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Showing papers by "Lehigh University published in 2001"


Journal ArticleDOI
26 Jan 2001-Science
TL;DR: The movement of liquid drops on a surface with a radial surface tension gradient is described here and has implications for passively enhancing heat transfer in heat exchangers and heat pipes.
Abstract: The movement of liquid drops on a surface with a radial surface tension gradient is described here. When saturated steam passes over a colder hydrophobic substrate, numerous water droplets nucleate and grow by coalescence with the surrounding drops. The merging droplets exhibit two-dimensional random motion somewhat like the Brownian movements of colloidal particles. When a surface tension gradient is designed into the substrate surface, the random movements of droplets are biased toward the more wettable side of the surface. Powered by the energies of coalescence and collimated by the forces of the chemical gradient, small drops (0.1 to 0.3 millimeter) display speeds that are hundreds to thousands of times faster than those of typical Marangoni flows. This effect has implications for passively enhancing heat transfer in heat exchangers and heat pipes.

914 citations


Journal ArticleDOI
TL;DR: A field demonstration was performed in which nanoscale bimetallic particles were gravity-fed into groundwater contaminated by trichloroethene and other chlorinated aliphatic hydrocarbons at a manufacturing site, showing rapid dechlorination of target chlorinated compounds accompanied by a sharp decrease of standard oxidation potential and an increase in pH.
Abstract: A field demonstration was performed in which nanoscale bimetallic (Fe/Pd) particles were gravity-fed into groundwater contaminated by trichloroethene and other chlorinated aliphatic hydrocarbons at a manufacturing site. With diameters on the order of 100−200 nm, the nanoparticles are uniquely suited to rapidly degrade redox-amenable contaminants and for optimal subsurface delivery and dispersion. Approximately 1.7 kg of the nanoparticles was fed into the test area over a 2-day period, resulting in minimal clogging of the injection well. The test area was located within a well-characterized region of the contaminant plume and included an injection well and three piezometer couplets spaced 1.5 m apart. Despite the low nanoparticle dosage, trichloroethene reduction efficiencies of up to 96% were observed over a 4-week monitoring period with the highest values observed at the injection well and adjacent piezometers. Data from the field assessment were consistent with the results of pre-injection laboratory st...

879 citations


Journal ArticleDOI
03 Apr 2001-Langmuir
TL;DR: In this article, the surfaces of hydrophilic and hydrophobic TiO2 particles were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrography (FTIR) to gain a better understanding of the adsorption mechanism of OLOA 370 (polybutene-succinimide pentamine) on TiO 2 particles dispersed in styrene monomer prior to miniemulsion encapsulation polymerizations.
Abstract: The surfaces of hydrophilic (P25) and hydrophobic (T805) TiO2 particles were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) to gain a better understanding of the adsorption mechanism of OLOA 370 (polybutene-succinimide pentamine) on TiO2 particles dispersed in styrene monomer prior to miniemulsion encapsulation polymerizations. XPS analysis revealed that both the P25 and T805 TiO2 particles had significant amounts of hydroxyl groups on their surfaces. The XPS results showed that the surface hydroxyl concentration on the hydrophilic (P25) particles was 3.3 OH/nm2, whereas the trimethoxy octyl silane (TMOS)-surface-modified hydrophobic (T805) particles unexpectedly contained 6.6 OH/nm2. This apparent increase in the hydroxyls was attributed to hydrolysis of −OCH3 on the TMOS. The majority of these groups, however, were apparently either not acidic or not accessible to the OLOA 370 in adsorption studies, where the concentration of reactive hydroxyls...

808 citations


Journal ArticleDOI
TL;DR: Preschool-age children with ADHD are at significant risk for behavioral, social, familial, and academic difficulties relative to their normal counterparts.
Abstract: Objective To examine differences in home, school, and medical functioning between preschool-age children with attention-deficit/hyperactivity disorder (ADHD) and normal control children. Method A sample of 94 children (58 with ADHD, 36 normal controls) between 3 and 5 years old participated. Dependent measures included parent and teacher ratings of problem behavior and social skills, parent ratings of stress and family functioning, medical functioning data, observations of parent–child interactions and classroom behavior, and a test of preacademic skills. Results Young children with ADHD exhibited more problem behavior and were less socially skilled than their normal counterparts according to behavior ratings. Parents of children with ADHD experienced greater stress and were coping less adaptively than parents of non-ADHD children. Children with ADHD exhibited more noncompliant and inappropriate behavior than normal controls, particularly during task situations. Parents of children with ADHD were more likely to display negative behavior toward their children. Children with ADHD exhibited more negative social behavior in preschool settings and scored significantly lower on a test of preacademic skills. No significant differences in injuries or utilization of medical services were found. Conclusions Preschool-age children with ADHD are at significant risk for behavioral, social, familial, and academic difficulties relative to their normal counterparts.

