All-Optical GeV Electron Bunch Generation in a Laser-Plasma Accelerator via Truncated-Channel Injection.

We describe a simple scheme, truncated-channel injection, to inject electrons directly into the wakefield driven by a high-intensity laser pulse guided in an all-optical plasma channel. We use this approach to generate dark-current-free 1.2 GeV, 4.5% relative energy spread electron bunches with 120 TW laser pulses guided in a 110 mm-long hydrodynamic optical-field-ionized plasma channel. Our experiments and particle-in-cell simulations show that high-quality electron bunches were only obtained when the drive pulse was closely aligned with the channel axis, and was focused close to the density down ramp formed at the channel entrance. Start-to-end simulations of the channel formation, and electron injection and acceleration show that increasing the channel length to 410 mm would yield 3.65 GeV bunches, with a slice energy spread ∼5×10^{-4}.

Gev-Scale Accelerators Driven by Plasma-Modulated Pulses from Kilohertz Lasers.

We describe a new approach for driving GeV-scale plasma accelerators with long laser pulses. We show that the temporal phase of a long, high-energy driving laser pulse can be modulated periodically by copropagating it with a low-amplitude plasma wave driven by a short, low-energy seed pulse. Compression of the modulated driver by a dispersive optic generates a train of short pulses suitable for resonantly driving a plasma accelerator. Modulation of the driver occurs via well-controlled linear processes, as confirmed by good agreement between particle-in-cell (PIC) simulations and an analytic model. PIC simulations demonstrate that a 1.7 J, 1 ps driver, and a 140 mJ, 40 fs seed pulse can accelerate electrons to energies of 0.65 GeV in a plasma channel with an axial density of 2.5×10^{17} cm^{-3}. This work opens a route to high repetition-rate, GeV-scale plasma accelerators driven by thin-disk lasers, which can provide joule-scale, picosecond-duration laser pulses at multikilohertz repetition rates and high wall-plug efficiencies.

Meter-scale conditioned hydrodynamic optical-field-ionized plasma channels.

We demonstrate through experiments and numerical simulations that low-density, low-loss, meter-scale plasma channels can be generated by employing a conditioning laser pulse to ionize the neutral gas collar surrounding a hydrodynamic optical-field-ionized (HOFI) plasma channel. We use particle-in-cell simulations to show that the leading edge of the conditioning pulse ionizes the neutral gas collar to generate a deep, low-loss plasma channel which guides the bulk of the conditioning pulse itself as well as any subsequently injected pulses. In proof-of-principle experiments, we generate conditioned HOFI (CHOFI) waveguides with axial electron densities of n_{e0}≈1×10^{17}cm^{-3} and a matched spot size of 26µm. The power attenuation length of these CHOFI channels was calculated to be L_{att}=(21±3)m, more than two orders of magnitude longer than achieved by HOFI channels. Hydrodynamic and particle-in-cell simulations demonstrate that meter-scale CHOFI waveguides with attenuation lengths exceeding 1 m could be generated with a total laser pulse energy of only 1.2 J per meter of channel. The properties of CHOFI channels are ideally suited to many applications in high-intensity light-matter interactions, including multi-GeV plasma accelerator stages operating at high pulse repetition rates.

Clinical experience with non-penetrating vascular clips in free-flap reconstructions.

To date, the gold standard for performing a microvascular anastomosis has been the penetrating suture with attached needle. During the last two decades, non-penetrating techniques have been introduced, including the Unilink system for end-to-end anastomoses, and the VCS clip-applier system for both end-to-end and end-to-side anastomoses. The aim of this study was to compare the results of different techniques used to create microvascular anastomoses in free-flap reconstructions. Between January 1995 and October 1999, we performed 474 microvascular anastomoses in 216 consecutive free-tissue transfers. The anastomosis techniques included manual sutures (42%), Unilink rings (34%) and VCS clips (24%). Seven combined sutured-clipped anastomoses were excluded from further analysis. The mean anastomotic time when rings were applied was significantly shorter than when using clips (P 0.0001) or sutures (P 0.0001). Venous anastomoses using clips took less time than those using sutures (P 0.05). There were 19 anastomotic failures, all of which lead to early flap failure. Ten flaps were salvaged by early reoperation; nine flaps were lost. Three more flaps were lost as a result of other causes, bringing the flap survival rate down to 94.4%. Early flap failure was caused by failure of the arterial anastomosis in eight cases; all of them were sutured (these represented 5% of all arterial anastomoses with sutures). None of the clipped arterial anastomoses failed. Early flap failure was caused by failure of the venous anastomosis in 11 patients. Three of these anastomoses were sutured (representing 6% of all venous anastomoses with sutures), seven were anastomosed with rings (representing 5% of all venous anastomoses with rings) and one was clipped (representing 2% of all venous anastomoses with clips). Both the VCS clip-applier system and the Unilink system are easy to handle and allow fast microvascular anastomoses without intraluminal penetration. The patency rate of clipped vessels is at least as good as the patency rates of vessels anastomosed using sutures or rings.

