343 research outputs found
Bank liquidity management through the issuance of bonds in the aftermath of the global financial crisis
Next to deposits, European banks have historically largely used bank obligations such as covered bonds (CB). Their US counterparties, on the contrary, heavily rely on securitization to fund mortgages. We assess how banks’ liquidity and funding position during and after the Global Financial Crisis (GFC) affects the decision to issue (private label) mortgage backed securities (MBS), covered bonds or senior unsecured bonds. Since the decisions to issue either instrument are not necessarily independent from each other, we estimate conditional probit and tobit models in order to account for the simultaneous nature of the issuances. We see that neither instrument plays any role in liquidity management during the GFC. In the post-GFC period, banks reach out to issuing MBS when facing short-term illiquidity. Banks could issue MBS as a way to comply with Basel III liquidity regulations. In turn, a bank’s decision to issue CB is not affected by bank’s liquidity and liquidity management occurs instead through managing the amount of CB. The issuance of SUB is also not affected by liquidity. Overall, the paper shows that only MBS have actively been issued as a response to liquidity shortages of banks’ balance sheets and shows that MBS and CB which often are seen as alternative instruments serve different purposes
Trends in the Management and Outcomes of Kidney Transplantation for Autosomal Dominant Polycystic Kidney Disease
Background. Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic disorder leading to end-stage renal failure. The objective of this study was to evaluate a longitudinal experience of kidney transplantation for ADPKD. Methods. A single center retrospective review of patients undergoing kidney transplantation was conducted, with comparisons across two time periods: early (02/2000–04/2007, n = 66) and late (04/2007–08/2012, n = 67). Results. Over the 13.5-year study period, 133 patients underwent transplantation for ADPKD. Overall, no significant difference between the early and late group with regard to intraoperative complications, need for reoperation, readmissions within 30 days, delayed graft function, and mortality was noted. There was a trend towards increase in one-year graft survival (early 93.1% versus late 100%, P = 0.05). In the early group, 67% of recipients had undergone aneurysm screening, compared to 91% of recipients in the late group (P < 0.001). Conclusions. This study demonstrates consistent clinical care with a trend towards improved rates of one-year graft survival. Interestingly, we also note a significantly higher use of cerebral imaging over time, with the majority that were detected requiring surgical intervention which may justify the current practice of nonselective radiological screening until improved screening criteria are developed
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Live Donor Partial Hepatectomy for Liver Transplantation: Is There a Learning Curve?
Background: Donor safety is the first priority in living donor liver transplantation (LDLT). Objective: To determine the characteristics and outcome of live liver donors who underwent donor hepatectomy from January, 1997 to May, 2007 at Massachusetts General Hospital. Methods: 30 patients underwent LDLT between January, 1997 and May, 2007 at our institution. Results: The type of graft was the right lobe (segments 5-8) in 14, left lobe (segments 2-4) in 4, and left lateral sector (segments 2 and 3) in 12 patients. The mean donor age was 36 (range: 26-57) years. The mean follow-up was 48 (range: 18-120) months. No deaths occurred. Overall, 8 (26.6%) patients experienced a total of 14 post-operative complications. Donor complications based on graft type were as follows: left lateral sector (16.7%), left lobe (25%), and right lobe (35.7%). The experience was divided into two periods 1997-2001 (n=15) and 2002-2007 (n=15). Overall complications during 2 periods were 40% and 13.3%, respectively (p<0.001). The incidence of grade III complication also significantly decreased; 66.7% vs 33.3% (p<0.01). Conclusion: Partial hepatectomy in living donors has a learning curve which appears to be approximately 15 cases. This learning curve is not restricted to the surgeons performing the procedure but involves all aspects of patient care
Transfection of Sertoli cells with androgen receptor alters gene expression without androgen stimulation
Background: Androgens play an important role for the development of male fertility and gained interest as growth and survival factors for certain types of cancer. Androgens act via the androgen receptor (AR/Ar), which is involved in various cell biological processes such as sex differentiation. To study the functional mechanisms of androgen action, cell culture systems and AR-transfected cell lines are needed. Transfection of AR into cell lines and subsequent gene expression analysis after androgen treatment is well established to investigate the molecular biology of target cells. However, it remains unclear how the transfection with AR itself can modulate the gene expression even without androgen stimulation. Therefore, we transfected Ar-deficient rat Sertoli cells 93RS2 by electroporation using a full length human AR.