678 citations


Journal ArticleDOI
TL;DR: This article proposed a method to design better multi-country samples for international business studies using Hofstede's framework and aimed at determining the effects of national culture on various business phenomena and developed sets of algorithms that calculate indexes reflecting the power of different samples for hypotheses testing.
Abstract: We propose a method to design better multi-country samples for international business studies using Hofstede's framework and aimed at determining the effects of national culture on various business phenomena We describe typical research scenarios, then develop sets of algorithms that calculate indexes reflecting the power of different samples for hypotheses testing The indexes were computed from Hofstede's data, then rank ordered The top multi-country samples are presented in tables for selection when designing studies

523 citations


Journal ArticleDOI
TL;DR: The temporal association between pamidronate therapy and the development of renal insufficiency, the use of escalating doses that exceed recommended levels, and the distinctive pattern of glomerular andtubular injury strongly suggest a mechanism of drug-associated podocyte and tubular toxicity.
Abstract: Collapsing focal segmental glomerulosclerosis (FSGS) is a distinct clinicopathologic entity seen most commonly in young African American patients who present with renal insufficiency and nephrotic syndrome. The only epidemiologic factor previously linked to collapsing FSGS is HIV infection. Here clinicopathologic findings are reported for a distinctive population of seven patients, who were older, Caucasian, and HIV negative and developed collapsing FSGS during active treatment of malignancy (multiple myeloma in six patients and metastatic breast carcinoma in one). Although oncologic treatment regimens included vincristine for four patients, doxorubicin for five patients, cisplatin for two patients, and total-body irradiation for one patient, the only agent common to all patients was pamidronate (Aredia). All patients had normal renal function before the administration of pamidronate. Patients began therapy with pamidronate at or below the recommended dose of 90 mg, intravenously, monthly, which was increased to 180 mg monthly in two patients and 360 mg monthly in three patients. Patients received pamidronate for 15 to 48 mo before presentation with renal insufficiency (mean serum creatinine, 3.6 mg/dl) and full nephrotic syndrome (mean 24-h urinary protein excretion, 12.4 g/d). Pamidronate, which is a member of the class of bisphosphonates, is widely used in the treatment of hypercalcemia of malignancy and osteolytic metastases. At the recommended dose of 90 mg, intravenously, monthly, renal toxicity is infrequent; however, higher doses have produced nephrotoxicity in animal models. The temporal association between pamidronate therapy and the development of renal insufficiency, the use of escalating doses that exceed recommended levels, and the distinctive pattern of glomerular and tubular injury strongly suggest a mechanism of drug-associated podocyte and tubular toxicity. These data provide the first association of collapsing FSGS with toxicity to a therapeutic agent.

418 citations


Journal ArticleDOI
TL;DR: In this paper, the integration of active matrix polysilicon TFT technology with organic light emitting diode (OLED) displays has been investigated with the goal of producing displays of uniform brightness.
Abstract: The integration of active matrix polysilicon TFT technology with organic light emitting diode (OLED) displays has been investigated with the goal of producing displays of uniform brightness. This work identifies and addresses several process integration issues unique to this type of display which are important in achieving bright and uniform displays. Rapid thermal processing has been incorporated to achieve uniform polysilicon microstructure, along with silicides to reduce parasitic source and drain series resistance. Using these processes, TFT drain current nonuniformity has been reduced below 5% for 90% of the devices. This work also introduces transition metals to produce low resistance contacts to ITO and to eliminate hillock formation in the aluminum metallization. These processes, along with spin on glasses for planarization, have been used to produce functional active matrix arrays for OLED displays. The final array pixel performance is also presented.

377 citations


Journal ArticleDOI
TL;DR: The main contribution of the paper is that the AWBT controller synthesis, using static compensation, is cast as a convex optimization over linear matrix inequalities.

