Quantitative analysis of the x-ray diffraction intensities of undulated smectic phases in bent-core liquid crystals

X-ray diffraction diagrams of undulated smectic phases in bent-core liquid crystals have been theoretically studied. The intensities of the reflections have been obtained for different layer modulations, and a general expression has been deduced for orthogonal cells in terms of the different harmonics of the distortion. The case of sinusoidal modulation is especially simple and has been studied also in oblique cells. High-quality x-ray measurements of three compounds reported in the literature have been analyzed as examples. In all cases it has been deduced that the modulation is sinusoidal and its amplitude has been easily obtained by fitting the experimental intensities. Equatorial (h0) reflections have been also considered to obtain information about the structure of defects at the maxima and minima of the undulation.

Energy level alignment at metal/organic semiconductor interfaces: “Pillow” effect, induced density of interface states, and charge neutrality level

A unified model, embodying the "pillow" effect and the induced density of interface states (IDIS) model, is presented for describing the level alignment at a metal/organic interface. The pillow effect, which originates from the orthogonalization of the metal and organic wave functions, is calculated using a many-body linear combination of atomic orbitals Hamiltonian, whereby electron long-range interactions are obtained using an expansion in the metal/organic wave function overlap, while the electronic charge of both materials remains unchanged. This approach yields the pillow dipole and represents the first effect induced by the metal/organic interaction, resulting in a reduction of the metal work function. In a second step, we consider how charge is transferred between the metal and the organic material by means of the IDIS model: Charge transfer is determined by the relative position of the metal work function (corrected by the pillow effect) and the organic charge neutrality level, as well as by an interface parameter S, which measures how this potential difference is screened. In our approach, we show that the combined IDIS-pillow effects can be described in terms of the original IDIS alignment corrected by a screened pillow dipole. For the organic materials considered in this paper, we see that the IDIS dipole already represents most of the realignment induced at the metal/organic interface. We therefore conclude that the pillow effect yields minor corrections to the IDIS model.

Haematopoietic stem cell transplantation trends in children over the last three decades: a survey by the paediatric diseases working party of the European Group for Blood and Marrow Transplantation

This paper describes the trends in haematopoietic stem cell transplantation (HSCT) activity for children in Europe over the last three decades. We analysed 31,713 consecutive paediatric HSCTs reported by the European Group for Blood and Marrow Transplantation (EBMT) centres between 1970 and 2002. Data were taken from the EBMT registry and were compared according to period and centre category (paediatric or combined). Since 1996, there has been a significant increase in the number of HSCTs performed exclusively by paediatric centres, as well as in the number of alternative donor HSCTs, and in the use of peripheral blood stem cells (P<0.0001). The number of allogeneic HSCTs (allo-HSCTs) for acute lymphoblastic leukaemia, acute myeloblastic leukaemia and chronic myeloid leukaemia remained stable, whereas it increased for myelodysplastic syndromes and lymphomas, and decreased significantly for non-malignant diseases (P<0.0001). Multivariate analysis showed that younger age, human leukocyte antigen genoidentical donors, HSCT performed after 1996 and transplant centres performing more than 10 allo-HSCT/year were all associated with decreased transplant-related mortality (TRM) (P<0.0001). The number of autologus HSCTs (auto-HSCTs) for acute leukaemia decreased significantly, whereas it increased for solid tumours (P<0.0001). Multivariate analysis showed that both auto-HSCT performed before 1996 and paediatric solid tumours (P<0.0001) had higher TRM. Indications for paediatric HSCT have changed considerably during the last seven years. These changes provide tools for decision making in health-care planning and counselling.

Structural study of a bent-core liquid crystal showing the B1-B2 transition

An experimental study of the B1-B2 transition is carried out in a bent-core liquid crystal. The study is essentially based on x-ray measurements as a function of temperature. The B1-B2 transition is extremely unusual and implies a deep structural change from a columnar phase to a lamellar phase. We have found that the B1 phase in our compound is similar to the so-called B1 reversed phase, with an additional splay of the polarization in the columns. On approaching the B2 phase the width of the cross section of the columns increases. The transition is clearly first order, with a large hysteresis though the enthalpy content is very small. A possible mechanism for the transition is briefly sketched.

