Effect of the cap layer growth temperature on the Sb distribution in InAs/InSb/InAs sub-monolayer heterostructures for mid-infrared devices.

Sub-monolayer (SML) deposition of InSb within InAs matrix by migration enhanced epitaxy tends to form type II SML nanostructures offering efficient light emission within the mid-infrared (MIR) range between 3 and 5 µm. In this work, we report on the Sb distribution in InSb/InAs SML nanostructures with InAs cap layers grown at temperatures lower than that associated with the under-grown InSb active layer. Analysis by transmission electron microscopy (TEM) in 002 dark field conditions shows that the reduction in the growth temperature of the InAs cap layer increases the amount of Sb deposited in the layers, in good agreement with the x-ray diffraction results. TEM micrographs also show that the layers are formed by random InSbAs agglomerates, where the lower cap temperature leads to a more continuous InSb layer. Quantitative atomic column resolved high angle annular dark field-scanning (S)TEM analyses also reveal atomic columns with larger composition of Sb for the structure with the lowest InAs cap layer temperature. The dependence of the Sb distribution on InAs cap growth temperature allows tuning the corresponding emission wavelength in the MIR range, as shown by the photoluminescence emission spectra.

Use of Peritoneovenous Shunt for the Management of Refractory Ascites.

BACKGROUND: Guidelines for the management of refractory ascites (RA) recommend transjugular intrahepatic portosystemic shunting (TIPS), diuretics, and paracentesis as the main strategies, discouraging use of surgical peritoneovenous shunts (PVSs). However, PVSs, including both Denver (DS) or saphenoperitoneal (SPS) modalities, may still have indications. Herein we report our experience with PVSs in the context of modern surgical and anesthetic management. METHODS: In our unit, PVSs are offered to patients with ascites refractory to diuretics in which TIPS are contraindicated. Heart function and spontaneous bacterial peritonitis must be assessed before surgical indication. RESULTS: Seven procedures were performed on 5 patients (6-DS, 1-SPS) in 2013. Their mean age was 61 (range, 54-68) years. In 3 patients, the indication was RA without options for liver transplant; 2 patients were on the waiting list for liver transplantation, which were performed to improve renal function and quality of life (QOL). The median hospital stay was 6.5 (range, 3-12) days. All patients were alive after 12 months. One patient died 2 years after the first DS and another later died due to liver insufficiency with patency of the DS. The ascites was well-controlled in 4 of 5 patients at up to 48 months of follow-up. Decreases in diuretics doses, proper weight maintenance, and a dramatic improvement in QOL (measured by a modified Ascites Symptom Inventory-7 [ASI-7] test) were observed after the procedures. CONCLUSION: PVSs are useful for the treatment of patients with RA who develop resistance to common therapies, leading to a major improvement in QOL. These surgical procedures should be included in the armamentarium of experienced liver surgeons.

Reduction of Thermal Conductivity in Nanowires by Combined Engineering of Crystal Phase and Isotope Disorder.

Nanowires are a versatile platform to investigate and harness phonon and thermal transport phenomena in nanoscale systems. With this perspective, we demonstrate herein the use of crystal phase and mass disorder as effective degrees of freedom to manipulate the behavior of phonons and control the flow of local heat in silicon nanowires. The investigated nanowires consist of isotopically pure and isotopically mixed nanowires bearing either a pure diamond cubic or a cubic-rhombohedral polytypic crystal phase. The nanowires with tailor-made isotopic compositions were grown using isotopically enriched silane precursors 28SiH4, 29SiH4, and 30SiH4 with purities better than 99.9%. The analysis of polytypic nanowires revealed ordered and modulated inclusions of lamellar rhombohedral silicon phases toward the center in otherwise diamond-cubic lattice with negligible interphase biaxial strain. Raman nanothermometry was employed to investigate the rate at which the local temperature of single suspended nanowires evolves in response to locally generated heat. Our analysis shows that the lattice thermal conductivity in nanowires can be tuned over a broad range by combining the effects of isotope disorder and the nature and degree of polytypism on phonon scattering. We found that the thermal conductivity can be reduced by up to ∼40% relative to that of isotopically pure nanowires, with the lowest value being recorded for the rhombohedral phase in isotopically mixed 28Si x30Si1- x nanowires with composition close to the highest mass disorder ( x ∼ 0.5). These results shed new light on the fundamentals of nanoscale thermal transport and lay the groundwork to design innovative phononic devices.