373 citations


Journal ArticleDOI
TL;DR: In this paper, the potential for using laboratory synthesized nanoscale Pd/Fe bimetallic particles to reduce chlorinated ethenes was examined, and the results showed that the nanosale particles can be useful in a wide array of environmental applications including subsurface injection for groundwater treatment.

338 citations


Journal ArticleDOI
19 Apr 2001-Langmuir
TL;DR: This work compares the spreading and relaxation rates of albumin and fibrinogen, inferred from single-component and competitive adsorption kinetic experiments, on model surfaces of varying hydrophobicity, to reveal a constant spreading rate and a larger extent of footprint growth and a lower ultimate coverage on hydrophobic surfaces when compared with hydrophilic surfaces at the same Adsorption conditions.
Abstract: This work compares the spreading and relaxation rates of albumin and fibrinogen, inferred from single-component and competitive adsorption kinetic experiments, on model surfaces of varying hydrophobicity. Kinetics from the single-component studies revealed a constant spreading rate, where the adsorbed protein footprint grew linearly in time for at least 15 min. This spreading rate increased with substrate hydrophobicity (ranging from 0.02 to 0.16 nm2/molecule/s for albumin and from 0.04 to 0.26 nm2/molecule/s for fibrinogen), resulting in a larger extent of footprint growth and a lower ultimate coverage on hydrophobic surfaces when compared with hydrophilic surfaces at the same adsorption conditions. Competitive adsorption studies were in qualitative agreement with the single-component experiments but were able to probe longer spreading time scales. Although spreading appeared to occur initially at a constant rate in the competitive experiments, after 2 h the spreading rate had slowed dramatically and the...

326 citations


Journal ArticleDOI
TL;DR: This article found that female accountants are more likely than males to indicate that they use an interactive style of management called transformational leadership, which is correlated with several management skills associated with success.
Abstract: The results of this study suggest that self‐reported leadership styles of female accountants differ somewhat from the leadership styles reported by male accountants. Females are more likely than males to indicate that they use an interactive style of management called transformational leadership. This leadership style was found to be correlated with several management skills associated with success. Female accountants reported somewhat higher perceived effectiveness on two of these management skills: coaching and developing and communicating. The findings also suggest that female accountants receive more developmental opportunities than do their male colleagues.

Journal ArticleDOI
TL;DR: A sample of 1,209 university students from three countries completed a 24-item self-report measure (the Young Adult Rating Scale) tapping ADHD symptomatology and reported significantly more inattention and hyperactivity-impulsivity symptoms than students from the United States and New Zealand.
Abstract: Little research has examined the structure and prevalence of attention-deficit/hyperactivity disorder (ADHD) symptoms in university students, including whether symptom structure conforms to the bidimensional (i.e., inattention and hyperactivity-impulsivity) conceptualization of the Diagnostic and Statistical Manual of Mental Disorders (DSMV-IV; American Psychiatric Association, 1994) and whether self-reported symptoms vary across gender and country. A sample of 1,209 university students from three countries (Italy, New Zealand, and the United States) completed a 24-item self-report measure (the Young Adult Rating Scale) tapping ADHD symptomatology. Factor analyses within the U.S. and New Zealand samples supported a bidimensional symptom structure, whereas weaker support for this conceptualization was provided by the Italian sample. Participants did not vary significantly by gender in symptom report; however, Italian students reported significantly more inattention and hyperactivity-impulsivity symptoms than students from the United States, and students from New Zealand reported more inattention symptoms than students from the United States. The prevalence of self-reported ADHD symptoms beyond DSM-IV thresholds for diagnosis ranged from 0% (Italian women) to 8.1% (New Zealand men). The implications of these results for the use of DSM-IV criteria in identifying university students with ADHD are discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors investigate how the marketing concept, the heart of the market orientation, may be established in a multinational setting and the effects of national culture on that process.
Abstract: A growing concern among international marketing managers is how to increase the market orientation and thereby performance of their transnational organizations. This study broaches this issue by investigating how the marketing concept, the heart of the market orientation, may be established in a multinational setting and the effects of national culture on that process. From a wide array of literature, the authors construct a theoretical framework and propositions on how global organizations may transform this philosophy from an abstract platitude to an operational reality. Their findings suggest that the process consists of complex, interdependent steps—interpretation, adoption, and implementation of the marketing concept. Cultural values shape interpretation and facilitate or impede adoption and implementation. The overall framework and findings can be used to guide institutionalization of the marketing concept across the organizational span, in particular by anticipating culture-based reactions from international subsidiaries.

