Conservative management of significant epidural haematomas in children

Objective: A significant epidural haematoma (EDH) is generally treated by craniotomy and evacuation. This is a report of conservative management following an EDH on computerized tomography (CT) in a paediatric population. The authors examined whether conservative treatment of radiologically significant EDH is a successful and safe therapeutic option. Methods: Retrospective data were collected from charts of patients with conservatively treated EDH in the Department of Surgery of the University Children's Hospital Zurich between September 1993 and January 2004. Included were patients without focal neurological deficits, with a Glasgow Coma Scale (GCS) of 15 and an initial CT demonstrating an EDH with a minimal thickness of 1cm. Mild clinical symptoms of raised intracranial pressure such as headache, nausea or vomiting were treated symptomatically. Follow-up included a standardized interview, a neuropaediatric examination and CT. Results: Thirteen children with EDH had successful conservative management. Only one 12-year-old female patient with a delayed diagnosed frontal EDH required surgical intervention 24h after admission and 5 days after the accident. Clinical follow-up showed patients without neurological deficits, a Glasgow Outcome Scale of 5 and no post-traumatic sequelae over an average of 4 4/12 years (range 4 months to 10 4/12 years). Follow-up CT showed complete resolution of the EDH within 2 to 3 months. Conclusions: Our results demonstrate that significant EDH can be treated non-operatively in neurologically normal children. We recommend that such treatment be performed in specialised paediatric centres under adequate neurological observation since prompt emergency operation in case of neurological deterioration should be provide

Lack of benefit of preoperative antimicrobial prophylaxis in children with acute appendicitis: a prospective cohort study

Background: Preoperative antimicrobial prophylaxis is widely used in pediatric patients undergoing appendectomy, but evidence showing a reduction of postoperative infectious complications is lacking. Methods: A prospective consecutive cohort study on changing from preoperative antimicrobial prophylaxis to no prophylaxis in children undergoing urgent appendectomy was undertaken. The impact of this change in management on postoperative infectious complications was evaluated by comparing the outcome in 100 patients receiving (group A) and a subsequent 100 patients not receiving prophylaxis (group B), which consisted of a preoperative single dose of intravenous metronidazole (10mg/kg body weight). Results: Histology confirmed acute appendicitis in 92 patients of group A and 95 patients of group B. In patients with histological simple appendicitis, postoperative infectious complications were noted in 2 (3.0%) of 69 patients from group A and in none of 70 patients from group B, and in patients with histological perforated appendicitis in 5 (22%) of 23 and 4 (16%) of 25 patients from groups A and B, respectively. Postoperative infectious complications were more frequent (p<0.05) in perforated than in simple appendicitis. These infectious complications included in simple appendicitis two wound infections in group A, and in perforated appendicitis four intraabdominal abscesses and one wound infection in group A and two intraabdominal abscesses and two wound infections in group B. Conclusion: Postoperative infectious complications were seen more often in patients with perforated appendicitis than in those with simple appendicitis. Preoperative antimicrobial prophylaxis with metronidazole did not reduce the rates of postoperative infectious complication

A Combined Statistical and TCAD Model as a Method for Understanding and Reducing Variations in Multicrystalline Si Solar Cell Production

AbstractMonitoring the I-V parameters in mass production yields a distribution that cannot be understood in a simple manner. For example, if Voc varies greatly, it is not obvious whether this is mainly due to variations in the bulk lifetime or in the surface passivation or due to other sources.In this work, we develop a method where statistics is combined with numerical device modeling to obtain a physical interpretation of the observed variations. In the first part, we derive a multivariate statistical model to extract the main influences of fabrication fluctuations on the I-V parameters. This statistical model is based on cell parameters measured on a representative sample of solar cells from production. In the second part, we develop a computer-aided design (TCAD) device simulation model for multicrystalline Si solar cells. This TCAD model quantifies the I-V variations on a physically sound basis. However, the number of simulations is grossly reduced by feeding in solely the main influences obtained from the statistical model. In the third part, we verify this method by comparing the calculated distribution with production data.This model is used for optimization strategies for higher cell efficiency, smaller variations in cell parameters and improved yield in mass production. Furthermore, we will apply our methodology to advanced cell concepts. It will allow the early consideration of production fluctuation in device simulation of advanced cell concepts, and therefore a realistic assessment of such concepts

