Littérature scientifique sur le sujet « 941.06/2 »

AbstractC22H27NO4, triclinic, P1̅ (no. 2), a = 7.468(3) Å, b = 9.442(3) Å, c = 14.134(5) Å, α = 82.725(5)°, β = 84.077(5)°, γ = 72.585(5)°, V = 941.0(5) Å3, Z = 2, Rgt(F) = 0.0727, wRref(F2) = 0.1796, T = 296(2) K.

Background Patients with transfusion-dependent thalassemia (TDT) require red blood cell (RBC) transfusions as frequently as every 2-4 weeks to maintain a pre-transfusion hemoglobin of 9.0-10.5 g/dL for patients without cardiac complications. Chronic RBC transfusions increase body iron stores leading to iron deposition in liver, pancreatic, and cardiac tissues. Deferoxamine, deferiprone, and deferasirox are the iron chelators currently licensed for clinical use to manage iron overload in TDT patients with side effects ranging from nausea to nephrotoxicity and hearing loss. RBC exchange transfusion (RBCX), particularly in conjunction with isovolumic hemodilution, has been utilized for patients with sickle cell disease as a means of stabilizing iron overload. The 2015 ASFA Red Blood Cell Exchange consensus supports RBCX to reduce or prevent iron overload in sickle cell disease. Review of literature shows that RBCX can be beneficial as an acute intervention for patients with TDT and pulmonary hypertension however there is a paucity of literature documenting chronic RBCX use in TDT patients with iron overload. Case series This series presents five patients with TDT who were transitioned from chronic simple RBC transfusions to chronic RBCX after developing treatment-refractory iron overload as evidenced by serum ferritin elevation. Patients were treated on a transfusion schedule with a pre-transfusion goal hemoglobin of 9.5g/dL or higher and interval 4-6 weeks. Patient A is a 14 year-old male who developed significant iron overload (peak ferritin of 7077) on deferasirox 20 mg/kg/day and MRI T2 imaging suggestive of iron deposition. After transition to RBCX, ferritin decreased significantly with a post-RBCX mean of 1382. Blood utilization was 4200 ml three months pre-RBCX and 5625 ml three months post-RBCX. Patient B is a 23 year-old male with a peak ferritin of 1310 prior to RBCX on 23 mg/kg/day of deferasirox complicated by mild hearing loss. Serum ferritin has shown stabilization, with a mean post-RBCX ferritin of 880. Blood utilization was 2400 ml three months pre-RBCX and 8100 ml three months post-RBCX. Patient C is a 17 year-old male with a peak ferritin of 1400 with deferasirox management complicated by acute renal injury. Mean serum ferritin of 633 post-RBCX. Blood utilization was 1200 ml three months pre-RBCX and 5200 ml three months post-RBCX. Patient D is a 17 year-old male managed on 23 mg/kg/day of deferasirox with a peak ferritin of 3060 on pre-RBCX. The patient transitioned to chronic RBCX with mean serum ferritin of 1073. Blood utilization was 1800 ml three months pre-RBCX and 7700 ml three months post-RBCX. Patient E is a 17 year-old male with peak ferritin of 3404 despite 20 mg/kg/day of deferasirox prior to chronic RBCX. Mean serum ferritin after transition to RBCX was found to be 1282. Blood utilization was 1500 ml three months pre-RBCX and 4900 ml three months post-RBCX. All 5 patients have tolerated RBC exchange procedures without complications. Serum ferritin levels pre- and post-RBC exchange were trended pre- and post- RBCX (Figure 1). Serum ferritins were averaged together for each patient to obtain an equal number of time points considered prior to and after starting RBCX therapy. Descriptive statistics (Table 1) were used to summarize average ferritin levels for the patient group. A Wilcoxon signed-rank test was performed to assess the median difference in ferritin level from pre-RBCX to post-RBCX. All analyses were conducted in SAS version 9.4. P <0.05 is considered statistically significant. Median pre-RBCX ferritin level for the study group is 2489.3 (Inter-quartile range (IQR): 1190.0, 2659.0). The median post-RBCX ferritin level for the series is 1329.3 (IQR: 941.0, 1711.0). After subtracting the post-RBCX ferritin level from the pre-RBCX ferritin level, the median change for the group is 457 (IQR: 249.0, 1160.0) (p=0.06). Conclusion This case series documents the successful clinical application of chronic RBCX in TDT patients as a means of stabilizing serum ferritin levels over time. Mean ferritin levels were significantly lower, clinically, after transitioning from chronic simple RBC transfusion to RBCX (Table 1), though analysis is limited due to cohort size. Blood utilization increased after transitioning to RBCX. Next steps in evaluating our practice for the patient group will be to evaluate iron deposition status with MRI T2* imaging.

Abstract C23H25FN2O, triclinic, P 1 ‾ $P\overline{1}$ (no. 2), a = 6.5011(2) Å, b = 11.2794(4) Å, c = 14.0796(6) Å, α = 110.246(4)°, β = 97.236(3)°, γ = 98.335(2)°, V = 941.01(6) Å3, Z = 2, Rgt (F) = 0.0476, wRref (F 2) = 0.1366, T = 293 K.

Sulfur hexafluoride (SF_６) is a greenhouse gas of very long lifetime. Its infrared absorption spectrum is very important for modeling the atmospheric radiation balances. SF_６ is also a prototypical system for studying the principles and techniques of laser isotope separation using powerful infrared lasers. As a very heavy molecule, the infrared spectrum of SF_６ at room temperature is very dense, which poses a great challenge for monitoring the relative abundances of different SF_６ isotopomers by direct absorption spectroscopy. Supersonic jet expansions have been used widely to simplify gas phase molecular spectra. In this work, astigmatic multi-pass absorption cell and distributed feed-back quantum cascade lasers (QCLs) are used to measure jet-cooled rovibrational absorption spectrum of ³²SF_６ and ³³SF_６ at 10.6 μm. The spectrometer works in a segmented rapid-scan mode. The gas mixtures (SF₆:Ar:He = 0.12:1:100) are expanded through a 80 mm×300 μm pulsed slit nozzle. Two QCLs running at room temperature are used and each one covers a spectral range of about 3.0 cm^-1. The <i>v</i>₃ fundamental bands of both ³²SF_６ and ³³SF_６ are observed. The rotational temperature of ³²SF_６ and ³³SF_６ in the ground state in the supersonic jet is estimated to be about 10 K and the linewidth is about 0.0008 cm^-1 by comparing the simulated and observed spectrum with the PGOPHER program. A new weak vibrational band centered around 941.0 cm^-1 is observed and tentatively assigned to the <i>v</i>₁+<i>v</i>₂+<i>v</i>₃-(<i>v</i>₁+<i>v</i>₂)hot band of ³²SF_６. The effective Hamiltonian used to analyze the rovibrational spectrum of SF_６ is briefly introduced. A simplified rotational analysis for this hot band is performed with the XTDS program developed by the Dijon group. The band-origin of this hot band is determined to be 941.1785(21) cm^-1. The rotational temperature of this hot band is estimated to be about 50 K. A new scheme by measuring the jet-cooled absorption spectrum of this hot band of ³²SF₆ and the <i>v</i>₃ fundamental band of ³³SF_６ is proposed for measuring the relative abundance of ³³SF_６／³²SF_６.