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Aim We present a case of a recurrent parastomal hernia with enterocutaneous fistula and subcutaneous abscesses and their management. Material & Methods 79-year-old patient with history of pT4b low rectal cancer treated with an abdominoperineal resection with adjuvant chemo-radiotherapy in 2000. Parastomal hernia repair was performed in 2016 with PTFEe mesh according to the Sugarbaker technique and closing midline with double-sided inlay mesh. A plastic peritonitis was found at this moment In July 2021 presented episodes of fever with spontaneous parastomal purulent drainage, deciding initially conservative treatment. Due to persistence of soft tissue infection local surgical drainage was performed in September 2021, removing previous parastomal PTFEe mesh. The patient presented multiple infectious relapses from January to March 2022, debridement was carried out combined with negative pressure therapy. During follow-up intestinal fluid was seen through the negative therapy what put on show an enterocutaneous fistula. Finally, we decided radical surgery in May 2022 performing an in-block resection of end colostomy, 30 cm of ileum and abdominal wall area affected of chronic infection and previous meshes. A 20×20cm defect was left. Reconstruction with double-sided inlay mesh and new colostomy in the right iliac fossa was performed. Skin closure required cutaneous plastia. Conclusions The use of suitable prosthetic material for the repair of parastomal hernia doesn't exclude the developing of severe complications. An early and decisive surgical approach is recommended in cases of chronic prosthetic material infection to avoid redundant and non-cost-effective treatments.

Aim Report an unusual late complication after laparoscopic IPOM Material & Methods Description of a clinical case Results An 84 years old patient who had previously undergone laparoscopic IPOM with ePTFE mesh in 2012 for supraumbilical primary hernia, arrived to the emergency room in March 2022 with a small bowel obstruction due to an intraluminal foreign body impacted at the distal jejunum. In the computerized tomography scan (CT) there was no evidence in the abdominal wall of the intraperitoneal mesh present in a previous CT from 2019. An exploratory laparotomy was warranted. A resection the affected jejunal loops was performed, without evident perforation and clear palpation of an intraluminal foreign body. When the piece was opened, the mesh was found intraluminally, causing the patient's bowel obstruction. Conclusions Intra-abdominal foreign bodies usually cause a chronic inflammatory process that isolate them from neighboring structures by a fibrous capsule. In this case, however, after detaching it from the abdominal wall, the mesh migrated into the intestinal lumen, probably through slow erosion by decubitus. Despite it being an unusual complication, its incidence could increase as the use of intra-abdominal mesh has multiplied in recent years. Given the appearance of non-specific abdominal pain in patients with intra-abdominal mesh, it may be advisable to perform a CT scan to rule out this or other complications associated with the mesh, even many years after the initial surgery.

Objective To study the effect of the incidence of parastomal hernia (PSH) through the prophylactic placement of a preformed intraperitoneal mesh in patients who must undergo a definitive colostomy. The comparison is made with a homogeneous control group that did not receive prophylactic mesh. Material and methods Unicentric, prospective, non-randomized and observational study was performed. Patients were divided in two groups: 30 patients with colorectal neoplastic disease, collected consecutively,who underwent an end colostomy with a profilactic preformed intraperitoneal mesh (Dynamesh IPST®) versus a homogeneous control group (30 patients) who also underwent a definitive end colostomy without prophylactic mesh placement. Primary objective is to determine incidence of PSH in both groups. Secondary objectives were mesh related complications. Demographic variables and early postoperative complications, clinical and radiological follow-up (18–24 months) and presence of clinical and/or radiological PSH were registered. The surgical technique performed in our center is described. Results In the Mesh group there were 0 mesh-related complications at 30 days. In the long term, only 6.6% PSH were recorded in mesh group, while in the control group, a 63% of PSH were observed. Conclusions The incidence of PSH is significantly reduced using prophylactic mesh. Our study corroborates what has already been stated in the literature and does not associate complications. The prophylactic placement of the IPST intraperitoneal mesh in patients who require a definitive end colostomy is a technique that is easy to use in the laparoscopic approach, safe, fast, and easily reproducible, without related complications.

