bluuebunny/crossref_metadata_2025 huggingface dataset:
Species richness in boreal swamp forests of SE Norway: The role of surface microtopography
Authors: Økland Rune H. , Rydgren Knut , Ø kland Tonje
Published: December 2007

Question: What is the relative importance of environmental gradients and surface microtopography (variation in vertical level within sampling units) for fine‐scale plant species richness in Picea abies swamp forests?

Location: 11 swamp forests in SE Norway.

Methods: We recorded species richness (number of species of vascular plants, mosses, Sphagnum and hepatics), depth to water table, soil base status and vertical range (microtopographic relief) in 2400 microplots, (each 1/16 m2), in 150 1‐m2 plots in the 11 swamp forests. Relationships between species richness and environmental predictors were modelled by GLMM.

Results: Moss and hepatic species richness increased with increasing microtopographic relief, most strongly for wet acid sites, in which similar trends were also found for Sphagnum. Relief was a poor predictor of vascular plant species richness.

Conclusions: Microtopographic relief is a good predictor of local species richness in Picea abies swamp forests, partly because larger vertical variability means higher within‐plot habitat diversity with respect to the wet‐dry gradient, and partly because qualitatively new microhabitats associated with steep slopes are added in drier sites. The relationship between species richness and microtopographic relief is context dependent, differing in complex ways among species groups and among sites with different environmental conditions.
Spatial patterns in cushion‐dominated plant communities of the high Andes of central Chile: How frequent are positive associations?
Authors: Fajardo Alex , Quiroz Constanza L. , Cavieres Lohengrin A.
Published: December 2007

Question:In stressful abiotic environments positive plant interaction is expected to be a frequent and an important process driving community composition and structure. In the high Andes in central Chile, the cushion plantAzorella madreporicadominates plant communities and appears to benefit the assemblage of species that grows within it. However, there are also many other species that grow outside this nurse cushion plant, which may or may not interact with this species. What is the prevailing type of spatial associations among the plant species that are not growing inside the nurse plant? What is the type of interactions between cushion plants and those species growing outside them?

Location:Molina River basin (33°20'S, 70°16’ W, 3600 m a.s.l.), in the Andes of central Chile, ca. 50 km east of Santiago.

Methods:Two accurate mapping plots of individual plants of different species were located at two summits (Franciscano and Tres Puntas sites). The spatial distributions and associations between species growing outside cushions and within cushions at each site were estimated by point‐pattern analyses using the univariate and bivariate transformations of Ripley'sK‐functions.

Results:We found both positive and, especially, negative spatial associations (8 out of 12 species in Franciscano site) betweenA. madreporicacushions and plants growing outside them. However, most of the species showed positive spatial associations among them. The variation in spatial association was site‐specific and also depended on the type of plants involved.Adesmiaspp., the second most abundant non‐cushion species, displayed negative associations with cushions and positive associations with other species growing outside cushions.

Conclusions:Our study suggests very complex interactions among species, which ranged from positive to negative, and are also affected by abiotic environmental conditions.
Are traits measured on pot grown plants representative of those in natural communities?
Authors: Mokany Karel , Ash Julian
Published: December 2007

Question: The quantification of functional traits in natural communities can be difficult (e.g. root traits, RGR). Can functional traits measured on pot grown plants be reliably applied to natural communities? Alternatively, can below‐ground plant traits be predicted from above‐ground traits?

Location: Southeastern Australia.

Methods: We compared 17 shoot, root and whole‐plant morphological traits measured on 14 plant species in a native grassland community to those measured under two different pot conditions: unfertilised and fertilised.

Results: The majority of trait values for pot grown plants differed to plants in the field, however, species ranking remained consistent for most leaf traits between the field and the two pot growing conditions. In contrast, species ranking was not consistent for most whole plant traits when comparing field plants to fertilised pot grown plants, providing a caution against the tendency to grow plants in controlled conditions at ‘optimal’ (high) resource levels. Moderate to strong correlations were found between below‐ground and above‐ground plant traits, including between root dry matter content and leaf dry matter content, and between specific root area and specific leaf area.

Conclusions: The utility of pot grown plants to quantify traits for field plants is highly dependent on the selection of the growing conditions in the controlled environment. The consistency we observed between above‐ground and below‐ground trait strategies suggests that below‐ground traits may be predictable based on above‐ground traits, reducing the need to quantify root traits on cultured plants.
Scale‐dependence of vegetation‐environment relationships in semi‐natural grasslands
Authors: Auestad Inger , Rydgren Knut , Økland Rune H.
Published: December 2007

Questions: Which environmental and management factors determine plant species composition in semi‐natural grasslands within a local study area? Are vegetation and explanatory factors scale‐dependent?

Location: Semi‐natural grasslands in Lærdal, Sognog Fjordane County, western Norway.

Methods: We recorded plant species composition and explanatory variables in six grassland sites using a hierarchically nested sampling design with three levels: plots randomly placed within blocks selected within sites. We evaluated vegetation‐environment relationships at all three levels by means of DCA ordination and split‐plot GLM analyses.

Results: The most important complex gradient determining variation in grassland species composition showed a broad‐scale relationship with management. Soil moisture conditions were related to vegetation variation on block scale, whereas element concentrations in the soil were significantly related to variation in species composition on all spatial scales. Our results show that vegetation‐environment relationships are dependent on the scale of observation. We suggest that scale‐related (and therefore methodological) issues may explain the wide range of vegetation‐environment relationships reported in the literature, for semi‐natural grassland in particular but also for other ecosystems.

