Hydrogen bonding interactions between indole and benzenoid-pi-bases

The NH-pi interactions of indole with benzene, naphthalene, phenanthrene, toluene, m-xylene, and mesitilene, in carbon tetrachloride solutions, have been studied by Fourier transform infrared spectroscopy. The experiments, carried out on the NH stretching band of indole, prove the formation of 1:1 complexes in which the NH bond of indole is engaged. The NH frequency shifts are independent of the number of rings in the base, but they progressively increase as the electron density is enhanced by methylation. The association constants increase with the increase of both, the number of rings and the methyl groups on the base. At higher base concentrations, further shifts on the free NH and associated bands indicate the formation of 1:2 complexes, which suggest hybride NH-pi and van der Waals interactions between one indole ring and two benzene acceptor molecules.

Results of kidney transplantation in recipients over 70 years of age: experience at a single center

We performed 41 kidney transplants in patients >70 years (35 single and 6 dual), with a mean recipient age of 72+/-2 years, from January 1990 to December 2001. Mean age of the donors was 69+/-12 years. Immunosuppression used triple therapy with steroids, mycophenolate mofetil, and cyclosporine or tacrolimus. Cold ischemia time was 23+/-3 hours. The incidence of primary nonfunction was 4.8%, and delayed graft function 58.5%. Acute rejection incidence was 12%. The actuarial patient survival rates at 12, 24, and 36 months were 82.5%, 82.5%, and 75%, respectively. Actuarial survival rates of the grafts censuring for death of the recipient with a functioning graft were 89.5%, 86%, and 68%, respectively. Nine of the 18 graft losses were due to recipient death. Overall, renal transplant recipients >70 years showed good results. The principal cause of graft loss was recipient death.

Nonequilibrium wetting transitions with short range forces

We analyze within mean-field theory as well as numerically a Kardar-Parisi-Zhang equation that describes nonequilibrium wetting. Both complete and critical wettitng transitions were found and characterized in detail. For one-dimensional substrates the critical weting temperature is depressed by fluctuations. In addition, we have investigated a region in the space of parameters (temperature and chemical potential) where the wet and nonwet phases coexist. Finite-size scaling analysis of the interfacial detaching times indicates that the finite coexistence region survives in the thermodynamic limit. Within this region we have observed (stable or very long lived) structures related to spatiotemporal intermittency in other systems. In the interfacial representation these structures exhibit perfect triangular (pyramidal) patterns in one dimension (two dimensions), which are characterized by their slope and size distribution.

Scale-free networks from varying vertex intrinsic fitness

A new mechanism leading to scale-free networks is proposed in this Letter. It is shown that, in many cases of interest, the connectivity power-law behavior is neither related to dynamical properties nor to preferential attachment. Assigning a quenched fitness value x(i) to every vertex, and drawing links among vertices with a probability depending on the fitnesses of the two involved sites, gives rise to what we call a good-get-richer mechanism, in which sites with larger fitness are more likely to become hubs (i.e., to be highly connected).

Is the particle current a relevant feature in driven lattice gases?

By performing extensive Monte Carlo simulations we show that the infinitely fast driven lattice gas (IDLG) shares its critical properties with the randomly driven lattice gas (RDLG). All the measured exponents, scaling functions, and amplitudes are the same in both cases. This strongly supports the idea that the main relevant nonequilibrium effect in driven lattice gases is the anisotropy (present in both IDLG and RDLG) and not the particle current (present only in the IDLG). This result, at odds with the predictions from the standard theory for the IDLG, supports a recently proposed alternative theory. The case of finite driving fields is also briefly discussed.

Critical behavior of a one-dimensional fixed-energy stochastic sandpile

We study a one-dimensional fixed-energy version (that is, with no input or loss of particles) of Manna's stochastic sandpile model. The system has a continuous transition to an absorbing state at a critical value of the particle density, and exhibits the hallmarks of an absorbing-state phase transition, including finite-size scaling. Critical exponents are obtained from extensive simulations, which treat stationary and transient properties, and an associated interface representation. These exponents characterize the universality class of an absorbing-state phase transition with a static conserved density in one dimension; they differ from those expected at a linear-interface depinning transition in a medium with point disorder, and from those of directed percolation.