This research is focused on the ammonoids of Oxynotum Zone and Raricostatum Zone (Densinodulum Subzone) from Asturian (Spain) and Lusitanian (Portugal) basins. They come from expanded sections from where 216 specimens have been collected. These have been classified in eight genera and 15 species that belong to families Echioceratidae, Oxynoticeratidae and Eoderoceratidae. Most of the ammonoids are typical of the Northwest European Province. Echioceratidae is the most frequent in the Asturian Basin, whereas Oxynoticeratidae is the predominant in the Lusitanian Basin. Eoderoceratidae specimens are scarcer, and they are registered only between the middle part of Oxynotum Subzone and the lower part of Densinodulum Subzone. A new species is proposed for the upper part of Oxynotum Subzone of the Lusitanian Basin, Plesechioceras rochai sp. nov., which is relatively frequent. As well, also in Portugal, Cheltonia sp. is registered in Densinodulum Subzone, which is a form different from Cheltonia accipitris. This provides new evidence to support the hypothesis of the relation micro-macroconch between the genera Oxynoticeras (M) and Cheltonia (m). Remarkable differences in the studied area are the presence of Paroxynoticeras salisburgense and Plesechioceras cf. delicatum in the Asturias Basin, and Crucilobiceras densinodulum, associated to Oxynoticeras lymense, in the Lusitanian Basin. https://zoobank.org/NomenclaturalActs/FEF11B83-03CA-4BD6-BB15-F3E9926B7C4F

Aim The Spanish Incisional Hernia Surgery Registry (EVEREG) is promoted by the Abdominal Wall section of the Spanish Association of Surgeons, starting data collection in July 2012 and currently has more than 13,500 cases. The objective of this study is to validate the data collected through a pilot audit process Material & Methods A sample of hospitals participating in the EVEREG registry since 2012 is selected. Patients registered in these centers in the period 2012–2019 are included. A stratified random sampling is carried out, with the inclusion of 10% of registered cases per center with a minimum of 20. In the 2020–2021 period, a selection of researchers, different from that of the center to be audited, checks the concordance between the registry data and the data collected in the patient's clinical history, either in person or online. Results 330 patients have been analyzed, out of a total of 2673 registered, in 9 participating centers. The average accuracy has been 95.7% (99.1–79.35%). With 1.5% incorrect data and 2.28% missing data Conclusions This is the first validity study of an abdominal wall registry The accuracy greater than 95% obtained allows us to determine an excellent quality in the data collection of the EVEREG registry. We believe that the confirmation of these data in all the centers participating in the registry would guarantee the quality of the studies carried out and their comparison with other international registries

Presentado en sesión de 10 de mayo de 1950

This work introduces a procedure based on the real time monitoring of the specimen's compliance for the experimental characterization of the fatigue behaviour of interlaminar cracks in composites. The methodology was applied to a mode II loading in a three-point end notch flexure test. The onset point for fatigue damage was determined with a precision of one cycle by establishing a threshold on the compliance variation from its initial value. On the other hand, the crack growth rate curve was derived from the continuous monitoring of the compliance and an experimental calibration of said compliance. The precision of this methodology allowed the effect of commonly neglected phenomena such as the thermal expansion of the testing system or the friction between the specimen and the fixture, to be unveiled This work has been funded by the Spanish Minsterio de Economía y Competitividad through the project MAT2012-37552-C03-03