Some aspects about the structure of the optically isotropic phase in a bent-core liquid crystal: chiral, polar, or steric origin

We have studied a bent-core liquid crystal where two different optically isotropic phases can be induced by a strong electric field. Depending on the field treatment the phases can present optical rotation or be optically inactive. The switching dynamics of the phases is studied by means of electrooptic and optical second-harmonic generation measurements. It is found that the ground state of the phases is locally antiferroelectric. The structure of the phases is consistent with a disordered version of the kind of structures recently proposed for the smectic blue phase: layered systems with high Gaussian curvature. The origin of the smectic layer distortion is discussed. It is concluded that the direct reason for the curvature of planes is of steric nature.

Pathological and aetiological studies of multifocal interstitial nephritis in wasted pigs at slaughter

Multifocal interstitial nephritis in pigs has been associated with several infectious agents. The objective of the present study was to investigate several different potential infectious agents associated with "white-spotted" kidneys in pigs suffering from wasting at slaughter (aged 6-8 months). Twenty-nine case kidneys (with a "white-spotted" gross appearance) classified into 3 macroscopic lesional grades, and 15 control kidneys (lacking gross lesions), were obtained from a pig abattoir. Laboratory analyses to detect potential associations with the aforementioned pathological condition with Leptospira spp., porcine circovirus type 2 (PCV2), porcine parvovirus (PPV), porcine reproductive and respiratory syndrome virus (PRRSV), and bacteria, were carried out. Microscopically, interstitial nephritis with a lymphofollicular inflammatory pattern (follicular nephritis) was observed in both case and control kidneys, with a higher frequency seen in the former ones. No leptospires were identified, although antibodies to the Pomona and Bratislava serovars were detected. Some pyogenic bacteria were also isolated from both case and control kidneys. PCV2 nucleic acid was only detected in 1 case kidney. PRRSV antigen was not found in any tested sample. Some pigs were tested positive for PPV by serology. Apparently, none of the studied agents were specifically associated as being the potential cause of the renal lesions in the studied wasted pigs. The fact that these chronic lesions may have been the consequence of a previous infection with one of these studied microorganisms, or more, and eventually with other non-tested infectious agents during the growing-finishing period, cannot be ruled out.

Soft phonon, dynamical fluctuations, and a reversible phase transition: indium chains on silicon

The In/Si(111)-(4 x 1) surface is a paradigmatic example of a quasi-one-dimensional system showing a reversible structural and electronic (metal-insulator) phase transition when the temperature is lowered. In this work, we use first-principles simulation techniques to uncover the atomic and electronic origin of this controversial transition. Our calculations show that the ground state consists of insulating (4 x 2) indium chains with a weak interchain coupling that induces opposite shear distortions in alternate chains. First-principles molecular dynamics simulations show that the (4 x 1) <--> (8 x 2) phase transition is due to the "dynamical fluctuations" the system undergoes when, at high temperature, it fluctuates chaotically between degenerate ground states. The metallicity of the In/Si(111)-(4 x 1) surface is related to the low energy cost for the shear distortion.

Structure of mesogens possessing B7 textures: the case of the bent-core mesogen 8-OPIMB-NO2

A structural investigation of the compound 8-OPIMB-NO2 is carried out. This material is a mesogen formed by bent-core molecules where the so-called B7 phase was originally proposed. X-ray data are successfully indexed in terms of a oblique two-dimensional lattice. Using additional information from optical second harmonic generation several possible structural models are proposed. The models are based on molecular packing considerations. All these structures are clearly different from those of other materials previously classified as B7. The necessity of a revised nomenclature for classifying the structures of these compounds is pointed out.

Convectively driven polymerase chain reaction thermal cycler

We have fabricated a low-cost disposable polymerase chain reaction thermal chamber that uses buoyancy forces to move the sample solution between the different temperatures necessary for amplification. Three-dimensional, unsteady finite element modeling and a simpler 1-D steady-state model are used together with digital particle image velocimetry data to characterize the flow within the device. Biological samples have been amplified using this novel thermal chamber. Time for amplification is less than 30 min. More importantly, an analysis of the energy consumption shows significant improvements over current technology.