Conclusions: Interpretation of the variation in species composition of semi‐natural grasslands requires consideration of the spatial scales on which important environmental variables vary.
Facilitation of Quercus ilex recruitment by shrubs in Mediterranean open woodlands
Authors: Smit Christian , den Ouden Jan , Díaz Mario
Published: December 2007

Question: Insufficient tree regeneration threatens the long‐term persistence of biodiverse Mediterranean open oak woodlands. Could shrubs, scarce due to decades of management (clearing and ploughing), facilitate holm oak recruitment at both acorn and seedling stages?

Location: Open oak woodlands in Central Spain.

Methods: Plots with four acorns were planted: (1) under the canopy of the spiny shrub Genista hirsuta, (2) in a small cage, protecting against ungulates, (3) in a shaded cage, protecting against ungulates and sun, and (4) in open grassland. Sets of these four treatments were spatially grouped according to a randomised block design, with 16 blocks near (< 10 m) and 16 away from (> 20 m) parent trees to test for distance‐related survival. Plots were regularly checked for seed removal. After emergence one seedling per plot (97 in total) was selected and its survival monitored.

Results: Three months after sowing, 199 of 512 acorns were removed, predominantly by rodents. Acorn removal occurred at each treatment but was highest under shrubs. Eight months after sowing, seedling survival was highest under shrubs (50%), followed by shaded cages (16%), open grassland (4%) and cages (0%). Main mortality cause was drought (90%), killing most seedlings between June and July. No seedlings died from ungulate browsing.

Conclusion: Shrubs demonstrated clear net facilitative effects for Quercus ilex recruitment, despite higher seed removal. Shading appears the crucial factor facilitating seedling survival. We therefore propose that lack of shrubs contributes largely to tree recruitment failure in Mediterranean open woodlands; management should aim at conserving shrubs.
Tolerance of Pinus taeda and Pinus serotina to low salinity and flooding: Implications for equilibrium vegetation dynamics
Authors: Poulter Benjamin , Christensen Norman L. , Qian Song S.
Published: December 2007

Questions: 1. Do pine seedlings in estuarine environments display discrete or continuous ranges of physiological tolerance to flooding and salinity? 2. What is the tolerance of Pinus taeda and P. serotina to low salinity and varying hydrologic conditions? 3. Are the assumptions for ecological equilibrium met for modeling plant community migration in response to sea‐level rise?

Location: Albemarle Peninsula, North Carolina, USA.

Methods: In situ observations were made to quantify natural pine regeneration and grass cover along a salinity stress gradient (from marsh, dying or dead forest, to healthy forest). A full‐factorial greenhouse experiment was set up to investigate mortality and carbon allocation of Pinus taeda and P. serotina to low‐salinity conditions and two hydrology treatments over 6 months. Treatments consisted of freshwater and two salinity levels (4 ppt and 8 ppt) under either permanently flooded or periodically flushed hydrologic conditions.

Results: Natural pine regeneration was common (5–12 seedlings per m2) in moderate to well‐drained soils where salinity concentrations were below ca. 3.5 ppt. Pine regeneration was generally absent in flooded soils, and cumulative mortality was 100% for 4 and 8 ppt salinity levels under flooded conditions in the greenhouse study. Under weekly flushing conditions, mortality was not significantly different between 0 and 4 ppt, confirming field observations. Biomass accumulation was higher for P. taeda, but for both pine species, the root to shoot ratio was suppressed under the 8 ppt drained treatment, reflecting increased below‐ground stress.

Conclusions: While Pinus taeda and P. serotina are commonly found in estuarine ecosystems, these species display a range of physiological tolerance to low‐salinity conditions. Our results suggest that the rate of forest migration may lag relative to gradual sea‐level rise and concomitant alterations in hydrology and salinity. Current bioclimate or landscape simulation models assume discrete thresholds in the range of plant tolerance to stress, especially in coastal environments, and consequently, they may overestimate the rate, extent, and timing of plant community response to sea‐level rise.
Vision loss after spine surgery: review of the literature and recommendations
Authors: Baig Mirza N. , Lubow Martin , Immesoete Phillip , Bergese Sergio D. , Hamdy Elsayed-Awad , Mendel Ehud
Published: December 2007

✓In recent studies spinal surgery has replaced cardiac surgery as a leading cause of postoperative vision loss (POVL). Estimates of the incidence of POVL after spinal surgery range from 0.028 to 0.2%, but with advances in complex spinal instrumentation and the rise in annual spinal operations, POVL may see an ominous increase in its incidence. Postoperative vision loss is an uncommon but devastating complication, with unknown origin and pathogenesis. The authors undertook a literature review and summarize the current understanding of its pathophysiology, highlight the limitations of existing knowledge, and recommend practical guidelines for avoiding this devastating outcome.
Neuroophthalmological management of optic pathway gliomas
Authors: Lee Andrew G.
Published: December 2007