PV and Wind energy have led the development and installation of Renewable Energy (RE) technologies worldwide, already reaching economic competitiveness against traditional fossil-fueled power plants in certain markets. However, Variable Renewable Energy or VRE is hard to control, requiring backup technologies to guarantee grid stability. The long-term target of decarbonizing the electric sector will therefore require additional flexibility and dispatchability from VRE generation. Weak and/or isolated grids, such as islands, are already dealing with these VRE limitations, with the additional burden of energy dependency leading to high electricity costs. GRIDSOL project presents a novel approach to increase RE penetration in these markets: Smart Renewable Hubs (SRH), where hybrid synchronous generators are integrated with VRE under a dynamic control system (DOME), self-regulating and providing ancillary grid services thanks to firm, flexible and mostly renewable generation on a single output, tailored to a specific location to maximize cost-effectiveness with no additional reserve required. A preliminary assessment of a Smart Renewable Hub (“HYSOL” (CSP+GT), PV and batteries) implementation is presented and compared with competing alternatives (gas turbine in open (OCGT) or combined (CCGT) cycle, PV and batteries) in an isolated grid (an island in the Mediterranean Sea), showing how GRIDSOL would reduce the overall operating cost in a high-RE scenario.

The Perforated Core Buckling Restrained Brace (PCBRB) is a new energy dissipation device for the seismic design of buildings. Its core consists of a perforated steel yielding plate which is guided and partially stabilized by the restraining unit. The core is mechanized to obtain two yielding lateral bands which are connected by several equidistant stabilizing bridges. The lateral bands are designed to yield to axial forces, as conventional BRBs do, so the force and the displacement at the yielding point can be calculated by the usual expressions of conventional buckling restrained braces, based on uniform strain distribution. To distribute the stabilizing bridges along the core, an expression based on Euler’s formulation is proposed. Under this formulation two types of specimens have been designed and tested (Type I and Type II) using three different loading protocols. The Type I specimens exhibited a stable response, while the Type II specimens suffered a progressive loss of compression capacity produced by the local buckling. Finally, the hysteretic behaviour of the tested braces and a large scale brace has been analysed with an FEM model which considers the interaction between the core and the encasing member. The model reproduces the hysteretic response during the first cycles and the influence of friction on the axial strain distribution along the yielding core.

The European Water Framework Directive has pointed out that the best model for water management is management by river basin. However, to obtain an overview of the water quality in a river basin system, one has to look at the individual components of the system such as the sewer network, the wastewater treatment plant and the receiving water bodies and the interaction between them. Within this study, we develop an adjusted model from the original state-of-the-art activated sludge ASM2d model with as main focus to maximize the compatibility with the sewage and river water quality models while still assuring a sufficient prediction capacity of the activated sludge system. To this end, and to avoid the commonly required fractionation into the classic activated sludge model state variables, the latter are directly derived from the outputs of the sewage model (e.g., BOD5, COD, TN or TP) for the adjusted model. Furthermore, the modified ASM2d model is made more realistic and can be more broadly applied due to the re-introduction of organic nitrogen and phosphorus component state variables. While developed on the basis of the data of a wastewater treatment plant in Belgium, the validation of the adjusted model on a data set of a wastewater treatment plant in Girona (Spain) is highly promising.

This paper proposes an innovative BRB as a new energy dissipation device for earthquake resistant buildings. Its steel yielding core is modular, and this very design enables the yielding force and plastic deformation to be adjusted according to building requirements. Based on connecting several Seriated Modules, which are comprised of any constant number of Shear Basic Dissipation Units, deformation is proportional to the number of Seriated Modules and force to the number of Shear Basic Dissipation Units (on the Seriated Modules). Assembling the brace consists of sliding the greased yielding core into the restraining unit and coupling it with pins, thus providing easy inspection or replacement of the dissipation unit if required. Fully-scaled prototypes have been tested under reversal cyclic displacements and the hysteretic response has been proved stable and with a high cumulative ductility. The main parameters are the yielding force and the yielding displacement; which can be predicted with simple expressions. A methodology to design a restraining unit able to tackle of buckling by taking into account the initial sway deformation and the functional gap between the yielding core and the restraining unit is proposed. The hysteretic behavior has been simulated with conventional FEM software.