Towards defect-free 1-D GaAs/AlGaAs heterostructures based on GaAs nanomembranes.

We demonstrate the growth of defect-free zinc-blende GaAs nanomembranes by molecular beam epitaxy. Our growth studies indicate a strong impact of As4 re-emission and shadowing in the growth rate of the structures. The highest aspect ratio structures are obtained for pitches around 0.7-1 µm and a gallium rate of 1 Å s(-1). The functionality of the membranes is further illustrated by the growth of quantum heterostructures (such as quantum wells) and the characterization of their optical properties at the nanoscale. This proves the potential of nanoscale membranes for optoelectronic applications.

Optimizing the management of patients with BCLC stage-B hepatocellular carcinoma: Modern surgical resection as a feasible alternative to transarterial chemoemolization.

OBJECTIVE: To analyse the impact of liver resection (LR) in patients with Hepatocellular Carcinoma (HCC) within the Barcelona-Clinic-Liver-Cancer (BCLC)-B stage. METHODS: Analysis of patients with BCLC-B HCC treated with LR or transarterial chemoembolization (TACE) between 2007 and 2012 in our hospital. Survival/recurrence analyses were performed by log-rank tests and Cox multivariate models. Further analyses were specifically obtained for the HCC subclassification (B1-2-3-4) proposed recently. RESULTS: Eighty patients were treated (44-TACE/36-LR). Number of nodules was [1.8(1.1)], being multinodular in 50% of cases. Although resected patients had a higher hospital stay than those who underwent TACE (14 ± 13 vs 7 ± 6; P = 0.004), the rate and severity of complications was lower measured by Dindo-Clavien scale (P < 0.05). Overall survival was 40% with a median follow-up of 29.5 months (0.07-96.9). Five-years survival rates were 62.9%, 28.1% and 15.4%, respectively (P = 0.004) for B1, B2 and B3-4 stages. Cox model showed that only total bilirubin [OR = 2.055(1.23-3.44)] and BCLC subclassification B3-4 [OR = 2.439(1.04-5.7)] and B2 [OR = 2.79(1.35-5.77)] vs B1 were independent predictors of 5-years-survival. In B1 patients, surgical approach led a significant decrease in 5-years recurrence-rate (25% vs 60%; P = 0.018). In the surgical subgroup analysis, better results were observed if well/moderate differentiation combined with no microvascular-invasion (VI) in 5-years-survival (84.6%; P = 0.001) and -recurrence (23.1%; P = 0.041), respectively. These survival and recurrence trends were remarkable in B1 stages. CONCLUSIONS: Management of Intermediate BCLC-B HCC stage should be more complex and include updated criteria regarding B-stage subclassifications, VI and tumour differentiation. Modern surgical resection would offer improved survival benefit with acceptable safety in selected BCLC-B stage patients.

Phonon Engineering in Isotopically Disordered Silicon Nanowires.

The introduction of stable isotopes in the fabrication of semiconductor nanowires provides an additional degree of freedom to manipulate their basic properties, design an entirely new class of devices, and highlight subtle but important nanoscale and quantum phenomena. With this perspective, we report on phonon engineering in metal-catalyzed silicon nanowires with tailor-made isotopic compositions grown using isotopically enriched silane precursors (28)SiH4, (29)SiH4, and (30)SiH4 with purity better than 99.9%. More specifically, isotopically mixed nanowires (28)Si(x)(30)Si(1-x) with a composition close to the highest mass disorder (x ∼ 0.5) were investigated. The effect of mass disorder on the phonon behavior was elucidated and compared to that in isotopically pure (29)Si nanowires having a similar reduced mass. We found that the disorder-induced enhancement in phonon scattering in isotopically mixed nanowires is unexpectedly much more significant than in bulk crystals of close isotopic compositions. This effect is explained by a nonuniform distribution of (28)Si and (30)Si isotopes in the grown isotopically mixed nanowires with local compositions ranging from x = ∼0.25 to 0.70. Moreover, we also observed that upon heating, phonons in (28)Si(x)(30)Si(1-x) nanowires behave remarkably differently from those in (29)Si nanowires suggesting a reduced thermal conductivity induced by mass disorder. Using Raman nanothermometry, we found that the thermal conductivity of isotopically mixed (28)Si(x)(30)Si(1-x) nanowires is ∼30% lower than that of isotopically pure (29)Si nanowires in agreement with theoretical predictions.