✓ The growth rate of optic pathway gliomas (OPGs) is unpredictable and quite variable, especially in children with neurofibromatosis Type 1 (NF1). Close neuroophthalmalogical clinical follow-up with serial imaging (magnetic resonance imaging of the brain with and without contrast enhancement) is the recommended initial step in management to establish the growth rate of the lesion in an individual patient. Typically, only symptomatic and/or radiographically growing tumors require treatment, and observation is the accepted first-line option. Although both chemotherapy and radiotherapy can stabilize growth or even decrease the size of tumors, chemotherapy, especially in younger patients, has fewer side effects than radiation therapy (such as secondary tumors, radiation necrosis, and Moyomoya disease) and is generally considered the first-line treatment for progressive lesions in younger patients. The tumor location defines prognosis in OPGs; optic nerve gliomas (ONG) have the lowest rate of complications and death, and optic chiasm and retrochiasmal gliomas the highest. Although the major complication of an OPG is visual loss, hypothalamic involvement can lead to death. Resection is an option for ONGs but is generally reserved for tumors confined to the optic nerve with poor or no vision, or for patients with severe, cosmetically unappealing proptosis, producing severe pain or exposure keratopathy in a blind eye. Resection is generally not an option for intrinsic chiasmal or retrochiasmal OPGs. Extrinsic (exophytic) components can be debulked surgically, and surgery can be performed for hydrocephalus (ventriculoperitoneal shunt placement). The approach to a patient with OPG must be individualized based on tumor location, radiographic or clinical progression, the presence of NF1, and a risk–benefit comparison for treatment.
Combined transconjunctival–eyebrow approach providing minimally invasive access to all orbital quadrants
Authors: Koerbel Andrei , Ferreira Veralucia R. , Kiss André
Published: December 2007

✓Surgical approaches to treat orbital disease should provide a good exposure of intraorbital anatomical structures, allow their functional preservation, and provide good cosmetic results. The authors describe a minimally invasive, combined transconjunctival–eyebrow approach to all orbital quadrants in a step-wise manner. The indications, advantages, and limitations of the technique are highlighted.

A transconjunctival approach via the postseptal area is described. It allows exposure of the medial, inferior, and lateral parts of the orbit. Depending on the orbital space to be exposed, a lateral or a medial eyebrow incision is then made. The eyebrow and the conjunctival incisions are connected by subperiosteal dissection. This combined access provides exposure to all intraconal muscles and to the superior, medial, lateral, and inferior portions of the optic nerve.

The combined transconjunctival–eyebrow approach provides an excellent orbital exposure, with minimal damage to the circumjacent structures. It requires less operative time than other approaches and yields good cosmetic results. Intracranial or intrafacial tumor extension and tumors located purely in the orbital apex are limitations for the use of this technique.
Orbital tumors treated using transcranial approaches: surgical technique and neuroophthalmogical results in 41 patients
Authors: Margalit Nevo , Ezer Haim , Fliss Dan M. , Naftaliev Elvira , Nossek Erez , Kesler Anat
Published: December 2007

Object

Orbital tumors can be divided schematically into primary lesions, originating from the orbit itself, and secondary lesions, extending to the orbit from neighboring structures. These tumors are variable in their biological nature and in their location. The authors evaluate 41 cases of benign and malignant tumors involving the orbit and discuss the surgical challenge, which involves tumor removal, preserving visual function and cosmetic reconstruction.

Methods

The authors performed a retrospective analysis of a series of all cases involving patients who underwent surgery for treatment of orbital tumors in their hospital between December 2003 and December 2006. Data were collected from the patients' files in the hospital's outpatient clinic, operative notes, and pre- and postoperative imaging studies.

Results

The authors identified 41 patients who met the inclusion criteria (age range 14–82 years, mean 42.2 years, standard deviation 22.4 years). The most common presenting symptoms were proptosis and/or partial ptosis (11 cases [27%]) and headache (7 cases [17%]). In 5 (12%) cases, the tumors were primary intraorbital lesions, and in 34 cases (83%) they were secondary. Two patients had metastases to the orbit. The most common lesion types were meningioma (10 cases [24%]) and osteoma (7 cases [17%]). In 24 cases a midline approach through a frontal craniotomy or a subcranial approach was used; in 13 a lateral approach was used; and in 4 a biopsy procedure was performed. Maxillectomy through a Weber–Ferguson approach or a facial degloving approach was added in 5 cases to complete tumor removal. Duration of follow-up was 1–38 months (mean 20 months). None of the patients died as a result of the procedure, and there were relatively few complications. Excluding the patients who underwent orbital exenteration, none of the patients had visual deterioration following surgery, and most had no change in their visual condition. Two patients had temporary diplopia, 1 had a cerebrospinal fluid leak, and 1 had enophthalmos following removal of an orbital osteosarcoma.

Conclusions

Orbital tumors can be treated safely using transcranial approaches in many cases. Preoperative imaging can accurately define the compartments involved and the surgical approach needed for tumor removal. A multidisciplinary team of surgeons facilitates optimal tumor removal and skull base sealing as well as good cosmetic results.
Optic pathway gliomas: a review
Authors: Binning Mandy J. , Liu James K. , Kestle John R. W. , Brockmeyer Douglas L. , Walker Marion L.
Published: December 2007

✓Optic pathway gliomas represent approximately 3–5% of childhood intracranial tumors. They usually occur in children during the first decade of life and are seen in 11–30% of patients with neurofibromatosis Type 1 (NF1). Although these tumors are typically low-grade gliomas, the clinical course and natural history are highly variable, making treatment paradigms difficult. Overall, however, they are often indolent tumors that can be observed over time for progression without initial treatment, especially in patients with NF1. Chemotherapy is the first-line treatment for progressive tumors, and radiation therapy is reserved for patients with progressive disease who are older than 5–7 years. Surgery is reserved for large tumors causing mass effect or hydrocephalus and tumors confined to the orbit or unilateral optic nerve.
Syndromic and sporadic pediatric optic pathway gliomas: review of clinical and histopathological differences and treatment implications
Authors: Shamji Mohammed F. , Benoit Brien G.
Published: December 2007