One of the main controversial items in palaeoclimatology is to elucidate if climate during the Jurassic was warmer than present day, with no ice caps, or if ice caps were present in some specific intervals. The Pliensbachian Cooling event (Lower Jurassic) has been pointed out as one of the main candidates to have developed ice caps on the poles. To constrain the timing of this cooling event, including the palaeoclimatic evolution before and after cooling, as well as the calculation of the seawater palaeotemperatures are of primary importance to find arguments on this subject. For this purpose, the Rodiles section of the Asturian Basin (Northern Spain), a well exposed succession of the uppermost Sinemurian, Pliensbachian and Lower Toarcian deposits, has been studied. A total of 562 beds were measured and sampled for ammonites, for biostratigraphical purposes and for belemnites, to determine the palaeoclimatic evolution through stable isotope studies. Comparison of the recorded uppermost Sinemurian, Pliensbachian and Lower Toarcian changes in seawater palaeotemperature with other European sections allows characterization of several climatic changes of probable global extent. A warming interval which partly coincides with a negative δ13Cbel excursion was recorded at the Upper Sinemurian. After a "normal" temperature interval, a new warming interval that contains a short lived positive δ13Cbel peak, was developed at the Lower-Upper Pliensbachian transition. The Upper Pliensbachian represents an outstanding cooling interval containing a positive δ13Cbel excursion interrupted by a small negative δ13Cbel peak. Finally, the Lower Toarcian represented an exceptional warming period pointed as the main responsible for the prominent Lower Toarcian mass extinction.

In this paper we describe T. pallisei sp. n., a new representative of the genus Troglocharinus Reitter, 1908 (Coleoptera, Leiodidae, Leptodirini), a strictly subterranean genus restricted to the Eastern Pyrenees and some coastal areas in Catalonia. All known specimens of T. pallisei sp. n. were collected in a cave next to the town of La Riba, in the province of Tarragona (Spain), situated between the distribution areas of the species of the T. orcinus complex and T. espanoli Jeannel, 1930. It can be separated from the other members of the T. orcinus complex by the presence of penicillus in the apex of the parameres of the aedeagus and from T. espanoli by the presence of a mesoventral keel; it also differs from both by its long and erect pubescence. A Bayesian molecular phylogeny including representatives of the main lineages within the genus Troglocharinus, based on ca. 5211 Kb of 5 mitochondrial and 4 nuclear genes, placed T. pallisei sp. n. as sister to T. orcinus Jeannel, 1910, and both sister to T. espanoli, in perfect agreement with their geographic distributions and the inferred geographic expansion of the genus to the south, with an estimated divergence of ca. 1.3 Ma. In agreement with the results of a previous phylogenetic study, the subgenus Antrocharidius Jeannel, 1910 is synonymised with Troglocharinus (syn.n.).

This chapter reviews the structure and properties of silica nanomaterials and their use in photodynamic therapy, encapsulation of antioxidants and ultraviolet filters. Examples showing state of the art of the subject and the advantages of the use of these materials will be discussed.

Wastewater treatment plant operators encounter complex operational problems related to the activated sludge process and usually respond to these by applying their own intuition and by taking advantage of what they have learnt from past experiences of similar problems. However, previous process experiences are not easy to integrate in numerical control, and new tools must be developed to enable re-use of plant operating experience. The aim of this paper is to investigate the usefulness of a case-based reasoning (CBR) approach to apply learning and re-use of knowledge gained during past incidents to confront actual complex problems through the IWA/COST Benchmark protocol. A case study shows that the proposed CBR system achieves a significant improvement of the benchmark plant performance when facing a high-flow event disturbance.

In this paper the development of an extension module to the IWA/COST simulation benchmark to include expert reasoning is presented. This module enables the detection of suitable conditions for the development of settling problems of biological origin (filamentous bulking, foaming and rising sludge) when applying activated sludge control strategies to the simulation benchmark. Firstly, a flow diagram is proposed for each settling problem, and secondly, the outcome of its application is shown. Results of the benchmark for two evaluated control strategies illustrate that, once applied to the simulation outputs, this module provides supplementary criteria for plant performance assessment. Therefore, simulated control strategies can be evaluated in a more realistic framework, and results can be recognised as more realistic and satisfactory from the point of view of operators and real facilities.