Medial clavicular epiphysiolysis in children: the so-called sterno-clavicular dislocation

We retrospectively reviewed six pediatric cases of medial clavicular injury, i.e., epiphyseal separation (Salter/Harris type I or II injury), diagnosed between 1993 and 1997. The clavicular metaphysis was displaced posteriorly in three cases and anteriorly in three. On conventional radiographic views the diagnosis was initially missed in two of three retrosternal dislocations. A special X-ray projection (described by Heinig) or computed tomography (CT) permitted correct diagnosis. Anterior dislocations were immediately and correctly diagnosed. Closed reduction successfully treated retrosternal displacement in two of the three patients. The third patient needed open reduction and internal fixation. Open reduction and internal fixation had to be performed in all three patients with anterior displacement. Follow-up assessment showed perfect functional results in all cases. Direct visualization during open reduction, which was necessary in four of six cases, yielded clear evidence that the so-called sternoclavicular dislocation in children and young adults is, in fact, a fracture of the medial growth plate with posterior or anterior displacement of the metaphysi

Pitfalls of lateral external fixation for supracondylar humeral fractures in children

Introduction: Closed reduction and percutaneous pinning is a standard treatment for dislocated supracondylar humeral fractures in children. However, the management of these fractures remains challenging. The aim of this study was to evaluate lateral external fixation as a treatment alternative for these fractures. Materials and methods: All supracondylar fractures treated with lateral external fixation between 2005 and 2007 were evaluated retrospectively. Long-term outcome was assessed with regards to carrying angle, malalignment, and motion. Results: Twenty-eight patients with Gartland type III fractures and one with a Y-type fracture were included in the study (mean age 6.5years). Cosmetic results were excellent in 88%, good in 8%, and fair in one patient. Functional results were excellent in 83%, good in 10%, and fair in 7%. However, 3 patients (10%) showed complete radial palsy postoperatively. In all of these patients, high insertion of the proximal pin (2.9-3.6cm above the fracture) was noted. On revision, one superficial lesion and one total transection of the nerve at the level of the proximal pin was detected. One patient showed no macroscopic damage. The transected nerve was reconstructed using an autograft, and all patients completely recovered within 2-6months. Conclusion: Lateral external fixation is an alternative method for the treatment of displaced or unstable supracondylar fractures in children, facilitating reduction and improving fracture stability. However, iatrogenic radial nerve injury is a risk, and we therefore strongly recommend inserting the proximal pin under direct vision within 2cm from the fracture line using a drill sleev

Optimized stencil print for low Ag paste consumption and high conversion efficiencies

We evaluate industrial-type PERC solar cells applying a dual printed front grid with stencil printed Ag fingers. We vary the Ag paste consumption for the finger print between 8.4 mg and 120.4 mg per 156 x 156 mm(2) wafer (weighted after printing before drying) by using polyurethane squeegees with different shore hardness as well as a metal squeegee and by varying the printing pressure to obtain different finger heights. The busbar consumes additional 19.5 mg Ag paste. We obtain average finger heights from 5.9 mu m up to 24.3 mu m for 55 mu m to 65 mu m wide fingers. The resulting PERC solar cells show an average efficiency of 20.2% for finger paste consumptions above 60 mg. In contrast, a strong reduction of the conversion efficiency with less than 60 mg finger paste consumption is observed since the increased series resistance reduces the FF. By analytical modelling, we compare the calculated series resistance to the experimental data and observe a good accordance for more than 40 mg finger paste consumption whereas the experimental series resistance slightly exceed the modelled values below 40 mg. In addition, we use numerical simulations to investigate the series resistance dependence on the finger height which shows higher experimental values for finger height below 10 mu m. The deviation of the measured series resistance and the two modelled cases is mostly due to inhomogeneous distribution of finger height profiles and finger interruptions on the solar cells with front finger paste consumption of less than 40 mg. For finger paste consumption below 60 mg, we find that also the specific contact resistance increases. A physical model of the root cause for this dependence still has to be found