Survey on haematopoietic stem cell transplantation for children in Europe

A recent report, prepared in March 2003, regarding the paediatric transplantation activity registered between 1970 and 2002 in the European Bone Marrow Transplantation (EBMT) database showed a decrease in the number of registrations in 2001 and in 2002. In order to validate this observation, the Paediatric Diseases Working Party (PDsWP) secretariat distributed a questionnaire to 395 institutions participating in the EBMT Registry. Each institution was requested to check the number of transplants they reported and to confirm or to correct the figures. As of 15 March 2004, replies had been received from 135 centres reporting a median of 48 transplants per centre over the study period, total 17 891 (58% of the total number). Among them, 55 confirmed their original figures, while 80 corrected the numbers. The overall number of autologous and allogeneic SCTs performed and not reported were 461 and 692, respectively. Most of the teams that corrected their figures stated that their data managers could provide missing data to the EBMT; 260 other teams, each reporting a median of 15 transplants during the study period, total 12 866 (42% of the total number) chose not to reply. A report prepared in March 2004, following the PDsWP survey, showed an increasing number of transplants performed on patients below 18 years of age between 1973 and 2002 and reported to the EBMT Registry (328 autologous and 628 allogeneic) as compared to the 2003 report. This first PDsWP survey, reaching more than 50% of activity in the field, illustrates that the decrease in activity we observed in the 2003 report does not correspond to a decrease in the number of transplants that were actually performed. It demonstrates the compliance of most major paediatric institutions and confirms the important role of cooperation between National Registries and EBMT Registries.

Formation of atom wires on vicinal silicon

The feasibility of creating atomic wires on vicinal silicon surfaces via pseudomorphic step-edge decoration has been analyzed for the case of Ga on Si(112). Scanning tunneling microscopy and density functional theory calculations indicate the formation of Ga zigzag chains intersected by quasiperiodic vacancy lines or "misfit dislocations." This structure strikes a balance between the system's drive towards chemical passivation and its need for strain relaxation in the atom chains. Spatially fluctuating disorder, intrinsic to the reconstruction, originates from the two symmetry-degenerate orientations of the zigzag chains on vicinal Si.

Electric-field-induced B1-B2 transition in bent-core mesogens

We report experimental results on two bent-shaped mesogens showing the B1 phase. Contrary to the conventional B1 structures, we have found that our compounds display a clear electro-optic effect in this phase. Under the influence of a 100-Hz square-wave electric field of moderate amplitude, an increase of the birefringence is observed. However, no switching current is detected, indicating that the materials remain antiferroelectric. For high enough fields, a drastic change in the texture occurs. This change is a phase transition to a B2 phase, and shows the typical antiferroelectric switching of this phase. The induced B2 phase has been identified to be homochiral. Upon removal of the field, the B1 structure is recovered. Our study is based on differential scanning calorimetry, x-ray, electro-optics, polarization reversal, and dielectric measurements.

Outcome of 28 split liver grafts

Our aim is to present our experience with split liver transplantation. From 1992-2002, 14 livers were split to obtain 28 grafts that were transplanted to 12 adults and 16 children. Ex situ splitting was performed in all cases. The left graft consisted of the left lateral segment (segments II-III) in 11 cases and the left lobe in three, depending on the size of the pediatric recipient. Pediatric recipients were of mean age 3, 4 years; mean weight 13 kg; six emergency cases for fulminant hepatic failure or urgent retransplantation and seven of 10 elective cases for biliary atresia. Postoperative mortality rate was 31% (five cases), including four of six emergency cases and one elective case (10%). The main cause was multiorgan failure. Technical complications were: one arterial thrombosis, one portal vein thrombosis, and four biliary complications. Eleven patients are alive and well. Adult recipients were of mean age 53 years. The indications were hepatocellular carcinoma in six cases, liver cirrhosis of various etiologies in five, and one recurrence of hepatitis C in a graft. Two patients died during the postoperative period from sepsis after retransplantation for primary nonfunction of the split graft and multiorgan failure with sepsis. One-year actuarial survival was 84%.

CONCLUSIONS

The results of split liver transplantation in elective cases are similar to whole liver transplantation, whereas patient survival among emergency cases is low due to the critical condition of the patients.

Influence of preservation solution on early lung function (Euro-Collins vs Perfadex)

BACKGROUND

This clinical study was performed to evaluate the efficiency of 2 different preservation solutions (Euro-Collins [EC] vs Perfadex [P]) on organ function in human lung transplantation.

METHODS

The donor lungs for 46 patients were flushed either with EC solution (25 cases, EC group) or Perfadex (21 cases, P group). Transplant function was assayed using PaO2/FiO2 ratio after transplantation upon intensive care unit (ICU) arrival and at 12 and 24 hours later (T1, T2, and T3, respectively). We also compared the duration of mechanical ventilatory support and ICU stay.

RESULTS

The PO2/FiO2 ratio was significantly better in the P than EC group at T1, T2, and T3. The duration of mechanical ventilatory support and ICU stay were lower also in P group, whereas age, sex, aetiology of lung disease, donor, PaO2/FiO2 ratio, and ischemia time did not show differences between the 2 groups.