Aims: In the present study we evaluated the potential application of the flow cytometry (FC) technique to determine the growth rates of Mycoplasma hyopneumoniae in a broth medium. Methods and Results: The FC analysis was performed using the fluorochromes Syto 9, propidium iodide (PI) or a combination of both dyes and results were compared with those obtained by colour-changing units (CCU) and pH measurements. While CCU counts ml−1 were higher than those obtained from the FC technique, a good relation between M. hyopneumoniae growth rates was observed in the different phases of the growth curve (logarithmic, stationary and senescence phases). Labelling with Syto 9 alone was sufficient to differentiate M. hyopneumoniae cells with different amounts of nucleic acids, in the stationary and senescence phase of the M. hyopneumoniae growth curve. PI labelling did not detect cell death in the end phase of M. hyopneumoniae growth. Conclusions: These data show that FC is a very useful, practical and fast technique to study the growth rates of M. hyopneumoniae in broth medium. Significance and Impact of the Study: This is to our knowledge the first application of FC to the study of M. hyopneumoniae growth in broth culture.

We report a novel application of calcein-acetomethyl ester in flow cytometry for rapid estimation of the number of G+-bacteria in rodent feces (Apodemus sylvaticus and Mus sp.f. muridae). We also use the combined application of flow cytometry and Syto-13 or Sypro Orange staining to count rapidly the total bacterial population and to describe bacterial subpopulations in the intestine.

Objectives: Quality control is difficult to achieve in Congenital Heart Surgery (CHS) because of the diversity of the procedures. It is particularly needed, considering the potential adverse outcomes associated with complex cases. The aim of this project was to develop a new method based on the complexity of the procedures. Methods: The Aristotle project, involving a panel of expert surgeons, started in 1999 and included 50 pediatric surgeons from 23 countries, representing the EACTS, STS, ECHSA and CHSS. The complexity was based on the procedures as defined by the STS/EACTS International Nomenclature and was undertaken in two steps: the first step was establishing the Basic Score, which adjusts only the complexity of the procedures. It is based on three factors: the potential for mortality, the potential for morbidity and the anticipated technical difficulty. A questionnaire was completed by the 50 centers. The second step was the development of the Comprehensive Aristotle Score, which further adjusts the complexity according to the specific patient characteristics. It includes two categories of complexity factors, the procedure dependent and independent factors. After considering the relationship between complexity and performance, the Aristotle Committee is proposing that: Performance ¼ Complexity £ Outcome. Results: The Aristotle score, allows precise scoring of the complexity for 145 CHS procedures. One interesting notion coming out of this study is that complexity is a constant value for a given patient regardless of the center where he is operated. The Aristotle complexity score was further applied to 26 centers reporting to the EACTS congenital database. A new display of centers is presented based on the comparison of hospital survival to complexity and to our proposed definition of performance. Conclusion: A complexity-adjusted method named the Aristotle Score, based on the complexity of the surgical procedures has been developed by an international group of experts. The Aristotle score, electronically available, was introduced in the EACTS and STS databases. A validation process evaluating its predictive value is being developed. q 2004 Published by Elsevier B.V.

Histogram comparison and meaningful statistics in flow cytometry is probably the most widely encountered mathematical problem in flow cytometry. Ideally, a test for determining the statistical equality or difference of flow cytometric distributions will identify the significant differences or similarities of the obtained histograms. This situation is of particular interest when flow cytometry is used to study the heterogeneity of axenic bacterial populations. We have statistically measured the heterogeneity of successive cytometric measures, the modifications produced after 20 transfers from the same culture, and the differences between 20 subcultures of identical origin. The heterogeneity of the bacterial populations and the similarity of the obtained 360 histograms were analysed by standard statistical methods. We have studied bacterial axenic cultures in order to detect, quantify and interpret their cytometric heterogeneity, and to assess intrinsic differences and differences produced by laboratory manipulations. We concluded that the standard axenic cultures have a considerable intrinsic cellular and molecular heterogeneity. We suggest that the heterogeneity we have detected basically has two origins: cell size diversity and cell cycle variations.