Breathing obstruction in relation to craniofacial and dental arch morphology in 4-year-old children.

The prevalence of breathing obstruction was determined in a cohort of 4-year-old children. Craniofacial morphology was studied in obstructed children and compared with data from a control group of 4-year-old children with ideal occlusion. Dental arch morphology was compared in obstructed and non-obstructed children in the group. Parents of 95.5 per cent of the study base of 644 children answered a questionnaire concerning their child's nocturnal behaviour and related questions. The 48 children who, based on parental report, snored every night or stopped breathing when snoring (the 'snoring group'), showed a higher rate of disturbed sleep, mouth-breathing, and a history of throat infections as compared with the rest of the cohort. These children were examined by both an orthodontist and an otorhinolaryngologist and, when indicated, they were also monitored in a sleep laboratory. Twenty-eight of the children were diagnosed as having a breathing obstruction (4.3 per cent of the cohort) and six children (0.9 per cent) had sleep apnoea (mean apnoea-hypopnoea index of 17.3), using the same definition as that for adults. Cephalometric values among the obstructed children differed from those of a Swedish sample of the same age with ideal occlusion. Thy had a smaller cranial base angle and a lower ratio of posterior/anterior total face height. Small, but not significant differences were seen for NSL-ML and NL-ML. Compared with 48 asymptomatic children from the same cohort, the obstructed children had a narrower maxilla, a deeper palatal height, and a shorter lower dental arch. In addition, the prevalence of lateral crossbite was significantly higher among the obstructed children.

Classification, recording, and cleft palate surgery at the Uppsala Cleft Palate Centre.

This paper describes the classification system, method of recording, and surgical techniques used in Uppsala for children with isolated cleft palate. The classification is based on the system described by Kernahan and Stark and the more detailed system described by the American Cleft Palate Association. Separation of the hard palate into thirds, and into right and left sides, assures a detailed description of the cleft, and separates small morphological differences. The longitudinal registration system was introduced into the Uppsala Cleft Palate Centre in 1967. After the initial recording at the time of primary surgery, it is repeated at 5, 8, 11, 14, 17, and 20 years. By emphasising the therapeutic aspects of various stages of growth, it has been possible to limit the recording to once every third year. This has resulted in an important reduction in the dose of radiation without compromising the reliability of the results. Children born before 1975 had clefts of both the soft and hard palate closed at 18-24 months in a one-stage procedure. For children born in 1975 and later a two stage technique has been used, while clefts limited to the soft palate only have been closed entirely in the first operation. At first, the soft palate cleft was closed at 18 months of age and the hard palate at 4 to 5 years. The timing was changed in several steps to the present soft palate closure at 6 months and hard palate closure at 2 years of age.

Morphology of isolated cleft palate in children, including Robin sequence, treated with one or two-stage operations.

A classification developed at the Uppsala Cleft Palate Centre was used to describe isolated cleft palate in children with and without Robin sequence. The study included 109 patients born between 1968 and 1983 with isolated cleft palate. In 46 patients the cleft was closed in a single operation and 63 were treated by a two-stage procedure. Of the 109 patients 70 (64%) were girls. In 19 patients (17%), the cleft was limited to the soft palate. Ninety of the patients had clefts of the hard palate and in 39 (43%) of these patients the clefts involved less than a third of the hard palate. Only four children (4%) had total clefts of both the hard and soft palate. The Robin sequence was diagnosed in 14 children (13%), and it was more common in boys with isolated cleft palate (7/39; 18%) than in girls (7/70; 10%). In those with Robin sequence the cleft was U-shaped anteriorly in nine (64%), with great variations in width. Generally, however, the clefts were wider than other clefts involving the hard palate. In all cases, closure of the soft palate was followed by a spontaneous reduction in the width of the remaining cleft in the hard palate. The greatest improvement was noted in subjects with the U-shaped clefts, in whom the position of the tongue probably had the greatest influence on the development of wide primary clefts. In 10 subjects with clefts of the soft palate only and 12 patients in whom the cleft included part of the hard palate (35%), only the first operation of the two-stage procedure was done because there was no residual cleft. In these subjects the original cleft had involved less than a third of the length of the hard palate.

