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We compared the development of microalgal and bacterial-denitrifier communities within biofilms over 28 days in a restored-prairie stream (RP) and a stream receiving treated wastewater effluent (DER). Inorganic nutrient concentrations were an order of magnitude greater in DER, and stream waters differed in the quality of dissolved organics (characterized via pyrolysis-GC/MS). Biofilm biomass and the densities of algae and bacteria increased over time in both systems; however, algal and denitrifier community composition and the patterns of development differed between systems. Specifically, algal and denitrifier taxonomic composition stabilized more quickly in DER than RP, whereas the rates of algal and denitrifier succession were more closely coupled in RP than DER. We hypothesize that, under unenriched conditions, successional changes in algal assemblages influence bacterial denitrifiers due to their dependence on algal exudates, while under enriched conditions, this relationship is decoupled. Between-system differences in organic signatures supported this, as RP biofilms contained more labile, aliphatic compounds than DER. In addition, potential denitrification rates (DNP) were negatively correlated with the percentage of aromatic compounds within the biofilm organic signatures, suggesting a significant relationship between algal exudate composition and denitrification. These results are significant because anthropogenic factors that affect biofilm community composition may alter their capacity to perform critical ecosystem services.

The electrical properties of InP/Au dry contacts and the influence of electrodeposited gold on the electrochemical properties of InP electrodes were studied. From current and impedance measurements on InP/Au dry contacts it is concluded that the chemical composition of an interfacial layer strongly influences the electrical characteristics. Furthermore, interface states are shown to play an important role. The interfacial layer and the interface states also determine to a large extent the electrochemical properties of the gold‐plated electrodes.

Human galanin (hGAL) is a 30-amino acid neurohormone that has recently been shown to differ significantly from porcine and rat GAL. We investigated the endocrine and cardiovascular effects of hGAL in eight male volunteers. On three separate occasions, each received a 90-min infusion of saline, low dose (33 pmol/kg.min) and high (132 pmol/kg.min) dose hGAL, combined with an iv glucose bolus (to assess effects on insulin and GH release). hGAL was undetectable, 1.4 +/- 0.2 nmol/L, and 3.7 +/- 0.5 nmol/L during control, low dose, and high dose studies, respectively. The half-life of hGAL was 3.5 +/- 0.5 min. GH levels rose significantly in both studies (vs. control) and were not suppressed by hyperglycemia [low dose area under the curve (AUC), 1827 +/- 348 micrograms/min.L (P0.05); peak, 19.5 +/- 5.3 micrograms/L; high dose AUC, 1896 +/- 401 micrograms/min.L (P0.005); peak, 28.0 +/- 7.5 micrograms/L]. PRL levels rose significantly with the high dose study only (AUC, 12.8 +/- 1.1 micrograms/min.L; P0.01). FSH, LH, and catecholamine levels were unchanged. Glucose-stimulated insulin release was not inhibited. There was a dose-dependent increase in pulse rate and a profound decrease in sinus arrhythmia, but no change in blood pressure. These cardiovascular effects have not been reported with studies in humans using GAL of other species. We conclude that hGAL may play an important role in man in modulating GH secretion and cardiac vagal tone, but not insulin release.

The influence of electrodeposited gold on the current—potential and impedance characteristics of n-GaAs electrodes was studied in various electrolyte solutions. The potential of the gold layer on n-GaAs was measured as a function of the bias applied to the electrode. It is concluded that the same processes occur as previously proposed for gold-plated p-GaAs electrodes. A model involving gold- related surface states which interact with both the valence band and the electrolyte solution was used to explain the results for p-GaAs. For n-GaAs, an additional process is found to play an important role: recombination of thermally produced holes with conduction band electrons.

The visible luminescence of porous silicon electrodes is reported. Both n-type and p-type material show similar characteristics. Three potential ranges can be distinguished. At open-circuit potential in the presence of certain strong oxidizing agents, e.g. Ce 4+ and MnO - 4 , emission due to chemiluminescence (CL) occurs. At negative potential in the range of H 2 evolution, hole injection by a strong oxidizing agent, e.g. H 2 O 2 and S 2 O 2- 8 , results in electroluminescence (EL). The intensities of CL and EL depend on the applied potential. When porous silicon is anodically oxidized, emission also occurs; this is probably due to CL. Because of the close resemblance of the luminescence of porous silicon to the photo- and chemiluminescence of siloxene, the emission from porous silicon is ascribed to the presence of siloxene or siloxene-like groups. The porous layer can be described as a discrete semiconductor with a large band-gap.

