Globally optimal synthesis of heat exchanger networks. Part I: Minimal networks

This article introduces the concept of minimal structure (MSTR) and presents an enumeration algorithm for the synthesis of heat exchanger networks based on MSTR. Minimal Structures refer to a class of heat exchanger networks featuring acyclic heat transfer networks without energy loops. The enumerations used are either exhaustive or smart with a stopping criterion. Without loss of generality we use the isothermal mixing Synheat model, that is, the method applies identically to other superstructures, with likely variations in the optimization models associated to each step. A conjecture is used to state that the algorithm renders solutions that are globally optimal. Literature examples are used to demonstrate the capabilities of the enumeration algorithm. Most of our solutions compare favorably with the best reported ones in literature, with exceptions where the reported solution is not minimal.     

Planning strategies for a resilient urban fringe in three medium-sized Spanish cities

The fringes between urban areas and their surrounding territory usually concentrate strains of transformation and urban growth. Equally, planning strategies that promote the adaptation of urban development to the identity of territory contribute to the resilience of these urban fringes. This paper aims to illustrate this idea through the analysis of three of Spain’s inland medium-sized cities during the period of intense urban growth that started in the eighties and concluded in 2008. The cases of Vitoria, Zaragoza, and Valladolid clearly show the negative consequences of an expansive urban model in their urban fringes, but also the alternatives that slowly emerged over this period. While the main urban planning tools enabled an unsustainable urban expansion, other planning proposals introduced an alternative approach that mitigated the effects of the real estate boom and have paved the way towards a better future: Vitoria with its green infrastructure, Zaragoza with its integrated development effort that took advantage of an International Exhibition and Valladolid with its coordinated planning. These different tools have a key feature in common: a deep comprehension of their territories as the strongest foundation for conducting urban development in more sustainable ways.     

Parallel computing in bioinformatics: a view from high-performance,heterogeneous, and cloud computing

The Journal of Supercomputing - Bioinformatics allows and encourages the application of many different parallel computing approaches. This special issue brings together high-quality...     

Computational Evolution of Beta-2-Microglobulin Binding Peptides for Nanopatterned Surface Sensors

The bottom-up design of smart nanodevices largely depends on the accuracy by which each of the inherent nanometric components can be functionally designed with predictive methods. Here, we present a rationally designed, self-assembled nanochip capable of capturing a target protein by means of pre-selected binding sites. The sensing elements comprise computationally evolved peptides, designed to target an arbitrarily selected binding site on the surface of beta-2-Microglobulin (β2m), a globular protein that lacks well-defined pockets. The nanopatterned surface was generated by an atomic force microscopy (AFM)-based, tip force-driven nanolithography technique termed nanografting to construct laterally confined self-assembled nanopatches of single stranded (ss)DNA. These were subsequently associated with an ssDNA–peptide conjugate by means of DNA-directed immobilization, therefore allowing control of the peptide’s spatial orientation. We characterized the sensitivity of such peptide-containing systems against β2m in solution by means of AFM-based differential topographic imaging and surface plasmon resonance (SPR) spectroscopy. Our results show that the confined peptides are capable of specifically capturing β2m from the surface–liquid interface with micromolar affinity, hence providing a viable proof-of-concept for our approach to peptide design.     

Ceramic processing and multiferroic properties of the perovskite YMnO3-BiFeO3 binary system

The perovskite (1−x)YMnO₃−xBiFeO₃ binary system is very promising because of its multiferroic end members. Nanocrystalline phases have been recently obtained by mechanosynthesis across the system, and the perovskite structural evolution has been described. Two continuous solid solutions with orthorhombic Pnma and rhombohedral R3c symmetries were found, which coexist within a broad compositional interval of 0.5 ≤ x ≤ 0.9. This might be a polar-nonpolar morphotropic phase boundary region, at which strong phase-change magnetoelectric responses can be expected. A major issue is phase decomposition at moderate temperatures that highly complicates ceramic processing. This is required for carrying out a sound electrical characterization and also for their use in devices. We present here the application of Spark Plasma Sintering to the ceramic processing of YMnO₃-BiFeO₃ phases. This advanced technique, when combined with nanocrystalline powders, allowed densifying phases at reduced processing temperatures and times, so that perovskite decomposition was avoided. Electrical measurements were accomplished, and the response was shown to be mostly dominated by conduction. Nonetheless, the intrinsic dielectric permittivity was obtained, and a distinctive enhancement in the phase coexistence region was revealed. Besides, Rayleigh-type behavior characteristic of ferroelectrics was also demonstrated for all rhombohedral phases. Magnetic characterization was performed in this region, and antiferromagnetism was shown.     