✓Optic pathway gliomas (OPGs) are the most common primary neoplasm of the optic pathway. These lesions usually present in childhood and can arise anywhere along the optic pathway; they occur more frequently in women; and they rarely undergo late progression. Management strategies after the initial diagnosis are controversial, compounded by the different behaviors exhibited by sporadic and syndromic tumors. Neurofibromatosis Type 1 (NF1), with aberrant oncogenic signaling and consequent predisposition to intracranial tumors, is the most common associated syndrome, with nearly 20% of NF1 patients developing OPGs. A comorbid NF1 diagnosis has implications for tumor location with greater predilection for optic nerve involvement, whereas chiasmal and postchiasmal lesions are more frequently seen in sporadic cases. Syndromic OPGs often exhibit more indolent behavior and lower rates of clinical progression, and the majority of these are diagnosed by routine neuroophthalmological screening. When treatment is indicated, however, the molecular abnormalities that constitute this syndrome can limit the available chemotherapy and radiotherapy options because clinicians fear secondary malignancy and cerebrovascular complications. Furthermore, radiotherapy early in life can impair an individual's intellectual development, endocrine function, and physical growth, thereby limiting the role of this modality in the treatment of this childhood lesion. Differential gene expression and histogenesis among sporadic and syndromic OPGs may account for the different tumor behaviors, but studies correlating specific genetic and proteomic changes with patient outcome are pending. Loss of heterozygosity at 10 and 17q are more common among patients with NF1, and Ki67 labeling intensity of 2–3% and low p53 labeling intensity seem prognostic of aggressive tumor behavior. Recent advances in the development of a preclinical mouse model of NF1-associated OPG will permit investigation into improved detection strategies and chemotherapeutic and radiotherapy treatment protocols.
Optic nerve sheath meningioma: current diagnosis and treatment
Authors: Eddleman Christopher S. , Liu James K.
Published: December 2007

✓Optic nerve sheath meningiomas (ONSMs) are rare tumors of the anterior visual pathway and constitute approximately 2% of all orbital tumors and 1–2% of all meningiomas. Untreated ONSMs almost always lead to progressive visual decline, color blindness, and finally complete loss of vision. Although resection is warranted in cases of widespread ONSM, surgery can lead to significant morbidity. Recently, stereotactic fractionated radiotherapy has shown effectiveness in improving or stabilizing remaining visual function with minimal procedural morbidity in patients with ONSM. The authors review the incidence, histopathological characteristics, clinical presentation, neuroimaging findings, and current treatment modalities for ONSMs, with an emphasis on fractionated stereotactic radiotherapy.
Mechanisms of visual loss in papilledema
Authors: Schirmer Clemens M. , Hedges Thomas R.
Published: December 2007

✓ The term “papilledema” indicates swelling of the optic discs secondary to increased intracranial pressure. Papilledema can be caused by an intracranial mass lesion or by other factors. Visual symptoms frequently accompany papilledema, which can lead to permanent visual loss if left untreated. Starting with an illustrative case, the authors review the pathophysiology of the visual signs and symptoms of papilledema. They also briefly review potential treatment options, focusing on the role of the neurosurgeon in the treatment of patients with papilledema.
Visual outcomes comparing surgical techniques for management of severe idiopathic intracranial hypertension
Authors: Feldon Steven E.
Published: December 2007

Object

The object of this study was to compare surgical techniques for management of visual loss in idiopathic intracranial hypertension (IIH) unresponsive to medical treatment.

Methods

The published literature was reviewed using electronic and manual search techniques. Articles were categorized based upon the surgical procedure performed, including optic nerve sheath decompression (ONSD), also called optic nerve sheath fenestration; intracranial venous sinus stent placement; ventriculoperitoneal (VP) shunt placement; and lumboperitoneal (LP) shunt placement. Demographic data and visual outcome of the cumulative experience were compiled and compared for each type of surgical intervention.

Results

Seventeen patients treated by stent placement, 31 by VP shunt placement, 44 by LP shunt placement, and 252 patients by ONSD were identified in the literature; average follow-up ranged from 11.8 months for patients treated with stents to 57.2 months for those treated with LP shunts. Improved or resolved vision deficit was noted in 38.7% of patients after VP shunt placement, 47% of patients after stent placement, 44.6% of patients after LP shunt placement, and 80% of eyes after ONSD. Visual worsening was rare for all procedures evaluated.

Conclusions

There is a paucity of information regarding visual outcomes from intracranial venous stent placement and cerebrospinal fluid diversion procedures. Visual outcomes from ONSD are better documented and appear to be superior to other surgical techniques for management of IIH. Further studies with improved data collection regarding visual outcomes are needed for surgical procedures other than ONSD in order to assess their possible value as treatments for visual loss in IIH.
Optic nerve sheath fenestration for vision preservation in idiopathic intracranial hypertension
Authors: Agarwal Madhu R. , Yoo Ji Hye
Published: December 2007

✓Idiopathic intracranial hypertension, also known as pseudotumor cerebri, is a condition of increased intracranial pressure without the presence of mass lesions and with normal cerebrospinal fluid composition. Patients may experience papilledema and vision loss. Optic nerve sheath fenestration (ONSF) is one method of stabilizing visual function and decreasing optic nerve edema. The authors report on 10 patients who underwent bilateral ONSF and in whom visual function was stable or improved postoperatively. The results obtained in these cases suggest that ONSF plays a role in visual preservation in idiopathic intracranial hypertension patients in the acute setting.
A review of ocular manifestations in intracranial hypotension
Authors: Zada Gabriel , Solomon Thomas C. , Giannotta Steven L.
Published: December 2007

Object

Intracranial hypotension (ICH) can present with a wide variety of visual symptoms and findings. Deficits in visual acuity and visual fields as well as ophthalmoplegia due to cranial nerve dysfunction have been frequently described. The aim of this review was to identify the most commonly reported ocular manifestations associated with ICH.