The rotating ring-disk electrode configuration, consisting of a Au disk and an InP ring, was used to investigate the electroluminescence (EL) of p-Inp during electron injection by Cr(CN)64− generated at the disk. The EL intensity depends strongly on the surface properties of the electrode, as is commonly found for EL of n-type semiconductors. The emission is due to a band-band transition similar to that of n-InP in the presence of Fe(CN)63−.

The impedance corresponding to charge transfer and storage at p-GaAs electrodes provided with electrodeposited gold is calculated and compared to results of measurements in various electrolyte solutions. It is concluded that the results are in good agreement with the predictions based on a model in which the interactions between gold-related surface states and both the valence band and an oxidizing agent in the electrolyte solution play a central role.

The influence of electrodeposition of gold on the electrochemical properties of p-type GaAs has been studied. From current—potential and impedance measurements performed in solutions containing various redox-couples it was concluded that gold-related surface states play a central role in the interaction between semiconductor, metal and electrolyte solution. A kinetic model is presented which comprises three processes: (i) excitation of valence band electrons to the surface states, (ii) recombination of these electrons with holes in the valence band and (iii) transfer of electrons from the surface states to an electron acceptor in solution.

A new approach is used for the study of the semiconductor—solution interface with Fourier transform IR spectroscopy (FTIRS) in the multiple total internal reflection mode. In this method, a thin semiconductor wafer is mounted on a germanium internal reflection crystal by wafer-bonding. Measurements are possible in a wide frequency range (800–4000 cm−1). The potential of the method is demonstrated by measurements on the anodic oxidation in acetonitrile containing a low concentration water of n-type silicon (111) surfaces pretreated in hydrofluoric acid solution. The experiments show that detection of surface bound species (SiH, SiOSi) is possible with submonolayer sensitivity.

The reproducibility of ambulatory blood pressure measurements was assessed in eight normotensive subjects who underwent three separate days of recording, using Takeda Medical TM-2420 (TM-2420) blood pressure monitors. The coefficients of variation of mean 24 hour systolic and diastolic blood pressure were 2.1% and 2.8% respectively. The corresponding values for systolic and diastolic blood pressure variability, were 19% and 14% respectively. Measurement intervals of greater than 30 minutes significantly reduced the reproducibility of mean day interval systolic measurements. The bias of the TM-2420 systolic and diastolic blood pressure measurements compared to standard sphygmomanometer measurement were 0 +/- 7 mmHg and 1 +/- 6 mmHg respectively. Ambulatory blood pressure monitoring provides reproducible estimates of mean systolic and diastolic blood pressure, however, blood pressure variability is poorly reproducible.

A chemical synthesis is described in which ZnSe:Cu particles slowly grow to a final size of ∼3.5 nm radius in 4 h reaction time. During particle growth, samples are extracted to study the luminescence as a function of particle size and temperature. Quantum size effects are observed to influence both the ZnSe and the Cu2+ luminescence. Temperature-dependent measurements on the luminescence intensity, lifetime, and peak positions are reported and discussed.

A 44-year-old man presented with a 1-year history of progressive muscle weakness and cramping. Neurophysiology study, along with clinical presentation, was diagnostic. The differential diagnosis, diagnostic testing, treatment, and prognosis of this rare disease are discussed.

The rotating ring-disk configuration, consisting of a Pt disk and Si ring, was used to investigate light emission from porous Si in acetonitrile. The electroluminescence (EL) of n-type porous Si and the chemiluminescence (CL) of n- and p-type porous Si in the presence of an oxidizing agent in solution are reported. The EL and CL characteristics are similar to those observed in aqueous solution. No EL of p-type porous Si could be observed in the presence of a strong reducing agent, probably due to bandedge unpinning. The photon energy of the EL of n-type porous Si is in good agreement with that deduced from the relative positions of the redox energy level and the semiconductor bandedges

The surface chemistry of epitaxially grown p-type and n-type ZnSe in aqueous solutions was studied by photoelectrochemical methods. The first measurements on p-ZnSe in indifferent electrolyte solution show typical semiconductor electrode properties: dissolution of the solid in the dark at positive potentials and reduction of water to hydrogen under illumination at negative potentials. The influence of band gap mismatch between ZnSe and the GaAs substrate is clear for the n-type semiconductor. From a comparison of results obtained with p-type and n-type ZnSe electrodes at pH 7.0, it is concluded that the electrochemical reduction of hypochlorous acid occurs via the conduction band of the semiconductor. It is shown that ZnSe is etched chemically in hypochlorous acid solution and that selective etching with respect to the GaAs substrate is possible.