Fibrosing cholestatic hepatitis-like syndrome in hepatitis B virus-negative and hepatitis C virus-negative renal transplant recipients

Cholestatic hepatitis and diffuse liver fibrosis have been described in immunosuppressed patients with hepatitis B virus or hepatitis C virus infection as fibrosing cholestatic hepatitis (FCH). FCH is characterized by cholestasis, with only a modest increase in aminotransferase levels. The pathologic picture typically shows periportal and perisinusoidal fibrosis, scarce mixed infiltrates, hepatocellular ballooning, and histologic cholestasis. We report two patients with diffuse fibrosis and cholestasis quite similar to the histologic picture of FCH, but in whom neither hepatitis B virus nor hepatitis C virus infection could be shown, highlighting the potential contribution of cytomegalovirus infection and azathioprine toxicity in the development of this severe complication of solid-organ transplantation.

Field theory of self-organized fractal etching

We propose a phenomenological field theoretical approach to the chemical etching of a disordered solid. The theory is based on a recently proposed dynamical etching model. Through the introduction of a set of Langevin equations for the model evolution, we are able to map the problem into a field theory related to isotropic percolation. To the best of the author's knowledge, this constitutes the first application of field theory to a problem of chemical dynamics. By using this mapping, many of the etching process critical properties are seen to be describable in terms of the percolation renormalization group fixed point. The emerging field theory has the peculiarity of being self-organized in the sense that without any parameter fine tuning the system develops fractal properties up to a certain scale controlled solely by the volume V of the etching solution. In the limit V-->infinity the upper cutoff goes to infinity and the system becomes scale invariant. We present also a finite size scaling analysis and discuss the relation of this particular etching mechanism to gradient percolation. Finally, the possibility of considering this mechanism as a generic path to self-organized criticality is analyzed, with the characteristics of being closely related to a real physical system and therefore more directly accessible to experiments.

Hydrogen bonding NH/pi interactions between betacarboline and methyl benzene derivatives

In the presence of benzene, toluene, m-xylene, mesitylene and durene, the pyrrolic NH stretching band of betacarboline, 9H-pyrido[3,4-b]indole, and its 1-methyl derivative, harmane, in tetrachloroethane diminishes in intensity while a new red-shifted band grows up. The shifts of the associated bands increase linearly with the pi-electron density of the substrates. These spectral changes are attributed to the formation of 1:1 molecular association complexes between the betacarbolines and the benzenoid substrates. The complexes are stabilized by the hydrogen-bonding interaction between the pyrrolic NH group of betacarboline and the pi-delocalized electrons of the benzene derivatives. The influence of these NH/pi hydrogen-bonding interactions in the fluorescence spectra of betacarboline is discussed.

Numerical study of persistence in models with absorbing states

Extensive Monte Carlo simulations are performed in order to evaluate both the local (straight theta(l)) and global (straight theta(g)) persistence exponents in the Ziff-Gulari-Barshad (ZGB) [Phys. Rev. Lett. 56, 2553 (1986)] irreversible reaction model. At the second-order irreversible phase transition (IPT) we find that both the local and the global persistence exhibit power-law behavior with a crossover between two different time regimes. On the other hand, at the ZGB first-order IPT, active sites are short lived and the persistence decays more abruptly; it is not clear whether it shows power-law behavior or not. In order to analyze universality issues, we have also studied another model with absorbing states, the contact process, and evaluated the local persistence exponent in dimensions from 1 to 4. A striking apparent superuniversality is reported: the local persistence exponent seems to coincide in both one- and two-dimensional systems. Some other aspects of persistence in systems with absorbing states are also analyzed.

[Experience in the treatment of 98 carcinomas of the nasopharynx. Long-term follow-up and analysis of prognostic factors]

This was a retrospective study of 98 patients (pts.) with histologically confirmed nasopharyngeal carcinoma. The clinico-demographic characteristics were: median age of 53 years (11-83); 74 males and 24 females (ratio 3:1); histology subtype OMS 2-3 in 89 pts. (90.8%); cranial nerve deficits in 11 pts. (11.2%); 50 (51%) were stage T3T4; 68 pts. (69.4%) N2N3 and 77 pts. (78.6%) stage IV. The therapeutic modalities were: radical radiotherapy (RT) alone in 42 pts., chemotherapy (CT) alone in 4 pts., RT + adjuvant CT in 10 pts. and neoadjuvant CT + RT in 42 pts. RT was delivered in wide fields, doses between 50-75 Gy with conventional fractionation. CT consisted in cisplatinum-based schedules (PF in 34 pts., BEC in 9 and others in 13 pts.). Analyzed by treatment, more males and stages N2N3 and IV were accrued in neoCT + RT arm (p < or = 0.05). For the entire population, the overall complete response was achieved in 65 pts. (66.3%); in 27/35 pts. (77.1%) of the RT group and 30/51 pts. (58.8%) of CT + RT group (p 0.07) of pts. with III-IV stages. With a median follow-up of 74.5 months, 32 pts. (32.65%) are alive and free of disease. The projected OS for all pts. was 40 months (m), 51.4% at 3 years (y) and 45.5% at 5 y with a disease free survival of 37 m (0-236). No differences between treatment arms were found (p 0.4). In univariant analysis for OS in stage III-IV pts., age > 50 y, histology OMS1, cranial nerve deficits, stage T3T4 and N2N3, were considered adverse prognostic factors (p < or = 0.05). In multivariant analysis, only age > 50 y and stages T3-T4, N2-N3 were significant (p < or = 0.05). In conclusion, we demonstrated good long term survival without any differences among treatment modalities in pts. with advanced nasopharyngeal carcinomas. New therapeutic approaches are warranted in order to improve the outcome of this patients.