Methods

The authors conducted a review of the literature to date to identify all studies of patients with ICH and ocular manifestations.

Results

The most commonly encountered cranial nerve deficit resulting from ICH (> 80% of reported cases) is an abducens nerve paresis, which may occur unilaterally or bilaterally. Although less common, oculomotor and trochlear nerve palsies have been reported as well. The optic nerve complex is frequently involved in ICH and may manifest as deficits in visual acuity and field cuts. Visual deficits and ophthalmoplegia improved following appropriate management in 97% of reported cases.

Conclusions

Intracranial hypotension can present with a wide spectrum of visual deficits, the causes of which are multifactorial. Cranial nerve paresis, especially of the abducens nerve, is frequently reported. The majority of symptoms and cranial nerve deficits reviewed respond favorably to conservative management, epidural blood patch administration, or in a minority of cases, surgical intervention.
Neuroimaging in neuroophthalmology
Authors: Bose Swaraj
Published: December 2007

✓Recent advancements in the speed and accuracy of data acquisition and resolution of neuroimaging and interventional techniques have revolutionized the early anatomical and functional diagnosis, prognosis, and treatment of many neuroophthalmological disorders. The relatively new techniques include magnetic resonance (MR) spectroscopy, computed tomography angiography, positron emission tomography, and functional MR imaging. In this paper the author describes the principles of the current techniques used by neuroophthalmologists and their value in the diagnosis, localization, and treatment of various afferent and efferent visual and ocular disorders.
Pyruvate–Ferredoxin Oxidoreductase
Authors: Chabriere Eric , Cavazza Christine , Contreras‐Martel Carlos , Fontecilla‐Camps Juan C.
Published: December 2007

Pyruvate decarboxylation in many anaerobic organisms is catalyzed by the thiamine diphosphate (ThDP)‐dependent pyruvate–ferredoxin oxidoreductase. We have determined the native structure of this ancient enzyme, as well as of several reaction intermediates, by soaking crystals in a pyruvate‐containing solution. As the reaction progresses, ThDP approaches the substrate and cleaves a CC bond generating an acetyl‐ThDP radical intermediate and CO
2
. The comparison of this structure with a similar intermediate in transketolase (TK), another ThDP‐dependent enzyme, reveals significant differences in the cofactor conformation.
Metropolitan Area Networks
Authors: Maxemchuk N. F.
Published: December 2007

A metropolitan area network (MAN) is a shared network that covers the distances in most cities. The applications of MANs and the techniques that are used for communications is rapidly changing. MANs were originally used to interconnect the users in a single organization, and several specialized networks were developed. However, the Internet has increased the demand for high‐speed communications to individual consumers. In consumer applications, cost is particularly important. The networks use existing infrastructure or infrastructure that can be deployed with minimal investment and use access devices that are popular in other applications and therefore cost less than new devices.

The first generation of MANs used protocols and network topologies that are similar to local area networks but are specifically designed to span the greater distances and operate at the higher transmission rates that occur in a MAN. We describe three of these protocols: the American National Standards Institute (ANSI) X3T9 standard, fiber distributed data interface, (FDDI), the IEEE 802.6 standard, dual bus distributed queue protocol, (DQDB), and an experimental network, the Manhattan Street Network, (MSN).

Currently, the most widely used MANs use the existing cable TV (CATV) network and easily deployed wireless networks. The CATV standards are not keeping pace with the applications. We describe the common characteristics of the applications and describe in detail an application that is based on Ethernet technology and that can be extended to carry packet voice communications. The IEEE 802.11 standard, wireless fidelity (WiFi), is the most widely used wireless access technology. This standard is described in detail, along with a competing access technique, Bluetooth, and the IEEE 802.16 standard that can be used to extend the range of wireless access techniques to the metropolitan area.

In the conclusion we predict future changes. These changes are fueled by the need for improved reliability, the emergence of IP‐voice, the increased use of wireless technologies, the overuse of the cellular bands, the eventual deployment of fiber to the home, and a resurgence of ATM‐like, cell‐based transmission.
Biology Computing
Authors: DasGupta Bhaskar , Wang Lusheng
Published: December 2007

In this chapter, we survey recent results on evolutionary tree construction and comparison, computing syntenic distances between multi‐chromosome genomes, and multiple sequence alignment problems.
Electrochemical Interfaces: At the Border Line
Authors: Kornyshev Alexei A. , Spohr Eckhard , Vorotyntsev Michael A.
Published: December 2007

The sections in this article are

Introduction

Basic Concepts

Thermodynamics of Electrified Interfaces

Classical Models of Electrified Interfaces

Helmholtz Model

Gouy–Chapman–Stern–Grahame Model

Diffuse and Compact Layer Properties

Grahame Model in Comparison with Capacitance Data for Liquid Electrodes

Compact Layer Properties

Manifestations of the Diffuse Layer in Kinetics of Electrode Reactions

Electrokinetic Phenomena

Solid Electrodes: Effects of Polycrystallinity and Surface Roughness

“Uniform” Model of Solid Electrodes. Surface Roughness

Crystallographic Inhomogeneity Effects for Solid Electrode Surfaces

EDLStructure for NonUniform Electrode Surfaces

Surface Roughness Effect on the Diffuse‐Layer Capacitance

Semi‐phenomenological Nonlocal Theory of the Double Layer

Basic Equations

“Dipolar” Models of the Compact Layer

Two‐State Model

Multistate Models

The Role of Metal Electrons

Surface Electronic Profile and its Response to Charging

Response to Charging of the Electrochemical Interface and the Compact‐Layer Capacitance: Main Qualitative Effects