Prediction model to discard a priori liver allografts.

BACKGROUND: The use of expanded criteria for donors to expand the donor pool has increased the number of discarded liver grafts in situ. The aim of our study was to elaborate a prediction model to reduce the percentage of liver grafts discarded before the procuring team is sent out. METHODS: We analyzed the donor factors of 244 evaluated candidates for liver donation. We performed a multiple logistic regression to evaluate the probability of liver grafts discarded (PD). RESULTS: The PD was determined by use of 3 variables: age, pathological ultrasonography, and body mass index >30. The area under curve was 82.7%, and, for a PD of 70%, the false-positive probability was 1.2%. CONCLUSIONS: We have created a useful clinical prediction model that could avoid up to 20% of discarded liver grafts.

Stabilization of apoptotic cells: generation of zombie cells.

Apoptosis is characterized by degradation of cell components but plasma membrane remains intact. Apoptotic microtubule network (AMN) is organized during apoptosis forming a cortical structure beneath plasma membrane that maintains plasma membrane integrity. Apoptotic cells are also characterized by high reactive oxygen species (ROS) production that can be potentially harmful for the cell. The aim of this study was to develop a method that allows stabilizing apoptotic cells for diagnostic and therapeutic applications. By using a cocktail composed of taxol (a microtubule stabilizer), Zn(2+) (a caspase inhibitor) and coenzyme Q10 (a lipid antioxidant), we were able to stabilize H460 apoptotic cells in cell cultures for at least 72 h, preventing secondary necrosis. Stabilized apoptotic cells maintain many apoptotic cell characteristics such as the presence of apoptotic microtubules, plasma membrane integrity, low intracellular calcium levels and mitochondrial polarization. Apoptotic cell stabilization may open new avenues in apoptosis detection and therapy.

Intraband absorption in self-assembled Ge-doped GaN/AlN nanowire heterostructures.

We report the observation of transverse-magnetic-polarized infrared absorption assigned to the s-p(z) intraband transition in Ge-doped GaN/AlN nanodisks (NDs) in self-assembled GaN nanowires (NWs). The s-p(z) absorption line experiences a blue shift with increasing ND Ge concentration and a red shift with increasing ND thickness. The experimental results in terms of interband and intraband spectroscopy are compared to theoretical calculations of the band diagram and electronic structure of GaN/AlN heterostructured NWs, accounting for their three-dimensional strain distribution and the presence of surface states. From the theoretical analysis, we conclude that the formation of an AlN shell during the heterostructure growth applies a uniaxial compressive strain which blue shifts the interband optical transitions but has little influence on the intraband transitions. The presence of surface states with density levels expected for m-GaN plane charge-deplete the base of the NWs but is insufficient to screen the polarization-induced internal electric field in the heterostructures. Simulations show that the free-carrier screening of the polarization-induced internal electric field in the NDs is critical to predicting the photoluminescence behavior. The intraband transitions, on the other hand, are blue-shifted due to many-body effects, namely, the exchange interaction and depolarization shift, which exceed the red shift induced by carrier screening.

Apoptotic microtubules delimit an active caspase free area in the cellular cortex during the execution phase of apoptosis.

