Single Molecule Study of Perylene Orange Photobleaching in Thin Sol−Gel Films

The paper reports on photobleaching mechanisms of perylene orange embedded in thin sol-gel films, derived from single molecule studies. The experimental configuration uses wide-field illumination and one photon excitation of the molecules. Measurements have been performed both at ambient conditions and under vacuum in order to get information on the influence of oxygen on photobleaching in such porous samples. We have also recorded the evolution of photobleaching with respect to the excitation intensity. The results demonstrate that photobleaching from excited states higher than the first singlet and triplet states has a nonnegligible contribution as soon as the excitation energy exceeds a few hundred W/cm2 and that this process is favored in the presence of air. The study also demonstrates that perylene orange in sol-gel films is not a very efficient emitter but that photobleaching can be slow, which explains the interest for perylene orange as a good candidate to produce long lifetime solid-state lasers when embedded in monoliths of sol-gel.

Omega- and Omega+ production in central Pb + Pb collisions at 40 and 158A GeV

Results are presented on Omega production in central Pb+Pb collisions at 40 and 158A GeV beam energy. For the first time in heavy ion reactions, rapidity distributions and total yields were measured for the sum Omega(-) + Omega(+) at 40A GeV and for Omega(-) and Omega(+) separately at 158A GeV. The yields are strongly underpredicted by the string-hadronic UrQMD model but agree better with predictions from hadron gas models.

Facteurs influençant la délivrance de substances perfusées à faible débit par seringue autopulsée : conséquences sur la perfusion de médicaments vasoactifs chez l'enfant prématuré

The infusion of vasoactive drugs in preterm babies using syringe pumps can be complicated by important variations in the infusion rate.

AIMS OF THE STUDY

1) to assess the time between pump start and the actual presence of a substance in the circulation, when using slow rates; 2) to evaluate the effects of changes in the main infusion rate on substance rates infused on the same line.

METHODS

We used 10% glucose to mimic vasoactive drugs. The main infusion consisted of saline, and both were infused on the same line using syringe pumps. Glucose concentration was measured at the end of the line.

RESULTS

The time between pump start and the actual infusion of glucose depended on syringe volume and on the adjustment of the syringe in the pump. There was a transient increase in glucose rate when the main rate increased, and a transient decrease when the main rate decreased.

CONCLUSION

To minimize the time before a substance is actually infused, one should use low volume syringes and correctly adjust the syringe in the pump. Moreover, when a steady infusion rate is necessary, one should avoid variations in the main infusion rate.

System-size dependence of strangeness production in nucleus-nucleus collisions at squareroot[sNN]=17.3 GeV

Emission of pi+/-, K+/-, phi, and Lambda was measured in near-central C+C and Si+Si collisions at 158 AGeV beam energy. Together with earlier data for p+p, S+S, and Pb+Pb, the system-size dependence of relative strangeness production in nucleus-nucleus collisions is obtained. Its fast rise and the saturation observed at about 60 participating nucleons can be understood as the onset of the formation of coherent systems of increasing size.

[Revision total knee arthroplasty after unicompartmental femorotibial prosthesis: 54 cases]

PURPOSE OF THE STUDY

We analyzed technical difficulties encountered when performing revision total knee arthroplasty in patients with unicompartmental femorotibial prostheses.

MATERIAL AND METHODS

This multicentric retrospective study included 54 revisions of unicompartmental femorotibial prosthesis with implantation of a total knee prosthesis. The series included 45 medial and nine lateral compartment prostheses. A gliding total knee prosthesis was implanted in 53 cases (98%) (39 standard, 14 revision). Mean time to failure of the unicompartmental prosthesis was four years. IKS scores were established at review. The radiological work-up included AP and lateral views in single leg stance and goniometry for 22 medial compartment revisions. Twenty-seven patients were seen for physical examination and x-rays and eight were lost to follow-up; data were recorded from medical files for 19 patients.

RESULTS

The revision procedure was considered easy in 82% of the cases. Mean follow-up after revision was four years (range 2 - 12 years). Subjective outcome was very satisfactory for 56% of the patients, satisfactory for 36% and unsatisfactory for 8%. The mean function score was 62 points, the mean knee score 85 points, and the mean flexion was 113 degrees. No laxity was found for 90% of the knees. The femorotibial angle was 180 +/- 2 degrees in 46% of the patients. The mechanical femoral angle was 90 degrees in 54% of the patients with 2-4 degrees varus in 42%. The mechanical tibial angle was 90 degrees in 46% of the patients with 2-8 degrees valgus in 37%. Complications included pulmonary embolism (n=2), mobilization under general anesthesia (n=3), arthrolysis (n=1), lateral vertical patellectomy (n=1), and secondary infection (n=1). There were five failures requiring changing the total knee prosthesis.