Optical Response and the Interfacial Structure

Effects of the Molecular Nature of Electrolyte Solutions

Ionic Adsorption

Qualitative Aspects

Ion Adsorption Models

Image Potential for Ions in the Diffuse or Compact Layer

Interaction Between Adsorbed Ions

Statistical Mechanics of Adsorbed Ion Ensemble

Ion Adsorption Isotherm

Electric Field‐Induced Modifications of the Surface Structure

Electrochemical Missing Row Reconstruction: Facts and Speculations

Driving Force for Reconstruction

Ising Model. Order–Disorder Transitions

Roughening Transitions

Soft Electrochemical Interfaces

Capillary Waves atITIES. Field Effect on Capillary Waves and Capillary Waves Effect on Capacitance

Ion Penetration into an “Unfriendly Medium”

From Basic Concepts to Surface Electrochemistry
Introduction to Specific Adsorption
Authors: Damaskin Boris B. , Petrii Oleg A.
Published: December 2007

The sections in this article are
Quantum Theory of Electrochemical Electron‐Transfer Reactions
Authors: Schmickler Wolfgang , Frank Stefan
Published: December 2007

The sections in this article are

Introduction

A Simple Introduction to Marcus Theory

Energy of Reorganization

Quantum‐mechanical Theory

A Model for Electron Exchange Between a Metal and a Solvated Reactant

The Model Hamiltonian

First‐order Perturbation Theory

Semiclassical Systems

Quantum Modes

Adiabatic Reactions

Solvent Dynamics

Computer Simulations

Bond Breaking Reactions

Conclusion

Acknowledgment
The Digital Simulation of Voltammetry under Stagnant and Hydrodynamic Conditions
Authors: Gooch Kerry A. , Qiu Fulian L. , Fisher Adrian C.
Published: December 2007

The sections in this article are

Introduction

Digital Simulations

Simulation Methods. The Fundamentals

The Methods. An Overview

Finite Difference Methods

Introduction

The Explicit Finite Difference (
EFD
) Method

The Crank & Nicolson (
CN
) Method

The Alternating Direction Implicit (
ADI
) Method

The Hopscotch (
HS
) Method

The Backwards Implicit (
BI
) Method

The Fast Implicit Finite Difference (
FIFD
) Method

The Strongly Implicit Procedure (
SIP
)

Finite Element Methods

Introduction

Formulation

Applications

Boundary Element Method

Introduction

Formulation

Applications

Alternative Simulation Strategies

Acknowledgments
NMR
Spectroscopy in Electrochemistry
Authors: Tong YuYe , Oldfield Eric , Wieckowski Andrzej
Published: December 2007

The sections in this article are

Introduction

Principles of Solid‐State Surface
EC
‐
NMR
Spectroscopy

Metal
NMR
Basics

EC
‐
NMR
Instrumentation

Applications of Solid‐state Surface
EC
‐
NMR
Spectroscopy

195
Pt
NMR
of Carbon‐supported Electrocatalysts and a Potential‐scan‐ generated Sintering Effect

Correlation between the Knight Shift of a Platinum Surface and the Electronegativity of the Adsorbate

Correlation between the Clean‐surface

E
F

‐
LDOS
of Metals and the Knight Shift of Adsorbates

Coupling
EC
‐
NMR
with In Situ Infrared Spectroelectrochemistry

Surface Diffusion

Isotopic Labeling for Site Selectivity

Potential‐dependent
EC
‐
NMR

Future Perspectives

Acknowledgments
EPR
Spectroscopy in Electrochemistry
Authors: Wadhawan Jay D. , Compton Richard G.
Published: December 2007

The sections in this article are

Introduction

Principles of
EPR
Spectroscopy

EPR
Theory

The

g

‐value

Linewidths

Spin‐lattice Relaxation

Spin–spin Relaxation

Hyperfine Structure

EPR
Instrumentation

In Situ Electrochemical
EPR
: Cell Design

The Bard–Goldberg Cell

Cell Design

Typical Applications

The Allendoerfer Cells

Cell Design

The Coaxial Cell

Application

The Loop‐gap Resonator Cell

Application

The Channel Electrode Cell

Cell Design

Application

The Albery In Situ Tube Electrode Cell

Cell Design

Application

The In Situ Coaxial Flow Cell

Cell Design

Application

The Bond In Situ Microelectrode Cell

Cell Design

Application

The In Situ Wall‐jet Electrode Cell

Cell Design

Application

The Dunsch–Petr–Neudeck Cell for In Situ
UV
‐
VIS EPR
Spectroelectro‐ chemistry

Cell Design

Application

The Dryfe–Webster Cell for Charge Transfer Across a Liquid|Liquid Phase Boundary

Cell Design

Typical Applications

Illustrative Examples of
EPR
in Electrochemistry

Radical and Radical Ion Identification

The Anodic Oxidation of
para
‐Aminodiphenylamine (
PAD
)

The Reduction of Dicyanobenzene

The Reduction of
C
60

Spin Trapping

Electrode Reaction Kinetics and Mechanism

EC
Versus
ECE

ECE
Versus
DISP
1

EC
′

Comproportionation Reactions

Photoelectrochemical
EPR

Modified Electrodes

Electrochemical
EPR
in Ionic Liquids

Conclusion

Acknowledgments
The Electrochemical Quartz Crystal Microbalance
Authors: Hillman A. Robert
Published: December 2007