CONCLUSIONS

Our data on graft function tend to confirm better graft preservation using the P preservation solution.

Phonon softening, chaotic motion, and order-disorder transition in Sn/Ge(111)

The phonon dynamics of the Sn/Ge(111) interface is studied using high-resolution helium atom scattering and first-principles calculations. At room temperature we observe a phonon softening at the Kmacr; point in the (sqrt[3]xsqrt[3])R30 degrees phase, associated with the stabilization of a (3x3) phase at low temperature. That phonon band is split into three branches in the (3x3) phase. We analyze the character of these phonons and find out that the low- and room-temperature modes are connected via a chaotic motion of the Sn atoms. The system is shown to present an order-disorder transition.

Interpretation of unusual textures in the B2 phase of a liquid crystal composed of bent-core molecules

A liquid crystal material of bent-core molecules is investigated by means of optical texture observations, x-ray measurements, and miscibility studies. While the x-ray and miscibility data point towards a B2 phase, the texture is however unusual, showing optical isotropy and segregation in two domains with opposite gyrations. It is shown that the texture can be interpreted successfully in terms of a smectic-C(A)P(A) structure in small domains with random orientations. The optical activity data are also explained semiquantitatively.

Induction of ferroelectricity in the B2 phase of a liquid crystal composed of achiral bent-core molecules

We report the observation of a transition from the antiferroelectric B2 phase to a ferroelectric phase in a liquid crystal composed of achiral bent-core (banana-shaped) molecules. The transition is induced by an electric field of magnitude larger than the switching threshold and is not reversible, i.e., the original B2 phase does not reappear upon field removal. The transformation is accompanied by a dramatic texture change, resulting in an almost optically isotropic structure in the absence of field. The ferroelectric character assigned to the structure is based on the electro-optic behavior of the material and on previously reported dielectric measurements. A short-pitch smectic-C*-type structure is proposed for the ferroelectric phase.

Pathological and immunohistochemical study of the liver and hepatic lymph nodes of sheep chronically reinfected with Fasciola hepatica, with or without triclabendazole treatment

Hepatic lesions and changes in the hepatic lymph nodes were examined in groups of sheep infected, and sometimes reinfected, with metacercariae of Fasciola hepatica, with or without treatment with triclabendazole (TCBZ). Hepatic damage was more severe in sheep given small repeated ("trickle") infections than in those given two larger, spaced doses. Inflammatory infiltrates of eosinophils, CD3+ T cells, CD79 alpha+ B cells and IgG+ plasma cells, and the presence of granulomata, were particularly marked in trickle-infected groups, suggesting that the host response to certain fluke or egg antigens causes severe hepatic damage. TCBZ administration induced the elimination of flukes and healing of the majority of hepatic lesions but did not prevent severe hepatic damage produced by later infections.

The need for a statewide pediatric trauma program

Development and maintenance of an effective regional trauma care system mandates on-going assessment of those at risk, patterns of injury and types of resources available. It is known that a significantly higher injury and traumatic death rates exists for children in a rural environment, and there is also evidence to support improved outcomes for children treated at verified trauma centers. While many still rely on practice-based statistics, we postulated that population-based statistics are much more reflective as to what is actually happening and provide crucial information on how improvements can be achieved. To test this theory, we reviewed all pediatric traumatic deaths for children 18 years old and younger from Jan. 1, 1990 to Dec. 31, 1998 at the Jon Michael Moore Trauma Center at West Virginia University, a rural pediatric trauma center. We compared this data to trauma mortality within the center's 13 county primary region from the Office of Vital Statistics. Our research revealed that mortality from pediatric trauma is higher in rural environments than in urban environments, and that population-based statistics more accurately reflect the true impact of what is actually happening in any given region. Age appears to be an important factor in determining which children are transferred to the trauma center and this may represent a critical factor in outcome.

Structural normalization of the lymphoid tissue in asymptomatic HIV-infected patients after 48 weeks of potent antiretroviral therapy

BACKGROUND

The hallmark of HIV infection is the involution and destruction of lymphoid tissue. However, very little information exists on the effect of highly active antiretroviral therapy (HAART) on lymphoid tissue structure.

OBJECTIVE

To evaluate the effect of a HAART regimen after 48 weeks on the architecture and cell regeneration of tonsil lymphoid tissue in HIV-infected patients with CD4 T cell counts > or = 500/microl.