Journal ArticleDOI
TL;DR: A theory is presented for the crossover from BNP to the reverse Brazil nut problem based on a competition between the percolation effect and the condensation of hard spheres.
Abstract: In the Brazil nut problem (BNP), hard spheres with larger diameters rise to the top. There are various explanations (percolation, reorganization, convection), but a broad understanding or control of this effect is by no means achieved. A theory is presented for the crossover from BNP to the reverse Brazil nut problem based on a competition between the percolation effect and the condensation of hard spheres. The crossover condition is determined, and theoretical predictions are compared to molecular dynamics simulations in two and three dimensions.

Journal ArticleDOI
TL;DR: In this article, a novel chemisorption method was employed for the dissociative adsorption of methanol to surface methoxy intermediates in order to quantitatively determine the number of surface active sites on one-component metal oxide catalysts.
Abstract: A novel chemisorption method was employed for the dissociative adsorption of methanol to surface methoxy intermediates in order to quantitatively determine the number of surface active sites on one-component metal oxide catalysts (MgO, CaO, SrO, BaO, Y2O3, La2O3, CeO2, TiO2, ZrO2, HfO2, V2O5, Nb2O5, Ta2O5, Cr2O3, MoO3, WO3, Mn2O3, Fe2O3, Co3O4, Rh2O3, NiO, PdO, PtO, CuO, Ag2O, Au2O3, ZnO, Al2O3, Ga2O3, In2O3, SiO2, GeO2, SnO2, P2O5, Sb2O3, Bi2O3, SeO2 and TeO2). The number of surface active sites for methanol dissociative adsorption corresponds to ∼3 μmol/m2 on average for many of the metal oxide catalysts. Furthermore, the methanol oxidation product distribution at low conversions reflects the nature of the surface active sites on metal oxides since redox sites yield H2CO, acidic sites yield CH3OCH3 and basic sites yield CO2. The distribution of the different types of surface active sites was found to vary widely for the different metal oxide catalysts. In addition, the commonality of the surface methoxy intermediate during dissociative chemisorption of methanol and methanol oxidation on oxide catalysts also allows for the quantitative determination of the turnover frequency (TOF) values. The TOF values for the various metal oxide catalysts were found to vary over seven orders of magnitude (10−3 to 104 s−1). An inverse relationship (for metal oxide catalysts displaying high (>85%) selectivity to either redox or acidic products) was found between the methanol oxidation TOF values and the decomposition temperatures of the surface M–OCH3 intermediates reflecting that the decomposition of the surface M–OCH3 species is the rate-determining step during methanol oxidation over the metal oxide catalysts.

Journal ArticleDOI
TL;DR: Triage nurses at these two hospitals successfully implemented the ESI algorithm and provided useful feedback for further refinement of the instrument, which reproducibly stratifies patients into five groups with distinct clinical outcomes.
Abstract: . Objectives: To implement a new five-level emergency department (ED) triage algorithm, the Emergency Severity Index (ESI), into nursing practice, and validate the instrument with a population-based cohort using hospitalization and ED length of stay as outcome measures. Methods: The five-level ESI algorithm was introduced to triage nurses at two university hospital EDs, and implemented into practice with reinforcement and change management strategies. Interrater reliability was assessed by a posttest and by a series of independent paired patient triage assignments, and a staff survey was performed. A cohort validation study of all adult patients registered during a one-month period immediately following implementation was performed. Results: Eight thousand two hundred fifty-one ED patients were studied. Weighted kappa for reproducibility of triage assignments was 0.80 for the posttest (n= 62 nurses), and 0.73 for patient triages (n= 219). Hospitalization was 28% overall and was strongly associated with triage level, decreasing from 5863 (92%) of patients in triage category 1, to 12/739 (2%) in triage category 5. Median lengths of stay were two hours shorter at either triage extreme (high and low acuity) than in intermediate categories. Outcomes followed a-priori predictions. Staff nurses rated the new program easier to use, and more useful as a triage instrument than previous three-level triage. They provided feedback, which resulted in significant revisions to the algorithm and educational materials. Conclusions: Triage nurses at these two hospitals successfully implemented the ESI algorithm and provided useful feedback for further refinement of the instrument. Emergency Severity Index triage reproducibly stratifies patients into five groups with distinct clinical outcomes.