Apoptotic microtubule network (AMN) is organized during apoptosis, forming a cortical structure beneath plasma membrane, which has an important role in preserving cell morphology and plasma membrane permeability. The aim of this study was to examine the role of AMN in maintaining plasma membrane integrity during the execution phase of apoptosis. We demonstrated in camptothecin-induced apoptosis in H460 cells that AMN delimits an active caspase free area beneath plasma membrane that permits the preservation of cellular cortex and transmembrane proteins. AMN depolymerization in apoptotic cells by a short exposure to colchicine allowed active caspases to reach the cellular cortex and cleave many key proteins involved in plasma membrane structural support, cell adhesion and ionic homeostasis. Cleavage of cellular cortex and plasma membrane proteins, such as α-spectrin, paxilin, focal adhesion kinase (FAK), E-cadherin and integrin subunit ß4 was associated with cell collapse and cell detachment. Otherwise, cleavage-mediated inactivation of calcium ATPase pump (PMCA-4) and Na(+)/Ca(2+) exchanger (NCX) involved in cell calcium extrusion resulted in calcium overload. Furthermore, cleavage of Na(+)/K(+) pump subunit ß was associated with altered sodium homeostasis. Cleavage of cell cortex and plasma membrane proteins in apoptotic cells after AMN depolymerization increased plasma permeability, ionic imbalance and bioenergetic collapse, leading apoptotic cells to secondary necrosis. The essential role of caspase-mediated cleavage in this process was demonstrated because the concomitant addition of colchicine that induces AMN depolymerization and the pan-caspase inhibitor z-VAD avoided the cleavage of cortical and plasma membrane proteins and prevented apoptotic cells to undergo secondary necrosis. Furthermore, the presence of AMN was also critical for proper phosphatidylserine externalization and apoptotic cell clearance by macrophages. These results indicate that AMN is essential to preserve an active caspase free area in the cellular cortex of apoptotic cells that allows plasma membrane integrity during the execution phase of apoptosis.

Chromatin and alternative splicing.

Alternative splicing affects more than 90% of human genes. Coupling between transcription and splicing has become crucial in the complex network underlying alternative splicing regulation. Because chromatin is the real template for nuclear transcription, changes in its structure, but also in the "reading" and "writing" of the histone code, could modulate splicing choices. Here, we discuss the evidence supporting these ideas, from the first proposal of chromatin affecting alternative splicing, performed 20 years ago, to the latest findings including genome-wide evidence that nucleosomes are preferentially positioned in exons. We focus on two recent reports from our laboratories that add new evidence to this field. The first report shows that a physiological stimulus such as neuron depolarization promotes intragenic histone acetylation (H3K9ac) and chromatin relaxation, causing the skipping of exon 18 of the neural cell adhesion molecule gene. In the second report, we show how specific histone modifications can be created at targeted gene regions as a way to affect alternative splicing: Using small interfering RNAs (siRNAs), we increased the levels of H3K9me2 and H3K27me3 in the proximity of alternative exon 33 of the human fibronectin gene, favoring its inclusion into mature messenger RNA (mRNA) through a mechanism that recalls RNA-mediated transcriptional gene silencing.

Use of mycophenolate mofetil in liver transplantation: Andalusian Liver Registry.

OBJECTIVE: To evaluate the safety and efficacy of various immunosuppressant regimens using mycophenolate mofetil (MMF). PATIENTS AND METHODS: This prospective, observational, multicenter study of 226 patients undergoing liver transplantation was carried out in 2005-2006, with 24-month follow-up. Studied variables were as follows: indicators of kidney, liver, and blood function; intercurrent infections; cardiovascular risk; acute and chronic episodes of rejection; recurrent hepatitis C virus infection; de novo tumors; and survival. Patients were classified into 4 groups according to treatment: no MMF (group 1, n = 91); MMF from induction (group 2, n = 83); late administration of MMF (group 3, n = 30); and MMF at induction, with early withdrawal (group 4, n = 22). RESULTS: Biodemographic characteristics were similar in all 4 groups. The MMF groups were at higher risk and had worse Model for End-Stage Liver Disease and Child-Pugh scores and worse pretransplantation blood and kidney function values. Significant differences were observed in creatinine concentration between groups 2 and 3: 0.45 mg/dL at 1 month (P < .01), 0.27 mg/dL at 3 months (P < .01), and 0.3 mg/dL at 6 months (P < .05). In contrast, differences of 0.34 mg/dL (P < .01) were observed between groups 1 and 3 at 1 month and 0.17 mg/dL (P < .05) between groups 1 and 2 at 3 months. No differences were noted in white blood cell counts, episodes of acute rejection (19%) and chronic rejection (5%), graft survival (80%), and rate of recurrent hepatitis C virus infection (75%) between the 4 groups. The infection rate at 3 months in groups 2 and 4 was 34.5%, and in groups 1 and 3 was 34.5% (P < .05). CONCLUSIONS: Use of MMF at induction and introduction of MMF in the first 3 months posttransplantation helps to preserve and restore creatinine levels in patients with worsened kidney function, and aids in keeping them stable, without increasing the risk of rejection while optimizing the anticalcineurin dosage.