METHODS

From June 1997 to February 1998 all asymptomatic HIV-infected patients with CD4 T cell counts > or = 500/microl seen at our unit were offered quadruple antiretroviral therapy. Tonsil biopsies were obtained at baseline and at 48 weeks. Tonsil tissue sections were examined to evaluate structural and immunohistochemical changes by two blinded and independent pathologists. Cell numbers were counted for selected markers in T-dependent zones.

RESULTS

Eleven patients were evaluable, six were excluded because of insufficient or inadequate sampling in at least one of the biopsies. Cellular depletion, plasma cell accumulation and prominent vessels were observed in all cases; three excluded patients with evaluable baseline biopsies showed similar tissue lesions. Follow-up biopsies demonstrated some degree of improvement in all patients. Germinal centres appeared in seven cases that were not seen at baseline. CD4 cell counts increased and CD8 cell counts decreased significantly in lymphoid tissue. An increase in CD45RA+ cells was observed; however, the proportion of CD45+Ki67+ cells did not differ between baseline and 48 weeks.

CONCLUSION

This study shows an unexpected range of moderate to severe lymphoid tissue lesions in mildly immunosuppressed HIV-infected patients, which was partly restored after 48 weeks of HAART.

[Diagnosis of apical hypertrophic cardiomyopathy using contrast echocardiography]

Apical hypertrophic cardiomyopathy is a disease with clear electrocardiographic and echocardiographic characteristics. However, poor visualization of apical endocardial border is a limiting factor to diagnose apical hypertrophic cardiomyopathy by echocardiography. We present a case report of a patient with a characteristic electrocardiogram but poor apical endocardial border delineation. A contrast-enhanced echocardiography was performed to confirm the diagnosis of apical hypertrophic cardiomyopathy. We discuss the role of echocardiographic image enhancement with contrast to diagnose apical hypertrophic cardiomyopathy.

Functional domains of the ClpA and ClpX molecular chaperones identified by limited proteolysis and deletion analysis

Escherichia coli ClpA and ClpX are ATP-dependent protein unfoldases that each interact with the protease, ClpP, to promote specific protein degradation. We have used limited proteolysis and deletion analysis to probe the conformations of ClpA and ClpX and their interactions with ClpP and substrates. ATP gamma S binding stabilized ClpA and ClpX such that that cleavage by lysylendopeptidase C occurred at only two sites. Both proteins were cleaved within in a loop preceding an alpha-helix-rich C-terminal domain. Although the loop varies in size and composition in Clp ATPases, cleavage occurred within and around a conserved triad, IG(F/L). Binding of ClpP blocked this cleavage, and prior cleavage at this site rendered both ClpA and ClpX defective in binding and activating ClpP, suggesting that this site is involved in interactions with ClpP. ClpA was also cut at a site near the junction of the two ATPase domains, whereas the second cleavage site in ClpX lay between its N-terminal and ATPase domains. ClpP did not block cleavage at these other sites. The N-terminal domain of ClpX dissociated upon cleavage, and the remaining ClpXDeltaN remained as a hexamer, associated with ClpP, and expressed ATPase, chaperone, and proteolytic activity. A truncated mutant of ClpA lacking its N-terminal 153 amino acids also formed a hexamer, associated with ClpP, and expressed these activities. We propose that the N-terminal domains of ClpX and ClpA lie on the outside ring surface of the holoenzyme complexes where they contribute to substrate binding or perform a gating function affecting substrate access to other binding sites and that a loop on the opposite face of the ATPase rings stabilizes interactions with ClpP and is involved in promoting ClpP proteolytic activity.

Lysine 188 substitutions convert the pattern of proteasome activation by REGgamma to that of REGs alpha and beta

11S REGs (PA28s) are multimeric rings that bind proteasomes and stimulate peptide hydrolysis. Whereas REGalpha activates proteasomal hydrolysis of peptides with hydrophobic, acidic or basic residues in the P1 position, REGgamma only activates cleavage after basic residues. We have isolated REGgamma mutants capable of activating the hydrolysis of fluorogenic peptides diagnostic for all three active proteasome beta subunits. The most robust REGgamma specificity mutants involve substitution of Glu or Asp for Lys188. REGgamma(K188E/D) variants are virtually identical to REGalpha in proteasome activation but assemble into less stable heptamers/hexamers. Based on the REGalpha crystal structure, Lys188 of REGgamma faces the aqueous channel through the heptamer, raising the possibility that REG channels function as substrate-selective gates. However, covalent modification of proteasome chymotrypsin-like subunits by 125I-YL3-VS demonstrates that REGgamma(K188E)'s activation of all three proteasome active sites is not due to relaxed gating. We propose that decreased stability of REGgamma(K188E) heptamers allows them to change conformation upon proteasome binding, thus relieving inhibition of the CT and PGPH sites normally imposed by the wild-type REGgamma molecule.