Background The fusogenic (F) membrane glycoprotein of the paramyxovirus SV5 allows virus to enter host cells and mediates fusion between neighboring cells, which leads to cell death. F glycoprotein is synthesized as an inactive precursor (F0) that is cleaved by cellular protease furine to form the active heterodimer F1 + F2. The active protein can induce syncytium formation in the absence of another integral glycoprotein (HN), a property that appears to be unique among paramyxoviruses. Methodology We constructed a non-replicative adenovirus to express SV5 F protein in tumor cells, and its fusion capacity was analyzed by fluorescent and confocal microscopy. Cell viability and bystander effect were compared with the thymidine kinase/ganciclovir suicide gene therapy. The structure of F-expressing cells was studied using electron microscopy. Results F glycoprotein expression induced syncytium formation to a maximum at 72 h, after which syncytia progressively lost viability and detached. The cell membrane was disrupted while nuclear structure was preserved. Over-expression of SV5 F protein in tumor cells led to high cytotoxicity comparable with that associated with the thymidine kinase/ganciclovir. A potent bystander killing effect was detected until the ratio of F-transduced to non-transduced cells was 1 : 100. Conclusions These results indicate that the fusogenic glycoprotein of the paramyxovirus SV5 could be used to eliminate tumor cells and may encourage studies aimed at modifying its selectivity and combining its expression with other cytotoxic strategies to improve their efficacy. Copyright © 2003 John Wiley & Sons, Ltd.

Streptococcus agalactiae causes a severe systemic disease in fish, and the routes of entry are still ill-defined. To address this issue, two groups of 33 red tilapia Oreochromis spp. each of 10 g were orally infected with S. agalactiae (n = 30), and by immersion (n = 30), six individuals were control-uninfected fish. Three tilapias were killed at each time point from 30 min to 96 h post-inoculation (pi); controls were killed at 96 h. Samples from most tissues were examined by haematoxylin-eosin (HE), indirect immunoperoxidase (IPI) and periodic acid-Schiff; only intestine from fish infected by gavage was evaluated by transmission electron microscopy. The results of both experiments suggest that the main entry site of S. agalactiae in tilapia is the gastrointestinal epithelium; mucus seems to play an important defensive role, and environmental conditions may be an important predisposing factor for the infection.

This report provides an overview of expected housing density changes and related impacts to private forests on America's islands in the Pacific and Caribbean, specifically Hawaii, Guam, American Samoa, the Commonwealth of the Northern Mariana Islands, Puerto Rico, and the U.S. Virgin Islands. We discuss the vulnerability of island forests to conversion for housing development, introduction and spread of invasive species, and risk of uncharacteristic wildfire, among other concerns. Our maps and projections suggest that in localized areas from 3 to 25 percent of private forest land is likely to experience a substantial increase in housing density from 2000 to 2030. Resource managers, developers, community leaders, and landowners should consider the impacts of housing development and invasive species on ecosystem services in coming decades.

Congenital tracheal stenosis (CTS) is a rare malformation that usually require corrective surgery. Resection and tracheal anastomosis is the treatment of choice when the stenosis is short. However, such an approach is not usually viable when the CTS is long, given that anastomotic pressure would be too great. New surgical techniques have allowed this serious airway malformation to be corrected satisfactorily. We report the case of a three-year-old boy with a long CTS (51% of the length of the trachea) treated with a new reconstructive technique called slide tracheoplasty. Outcome was excellent.