Journal ArticleDOI
TL;DR: In this article, closed-form solutions for stresses and displacements in functionally graded cylindrical and spherical vessels subjected to internal pressure alone are obtained using the infinitesimal theory of elasticity.
Abstract: Closed-form solutions for stresses and displacements in functionally graded cylindrical and spherical vessels subjected to internal pressure alone are obtained using the infinitesimal theory of elasticity. The material stiffness obeying a simple power law is assumed to vary through the wall thickness and Poisson's ratio is assumed constant. Stress distributions depending on an inhomogeneity constant are compared with those of the homogeneous case and presented in the form of graphs. The inhomogeneity constant, which includes continuously varying volume fraction of the constituents, is empirically determined. The values used in this study are arbitrarily chosen to demonstrate the effect of inhomogeneity on stress distribution.

Journal ArticleDOI
TL;DR: In this paper, it was shown that discrete solitons can be navigated in two-dimensional networks of nonlinear waveguide arrays via vector interactions between two classes of discrete solITons: signals and blockers.
Abstract: It is shown that discrete solitons can be navigated in two-dimensional networks of nonlinear waveguide arrays. This can be accomplished via vector interactions between two classes of discrete solitons: signals and blockers. Discrete solitons in such two-dimensional networks can exhibit a rich variety of functional operations, e.g., blocking, routing, logic functions, and time gating.

Book ChapterDOI
TL;DR: This review summarizes the functional activities of MAPs found in animal cells and discusses how these MAPs are regulated.
Abstract: Microtubule-associated proteins (MAPs) function to regulate the assembly dynamics and organization of microtubule polymers. Upstream regulation of MAP activities is the major mechanism used by cells to modify and control microtubule assembly and organization. This review summarizes the functional activities of MAPs found in animal cells and discusses how these MAPs are regulated. Mechanisms controlling gene expression, isoform-specific expression, protein localization, phosphorylation, and degradation are discussed. Additional regulatory mechanisms include synergy or competition between MAPs and the activities of cofactors or binding partners. For each MAP it is likely that regulation in vivo reflects a composite of multiple regulatory mechanisms.

Journal ArticleDOI
TL;DR: In this article, the second-order rate constant for the reaction of chlorauric acid with pyrrole in dilute solution was found to he 13 M -1 s -1.
Abstract: Composite colloids of gold and polypyrrole were prepared using two different methods: 1, using pyrrole colloid, created by the oxidation of pyrrole by ferric chloride, to subsequently reduce chlorauric acid and, 2, oxidizing pyrrole monomer with chlorauric acid in a sodium dodecylbenzene sulfonate solution. In each case, the polypyrrole colloid consisted of irregularly shaped particles approximately 500 nm in diameter. The gold produced in each case was in the form of irregular spheres, approximately 407 nm in diameter in method 1 and 13 nm in method 2. X-ray photoelectron spectroscopy was used to determine the oxidation state of the species present. Transmission electron microscopy and light scattering data were used to determine the particle sizes of both gold and polypyrrole colloids. Energy dispersed spectrum X-ray analysis and electron diffraction were used to confirm the presence of metallic gold in the composite colloids. The second-order rate constant for the reaction of chlorauric acid with pyrrole in dilute solution was found to he 13 M -1 s -1 . Aqueous solutions of palladium, platinum, rhodium, cobalt, tin, silver, zinc, nickel, titanium, cadmium, mercury, arsenic, and selenium were also examined for their potential to act as oxidants to produce composite polypyrrole colloids. Palladium, platinum, and rhodium salts were suitable oxidants, producing polypyrrole in less than 12 h.