This chapter reviews the development and use of the electrochemical quartz crystal microbalance (EQCM) as an in situ probe of interfacial processes involving the formation, properties, and redox switching of multilayer films. For films that are sufficiently rigid and/or thin (termed
acoustically thin
), the EQCM functions as a quantitative gravimetric probe of surface population changes. This well‐established methodology is now being used to explore both thermodynamic and kinetic aspects of film compositional changes, for example, in response to electrochemical stimuli. Correlation of mobile species (ion and solvent) population changes—within the effectively static film matrix—with electrochemical control and response functions (potential, current, and charge) now provides mechanistic information. Combination with other in situ (e.g. optical or spectroscopic) techniques is a developing area and can facilitate separation of individual ion and solvent transfers. For films that are softer and/or thicker (termed
acoustically thick
), the acoustic wave is attenuated during passage across the film, which in turn undergoes acoustic deformation. The EQCM now responds primarily to film viscoelastic properties, that is, film (rather than mobile species) dynamics. This is a developing area, but it is now possible to extract film shear modulus components (storage and loss moduli); these are found to respond significantly to the film redox state (controlled via potential or charge), temperature, timescale (frequency), and environment (both solvent and electrolyte ions). These effects are reviewed with selected examples from a diverse range of materials, encompassing metals, metal oxides, semiconductors, metal coordination complexes, and redox, conducting, and insulating polymers.
ElectrochemicalSTM
Authors: Moffat Thomas Polk
Published: December 2007

The sections in this article are

Introduction

STMand Modes of Operation

Atomically Resolved Imaging

Double‐layer Overlap and Tip‐screening Effects

Experimental Considerations

Electrochemical Cell

Tip Selection and Preparation

Substrate Preparation

Applications

Imaging Two‐dimensional Structures

Imaging Surface Dynamics

Morphological Evolution during Phase Transitions

Surface Modification
Conversion Coatings
Authors: Ogle Kevin , Buchheit Rudolph G.
Published: December 2007

The sections in this article are

Phosphate Conversion Coatings

Overview

Historical Perspectives

Overview of Process and Reaction Mechanisms

Degreasing

Activation

Phosphating

Posttreatment

The Nature of the Phosphate Layer

Morphology

Chemical and Surface Composition

Thermal and Chemical Properties

Electrochemical Properties and Characterization Methods

Porosity and Coverage Measurements

In Situ Monitoring of the Phosphating Reaction

Corrosion Resistance Measurements

Chromate Conversion Coatings

Overview

Chromate Conversion Coatings: Definition and Applications

Historical Perspectives

Substrates

Aluminum

Zinc

Magnesium

Cadmium

Steel

Stainless Steels

Chromate Conversion Coating Types

Alkaline Chromate and Dichromate Formulations

Acidic Chromium–phosphate

Acidic Chromium–chromate

Accelerated Chromium–chromate

Chromate Conversion Coating Formation

Chromium–chromate Coatings

Chromium–phosphate Coatings

Cr(VI) andCr(VI) Speciation

Activators and Accelerators

Coating Formation on Metallurgical and Structural Defects

CCCMorphology, Structure, and Composition

Corrosion Protection

Corrosion Protection Mechanisms

Aging and Heating

Macroscopic Characteristics of Chromate Conversion Coatings

CCCWeight, Thickness, and Color

Chemical and Corrosion Resistance

Mechanical and Thermal Stability

Paint Adhesion

Electrical Contact Resistance

Chromate‐free Coatings

Sol–gel Coatings

Hydrothermal Coatings from Alkaline Solutions

Rare Earth Metal Coatings
Electrochemistry Applied to Organic Synthesis: Principles and Main Achievements
Authors: Simonet Jacques
Published: December 2007

The sections in this article are

Introduction

General Feature of Electroorganic Synthesis

Specificity and Prospects

Choice of a Cell

Choice of Electrode Material

Materials for Cathodes

Materials for Anodes

Main Reactions Achievable Electrochemically: A Survey of Experimental Conditions

Some Specific Electrochemical Reactions Involving Carbon Atoms

Building of CarbonCarbon Bonds at the Anode and the Cathode

Kolbe Reaction: Anodic Oxidation of Carboxylates: Coupling of Aliphatic Free Radicals

Anodic Oxidation of Carbanions and Symmetrical Coupling

Anodic Oxidation of Aromatic Systems via Cation Radicals (Dimerizations, Trimerizations, Oligo, and Polymerizations)

Cathodic Coupling of Aryl Groups via Transition Metals Catalysis

Other Activation Reactions Involving Aromatic Halides in the Presence of Metal Catalysts

Aromatic Carboxylations

Electrosynthesis as a Tool to Afford Cyclizations

Anodic Substitution of Organic Derivatives Possessing a Mobile Hydrogen

Functionalizations of Nitrogen‐containing Compounds

Oxidation ofCHFunctions

Anodic Functionalization of Ethers

Anodic Oxidation of Thioethers

Electrochemical Conversion of Main Organic Functions in Aqueous and Protic Organic Media

Reduction of Unsaturated Compounds

Nitro Group

Reduction of Functions Possessing at Least One Nitrogen Atom

Reduction of the Carbonyl Group

Organic Acids and Derivatives

Scission of Chemical Bonds by Means of Cathodic or Anodic Electron Transfers

Main Cathodic Scission Reactions of CarbonHeteroatom Bonds

Other Types of Bond Scissions

Application of the Electrochemical Scission of Bonds to the Chemical Deprotection

Anodic Deprotection of the Carbonyl Group: Cleavage ofCSBonds

Amine Function Deprotection: Cathodic Cleavages ofCSandNSBonds

Protection and Deprotection of Alcohols and Thiols

Electrosynthesis as a Tool for a New Solid‐Phase Methodology

What is the State of the Art for Organic Silicon Derivatives?