Results: Transfection success was confirmed by Western Blotting, immunofluorescence and RT-PCR. AR transfection-related gene expression alterations were detected with microarray-based genome-wide expression profiling of transfected and non-transfected 93RS2 cells without androgen stimulation. Microarray analysis revealed 672 differentially regulated genes with 200 up- and 472 down-regulated genes. These genes could be assigned to four major biological categories (development, hormone response, immune response and metabolism). Microarray results were confirmed by quantitative RT-PCR analysis for 22 candidate genes.
Conclusion: We conclude from our data, that the transfection of Ar-deficient Sertoli cells with AR has a measurable effect on gene expression even without androgen stimulation and cause Sertoli cell damage. Studies using AR-transfected cells, subsequently stimulated, should consider alterations in AR-dependent gene expression as off-target effects of the AR transfection itself
Narrow-band injection seeding of a terahertz frequency quantum cascade laser: Selection and suppression of longitudinal modes
A periodically poled lithium niobate (PPLN) crystal with multiple poling periods is used to generate tunable narrow-bandwidth THz pulses for injection seeding a quantum cascade laser (QCL). We demonstrate that longitudinal modes of the quantum cascade laser close to the gain maximum can be selected or suppressed according to the seed spectrum. The QCL emission spectra obtained by electro-optic sampling from the quantum cascade laser, in the most favorable case, shows high selectivity and amplification of the longitudinal modes that overlap the frequency of the narrow-band seed. Proper selection of the narrow-band THz seed from the PPLN crystal discretely tunes the longitudinal mode emission of the quantum cascade laser. Moreover, the THz wave build-up within the laser cavity is studied as a function of the round-trip time. When the seed frequency is outside the maximum of the gain spectrum the laser emission shifts to the preferential longitudinal mode
Selection of longitudinal modes in a terahertz quantum cascade laser via narrow-band injection seeding
A terahertz quantum cascade laser is injection seeded with narrow-band seed pulses generated from a periodically poled lithium niobate crystal. The spectral emission of the quantum cascade laser is controlled by the seed spectra
Investigation of time-resolved gain dynamics in an injection seeded terahertz quantum cascade laser
The evolution of the gain of terahertz quantum cascade laser during injection seeding is probed as a function of time. Oscillations of the gain are commensurate with the variations of the field envelope
Observation of Time-resolved Gain Dynamics in a Terahertz Quantum Cascade Laser
The dynamic response of a terahertz quantum cascade laser is probed as a function of time. The gain of the THz QCL is saturated by injection seeding the laser with an initial THz seed pulse. The time-resolved gain of the injection seeded laser is then probed with a second THz pulse
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Induction with Rabbit Antithymocyte Globulin following Orthotopic Liver Transplantation for Hepatitis C
Background: Hepatitis C (HCV) is the most common indication for liver transplantation in the US. Objective: Since steroids are the major stimulus of viral replication, we postulated that steroid-free immunosuppression might be a safer approach. Methods: From January 1995 to October 2002, we used steroid plus calcineurin inhibitor (CNI) immunosuppression after liver transplantation for HCV (steroid group, n=81). From October 2002 to June 2007, rabbit antithymocyte globulin (RATG) induction, followed by CNI and azathioprine (RATG group, n=73) was utilized. Results: There were no differences in 1- and 3-year patient/allograft survival rates. The incidence of acute rejection rate (19% vs. 28%), of biopsy-proven HCV recurrence (70% vs. 75%), and chronic rejection (6% vs. 9%) were comparable. The mean time to develop recurrent HCV was significantly longer in the RATG group (16.2 vs. 9.2 months, p=0.008). The incidence of severe portal fibrosis appears to be lower in RATG group compared to the steroid group; 14% vs. 4% (p=0.07). Conclusions: RATG induction is safe and effective after liver transplantation for HCV, but has no impact on the incidence of HCV recurrence and patient/allograft survival. However, a significant delay in time to HCV recurrence and a trend toward less rejection and portal fibrosis was observed
Metal-Metal Terahertz Quantum Cascade Laser with Hybrid Mode Section
A hybrid mode section is integrated into the end of the metal-metal (MM) waveguide of a terahertz (THz) frequency quantum cascade laser (QCL) by removing sub-wavelength portions of the top metal layer. This allows a hybrid mode to penetrate into the air, which reduces the effective index of the mode and improves the out-coupling performance at the facet. The transmission of the processed metal-metal hybrid section (MMHS) waveguide is further increased by ensuring its length fulfills the criterion for constructive interference. These simple modifications to a 2.5 THz MM QCL waveguide result in a significant increase in the output emission power. In addition, simulations show that further improvements in out-coupling efficiency can be achieved for lower frequencies with effective refractive indices close to the geometric mean of the indices of the MM waveguide and air
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