Normal values for serum, ultrafilterable and intraerythrocytic magnesium in children

Serum magnesium (MgS), levels were determined in 137 children age range 2 months to 16 years. Ultrafilterable magnesium (MgU) and intraerythrocytic magnesium (MgI) concentrations were determined in 37 of these children. MgS was 0.83 +/- 0.1 mmol/L (range 0.66-1.36 mmol/L), with no differences between sexes. Children under 2 years had higher MgS levels (0.92 +/- 0.13 mmol/L) than children over 2 years (0.81 +/- 0.08 mmol/L; p < .001). Mean MgU was 0.60 +/- 0.07 mmol/L (range 0.50-0.87 mmol/L), with no differences between sexes. Mean MgI in children was 2.58 +/- 0.33 mmol/L (range 2.06-3.6 mmol/L), with no differences between sexes. MgS correlated with MgU, age, theoretical growth rate, and serum calcium, phosphorus and alkaline phosphatase; MgU correlated with MgI, age, theoretical growth rate, and serum phosphorus. MgS concentration was higher in children under 2 years than in children over 2 years. In healthy children, MgS concentration correlated with MgU, and MgU correlated with MgI, but MgS and MgI showed no correlation.

Serum endothelial adhesion molecules levels correlate with lesion burden in multiple sclerosis patients treated with interferon beta-1b

The levels of serum-soluble intracellular adhesion molecule-1 and soluble endothelial-leukocyte adhesion molecule-1, and the Gadolinium-enhanced T1-weighted MRI were studied in a group of patients with relapsing-remitting multiple sclerosis treated with interferon beta-1b and compared to a non-treated control group. The levels of serum-soluble intracellular adhesion molecule-1 and soluble endothelial-leukocyte adhesion molecule-1 increased, after three months treatment, as compared to baseline and the non-treated MS patients. A significant correlation was found in the treated group between serum-soluble endothelial-leukocyte adhesion molecule-1 and the lesion area in the Gadolinium-enhancing (T2 weighted scan) MRI.

A spectroscopic study of the molecular interactions of harmane with pyrimidine and other diazines

FTIR, UV-vis, steady state and time-resolved fluorescence measurements show that harmane (1-methyl-9H-pyrido/3,4-b/indole) interacts with pyrimidine and its isomers pyrazine and pyridazine in its ground and lowest singlet states. The mechanisms of interaction are dependent on both the structure of the diazine and the nature of the solvent. Thus, in a low polar solvent such as toluene, harmane forms ground state 1:1 hydrogen-bonded complexes with all the diazines. These complexes quench the fluorescence of harmane and diminish its fluorescence lifetime. Conversely, in buffered (pH 8.7) aqueous solutions, pyrimidine behaves differently from the other diazines. Thus, whereas pyrimidine only interacts with harmane in its ground state, pyrazine and pyridazine also interact in the excited state. The harmane-pyrimidine ground state interaction is an entropic controlled process. Therefore, we propose the formation of pi-pi stacked 1:1 complexes between these substrates. Association constants for the different types of complexes and quenching parameters are reported.

Renormalization-group study of one-dimensional systems with roughening transitions

A recently introduced real-space renormalization-group technique, developed for the analysis of processes in the Kardar-Parisi-Zhang universality class, is generalized and tested by applying it to a different family of surface-growth processes. In particular, we consider a growth model exhibiting a rich phenomenology even in one dimension. It has four different phases and a directed percolation-related roughening transition. The renormalization method reproduces extremely well all of the phase diagram, the roughness exponents in all the phases, and the separatrix among them. This proves the versatility of the method and elucidates interesting physical mechanisms.