DISCUSSION

Loss of bone stock raises specific problems during revision of unicompartmental knee prostheses. Loss of tibial bone is more frequent but it is more difficult to correct for loss of femoral bone. A gliding knee prosthesis is generally preferred for first intention revision. We recommend a long stem when the bone defect is important or involves loss of cortical bone. We have had good mid-term results with revision total knee prostheses after unicompartmental prostheses. Longer follow-up is needed. Poor results were obtained when revision was performed for persistent pain without a clearly defined cause. The presence or not of significant bone loss did not appear to affect outcome. The observation of medial laxity in case of failed lateral unicompartmental prostheses suggests a more constrained total knee prosthesis might be indicated. Compared with earlier series, our results with total knee prostheses after unicompartmental prostheses appear to be better than after tibial valgus osteotomy and also better than after total knee arthroplasty. Conversely, they would be less satisfactory than for primary total knee arthroplasty. The surgical procedure for revision total knee arthroplasty after unicompartmental prosthesis requires precision and skill but is not technically difficult.

Résection d’un schwannome rétropéritonéal en sablier par abord combiné

BACKGROUND AND PURPOSE

We report a remarkable case of retroperitoneal schwannoma with significant spinal growth illustrating the effectiveness of a combined surgical approach.

METHODS

A 41-year-old man presented with a long history of back pain and unexplained weight loss. An abdominal mass was found in the right upper quadrant. The CT-scan revealed a partially cystic lesion located in the right psoas muscle. Spinal extension was noticed through the L1-L2 neural foramen. MRI better showed the wide rostro-caudal extension in the spinal canal.

RESULTS

Bilateral L1 and L2 laminectomy was performed to remove the spinal portion of the tumor. It was extradural but attached to the dura. The roots were not infiltrated. The retroperitoneal mass was removed by an anterior transperitoneal approach. The histological examination did not reveal criteria of malignancy.

CONCLUSIONS

Retroperitoneal schwannomas are rare and their preoperative diagnosis remains difficult. In case of significant spinal growth, a combined surgical exposure should be preferred to allow total removal of the lesion and control of the neurological structures.

Specific Raman signatures of a dimetallofullerene peapod

We report on the Raman spectroscopy of a dimetallofullerene peapod, (La(2)@C(80))(m)@SWNT. Drastic changes are observed with respect to pristine nanotubes. A sharp intense line at 142 cm(-1) is interpreted as a signature of polymerization of the encapsulated metallofullerenes. Additional strong signatures appear at about 400, 520, and 640 cm(-1), respectively. Their intensity suggests the existence of an enhancement effect. The stiffening and the up-shift of the G-band modes appear to imply that a charge transfer process between the nanotube and the peas occurs.

[Evolution of medical practice in the care of anemia amd the use of erythropoietin in chronic renal insufficiency hemodialysis in the past six years]

In order to analyze changes in anemia management in the hemodialysis patients, a retrospective survey was performed in 1999 on a representative French sample of patients in hemodialysis treated by EPO since 1992, 1994, 1996, and 1998 respectively. 368 patients were enrolled in 97 centres. At treatment initiation, some patients characteristics have significantly changed: the percentage of type 2 diabetic patients has increased marquedly from 4.5% in 1992 to 22.1% in 1998. The mean time lag between dialysis and EPO treatment initiation has decreased from 3.3 years to 0.9 on the 6-year period. Lastly, the mean hemoglobin level has increased from 73.7 to 78.5 g/l. No significant evolution in the EPO protocol was observed at the initiation as well as in the maintenance phase. An average percentage of 33.7% of patients were treated in i.v. route at initiation with a mean posology of 105.2 IU/kg (respectively 91.4 in s.c.). In the first year of follow-up, the overall mean posology was 84 IU/kg. In conclusion, this survey suggests that anemia management has been optimized over the last 6 years follow-up, including an earlier initiation of EPO treatment and a higher target of hemoglobin while EPO needs were reduced in the same time.