In order to avoid the problem of gas bubbles blocking the surfaces of rotating disk electrodes, we propose a new cell configuration for an inverted rotating disk electrode. This simple construction gives the same hydrodynamic conditions as a conventional rotating disk electrode.

Electroluminescence from n-type porous silicon can be generated in solution by reduction of peroxodisulfate. It has been assumed that the SO4•- radical ion, formed in the first reduction step, injects a hole into the valence band of the porous semiconductor. The hole should subsequently undergo radiative recombination with a conduction band electron. Using two techniques, viz., photocurrent quantum efficiency measurements with p-type porous and crystalline silicon electrodes and minority carrier injection studies with the “transistor technique”, we found that the reduction of peroxodisulfate is, however, not always accompanied by hole injection. The silicon results are compared with results obtained on GaAs electrodes.

Using electrochemical and in situ luminescence measurements we show that ferricyanide ions are reduced at n-type ZnSe electrodes by hole injection into the valence band of the semiconductor. At negative potentials the holes recombine with electrons and electroluminescence is observed. At the open-circuit potential, the injected holes are used for the oxidation and dissolution of the semiconductor. This electroless etching reaction is under mixed diffusion/kinetic control at 20°C, but becomes diffusion controlled at higher temperature. U7 - Export Date: 2 August 2010 U7 - Source: Scopus

Objective We investigated the relationship between reflux and aberrant deoxyribonucleic acid (DNA) methylation, comparing methylation in the columnar epithelium following successful fundoplication to that in subjects with a failed fundoplication. Summary background data Gastroesophageal reflux is the main risk factor for Barrett esophagus and adenocarcinoma. In these diseases, there is a high level of DNA methylation. Methods We enrolled 41 patients with Barrett esophagus and a fundoplication at least 5 years earlier for a 24-hour pH study, endoscopy, and collection of biopsies. Biopsies were obtained from 17 Barrett esophagus subjects who had not undergone esophageal surgery. Results At the time of the study, 31 subjects were pH normal, 10 abnormal. Columnar biopsies were collected from 21 of the pH normal and 9 pH abnormal subjects, and all no surgery subjects. Complete regression of columnar mucosa was seen in 7 subjects with pH normal and 1 with pH abnormal. The length of Barrett esophagus did not differ between groups preoperatively, but was significantly less at the time of the study in the pH normal compared with pH abnormal or no surgery groups. Significantly, fewer genes were methylated in the pH normal than the pH abnormal or no surgery groups, which did not differ from each other. The number of methylated genes correlated with increased reflux, intestinal metaplasia, and increased columnar-lined esophagus length, but not acid-suppression medication. Conclusions Fundoplication that reduces reflux to normal levels can lead to regression of the columnar mucosa. Reflux is associated with aberrant DNA methylation, and control of reflux reduces deleterious genomic changes associated with cancer.

Elevated atmospheric CO 2 can cause increased carbon fixation and altered foliar chemical composition in a variety of plants, which has the potential to impact forested headwater streams because they are detritus-based ecosystems that rely on leaf litter as their primary source of organic carbon. Fungi and bacteria play key roles in the entry of terrestrial carbon into aquatic food webs, as they decompose leaf litter and serve as a source of nutrition for invertebrate consumers. This study tested the hypothesis that changes in leaf chemistry caused by elevated atmospheric CO 2 would result in changes in the size and composition of microbial communities colonizing leaves in a woodland stream. Three tree species, Populus tremuloides , Salix alba , and Acer saccharum , were grown under ambient (360 ppm) or elevated (720 ppm) CO 2 , and their leaves were incubated in a woodland stream. Elevated-CO 2 treatment resulted in significant increases in the phenolic and tannin contents and C/N ratios of leaves. Microbial effects, which occurred only for P. tremuloides leaves, included decreased fungal biomass and decreased bacterial counts. Analysis of fungal and bacterial communities on P. tremuloides leaves via terminal restriction fragment length polymorphism (T-RFLP) and clone library sequencing revealed that fungal community composition was mostly unchanged by the elevated-CO 2 treatment, whereas bacterial communities showed a significant shift in composition and a significant increase in diversity. Specific changes in bacterial communities included increased numbers of alphaproteobacterial and cytophaga-flavobacter-bacteroides (CFB) group sequences and decreased numbers of betaproteobacterial and firmicutes sequences, as well as a pronounced decrease in overall Gram-positive bacterial sequences.