Leaf-associated macroinvertebrate assemblage and leaf litter breakdown in headwater streams depend on local riparian vegetation

Headwater streams harbor diverse macroinvertebrate communities and are hotspots for leaf litter breakdown. The process of leaf litter breakdown mediated by macroinvertebrates forms an important link between terrestrial and aquatic ecosystems. Yet, how the vegetation type in the local riparian zone influences leaf-associated macroinvertebrate assemblages and leaf litter breakdown rates is still not resolved. We investigated how leaf-associated macroinvertebrate assemblages and leaf litter fragmentation rates differ between forested and non-forested sites using experimental leaf litter bags in sixteen sites paired across eight headwater streams in Switzerland. Our results show that sensitive taxa of the invertebrate orders Ephemeroptera, Plecoptera and Trichoptera (EPT) and the functional group of shredders were strongly associated with forested sites with overall higher values of abundance, diversity, and biomass of EPTs in forested compared to non-forested sites. However, the importance of riparian vegetation differed between study regions, especially for shredders. Fragmentation rates, which are primarily the result of macroinvertebrate shredding, were on average three times higher in forested compared to non-forested sites. Our results demonstrate that not only the composition of the aquatic fauna but also the functioning of an essential ecosystem process depend on the vegetation type in the local riparian zone

Advances in the Surface Passivation of Silicon Solar Cells

AbstractThe surface passivation properties of aluminium oxide (Al2O3) on crystalline Si are compared with the traditional passivation system of silicon nitride (SiNx). It is shown that Al2O3 has fundamental advantages over SiNx when applied to the rear of p-type silicon solar cells as well as to the p+ emitter of n-type silicon solar cells. Special emphasis is paid to the transfer of Al2O3 into industrial solar cell production. We compare different Al2O3 deposition techniques suitable for mass production such as ultrafast spatial atomic layer deposition, inline plasma-enhanced chemical vapour deposition and reactive sputtering. Finally, we review the most recent cell results with Al2O3 passivation and give a brief outlook on the future prospects of Al2O3 in silicon solar cell production

Solar cell emitter design with PV-tailored implantation

A potentially cost-effective ion implanter for solar cells has become commercially available very recently. As the emitter dopant profiles differ from the standard diffusions, a combination of process simulation and device simulation is used to predict possible applications as front emitter. The simulations show that ion energies of 10 to 30 keV and doses in the range of 5×1014 to 7×1015 cm-2 are sufficient for reducing the phosphorus peak density and, hence, obtaining cell efficiency levels above 20%, if appropriate surface passivation and wafer materials are used. The simulations strongly indicate, however, that cell efficiency improves only marginally if the cell has a fully metallized rear Al-BSF and a boron-doped Cz base in the degraded state. Simulated cells with a local rear Al-BSF show an efficiency improvement of more than 0.3% absolute in the degraded state

Loss analysis and improvements of industrially fabricated Cz-Si solar cells by means of process and device simulations

We model currently fabricated industrial-type screen-printed boron-doped Cz silicon solar cells using a combination of process and device simulations. The model reproduces the experimental results precisely and allows us to predict both the efficiency gain after specific cell improvements and the associated thermal budgets. Separating the resistive losses (evaluated for various contributions) from the recombination losses (evaluated in different device regions) allows us to forecast the improvements of the emitter and the rear side necessary such that the recombination losses in the base dominate. We predict that to increase cell efficiency considerably beyond 19.7 %, the base material needs to be improved