Recent results on multiplicative noise

Recent developments in the analysis of Langevin equations with multiplicative noise (MN) are reported. In particular, we (i) present numerical simulations in three dimensions showing that the MN equation exhibits, like the Kardar-Parisi-Zhang (KPZ) equation, both a weak coupling fixed point and a strong coupling phase, supporting the proposed relation between MN and KPZ; (ii) present a dimensional and mean-field analysis of the MN equation to compute critical exponents; (iii) show that the phenomenon of the noise-induced ordering transition associated with the MN equation appears only in the Stratonovich representation and not in the Ito one; and (iv) report the presence of a first-order-like phase transition at zero spatial coupling, supporting the fact that this is the minimum model for noise-induced ordering transitions.

Scale invariant dynamics of surface growth

We describe in detail and extend a recently introduced nonperturbative renormalization group (RG) method for surface growth. The scale invariant dynamics which is the key ingredient of the calculation is obtained as the fixed point of a RG transformation relating the representation of the microscopic process at two different coarse-grained scales. We review the RG calculation for systems in the Kardar-Parisi-Zhang (KPZ) universality class and compute the roughness exponent for the strong coupling phase in dimensions from 1 to 9. Discussions of the approximations involved and possible improvements are also presented. Moreover, very strong evidence of the absence of a finite upper critical dimension for KPZ growth is presented. Finally, we apply the method to the linear Edwards-Wilkinson dynamics where we reproduce the known exact results, proving the ability of the method to capture qualitatively different behaviors.

Avalanche and spreading exponents in systems with absorbing states

We present generic scaling laws relating spreading critical exponents and avalanche exponents (in the sense of self-organized criticality) in general systems with absorbing states. Using these scaling laws we present a collection of the state-of-the-art exponents for directed percolation, dynamical percolation, and other universality classes. This collection of results should help to elucidate the connections of self-organized criticality and systems with absorbing states. In particular, some nonuniversality in avalanche exponents is predicted for systems with many absorbing states.

Sample Size Requirements of a Mixture Analysis Method with Applications in Systematic Biology

The available information on sample size requirements of mixture analysis methods is insufficient to permit a precise evaluation of the potential problems facing practical applications of mixture analysis. We use results from Monte Carlo simulation to assess the sample size requirements of a simple mixture analysis method under conditions relevant to biological applications of mixture analysis. The mixture model used includes two univariate normal components with equal variances but assumes that the researcher is ignorant as to the equality of the variances. The method used relies on the EM algorithm to compute the maximum likelihood estimates of the mixture parameters, and the likelihood ratio test to assess the number of components in the mixtures. Our results suggest that sample sizes close to 500 or 1000 data may be required to adequately solve mixtures commonly found in biology. Sample sizes of 500 or 1000 are difficult to achieve. However, use of this MA method may be a reasonable option when the researcher deals with problems which are intractable by other means. Copyright 1999 Academic Press.

Myelodysplastic syndrome with erythroid hypoplasia/aplasia: a case report and review of the literature

Myelodysplastic syndrome (MDS) with erythroid hypoplasia/aplasia has not yet been clearly defined, and in most patients it is mistaken for acquired pure red cell aplasia (PRCA). We report a patient with severe transfusion-dependent anemia (Hb 6.9 g/dl) and reticulocytopenia. WBC and platelet counts were normal. Bone marrow examination showed a marked trilineage dysplasia and a low percentage of erythroid precursors (3%). A diagnosis of MDS (refractory anemia according to FAB classification) with erythroid hypoplasia/aplasia was made. Repeated cytogenetic analysis of bone marrow showed normal karyotypes. Moreover, serial IgM serology and DNA analysis of the patient's sera for B19 parvovirus were negative. Other conditions known to be associated with erythroid aplasia were also absent. The patient failed hematinics and prednisone therapy. He next received r-HuEPO (200 U/kg three times weekly). This form of therapy achieved a rapid and complete erythroid response. He has remained in complete erythroid response after a 7-month period on maintenance therapy of 100 U/kg three times weekly. A review of the literature revealed only 15 well-documented cases of MDS with erythroid hypoplasia/aplasia. All had morphological evidence of myelodysplasia. These patients were predominantly elderly males, all required regular packed red cell transfusions, and had an unfavorable prognosis, mainly because of a high rate of blastic transformation (frequently preceded by a myeloproliferative phase). The mechanism of erythroid hypoplasia in this subgroup of MDS remains uncertain. However, laboratory and clinical data suggest the existence of an intrinsic stem cell defect. None of the patients received hematopoietic growth factors. To our knowledge, our patient is the first case of MDS with erythroid hypoplasia where r-HuEPO was successfully attempted. The description of more cases is necessary to delineate the value of r-HuEPO therapy in this rare variant of MDS.