Nanocrystalline ZnS:Pb2+ is synthesised ia a precipitation method. The influence of the size of the nanocrystals and the sulfide concentration used in the synthesis on the luminescence properties is investigated. Nanocrystalline ZnS:Pb2+ shows a white emission under UV excitation with a rather high quantum efficiency (∽5%). At least two luminescence centres are involved. One centre is identified as a Pb2+ ion located on a regular Zn2+ site and gives a red emission under 480 nm excitation. The luminescence properties of this emission are characteristic of 3P0 → 1S0 (A-band) or charge transfer (D-band) transitions on Pb2+ ions. The other centres are not as well defined and give a broad green emission band under 380 nm excitation and also show luminescence properties typically observed for Pb2+. The green emission probably originates from a charge-transfer like D-band emission of Pb2+ in ZnS close to a defect (e.g. an S2− vacancy or an O2− ion on an S2− site). A relation between the temperature quenching of the emissions and the band gap is observed and indicates that photoionisation occurs. The higher quenching temperature for the Pb2+ luminescence in smaller particles can be explained by widening of the band gap as a result of quantum size effects in the ZnS host.

A significant chemical stability has allowed us to perform photoelectrochemical measurements on the semiconducting state of the GdMg hydride system. With electrical impedance spectroscopy we confirm that GdMg hydride in the transparent state is an n-type semiconductor. The donor density was estimated to be 5 3 1021 cm23. Impedance measurements give information about the potential distribution at the semiconductor/solution interface. Photocurrent was observed in the transparent state. It is proposed that photoanodic etching of the GdMg hydride at high light intensities occurs along grain boundaries, leading to inhomogeneous destruction of the film.

In the present chapter we first briefly consider mechanisms for the etching of semiconductors (Sect. 43.1) and relate these principles to methods for controlling surface morphology and revealing defects (Sect. 43.2). Section 43.3 describes in some detail defect-sensitive etching methods. Results are presented for the classical (orthodox) method used for revealing dislocations in Sect. 43.3.1. More recently developed open-circuit (photo)etching approaches, sensitive to both crystallographic and electrically active inhomogeneities in semiconductors, are reviewed in Sect. 43.3.2. In particular, attention will focus on newly introduced etchants and etching procedures for wide-bandgap semiconductors.

Primary systemic amyloidosis (PSA) is a plasma cell dyscrasia. Organ damage is caused by deposition of amyloid, derived from monoclonal light chains, in tissues including nerves. PSA damages tissues and leads to combinations of neuropathy and renal, cardiac, and liver failure. The neuropathy of PSA is relatively stereotyped with damage to small and autonomic nerve fibers and superimposed carpal tunnel syndrome. The disease is progressive and mortality is high, especially when there is early involvement of vital organs. Treatment in the past was relatively ineffective. However, with the advent of peripheral blood stem cell transplantation and chemotherapy in selected patients, prolonged survival is possible if the weight of organ damage at onset of treatment is not too high. Thus, early detection is paramount.

The electrochemistry of CdS in aqueous solutions of HOCl/OCl − is reported. At negative potentials reduction of both HOCl and OCl − is observed and a strong luminescence is found indicating hole injection into the valence band by the oxidizing species. At positive potentials the semiconductor is etched at a considerable rate. The mechanisms of cathodic reduction of HOCl and dissolution of CdS are discussed.