[Comparative study of reduced-size and whole liver transplantation in children]

It is difficult to find adequate donors for many children with low weight. In order to increase the pool size of donors and decrease mortality on the waiting list, several reduction techniques have been developed in the last years (reduced, segmental and split liver). The aim of this study is to compare morbility and mortality in our serie between children who received a full-size liver and those who received a partial one. We retrospectively compared 27 cases of reduced-size liver transplants (RLTx) with 102 cases of full-size liver transplants (FLTx) performed between june of 1985 and february of 2000. Mean age in RLTx was 38.1 months (range 6-144) vs 70.8 months (range 5-192) in FLTx. Mean weight was 11.9 k (range 5.8-30) in RLTx vs 20.48 k (range 4.4-68) in FLTx. Mean donor/recipient body ratio was 4.88 in RLTx and 2.03 in FLTx. The indication of transplantation was urgent in 14 patients (51.8%) from the RLTx group and in 12 (11.7%) from the FLTx one. The requirements of transfusions during surgery was greater in the RLTx (177 cc/kg of RBC transfusions vs 124 cc in FLTx). There was no differences between both groups regarding other postoperative complications (portal thrombosis, need of reintervention and biliary complications). Arterial thrombosis was observed only in FLTx (12 cases). Graft survival at 3 months was 49% for the RLTx and 73% for the FLTx. It was 43% and 67%, respectively, at 1 year, and 43% and 53% at 5 years after liver transplantation (p = 0.06). If we consider only elective transplants, survival was 72% for RLTx and 75% for the FLTx at 3 months. Although survival is lower in the RLTx group, the difference is not significant. If we consider only the elective transplants, survival is almost the same in both groups. The reduction techniques are a good method to decrease mortality in the waiting list without increasing post-transplant morbidity and mortality.

Gyrotropy problem in nonhomogeneous media: The case of short-pitch chiral-smectic-C liquid crystals and incommensurate structures

The question about the existence of macroscopic models for gyrotropy in inhomogeneous materials is examined. We have carried out a detailed polarimetric study on a short-pitch chiral-smectic-C liquid crystal, which has been taken as an example of an inhomogeneous optical medium. In accordance to the theoretical predictions, we have found that, as a first approximation, the inhomogeneous liquid crystal can be modeled as a homogeneous uniaxial medium with huge optical activity in a direction perpendicular to the optic axis. However, some deviations have been determined in the precise values of the optical activity predicted by the theory. These discrepancies have been attributed to higher-order gyration-like effects, which are usually negligible and have not been considered in previous theoretical approaches. The agreement improves when these higher-order effects are incorporated. In the light of the above results, the theory is applied to the case of incommensurate structures. The origin of gyrotropy in these materials is clarified, and it is shown that this quantity can be described by a usual macroscopic tensor. If the incommensurate structure has an inversion center we deduce that all gyration effects rigorously vanish, contrary to the opinion maintained by several authors.

Analysis of risk factors following pediatric liver transplantation

Several recipient, donor and operation factors as well as postoperative complications related to patient survival after liver transplantation (LT) in children were studied by univariate and multivariate analyses. In a 13-year period, 103 patients under 15 years of age underwent 120 LT; the mean age was 63 months and 36% were under 2 years of age. Indications for LT were cholestatic disease in 68 (56%), metabolic diseases in 18 (14%), fulminant hepatic failure in 8 (7.5%), cirrhosis in 7 (5.8%), and retransplants in 17 (14%). Whole liver was transplanted in 79% of cases and partial liver in 21%. Actuarial survival at 1, 5, and 10 years was 70%, 61%, and 57%, respectively. United Network of Organ Sharing (UNOS) I recipients (RR = 2.7), primary non-function (PNF) (RR = 13.9), and hepatic artery thrombosis (HAT) (RR = 3.8) were independent factors for lower patient survival in multivariate analysis. Thus, in our experience, postoperative mortality as a consequence of the patient's condition before transplantation, or complications such as PNF or HAT, are the major causes of decreased survival in pediatric LT.