Dental abnormalities and ectopic eruption in patients with isolated cleft palate.

The aim of this study was to evaluate the influence of cleft size and surgical treatment on the development of permanent teeth in patients with isolated cleft palate. The series comprised 109 children with isolated cleft palate, 70 girls and 39 boys, including 14 patients with Robin sequence. The patients were grouped according to the sagittal extent of the palatal cleft, measured on dental casts obtained before the primary palate surgery. Forty-six children were treated by one-stage palatoplasty, and 63 in two stages. The dentition was studied on orthopantomograms taken at 5, 8, 11, and 14 years of age. Congenitally missing permanent teeth (third molars excluded) were found in 33 subjects (30%). Children with large clefts had significantly more missing teeth than children with small clefts. The tooth most usually missing was the mandibular second premolar, followed by the maxillary lateral incisor, and the upper second premolar. The incidence of dental malformation was 23%, mostly mild forms. Ectopic eruption of the upper first permanent molars was seen in 23 (45%) of the subjects with large clefts, and in 18 (31%) of those with small clefts. The surgical method did not significantly affect the direction of the eruption. There is a correlation between cleft size and hypodontia, dental deformity, and ectopic eruption. Children with Robin sequence had almost the same incidence of hypodontia, malformed teeth, and ectopic eruption as children with large clefts. There was no correlation between surgical method and ectopic eruption of the maxillary first permanent molars.

Reliability of radiological measurements of the distraction gap during leg lengthening.

PURPOSE: The aim of this study was to determine the accuracy of length measurements on plain radiographs during leg lengthening and to evaluate a reliable method of measuring the amount of lengthening suitable for clinical praxis. MATERIAL AND METHODS: In an experimental study, a plastic femur was lengthened 40 mm and assessed radiographically in different positions, and the orthoradiographically calculated total length of the femur was compared with the true value. In a clinical study, 96 radiographs encompassing 14 femoral and 2 tibial lengthenings were assessed on a digitized table with a computer program (PROFILE) with regard to the amount of lengthening and the degree of magnification. RESULTS: The radiographic magnification in the experimental study, depending on position of the femur, was 17% (5-25%), and in the clinical material it averaged 16% (0-36%). CONCLUSION: Radiographs obtained with a radiopaque ruler placed at the same level as the lengthened bone allowed reliable measurements of the distraction gap.

Transpedicular bone grafts misplaced into the spinal canal.

After open reduction of a burst fracture of L1, transpedicular bone grafting of the fractured vertebral body was performed. Bone grafts accidentally slipped into the spinal canal through the damaged medial wall of the pedicle. No adverse effects were noted clinically, but this case illustrates that transpedicular bone grafting is a potentially dangerous procedure. Computed tomography after 1 year showed complete resorption of the intraspinal bone grafts.

The influence of tonsillar obstruction and tonsillectomy on facial growth and dental arch morphology.

Children, who were tonsillectomized because of sleep apnea were examined with respect to facial growth and dental arch morphology. Dental casts and lateral roentgencephalograms were analysed before surgery and two years after tonsillectomy. The findings were compared to data from children without tonsillary obstruction. A higher proportion of malocclusion than normal, especially open bite and crossbite, was noticed before surgery. Two years after surgery, 77% of the open bites were normalised and 50-65% of the buccal and anterior crossbites. The best results were seen in children operated before the age of 6.

Closure of the cleft palate in one or two stages: the surgical methods.

The details of two consecutive groups of cleft palate patients treated with one- or two-stage palate repair are presented. The total number of patients is 237, with 128 operated in one stage, and 109 operated in two stages. In the two-stage group, the frequency of 'unintended' palatal fistulas decreased by 80%, and the use of blood transfusions was greatly reduced, but total operation time and hospital stay were longer. The results in terms of speech quality, facial growth and dental occlusion, will be reported on separately.