The dissolution and recombination processes at the CdS/electrolyte interface have been studied with the electrical and opto-electrical impedance methods. It has been found that dissolution intermediates can act as recombination centers and that thermal excitation of electrons from these intermediates to the conduction band can occur. In the case of the opto-electrical impedance it is shown that the modulation of the light intensity results in a modulation, not only of the minority carrier concentration, but also of the majority carrier concentration. As a consequence, a value for the Helmholtz capacitance could be determined from the opto-electrical impedance results

Study objective: To evaluate the impact of an emergency medicine residency training program on the cost of care in the emergency department. Design: A retrospective chart review was conducted of all ED encounters for a three-month period, six months before and six months after the introduction of an emergency medicine residency program into an urban community hospital. Physician staffing of this ED before the residency period was by nonemergency medicine residency-trained emergency physicians. Setting: A 27,000-visit-per-year urban community hospital ED. Type of patients: A consecutive sample of all patients discharged home from the emergency center with one of six diagnoses. The diagnoses studied were viral upper respiratory infection, pharyngitis, acute asthma, seizure, lumbosacral strain, and cervical strain. Main outcome measures: Frequency of laboratory test and radiograph ordering pertinent to the evaluation of each diagnostic category were used as a marker of cost of care. Results: The presence of the residency training program did not increase the cost of care as measured by test use and, for three of the six diagnoses, actually lowered the cost of care. This effect was most prominent in the evaluation of lumbosacral and cervical strain when the residency physicians ordered radiographs at a rate five and 2.3 times lower, respectively, than the previous group and in the approach to pharyngitis when they ordered throat cultures 2.8 times less frequently. Conclusion: As measured by selected test use for six common discharge diagnoses, the introduction of an emergency medicine residency program did not increase the cost of care in this urban community hospital ED.

Study objectives: To assess the impact of the introduction of an emergency medicine residency program on the quality of care in an urban community hospital emergency department. Design: A retrospective chart review of all ED encounters for a three-month period beginning six months before and six months after the introduction of an emergency medicine residency. Setting: A 27,000-visit-per-year urban community hospital ED. Type of participants: All patients who presented to the ED with one of five complaints and subsequently were discharged home. The five presenting categories examined were nontraumatic chest pain when age 30 years or more, lower abdominal pain in women aged 15 to 40 years, recent head trauma, headache of nontraumatic origin, and extremity laceration. Interventions: None. Measurements and main results: The frequency of physician documentation on the ED record of explicit criteria related to the five presenting complaints was used as a measure of the quality of care. Items sought for documentation included elements of. the history and physical examination and diagnostic evaluations. The explicit criteria lists were drawn from the literature, including clinical policy guidelines. For each of the presenting complaints evaluated, documentation of the majority of items reflecting the quality of care was higher during the residency period. In no instance did the level of documentation decrease. Conclusion: As measured by a process evaluation, documentation of the medical record, the introduction of an emergency medicine residency significantly improved the quality of care in this urban community hospital ED.

A review is presented of photoelectrochemical systems which at p-type semiconductor electrodes give a quantum efficiency greater than one. The use of intensity modulated photocurrent spectroscopy (IMPS) for studying such systems is considered. Special attention is devoted to the mechanism of current-doubling at p-GaAs caused by oxidizing agents which also etch the semiconductor chemically. New data are presented for the photocathodic reduction of iodate in alkaline solution at p-GaAs. At low light intensity this system gives a quantum efficiency ( Q ) close to 6.

We demonstrate the effect of sputter gas pressure and film thickness, d, on the coercivity of Co in Al/Co/Cu sputterdeposited on Si(001). Increased sputter gas pressure produces increased rms roughness and increased O content in our films. The deposited Co thickness at which the onset of ferromagnetism is first observed, dc, increases with sputter gas pressure. Above this thickness,d > dc, the coercivity increases with increasing Co thickness. For film thickness d ≫ dc, the coercivity is thickness independent. We show that coercivity is directly controllable at technologically relevant thicknesses by regulating sputter-deposition parameters.

Single-incision laparoscopic cholecystectomy (SILC) may increase the risk of bile duct injury due to compromised operative exposure. Dome-down laparoscopic cholecystectomy provides the ability to evaluate the cystic duct circumferentially prior to its division, thus minimizing the risks of bile duct injury. This study assesses the feasibility and safety of SILC using a modified dome-down approach with all conventional laparoscopic instruments. Three low-profile 5-mm trocars are placed via a single transumbilical incision. The two working trocars are aimed laterally via the rectus to achieve adequate triangulation. An extralong 5-mm 30o laparoscope with an L-shaped light-cord adaptor is used to yield more external working space. Cephalic liver retraction is achieved with one transabdominal suture through the gallbladder fundus. Leaving the gallbladder fundus attached to the liver bed, a window is first created between the gallbladder body and the liver. The dissection is then carried down retrograde toward the porta hepatis. A 360o view of the gallbladder–cystic duct junction is achieved prior to transecting the cystic duct. The gallbladder is then freed by separation of the fundal attachments. The specimen is retrieved by enlarging the fascial incision. All fascial defects are then primarily closed. Sixteen patients (mean age 31 years, mean BMI 26.3 kg/m2) were enrolled in this study. Thirteen had elective surgery for symptomatic cholelithiasis, and three had emergency surgery for acute cholecystitis. Mean operating time was 80.3 min, and blood loss was minimal. All patients were discharged within 24 h without complications. Follow-up at 1 month revealed a barely visible scar within the umbilicus. SILC using a modified dome-down approach is technically feasible with all straight instruments, and it is safe because of good delineation of ductal anatomy. Adoption of this approach may minimize the risk of bile duct injury during early experience of SILC.