Surface soft phonon and the sqrt[3] x sqrt[3] <--> 3x3 phase transition in Sn/Ge(111) and Sn/Si(111)

Density functional theory calculations show that the reversible Sn/Ge(111) sqrt[3]xsqrt[3]<-->3x3 phase transition can be described in terms of a surface soft phonon. The isovalent Sn/Si(111) case does not display this transition since the sqrt[3]xsqrt[3] phase is the stable structure at low temperature, although it presents a partial softening of the 3x3 surface phonon. The rather flat energy surfaces for the atomic motion associated with this phonon mode in both cases explain the experimental similarities found at room temperature between these systems. The driving force underlying the sqrt[3]xsqrt[3]<-->3x3 phase transition is shown to be associated with the electronic energy gain due to the Sn dangling bond rehybridization.

Comparison of outcomes of unrelated bone marrow and umbilical cord blood transplants in children with acute leukemia

In order to compare the outcomes of unrelated umbilical cord blood transplants (UCBTs) or bone marrow transplants, 541 children with acute leukemia (AL) transplanted with umbilical cord blood (n = 99), T-cell-depleted unrelated bone marrow transplants (T-UBMT) (n = 180), or nonmanipulated (UBMT) (n = 262), were analyzed in a retrospective multicenter study. Comparisons were performed after adjustment for patient, disease, and transplant variables. The major difference between the 3 groups was the higher number in the UCBT group of HLA mismatches (defined by serology for class I and molecular typing for DRB1). The donor was HLA mismatched in 92% of UCBTs, in 18% of UBMTs, and in 43% of T-UBMTs (P <.001). Other significant differences were observed in pretransplant disease characteristics, preparative regimens, graft-versus-host disease (GVHD) prophylaxis, and number of cells infused. Nonadjusted estimates of 2-year survival and event-free survival rates were 49% and 43%, respectively, in the UBMT group, 41% and 37% in the T-UBMT group, and 35% and 31% in the UCBT group. After adjustment, differences in outcomes appeared in the first 100 days after the transplantation. Compared with UBMT recipients, UCBT recipients had delayed hematopoietic recovery (Hazard ratio [HR] = 0.37; 95% confidence interval [95CI]: 0.27-0.52; P <.001), increased 100 day transplant-related mortality (HR = 2.13; 95CI: 1.20-3.76; P <.01) and decreased acute graft-versus-host disease (aGVHD) (HR = 0.50; 95CI: 0.34-0.73; P <.001). T-UBMT recipients had decreased aGVHD (HR = 0.25; 95CI: 0.17-0.36; P <.0001) and increased risk of relapse (HR = 1.96; 95CI: 1.11-3.45; P =.02). After day 100 posttransplant, the 3 groups achieved similar results in terms of relapse. Chronic GVHD was decreased after T-UBMT (HR = 0.21; 95CI: 0.11-0.37; P <.0001) and UCBT (HR = 0.24; 95CI: 0.01-0.66; P =.002), and overall mortality was higher in T-UBMT recipients (HR = 1.39; 95CI: 0.97-1.99; P <.07). In conclusion, the use of UCBT, as a source of hematopoietic stem cells, is a reasonable option for children with AL lacking an acceptably matched unrelated marrow donor.

Three-dimensional reconstruction of a recombinant influenza virus ribonucleoprotein particle

A three-dimensional structural model of an influenza virus ribonucleoprotein particle reconstituted in vivo from recombinant proteins and a model genomic vRNA has been generated by electron microscopy. It shows a circular shape and contains nine nucleoprotein monomers, two of which are connected with the polymerase complex. The nucleoprotein monomers show a curvature that may be responsible for the formation of helical structures in the full-size viral ribonucleoproteins. The monomers show distinct contact boundaries at the two sides of the particle, suggesting that the genomic RNA may be located in association with the nucleoprotein at the base of the ribonucleoprotein complex. Sections of the three-dimensional model show a trilobular morphology in the polymerase complex that is consistent with the presence of its three subunits.

[Reimplantation edema in the transplanted lung. Reperfusion-ischemia or hydrostatic edema?]

The development of non cardiogenic pulmonary edema or pulmonary reimplantation response after lung transplantation has been well described. The cause is ischemic vascular injury of the allograft, results in increased permeability of the lung after reperfusion, in turn leading to interstitial and alveolar edema. We report two cases of pulmonary reimplantation response after bilateral sequential lung transplantation. Massive pink frothy fluid was noted in the orifice of the double-lumen endobronchial tube. Blood and endobronchial fluid samples were collected for protein electrophoresis. We conclude that, in spite of the severity of reimplantation response, this complication can be resolved early when the cause is mainly hydrostatic.