Establishment of a pediatric liver transplantation program: experience with 100 transplantation procedures.

OBJECTIVE: To analyze the primary factors that influence the development and consolidation of a pediatric liver transplantation program. PATIENTS AND METHODS: This was a retrospective study of 100 liver transplantation procedures performed in 84 pediatric patients between May 1990 and November 2007. The male-female ratio was 40:60. Mean (SD) age was 5 years (40 patients were younger than 2 years); cold ischemia time was 7.10 (3.1) hours; surgery time was 5.2 (2.2) hours; and time on the waiting list for transplantation was 75 (range, 1-1012) days. Indications for transplantation included cholestatic disease (43%), acute hepatic failure (AHF; 34%), metabolic disorders (14%), and cirrhosis (9%). Transplanted organs included 3 split grafts, 29 partial grafts, and 8 living-donor grafts. RESULTS: Mean graft survival was 70.4%, 59.2%, and 58.1% at 1, 3, and 5 years, respectively. Factors that influenced graft outcome were age younger than 2 years; surgery time more than 6 hours; and AHF vs cholestatic disease, metabolic disorders, and cirrhosis. There were no significant differences in long-term (51% vs 59%) and short-term (71% vs 70%) graft survival between procedures performed in 1990-1998 compared with those performed in 1999-2007; however, there was a higher percentage (P = .005) of recipients at high risk (age younger than 2 years or with AHF) in the later period. All data were consistent with those of the European Liver Transplant Registry 2007. CONCLUSIONS: A pediatric liver transplantation program can be established by a group experienced in liver transplantation.

Liver transplantation for hepatocellular carcinoma: results of a multicenter study with common priorization criteria.

OBJECTIVE: To evaluate the results of liver transplantation (OLT) performed for hepatocellular carcinoma (HCC) among a multicenter cohort of patients with predefined common inclusion and priorization criteria. PATIENTS AND METHODS: Over a 5-year period (January 2002-December 2006), 199 HCC patients underwent OLT in four centers in Andalusia. The morphological (Milan) inclusion criteria were priorized in two consecutive periods, according to the Model for End-stage Liver Disease score: group I, 53 patients (HCC < 2 cm = 24 points; > or = 2 cm or multinodular = 29 points) and group II, 146 cases (HCC < 3 cm without priorization; HCC > or = 3 cm or multinodular = 18 points). RESULTS: Among the 199 HCCs, 186 (93.5%) subjects were transplanted and 13 (6.5%) were excluded. There were 18 cases (9.7%) where the diagnosis was incidental and 168 were known HCC cases; 144 (85.7%) complied with the Milan criteria (Milan+); 24 (14.3%) exceeded there criteria (Milan-). According to preoperative imaging, the number of nodules and tumor mean sizes among the excluded-Milan+ and Milan- groups-were 1.8/5.3 cm, 1.4/3.5 cm, and 2.3/6.7 cm, respectively (P < .001). Percutaneous treatment during listing was delivered to 55% of the excluded cases: 49% of Milan+ and 96% of Milan-. The median time on the list was 88 days for known HCC (53 days for group I, and 97 days for group II), and 172 days for the incidental HCCs. Staging (pTNM) was correct in 64% of cases: 23% were understaged and 13% were overstaged. Overall mortality within the first 90 days was 9%, and transplant patient survival at 5 years was 61%. No differences were observed in survival rates between both study periods, although there were differences between the Milan+ (65%) and Milan- (23%) groups (P < .04). In addition, the difference in the recurrence rates was also significant between the Milan+ (7%), Milan- (24%), and the incidental (25%) groups (P < .02). CONCLUSIONS: A common priorization policy of HCC for OLT based on morphological criteria results in a low exclusion rate on the waiting lists (6.5%). The Milan criteria are still a good cutoff to stratify the risk of recurrence, despite preoperative tumor staging being correct in only two-thirds of cases.

Model for end-stage liver disease can predict very early outcome after liver transplantation.