The choice of a contraceptive drug can be challenging for women with epilepsy due to possible interactions between antiepileptic drugs (AEDs) and hormonal contraception. Enzyme-inducing AEDs can cause hormonal contraception to fail and can increase the risk of teratogenicity. Higher doses of oral contraceptives can overcome pharmacologic failure but may create additional risks. The effects of reproductive hormones on individual AEDs have recently been clarified, providing helpful guidelines for physicians and patients. Studies show that lamotrigine has a significantly increased clearance (50%) when used with combined oral contraceptives, which results in an increased seizure frequency in most patients. Useful alternatives to oral contraceptives include depot injections and intrauterine devices. Subdermal implants may increase the risk of pregnancy in women with epilepsy on enzyme-inducing AEDs. Depot medroxyprogesterone acetate is effective but can increase side effects. Intrauterine devices are an alternative to pharmacologic approaches because they lack drug-drug interactions and side effects.

A SiC way to split water: Illuminated p-type 4H-SiC, as a photocathode short-circuited to Pt, was found to split water (see picture). The hydrogen generated is stored to a considerable extent in the solid.

The objective of this study is to update evidence-based best practice guidelines for specialized facilities and resources for weight loss surgery (WLS). We performed systematic search of English-language literature on WLS and facilities, equipment, and resources published between April 2004 and May 2007 in PubMed, MEDLINE, and the Cochrane Library. Keywords were used to narrow the search for a selective review of abstracts, retrieval of full articles, and grading of evidence according to systems used in established evidence-based models. Evidence-based best practice recommendations from the most recent literature on specialized facilities and resources for WLS were developed. We identified 1,647 papers in our literature search; the 46 most relevant were reviewed in detail. Regular updates of evidence-based recommendations for best practices in facilities and resources for WLS are required to address technology advances and growing recognition of the need for adequate equipment and specially built nursing units. Key factors in patient safety include availability of trained personnel and specialized equipment for the care of extremely obese WLS patients.

To update evidence-based best practice guidelines for surgical care in weight loss surgery (WLS). Systematic search of English-language literature on WLS in MEDLINE, EMBASE, and the Cochrane Library between April 2004 and May 2007. Use of key words to narrow the search for a selective review of abstracts, retrieval of full articles, and grading of evidence according to systems used in established evidence-based models. Evidence-based best practice recommendations from the most recent literature on surgical methods and technologies, risks and benefits, outcomes, and surgeon qualifications and credentialing. We identified >135 articles; the 65 most relevant were reviewed in detail. Regular updates of evidence-based recommendations for best practices in WLS are required to address rapid changes in surgical techniques and patient demographics. Key factors in patient safety include surgical risk factors, type of procedure, surgeon training, and facility certification.

The porous semiconductor electrode provides an interesting example for the theme of this volume: electrochemistry at the nanoscale. In porous etching, the anodic reaction can be considered to occur at an array of “nanoelectrodes”, the pore tips, while the remainder of the porous matrix remains electrochemically inactive. In this case, conditions are clearly different from those at a macroscopic surface. Porous electrodes can also exhibit another aspect, one in which charge transfer is not restricted to the pore fronts; instead, the whole internal surface of the matrix acts as an electrode with a very large area but with a reduced “thickness”, corresponding to the dimensions of the pore wall. Such small dimensions, which can even lead to size quantization, play a critical role in the electrochemistry. In this chapter, we consider the factors that decide whether the electrochemical reaction occurs exclusively at the pore fronts or at the whole internal surface of the porous layer. We review the electrochemistry of the two cases and related chemical and physical properties. In addition, we compare some results of porous-etched single crystals with those of nanoporous electrodes made by deposition from colloidal suspension.