Journal ArticleDOI
TL;DR: In this article, a model acrylic pressure-sensitive adhesives (PSAs) based on poly(2-ethylhexyl acrylate-stat-acrylic acid) and poly(n-butyl- acrylated-acrylatestat-ACrylic acid), at 97.5/2.5 wt % were synthesized using semicontinuous emulsion and solution polymerizations.
Abstract: Model acrylic pressure-sensitive adhesives (PSAs) based on poly(2-ethyl-hexyl acrylate-stat-acrylic acid) and poly(n-butyl acrylate-stat-acrylic acid) at 97.5/2.5 wt % were synthesized using semicontinuous emulsion and solution polymerizations. Microgels formed in the lattices retained their discrete network morphology in the film. In contrast, acrylic solution was essentially gel free and crosslinking in the film was provided by the reaction of acrylic acid and post added Al Acetyl Acetonate after solvent evaporation, which led to continuous network morphology. The difference in film network morphology caused significantly lower shear holding power for the film from emulsion PSA compared with that of solvent-borne film. Unlike shear holding power, loop tack and peel of acrylic PSAs were mainly controlled by the same sol/gel molecular parameters, regardless of emulsion or solution PSAs. The important molecular parameters are sol-to-gel ratio, entanglement molecular weight, weight average molecular weight, and to a lesser extent, glass transition temperature. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2230–2244, 2001

Journal ArticleDOI
TL;DR: This paper conducted interviews with 13 psychotherapy trainees about a counterproductive event that occurred in individual supervision, defined as any experience that was hindering, unhelpful, or harmful in relation to the trainee's growth as a therapist.
Abstract: The authors conducted interviews with 13 psychotherapy trainees about a counterproductive event that occurred in individual supervision, which was defined as any experience that was hindering, unhelpful, or harmful in relation to the trainee's growth as a therapist. A qualitative analysis revealed that trainees typically attributed their experiences of counterproductive events to their supervisors dismissing their thoughts and feelings. All trainees experienced a negative interaction with their supervisors following the counteractive event, yet most did not believe their supervisors were aware of the event's counterproductive nature. All trainees believed the counterproductive event weakened the supervisory relationship and led to a change in the way they approached their supervisors. Although trainees typically thought the counterproductive events negatively affected their work with clients, most did not disclose their counterproductive experience with their supervisors.

Journal ArticleDOI
TL;DR: Improved space-time coding for multiple-input multiple-output orthogonal frequency division multiplexing is studied for wireless systems using QPSK modulation for four transmit and four receive antennas and a 256-state code is shown to perform within 3 dB of outage capacity.
Abstract: Improved space-time coding for multiple-input multiple-output orthogonal frequency division multiplexing is studied for wireless systems using QPSK modulation for four transmit and four receive antennas. A 256-state code is shown to perform within 3 dB of outage capacity (and within 2 dB with perfect channel estimation), which is better than any other published result without using iterative decoding.

Journal ArticleDOI
TL;DR: This review covers the theoretical principles behind the ELNES technique, the experimental procedures necessary to acquire good ELNES spectra, including potential artefacts, and gives examples relevant to materials science.
Abstract: Electron energy-loss near-edge structure (ELNES) is a technique that can be used to measure the electronic structure (i.e. bonding) in materials with subnanometre spatial resolution. This review covers the theoretical principles behind the technique, the experimental procedures necessary to acquire good ELNES spectra, including potential artefacts, and gives examples relevant to materials science.

Journal ArticleDOI
01 Jun 2001-Wetlands
TL;DR: In this article, the authors assess the impact of individual plant species on biomass production and decomposition in salt marshes and find that Phragmites australis (common reed) is approximately three times greater for aboveground biomass, two times higher for below ground biomass, and 30% lower in root: shoot ratio than neighboring populations of S. patens.
Abstract: The recent expansion of Phragmites australis (common reed) from the marsh-upland interface into high marsh zones provides an opportunity to assess the impact of individual plant species on biomass production and decomposition in salt marshes. Seasonal harvests of aboveground and belowground biomass demonstrate that annual production of P. australis is approximately three times greater for aboveground biomass, two times greater for belowground biomass, and 30% lower in root: shoot ratio than neighboring populations of S. patens. Whole-plant litter (stems and leaves) also decomposes at a much slower annual rate for P. australis (k=0.25) than S. patents litter (k=0.57). By crossing litter type with site of litter decomposition, I found these plant species to influence decay rates through litter type and not through their effects on marsh surface conditions (e.g., temperature, sedimentation rates). Based on these calculations, annual rates of carbon accumulation in the peat of high marshes are likely to increase 5-fold once P. australis becomes established due to its greater rates of biomass production and residence time in infrequently flooded brackish marshes.