Postoperative Model for End-stage Liver Disease (MELD) values have never been assessed to predict very early (<1 week) death after liver transplantation (OLT). We retrospectively reviewed 275 consecutive OLTs performed in 252 recipients reported in a prospective database. We calculated the MELD score (pre-MELD) and consecutive postoperative MELD (post-MELD) scores computed daily during the first postoperative week and on days 15 and 30 after OLT. Post-MELD scores from nonsurviving recipients displayed on a scatterplot of immediate probability of death were adjusted to the best goodness-of-fit curve, and, finally, depicted graphically as a receiver operating characteristic (ROC) curve. Nonsurviving recipients showed higher post-MELD scores: day 1: 23.5 versus 16.6 (P = .05); day 3: 25.1 versus 12.5 (P = .000); day 5: 25.7 versus 11.8 (P = .000); and day 7: 22.1 versus 10.2 (P = .000). Overall comparisons were performed using a time-dependent general linear regression model, revealing higher post-MELD scores for nonsurviving recipients, irrespective of postoperative time (P = .002). The best goodness-of-fit curve was displayed when adjusting to a theoretical exponential regression curve calculated as follows: Probability of dying within the first week (%) = 3.36 x e(0.079 x (post-MELD)) (r = .89; P = .000). The area under the ROC curve was 0.783 (95% confidence interval, 0.630-0.935; P = .001). The model had a positive predictive value of 82.3%, a negative predictive value of 33.1%, and an accuracy of 79.2%. In conclusion, this study corroborated the suggestion that the MELD score may serve as a reliable tool to assess very early death after OLT.

Factors affecting survival and tumor recurrence in patients transplanted for hepatocellular carcinoma and coexistent hepatitis C virus.

A better understanding of tumor factors influencing patient and graft survival and recurrence of hepatocellular carcinoma (HCC) associated with hepatitis C virus (HCV) cirrhosis may be useful to maximize the benefits of liver transplantation (OLT). Sixty-three adults underwent OLT for end-stage liver disease secondary to HCV with concomitant HCC. The outcome measures were patient and graft survival, as well as recurrence-free survival, computed using a stepwise Cox proportional hazards regression analysis. Kaplan-Meier 1-, 3-, and 5-year patient survival rates were 82%, 80%, and 69%, respectively, they were better for incidentally discovered HCC compared with preoperatively diagnosed HCC (P = .04). The overall recurrence-free survival rates were 81%, 76%, and 61% at 1, 3, and 5 years, respectively. Univariate analysis showed that nonincidental HCC (P = .04), pTNM stage (P = .012) and vascular invasion (P = .003) correlated with recipient mortality. Vascular invasion (odds ratio [OR] = 2.12; P = .001) and pTNM (OR = 1.50; P = .008) were independent predictors of overall survival. A combination of tumor vascular invasion with advanced pTNM was associated with a dismal prognosis (log-rank = 21.89; P = .0001). Tumor grading (OR = 1.2; P = .04), pTNM (OR = 3.7; P = .001) and vascular invasion (OR = 1.6; P = .002) were independent predictors of recurrence. In conclusion, advanced pTNM and the presence of vascular invasion are strong predictors of poor survival and tumor recurrence.

[Prognostic factors associated with postoperative complications in liver transplant]. / Factores pronósticos de complicaciones postoperatorias en el transplante hepático.

OBJECTIVES: the postoperative evolution of patients submitted to orthotopic liver transplant (OLT) is frequently associated with the appearance of different types of complications such as renal failure, graft rejection, infections, and neurological disorders. These complications are the most significant causes of early morbidity and mortality in patients undergoing OLT. The purpose of the present study was the identification of factors related to the different postoperative complications after OLT. EXPERIMENTAL DESIGN: a prospective study was carried out. PATIENTS: seventy-eight variables were analyzed in 32 consecutive patients undergoing OLT. The factors independently associated with the appearance of postoperative complications were identified using a stepwise logistic regression analysis. RESULTS: the multivariate analysis showed that malondialdehyde and creatinine pretransplant serum levels were associated with the development of renal dysfunction. The pretransplant levels of haemoglobin and the units of platelets administered during surgery were prognostic factors of infections. Acute graft rejection was predicted by ?-glutamyl transpeptidase and total bilirubin serum levels. The pretransplant sodium and glutaredoxin levels in serum were associated with neurological complications. CONCLUSIONS: we propose these markers for the identification of high-risk patients allowing an early surveillance and/or treatment to improve morbidity and survival in patients submitted to OLT.