Anodic polarization of SiC at modest potential in dilute fluoride solution of pH 3 surprisingly gives rise to the growth of micrometer-thick surface layers, clearly revealed with scanning electron microscopy. The reaction occurs at p-type SiC in the dark and at n-type SiC under (supra)bandgap illumination. The surface layer was shown by Rutherford backscattering spectrometry (RBS) to consist of silicon dioxide and to contain excess oxygen. Elastic recoil detection (ERD) indicated only a low level of carbon and fluoride in the layer but a considerable content of hydrogen. The growth kinetics was characterized in situ by spectroscopic ellipsometry and electrical impedance spectroscopy. The results suggest the formation of a duplex layer: a thin inner dielectric oxide and a thick hydrated outer oxide. The latter must have a considerable degree of porosity to allow diffusion/migration of reactants and products during oxide growth.

Electrochemical etching of single-crystal SiC rotating disk electrodes in fluoride solution was studied at pH 3. Anodic dissolution and passivation are observed for p-type electrodes in the dark and for n-type electrodes under illumination. The dissolution of p-type (0 0 0 1) 4H–SiC is found to be under mixed transport/kinetic control; the diffusion current is first order in fluoride concentration. Polishing of p-type electrodes can be achieved at rates up to 5.8 μm/min. Porous etching was not observed in this case. The surface finish of n-type (0 0 0 1) 4H and 6H–SiC depends on the experimental conditions; both uniform and porous etching are observed. The results are compared with those of Si under comparable conditions.

We reviewed the role of electrodiagnostic testing in amyotrophic lateral sclerosis (ALS) in a large ALS clinic. Over 31 months, 133 patients with a clinical diagnosis of ALS were tested. In most, nerve conduction studies were normal, and needle electrode examination showed active denervation in the upper and lower limbs or the limbs and bulbar muscles (Lambert's criteria). However, 50 of 133 patients did not fulfill Lambert's criteria at presentation because of abnormal nerve conduction studies (11 patients), abnormal F-wave latencies (6 patients), or insufficiently distributed fibrillation potentials (40 patients). This study reveals that a large proportion of patients with a clinical diagnosis of ALS fail to have classical findings on initial electrodiagnostic studies, and reveals several caveats of electrodiagnostic testing in these patients: (1) Conduction studies may be unreliable in motor nerves with markedly low compound muscle action potential (CMAP) amplitudes. (2) Sensory nerve action potential (SNAP) amplitudes may be abnormal in a small percentage of otherwise typical ALS patients. However, better controls for elderly subjects are needed. (3) Needle electrode examination may not show widespread active denervation early in the disease. (4) Some patients may have a mild polyneuropathy. (5) The classic diagnostic criteria may need to be modified to allow earlier acceptance of many ALS patients into therapeutic trials.

The frequency dependence of the impedance of polarizable semiconductor/metal and semiconductor/electrolyte solution interfaces is reconsidered. No frequency dispersion of the polarization capacitance is found with n-GaAs/Au contacts whereas the capacitance of n-GaAs/electrolyte solution interfaces show considerable dispersion. The frequency dispersion depends on the microroughness of the electrode surface and on the specific conductivity of the electrolyte solution. As for polarizable metal electrodes, the relationship between the capacitance and the frequency is closely related to the relationship between the capacitance and the specific conductivity of the electrolyte solution. It is concluded that the main origin of frequency dispersion should not be sought in the solid but is related to the development of the electric double layer at the electrolyte side of the interface. A model is presented to account for these results.

Massive cervicofacial abscesses of dental origin are relatively rare, and may be associated with serious and grave morbidity. In extreme cases, an occasional fatality may result from regional complications. Three cases are presented that describe the clinical and radiographic evaluation and the surgical approaches for abscess drainage. Specific attention is directed toward 1) the management of imminent airway obstruction, 2) the application of computed tomographic technology for localization and surgical planning, and 3) current antibiotic therapy.

Dissolution of CdS in aqueous solutions of Br2 and I2 has been studied by ring-disc voltammetry and flow-cell measurements. The semiconductor is etched chemically at a considerable rate by Br2. CdS is dissolved in I2 solutions only when a high concentration of chloride ions is present. It is suggested that inter-halogen species play a role. A novel chemical etching reaction was observed in the iodine case: cathodic reduction of iodine produces an intermediate capable of oxidizing the semiconductor.