Computer data base for cleft lip and palate research.

This is a description of a comprehensive system for collection and storage of information about treatment and follow-up of cleft lip and palate (CLP) patients. The emphasis is on clinical research, including as much data as possible, and storing it according to the rules of the relational data base model to maintain flexibility. The information is derived from hospital records, clinical examinations, speech evaluations, and measurements of dental casts and cephalograms. In this complex setting, it is important to respect the rules of proper computer data base organization and implementation to insure the long-term correctness and integrity of stored data.

Repair of the triangular ligament in Colles' fracture. No effect in a prospective randomized study.

We present a prospective and randomized study of two different treatments of extraarticular Colles' fracture with a fractured ulnar styloid. The study comprised 41 patients with 2 years' follow-up; 22 patients were treated with closed manipulation and an above-the-elbow plaster cast, whereas in 19 patients the avulsed ulnar styloid was transfixed and/or the triangular ligament was repaired after closed reduction of the fractured radius. In all the operated on patients, a complete rupture of the triangular ligament was found. Good reduction of all the fractures was achieved primarily according to the radiographic examination. At follow-up the alignment had deteriorated, with no difference between the two treatment groups. Neither did the findings in the wrist arthrograms differ between the two groups nor did the subjective complaints of the patients. We conclude that repair of the ruptured triangular ligament in extraarticular fractures of the distal radius is not better than conventional treatment.

Database interface for digital calipers.

With emphasis on an advanced user interface this program was designed to collect measurements from digital sliding calipers and micrometers for subsequent inclusion into a database. The original project was measurements of dental casts, but the general nature of the program makes it adaptable to fields as diverse as medicine, archaeology and industrial quality control. The gain realized, compared to earlier manual methods, is a substantial reduction of the time spent on actual measuring, as the error-prone scale reading and handling of the results (writing down, entering, etc.) have been made superfluous. The CALIPER program runs on suitably equipped IBM personal computers while digital instruments, gauge blocks and multiplexer interface are supplied by Mitutoyo Co.

PROFILE: a user-configurable system for the measurements of angles and distances on pictures.

PROFILE is a user-configurable system to make series of predefined geometric measurements on various types of pictures. The primary use is for collecting data for statistical analysis. The computer-based method is much faster than manual measuring, effectively replacing the ruler and protractor traditionally used for this type of work with a digitizer. The results are available immediately as printed reports and as ASCII files which are easily imported by most database, spreadsheet and statistics programs for further study. The programs run on suitably equipped IBM and fully compatible personal computers.

Acral lentiginous malignant melanoma. Case report.

We present a case of a regressing acral lentiginous malignant melanoma of the sole with metastases en route and to regional lymph nodes. The histological findings at the primary site were classed as Clark's level I, stressing the difficulty in diagnosing this type of tumours early enough for effective treatment.

Oedema measurements in a standard burn model.

A highly standardized, reproducible burn model on rat hind paw as well as a method to measure oedema volume non-invasively is described. Along with a review of the literature on earlier methods to measure post-burn oedema we present a statistical evaluation of the present model with notes on its applicability in various experimental settings.

Early post-burn oedema in leucocyte-free rats.

A highly standardized, reproducible burn model on rat hind paws with objective measurement of oedema volume was used to study the post-burn oedema formation in leucocyte-free rats as compared to a matched group of normal rats. No difference in oedema volume could be detected during the first 4 h post-burn. Thus the mechanical effect of sticking leucocytes in the injured area or leucocyte derived substances do not seem to play any significant role in the early local oedema formation which we postulate is entirely mediated by local events.

The effect of prompt local cooling on oedema formation in scalded rat paws.

A standardized, reproducible burn model on rat paw was used and the effect of prompt local cooling on the oedema formation was measured using a newly developed non-invasive method. A transient reduction in oedema formation was observed lasting for a longer period of time with decreasing temperature down to 0 degrees C and increasing cooling time up to 120 min. The decrease in oedema formation was followed by an increase towards or above the amount of oedema in untreated scald injury. This post-cooling increase in oedema formation was related to the temperature and the exposure time of the cooling fluid. The immediate effects of cooling are most likely due to local restriction of the blood flow as a result of cold-induced vasoconstriction. The increase of the oedema formation after the cooling period may be due to reactive hyperaemia.