Vibrational states in low-dimensional structures: An application to silicon quantum wires

The Raman scattering in Si nanowires is studied by means of the local bond-polarization model based on the displacement–displacement Green's function within the linear response theory. In this study, the Born potential, including central and non-central interatomic forces, and a supercell model are used. The results show a notable shift of the main Raman peak towards lower energies, in comparison with the bulk crystalline Si case. This shift is compared with the experimental data and discussed within the quantum confinement framework.     

Early detection of breast cancer in Navarra. Diagnostic approach in women sent to a referral hospital

BACKGROUND: Breast cancer screening programs represent an important increase in the number of patients to be evaluated and a higher proportion of subclinical lesions detected in reference hospitals. The authors' experience related to an early detection program initiated in Navarra, Spain (PDPCM) is herein presented. METHODS: The diagnoses made in 319 women referred from the PDPCM to the authors' hospital for mammographic suspicion of malignancy were reviewed. Directed surgical biopsy was carried out in 89 women (27.9%) without previous cytologic study. Fine needle aspiration punction and cytology (FNAP-cytology) were performed as the first diagnostic test in 216 lesions (67.7%) 53 of which were palpable and 163 nonpalpable. Aggressive techniques were not indicated in 14 cases (4.4%). RESULTS: A total of 136 carcinomas (42.6%) were diagnosed and benign lesions were find at biopsy in 112 (35.1%) women. The fifty-seven lesions (17.9%) which did not show malignancy on FNAP-cytology were not biopsied given the insufficient degree of suspicion. Only one false negative has appeared in this group from 27 to 48 months after the first consultation. The global diagnostic reliability was of 99.68%. CONCLUSIONS: Directed surgical biopsy is the most reliable technique for the diagnosis of nonpalpable breast lesions in early stages and is always necessary when there is medium or high radiologic suspicion of malignancy. Fine needle aspiration puncture is a very useful technique to confirm malignancy and to avoid unnecessary biopsies in low suspicion lesions.     

Survival of multiple myeloma patients who are potential candidates for early high-dose therapy intensification/ autotransplantation and who were conventionally treated

PURPOSE: To analyze the outcome of patients with multiple myeloma (MM) who were potential candidates for early high-dose therapy (HDT) intensification followed by autotransplantation from a series treated with conventional chemotherapy. PATIENTS AND METHODS: From January 1985 through December 1989, 487 patients with symptomatic MM were entered onto a randomized study to compare melphalan and prednisone (MP) versus vincristine, cyclophosphamide, melphalan, and prednisone (VCMP) /vincristine, carmustine (BCNU), doxorubicin, and prednisone (VBAP). The sub-group of 77 patients who could have been candidates for early intensification with HDT followed by stem-cell support (ie, < 65 years of age, stage II or III disease, performance status < 3, and objective or partial response to initial chemotherapy) are the subjects of this report. RESULTS: Seventy-seven of 487 patients could have been candidates for early intensification. The median age was 56 years (range, 27 to 64). At diagnosis, 12% had abnormal renal function, 16% hypercalcemia, and 42% serum beta 2-microglobulin level > or = 6 mg/L; 62% had stage III disease at diagnosis. Thirty-six patients were initially treated with MP and 41 with VCMP/VBAP. The median response duration to initial chemotherapy was 22 months, and the actuarial probability of being in continued first response at 5 years was 14%. After a median follow-up time of 58 months, 59 patients have died, one was lost to follow-up evaluation, and 17 are still alive 69 to 119 months after initial chemotherapy. The median survival time from initiation of treatment was 60 months and from the time when autotransplantation would be considered, 52 months. The only independent prognostic parameter for survival was renal function at diagnosis. CONCLUSION: The median survival time of patients with MM who are less than 65 years of age and who respond to initial chemotherapy is 5 years. This survival duration is similar to that reported in selected series of patients given early HDT and stresses the importance of ongoing randomized trials to determine the role of HDT in the treatment of younger myeloma patients.