Several fluorochromes (rhodamine 123, bis-oxonol, propidium iodide, SYTO-13 and calcein) were tested by flow cytometry for their ability to determine cell density, viability and heterogeneity in Staphylococcus aureus cultures exposed to heating (60–70–80°C for 2 min), formaldehyde 2% for 20 min and gramicidin-S at 2–5–10 μg/ml for 20 min. Results were validated by viable plate count and counts performed with a particle analyser. Flow cytometry gave quicker results and more accurate information about intermediate states and heterogeneity of S. aureus cultures than viable plate counts. Rhodamine 123 and oxonol were found to be efficient dyes for the assessment of bacterial viability. SYTO-13 was an excellent marker for total counts and calcein can be used to assess metabolic activity.

Assessment of cell viability using methods which do not require cell culture is essential in the field of aquatic microbiology, since many bacteria known to be present in aquatic environments cannot be grown in culture. The study of bacterial biofilms, which previously needed an epifluorescent microscope, has recently been enhanced by the use of flow cytometry and confocal scanning laser microscopy (CSLM). A method based on the combination of several membrane potential related dyes, a membrane integrity dye and a redox probe was used to measure cell viability by flow cytometry and confocal laser microscopy. Rhodamine-propidium iodide (PI) double staining was used to discriminate viable from nonviable cells in CSLM observations. Membrane depolarization during E. coli and Salmonella starvation measured by DiBAC4(3) incorporation (flow cytometry and CSLM) was found to be in concordance with respiratory activity as detected by a tetrazolium salt (CTC) reduction.

We study the dependence of the Stark shift optical nonlinearity of GaAs-AlGaAs multiple quantum-well hetero n-i-p-i's on the number of quantum wells per intrinsic region in otherwise identical hetero n-i-p-i's. We determine that /spl sigma//sub eh/, the nonlinear absorption cross section, is proportional to the number of quantum wells per intrinsic region. A study of the fluence dependence of /spl sigma//sub eh/ shows that the saturation carrier density is inversely proportional to the number of wells per intrinsic region. We find that the turn-on time of the nonlinear absorption change in our samples is independent of the number of quantum wells per intrinsic region. All of these results are consistent with the absence of retrapping of photogenerated carriers. >

High resolution monochromatic synchrotron-radiation diffraction images of five, high quality epitaxial heterojunctions on silicon, gallium arsenide, and indium phosphide substrates display several forms of accommodation to lattice mismatch. From the images, we deduce a coherent set of factors for the loss of crystalline order in layered semiconducting crystals. Lattice mismatch is demonstrated in each of the systems by warping after layer deposition. Nevertheless, local lattice orientation is maintained across each layer interface. In two of the systems, one severely mismatched while the other is not, no arrays of dislocations appear. Sets of mixed linear lattice mismatch dislocations, consistent with identification as 60° dislocations, are found in two of the other systems with intermediate degrees of mismatch. A set of pure edge dislocations penetrating all layers is found in a system with a grid structure. These observations indicate that the formation of extensive arrays of dislocations during uniform one micrometer layer deposition depends not only on the extent of lattice mismatch and layer thickness but also on the degree of crystalline order of the substrate. Establishment of a nonpseudomorphic layer mismatched with the substrate by several tenths of a percent is an important factor, as previously determined. However, localized absence of crystalline order, e.g. in the form of scratches or dislocations in the substrate, appears also to be required for the formation of arrays of interface mismatch dislocations. Where these criteria are not fulfilled, the formation of dislocations in uniform layered systems is inhibited. Localized residual stress can initiate dislocation formation even where it would not appear in uniform layers. The images show also that crystalline disorder in state-of-the-art indium phosphide differs markedly from that in comparable gallium arsenide. Understanding of crystalline order in both monolithic materials is extended by this work.

Superlattices composed of III–V heterostructures have established applications in high‐speed electronic and optoelectronic devices. As layer thicknesses are reduced, the role of heterostructure interface sharpness becomes more critical to ensuring high quality two‐dimensional growth. In this work, short‐period (less than 1 nm) superlattices with active layer thicknesses of 31 nm were investigated to assess interface roughness in the initial stages of growth. X‐ray diffraction was used to evaluate interface roughness and to calculate superlattice periodicity. Results suggest that surface roughening by islanding may be promoted by GaAs buffer layers that are 10–100 nm thick. Smoother interfaces were obtained in samples with buffer layers 250 nm and greater.