Journal ArticleDOI
TL;DR: In this article, the authors used the common and widespread freshwater cladoceran Daphnia pulicaria as a model organism to demonstrate the potential importance of these wavelength-specific effects of UVR to the ecology of aquatic organisms.
Abstract: Solar ultraviolet radiation (UVR) may have beneficial as well as detrimental effects on living systems. For example, UV-B radiation (280-320 nm) is generally dam- aging, while UV-A radiation (320-400 nm) may cause damage or stimulate beneficial photorepair of UV-B damage. The nature of both direct and indirect effects of UVR in nature depends on both the photon flux density and the spectral composition of the radiation incident on aquatic organisms across environmental UVR gradients in space (depth, trans- parency, elevation) and time (diel, seasonal, interannual). Here we use the common and widespread freshwater cladoceran Daphnia pulicaria as a model organism to demonstrate the potential importance of these wavelength-specific effects of UVR to the ecology of aquatic organisms. UVR-exposure experiments are used to manipulate both natural solar and artificial UVR sources to examine the beneficial as well as detrimental effects of different wavelengths of UVR. Changes in the spectral composition of solar radiation are also examined along several natural environmental gradients including diel gradients, depth gradients, and dissolved organic carbon (DOC) gradients. The implications of variation in the spectral composition of UVR for aquatic organisms are discussed. The first biological weighting function (BWF) for a freshwater cladoceran is presented here. It demonstrates that the shortest UV-B wavelengths in sunlight are potentially the most damaging per photon. However, due to the greater photon flux density of longer wavelength UVR in sunlight, the net potential damage to Daphnia in nature is greatest for the longer wavelength UV-B and shorter wavelength UV-A radiation in the 305-322 nm range. Overall the contribution of UV-B to the total mortality response of Daphnia exposed to full-spectrum solar radiation for 7 h on a sunny summer day is 64% while UV-A con- tributes 36%. The BWF for Daphnia is used with the transmission spectrum for Mylar D to demonstrate that Mylar D cuts out only about half of the damaging UVR in sunlight. Following exposure to damaging UV-B, Daphnia exhibits a dramatic increase in survival in the presence of longer wavelength UV-A and visible radiation due to the stimulation of photoenzymatic repair. We present data that demonstrate the importance of both atmospheric ozone and DOC in creating strong environmental gradients in the intensity (irradiance) and spectral composition of solar UVR in nature. The light-absorbing component of DOC, chromophoric dissolved organic matter (CDOM), is particularly important in creating depth refugia from damaging UV-B in freshwater ecosystems. CDOM may also cause intense variations in the ratio of potentially beneficial UV-A to detrimental UV-B radiation to which aquatic organisms are exposed. In addition to changes in atmospheric ozone, future changes in CDOM related to climate change or other environmental disturbances may substantially alter the underwater exposure of a variety of aquatic organisms to different wavelengths of solar UVR.

Journal ArticleDOI
TL;DR: In this paper, the authors describe progress in the design and scaling of SONOS nonvolatile memory devices and describe a field programmable gate array-based measurement system for the dynamic characterization.
Abstract: Scaling the programming voltage, while still maintaining 10-year data retention time, has always been a big challenge for polysilicon–oxide–nitride–oxide–silicon (SONOS) researchers. We describe progress in the design and scaling of SONOS nonvolatile memory devices. We have realized −9+10 V (1 ms) programmable SONOS devices ensuring 10-year retention time after 107 erase/write cycles at 85°C. Deuterium anneals, applied in SONOS device fabrication for the first time, improves the endurance characteristics when compared with traditional hydrogen or forming gas anneals. We introduce scaling considerations and process optimization along with experiments and SONOS device characterization. A field programmable gate array-based measurement system is described for the dynamic characterization of SONOS nonvolatile memory devices.