Electroreduction

Electrooxidation

Some Words about the Use of Selenium in Organic Synthesis

Electroreduction

Electrooxidation

Electrochemical Activation of Small Inorganic Molecules Usable in Organic Synthesis

Cathodic Intermediates from Dioxygen and Principal Types of Reactions

Reduction of Carbon Dioxide

Cathodic Behavior of Sulfur, Tellurium, and Selenium: an Easy Way of Forming Specifically Reactive Nucleophiles

Anodic Activation of Molecular Sulfur and ofSSBonds

Oxidation of Halides

Anodic Fluorination

Zero‐current Electrolyses

Elements of Electrochemical Chiral Synthesis

Some Models of Electrolysis Cells: From Laboratory Cells to Scaling up

Laboratory Cells

Industrial Cells

Possible Industrial Applications of Organic Electrosynthesis
Photoelectrochemical Systems Characterization
Authors: Kelly John J. , Hens Zeger , Vanmaekelbergh Daniel , Hensalso Zeger
Published: December 2007

The sections in this article are

Introduction

Scope of the Chapter

Special Features of Photoelectrochemical Systems

Photoelectrochemical Characterization Methods

Steady State and Time‐resolved Methods

Current Density Versus Potential Techniques

PC
versus Light Intensity Techniques

Luminescence‐based Techniques

Bulk Systems

In Situ Energetics of Semiconductor/Electrolyte Interfaces

Electron‐hole Recombination Dynamics at the s/e Interface

Introduction

Current Density Versus Potential Measurements

The Electrochemical Impedance of Surface Recombination

The Optoelectrical Transfer Function of Surface Recombination

Recombination Studied by Luminescence

Complex Charge‐transfer Processes

PC
‐doubling Reactions

Dissolution of Semiconductors

Sensitizer‐based Photoelectrochemical Systems

Porous Photoelectrochemical Systems

Introduction

Special Properties of Porous Photoelectrochemical Systems

Penetration of the Interfacial Layer in a Porous Semiconductor Electrode

Charge Storage in a Porous Semiconductor Electrode

Charge Storage in a Quantum Dot System

Light Scattering in Macroporous Semiconductors

Electron‐hole Photoexcitation by Sub‐band Gap Light

Effective Electron‐hole Separation

Luminescence from Porous Electrodes

Electron Transport

Electron Diffusion, Collection, and Recombination

Characterization of Electron Diffusion and Back‐transfer by Light Intensity Modulated Techniques

Experimental Results on Electron Transport
Deposition of (Multiple Junction) Semiconductor Surfaces
Authors: Soga Tetsuo
Published: December 2007

The sections in this article are

Introduction

MOCVD

Deposition of Gallium Phosphide on Silicon Substrate

Nucleation of
Ga
P
on
Si
Substrate

Generation of Dislocation

Annihilation of
APD
Structure

Deposition of Gallium Arsenide on Silicon Substrate

Nucleation

Effect of
TCA

Effect of Hydrogenation

Application to Photovoltaic Device
Preparation of Nanocrystalline Semiconductor Materials
Authors: Hodes Gary , Mastai Yitzhak
Published: December 2007

The sections in this article are

Introduction

Electrochemical/Chemical Hybrid Deposition

Electrodeposition of Nanocrystals from Nonaqueous Solution

Size Control Using Semiconductor‐substrate Lattice Mismatch

Electrodeposition of Layered Nanostructures

Template‐directed Electrodeposition

Occlusion Electrodeposition of Composites

Sonoelectrochemical Formation of Nanocrystalline Semiconductors
Dyes for Semiconductor Sensitization
Authors: Nazeeruddin Md. Khaja , Grätzel Michael
Published: December 2007

The sections in this article are

Introduction

General Background

Operating Principles of the Dye‐Sensitized Solar Cell

Incident Photon to Current Efficiency and Open‐Circuit Photovoltage

Molecular Sensitizers

Formation of Complexes

Photophysical Properties

Ground and Excited State Redox Potentials

Requirements of the Sensitizers

Absorption Spectral Properties of Metal Complexes

Tuning of
MLCT
Transitions

Spectral Tuning in “Push‐Pull” Type of Complexes

Spectral Tuning in Complexes Containing Hybrid Donor Ligands

Influence of Nonchromophoric Ligands on
MLCT
Transitions

Influence of the Position of Carboxyl Groups on
MLCT
Transitions

MLCT
Transitions in Geometric Isomers

Spectral Tuning in Heteroleptic Sensitizers

Hydrophobic Sensitizers

Near
IR
Sensitizers

Phthalocyanines

Ruthenium Phthalocyanines

Phthalocyanines Containing 3
d
Metals

Mononuclear and Polynuclear Metal Complexes of Group
VIII

Iron Complexes

Osmium Complexes

Polynuclear Complexes

Surface Chelation of Polypyridyl Complexes onto the TiO
2
Surface

Anchoring Groups

Acid‐Base Equilibria of the Anchoring Groups

Acid‐Base Equilibria of the 4,4‐Dicarboxy‐2,2′‐Bipyridine and its Complexes

Acid‐Base Equilibria of the Phosphonato Group

Stability and Performance of the Dyes

Stability of the Inorganic Dyes

Effect of Protons Carried by the Sensitizer on the Performance

Comparison of
IPCE
Obtained with Various Sensitizers

Synthesis and Characterization

Synthetic Strategies for Ruthenium Complexes

Purification

Characterization

Conclusion

Acknowledgment