Lack of efficacy of atenolol for the prevention of neurally mediated syncope in a highly symptomatic population: a prospective, double-blind, randomized and placebo-controlled study

OBJECTIVES

This study was designed to evaluate the efficacy of atenolol for the long-term management of patients with vasovagal syncope. The primary hypothesis was that atenolol is not superior to placebo for the treatment of vasovagal syncope.

BACKGROUND

There is no definitive well-controlled analysis of the efficacy of beta-adrenergic blocking agents in patients with recurrent vasovagal syncope.

METHODS

This is a prospective, randomized, double-blind, placebo-controlled study. Fifty patients with recurrent vasovagal syncope were included (at least two episodes in the last year). A baseline tilt test was performed. Twenty patients (40%) had a positive tilt test. Intravenous atenolol prevented a second positive tilt in five patients. The patients were randomized to receive either atenolol or a placebo (26 patients atenolol 50 mg/day, 24 patients placebo). The follow-up procedure lasted one year. The primary end point of the study was the time to first recurrence of syncope.

RESULTS

In the intention-to-treat analysis, the group treated with atenolol had a similar number of patients with recurrent syncopal episodes as the placebo group. The Kaplan-Meier actuarial estimates of time to first syncopal recurrence showed that the probability of remaining free of syncope drops similarly in both groups and that there was no statistical difference between both curves (patients treated with atenolol vs. the placebo) with a log-rank test p value of 0.4517.

CONCLUSIONS

The recurrence of neurocardiogenic syncope in highly symptomatic patients treated with atenolol is similar to that of patients treated with placebo.

Sonographic findings in brucellar hepatic abscess

Brucellar hepatic abscesses are rare; to our knowledge, only 41 cases have been described in the literature. We report the case of a 29-year-old Spanish woman who was hospitalized because of fever, weakness, and weight loss. Abdominal sonography showed a hypoechoic lesion with central calcification. Brucella spp. were not isolated from an aspirate of the liver or blood cultures. The diagnosis was based on the association of characteristic sonographic features (central calcification and peripheral necrotic areas) and positive Brucella agglutination tests. The patient improved rapidly with antibiotic treatment.

[Yield of transthoracic echocardiography with high frequency transducer in the study of the anterior descending coronary artery]

INTRODUCTION AND OBJECTIVES

This study was performed to evaluate the feasibility and utility of a transthoracic high frequency transducer to detect and measure the left anterior descending coronary artery flow in patients with lesions in this artery or anterior myocardial infarction.

MATERIALS AND METHODS

We studied 11 subjects with lesions greater than 75% and another 10 with anterior myocardial infarction. We compared the results with a control group of 18 subjects. An ATL HDI 5000 ultrasound unit with a 5-8 MHz transducer was used to identify the left anterior descending in the anterior interventricular sulcus from an apical four chamber window. We considered that left anterior descending was detected when a diastolic predominant flow pattern was obtained with pulse Doppler.

RESULTS

Left anterior descending was detected in 37/39 of cases (94.4%). Patients with coronary lesions showed a decrease in the limit of significance in the diastolic/systolic peak velocity ratios: 2.5 (SD 0.7) vs 1.8 (SD 0.3) with a p = 0.024. Patients with anterior myocardial infarction obtained lower diastolic/systolic peak velocity ratios than controls: 2.5 (SD 0.7) vs 1.4 (SD 0.3) with a p = 0.001.

CONCLUSIONS

Left anterior descending coronary artery flow can be assessed by transthoracic high frequency echocardiography in greater than 90% of the cases. Patients with coronary lesions and those with anterior myocardial infarction have a decreased diastolic/systolic peak velocity ratio.

Second-harmonic generation studies in the B2 and B4 phases of a banana-shaped liquid crystal

Second-harmonic generation (SHG) measurements have been performed in the B2 phase of the achiral banana-shaped molecule with n=12 alkoxy end chains (P-12-O-PIMB). A quantitative value of the nonlinear efficiency has been obtained from SHG curves at oblique incidences, taking into account that the signal is generated by a random orientation of different domains. In the B4 phase, circular dichroism, optical absorption and SHG studies have been carried out. It has been found that there are no simple helical arrangements giving rise to selective reflection in the visible region of the spectrum. In addition, some unusual features of the SHG behavior are pointed out. It is concluded that the phase is intrinsically inactive for the SHG process. The detected signal is due to the presence of some birefringent inclusions that are created at the B2 to B4 transition and slowly disappear while the sample is maintained within the B4 phase. A structural model for these inclusions is presented.