Journal ArticleDOI
TL;DR: A review of the most recent developments in the application of thermochromic liquid crystals to fluid flow temperature measurement is presented in this paper, where the experimental aspects including application, illumination, recording, and calibration of liquid crystals on solid surfaces, as well as in fluid suspensions, are discussed.
Abstract: A review of the most recent developments in the application of thermochromic liquid crystals to fluid flow temperature measurement is presented. The experimental aspects including application, illumination, recording, and calibration of liquid crystals on solid surfaces, as well as in fluid suspensions, are discussed. Because of the anisotropic optical properties of liquid crystals, on-axis lighting/viewing arrangements, combined with in-situ calibration techniques, generally provide the most accurate temperature assessments. However, where on-axis viewing is not possible, calibration techniques can be employed, which reduce the uncertainty associated with off-axis viewing and lighting arrangements. It has been determined that the use of hue definitions that display a linear trend across the color spectrum yield the most accurate correlation with temperature. The uncertainty of both wide-band and narrow-band thermochromic liquid crystal calibration techniques can be increased due to hysteresis effects, which occur when the temperature of the liquid crystals exceeds their maximum activation temperature. Although liquid crystals are commonly used to provide time-mean temperature measurements, techniques are available which allow the monitoring of temporal changes. Selected examples illustrating the use of thermochromic liquid crystals are shown, and a survey of reported temperature measurement uncertainties is presented.

Journal ArticleDOI
TL;DR: In this article, the chemical and optical changes in the dissolved organic matter (DOM) from two freshwater lakes and a Sphagnum bog after exposure to solar radiation were studied, and the results suggest both photooxidation of allochthonous DOM in the epilimnion and autotrophic production of DOM by bacteria in the hypolimnions of two lakes in northeastern Pennsylvania.
Abstract: We studied the chemical and optical changes in the dissolved organic matter (DOM) from two freshwater lakes and a Sphagnum bog after exposure to solar radiation. Stable carbon isotopes and solid-state 13 C-NMR spectra of DOM were used together with optical and chemical data to interpret results from experimental exposures of DOM to sunlight and from seasonal observations of two lakes in northeastern Pennsylvania. Solar photochemical oxidation of humic-rich bog DOM to smaller LMW compounds and to DIC was inferred from losses of UV absorbance, optical indices of molecular weight and changes in DOM chemistry. Experimentally, we observed a 1.2‰ enrichment in δ 13 C and a 47% loss in aromatic C functionality in bog DOM samples exposed to solar UVR. Similar results were observed in the surface waters of both lakes. In late summer hypolimnetic water in humic Lake Lacawac, we observed 3 to 4.5‰ enrichments in δ 13 C and a 30% increase in aromatic C relative to early spring values during spring mixing. These changes coincided with increases in molecular weight and UV absorbance. Anaerobic conditions of the hypolimnion in Lake Lacawac suggest that microbial metabolism may be turning over allochthonous C introduced during spring mixing, as well as autochthonous C. This metabolic activity produces HMW DOM during the summer, which is photochemically labile and isotopically distinct from allochthonous DOM or autochthonous DOM. These results suggest both photooxidation of allochthonous DOM in the epilimnion and autotrophic production of DOM by bacteria in the hypolimnion cause seasonal trends in the UV absorbance of lakes.

Journal ArticleDOI
01 Oct 2001
TL;DR: The primary focus of the paper is the Lehigh Omnidirectional Tracking System (LOTS) and its components, which includes adaptive multibackground modeling, quasi-connected components (a novel approach to spatio-temporal grouping), background subtraction analyses, and an overall system evaluation.
Abstract: Autonomous video surveillance and monitoring of human subjects in video has a rich history. Many deployed systems are able to reliably track human motion in indoor and controlled outdoor environments, e.g., parking lots and university campuses. A challenging domain of vital military importance is the surveillance of noncooperative and camouflaged targets within cluttered outdoor settings. These situations require both sensitivity and a very wide field of view and, therefore, are a natural application of omnidirectional video. Fundamentally, target finding is a change detection problem. Detection of camouflaged and adversarial targets implies the need for extreme sensitivity. Unfortunately, blind change detection in woods and fields may lead to a high fraction of false alarms, since natural scene motion and lighting changes produce highly dynamic scenes. Naturally, this desire for high sensitivity leads to a direct tradeoff between miss detections and false alarms. This paper discusses the current state of the art in video-based target detection, including an analysis of background adaptation techniques. The primary focus of the paper is the Lehigh Omnidirectional Tracking System (LOTS) and its components. This includes adaptive multibackground modeling, quasi-connected components (a novel approach to spatio-temporal grouping), background subtraction analyses, and an overall system evaluation.