High resolution monochromatic synchrotron X-radiation diffraction images of several high quality multilayer systems suggest several factors in the establishment of irregularities in layerd semiconducting crystals. The nucleation of extensive arrays of dislocations during uniform one micro meter layer deposition appears to depend not only on the extent of lattice mismatch and layer thickness but also on the regularity of the substrate. Propagation of arrays of mismatch dislocations appears to depend on the character of the unit cell.

Etching studies involving citric acid/hydrogen peroxide (C 6 H 8 O 7 :H 2 O 2 ) at volume ratios from 0.5: 1 to 50: 1 were found to provide good selective etching of various III-V semiconductor materials grown on GaAs and InP substrates using molecular beam epitaxy. Both selective and uniform (nonselective) etching regions were found between these material systems by choosing different concentration volume ratios of citric acid/hydrogen peroxide (χC 6 H 8 O 7 :1H 2 O 2 )

Close to 80 percent of the U.S. population lives in urban areas and depends on the essential ecological, economic, and social benefits provided by urban trees and forests. However, the distribution of urban tree cover and the benefits of urban forests vary across the United States, as do the challenges of sustaining this important resource. As urban areas expand across the country, the importance of the benefits that urban forests provide, as well as the challenges to their conservation and maintenance, will increase. The purpose of this report is to provide an overview of the current status and benefits of America's urban forests, compare differences in urban forest canopy cover among regions, and discuss challenges facing urban forests and their implications for urban forest management.

Superlattices composed of aluminum, gallium and indium are currently employed in a variety of device-related applications. Among these are edge-emitting GRINSCH lasers and vertical cavity surface emitting laser diodes. As the individual layer thickness is reduced, the role of interface sharpness becomes more critical in ensuring good two-dimensional growth. This work addresses the relationship between interface roughness and superlattice crystallinity for short-period AlAs/GaAs superlattices. Thin short-period superlattices with active layer thicknesses of 30 nm or less were also investigated to help determine the interface sharpness in the initial stages of growth. X-ray diffraction was used to assess interface roughness and to calculate superlattice periodicity. These results are compared with those obtained by reflection high energy electron diffraction (RHEED), Raman spectroscopy, and spectroscopic ellipsometry. The results indicate that interface roughness is promoted by a reduced arsenic flux growth condition at normal growth temperatures for short-period superlattices. The results also suggest that, for thin superlattices, a 10 nm buffer layer enhances interface roughness in the initial stages of growth and compromises the subsequent epilayer crystallinity. An analysis of these results in the light of structural, dynamical, and optical data is presented.

Etching studies involving citric acid/hydrogen peroxide (C 6 H 8 O 7 :H 2 O 2 ) at volume ratios from 0.5: 1 to 50: 1 were found to provide good selective etching of various III-V semiconductor materials grown on GaAs and InP substrates using molecular beam epitaxy. Both selective and uniform (nonselective) etching regions were found between these material systems by choosing different concentration volume ratios of citric acid/hydrogen peroxide (χC 6 H 8 O 7 :1H 2 O 2 )

The authors examine ion implantation and rapid-thermal processing for the fabrication of quantum-well, compound-semiconductor heterostructure devices in strained and in lattice-matched material systems. The authors demonstrate improvements to the performance of two classes of devices that would be particularly sensitive to process-induced defects: p-channel strained-quantum-well field-effect transistors and single-quantum-well diode lasers. The authors correlated the device results with secondary-ion mass spectroscopy, Hall-effect, transmission-electron microscopy, and photoluminescence. >

H implantation into bulk and Ti-diffused LiNbO3 is shown to result in the creation of optically absorbing layers. The induced absorption is characterized, and application to the suppression of optical noise in Ti:LiNbO3 integrated optical spectrum analyzers is considered. Potential uses include beam dumps, spatial filters, and the absorption of substrate modes.