXZ1 on the X chromosome and for the Y probes on the marker chromosome. Molecular investigations with a panel of PCR markers spread over the whole Y chromosome indicated a deletion breakpoint between sY 78 (interval 4) and sY 151 (interval 5F). No mutation of the high mobility group-box (HMG-box) of the SRY gene could be found following sequence analysis. The phenotype/genotype correlation demonstrates the broad phenotypic range of low-level 45,X mosaicism with the resultant short stature and external female phenotype, despite the presence of SRY in a high proportion of cells in various tissues.

Management of pancreatic injury in pediatric blunt abdominal trauma.

BACKGROUND/PURPOSE: Nonoperative management of low-grade pancreatic injury is widely accepted. Management of major pancreatic parenchymal or ductal injury in children remains controversial. This study will review management strategies as they relate to site and type of pancreatic injury and their outcomes. METHODS: A total of 11,794 consecutive admissions to a regional pediatric trauma center from 1984 to 1997 were reviewed to identify children with pancreatic injury as documented by serum amylase; imaging by computed tomographic (CT) scan, ultrasonography (US), and endoscopic retrograde cholangiopancreatography (ERCP); and surgical or postmortem reports. RESULTS: Pancreatic injury was documented in 56 children, age 2 months to 14 years, with blunt mechanisms of injury. Serum amylase level was elevated on admission in 40 (71%), and no correlation was found between admission amylase values and severity of pancreas injury. An admission CT scan was obtained in 44 (79%) patients and was positive for pancreatic injury in 25 (57%). Twelve children, who had diagnoses of other intraabdominal injury by CT scan, had pancreatic injuries discovered on exploratory laparotomy. Seven children with normal admission CT scans, and the 12 children who did not undergo imaging on admission, had pancreatic injuries that were later documented by imaging, exploration, or autopsy. Thirty children were treated with immediate exploration, 17 for nonpancreatic indications and 13 with pancreatic injuries on admission CT scan. Of 19 minor injuries noted in the operating room, only three were treated with external drainage. Seven patients with distal duct injuries underwent distal pancreatectomy with splenic preservation. Twenty-six children were treated nonoperatively, including 19 with minor pancreas injuries, three with proximal pancreatic duct injuries, and four with duct injuries that were missed at admission. There were no advantages or complications of external drainage versus nondrainage of minor pancreatic injuries. There were seven deaths (overall mortality rate, 12.5%), none related to pancreatic injury. Of the seven patients in whom pseudocysts developed (two not imaged at admission, two from known proximal duct injuries treated nonoperatively, and three from injuries missed by initial studies), five were treated by delayed internal drainage and recovered promptly, and two resolved spontaneously. Pancreas-related complications included one persistent fistula and one prolonged hyperamylasemia, both of which resolved. CONCLUSIONS: Pancreatic injuries are uncommon in children. Initial serum amylase level does not correlate with the severity of pancreatic injury. The majority of pancreatic injuries can be managed nonoperatively. Initial nonoperative management of injuries of the proximal pancreatic duct allows for the formation and uneventful delayed drainage of a pseudocyst, rather than the risks of early radical interventions. Distal duct injuries are best managed by prompt spleen-sparing distal pancreatectomy. There is no benefit of closed drainage for management of minor pancreatic injuries discovered at laparotomy.

[Diagnosis of appendicitis in early childhood]. / Zur Diagnostik der Appendizitis im Kleinkindesalter.

89 preschool children, 2-4 years old, treated under the diagnosis of appendicitis were analyzed, 46 of them were operated. In 40% of those children the diagnosis of an acute nonperforated appendicitis could have been ensured, in 40% the diagnosis of a perforated appendicitis was found, in 20% the laparotomy was negative. In cases of an acute nonperforated appendicitis typical symptoms were vomiting (100%), general stomach-ache (89%) and fever (61%). In most cases of an perforated appendicitis the state of patients was reduced drastically (80%), in 50% an ileus could be observed. Duration of anamnesis was less than 24 hours with all the children who suffered from acute nonperforated appendicitis and with one fourth of the children suffering from perforated appendicitis.

[The diagnosis of appendicitis in childhood]. / Zur Diagnostik der Appendizitis im Kleinkindesalter.

89 preschool children, 2-4 years old, treated under the diagnosis of appendicitis were analyzed. 46 of them were operated. In 39% of those children the diagnosis of an acute nonperforated appendicitis could have been ensured, in 39% the diagnosis of a perforated appendicitis was found, in 22% the was found, in 22% the laparotomy was negative. In cases of an acute perforated appendicitis typical symptoms were vomiting (100%), general stomach-ache (89%) and fever (61%). In most cases of an perforated appendicitis the state of patients was reduced drastically (80%), in 50% an ileus could be observed. Half a children with an acute nonperforated appendicitis as well as an perforated appendicitis had got a respiratory disease additionally. This fact was the main reason for the to late diagnosis particularly in the age up to 3. In all cases being not sure a consequent control at a ward is necessary; an important fact for this recommendation is the shortness of the acute perforated appendicitis in early childhood.

[Knowledge about and therapy of Shepherd's fracture]. / Zur Kenntnis und Therapie der Shepherdschen Fraktur.

In literature the compression of the distal part of the talus is described as Sherpherd's fracture. Although many proposals of treatment have been made there is a high rate of complications. Well timed surgical reconstruction and implantation of autogenous cancellous bone is the therapy of choice. Avascular bone necrosis can be avoided in this way.

The permeability of large arteries to labeled protein.

Using labeled albumin, the permeability index was determined for the aorta and other arteries of the rabbit after different circulation times. The results were reproducible. Different indices of permeability were obtained for different arteries. When the circulation time of the tracer was extended, the increase in the permeability index was greater for the coronary and femoral arteries than for the aorta. 5-hydroxytryptamine, bradykinin and prostaglandin E2 tended to increase the permeability index. There was no relation to the level of blood pressure. The different indices of permeability obtained for the different arteries were not leveled by the mediators. The permeability index is seen to become greater postmortally.

[Permeability of the arterial vessel wall for labeled plasma proteins]. / Die Permeabilität der arteriellen Gefässwand für markiertes Blutplasms-Protein.

The permeability of the large arteries may be analysed by different methods. It is of different size in the individual arteries and is increased by hypoxia, by hypertension and by mediators. Thus increasedly atherogenic substances may enter the wall of the vessel.

Index of permeability of large arteries to labeled albumin after administration of prostaglandin E2.

Prostaglandin (PG)E2 tends to increase the permeability to labeled albumin of the arterial walls of rabbits. The blood pressure decreases after administration of PGE2. The increase in permeability is probably due to direct effects of prostaglandin upon the endothelium, perhaps to an increase of cytopempsis or formation of leaks in the integrity of the cell layer.

Arterial permeability to labeled protein.

Labeled albumin, which was administered intravenously, was detected, with the use of a scintillation counter, in the aortic wall of rabbits. Relative to weight, the permeability index was highest in the aortic arch and abdominal aorta and lowest in the medial thoracic aorta. Angiotensin II and various mediators were found to increase the permeability of the aortic wall.