Formulation and in-vitro evaluation of floating bilayer tablet of lisinopril maleate and metoprolol tartrate.

PubMed

Ijaz, Hira; Qureshi, Junaid; Danish, Zeeshan; Zaman, Muhammad; Abdel-Daim, Mohamed; Hanif, Muhammad; Waheed, Imran; Mohammad, Imran Shair

2015-11-01

The purpose of this study was to introduce the technology for the development of rate-controlled oral drug delivery system to overcome various physiological problems. Several approaches are being used for the purpose of increasing the gastric retentive time, including floating drug delivery system. Gastric floating lisinopril maleate and metoprolol tartrate bilayer tablets were formulated by direct compression method using the sodium starch glycolate, crosscarmellose sodium for IR layer. Eudragit L100, pectin, acacia as sustained release polymers in different ratios for SR metoprolol tartrate layer and sodium bicarbonate, citric acid as gas generating agents for the floating extended release layer. The floating bilayer tablets of lisinopril maleate and metoprolol tartrate were designed to overcome the various problems associated with conventional oral dosage form. Floating tablets were evaluated for floating lag time, drug contents and in-vitro dissolution profile and different kinetic release models were applied. It was clear that the different ratios of polymers affected the drug release and floating time. L2 and M4 showed good drug release profile and floating behavior. The linear regression and model fitting showed that all formulation followed Higuchi model of drug release model except M4 that followed zero order kinetic. From the study it is evident that a promising controlled release by floating bilyer tablets of lisinopril maleate and metoprolol tartrate can be developed successfully.

New insights on poly(vinyl acetate)-based coated floating tablets: characterisation of hydration and CO2 generation by benchtop MRI and its relation to drug release and floating strength.

PubMed

Strübing, Sandra; Abboud, Tâmara; Contri, Renata Vidor; Metz, Hendrik; Mäder, Karsten

2008-06-01

The purpose of this study was to investigate the mechanism of floating and drug release behaviour of poly(vinyl acetate)-based floating tablets with membrane controlled drug delivery. Propranolol HCl containing tablets with Kollidon SR as an excipient for direct compression and different Kollicoat SR 30 D/Kollicoat IR coats varying from 10 to 20mg polymer/cm2 were investigated regarding drug release in 0.1N HCl. Furthermore, the onset of floating, the floating duration and the floating strength of the device were determined. In addition, benchtop MRI studies of selected samples were performed. Coated tablets with 10mg polymer/cm2 SR/IR, 8.5:1.5 coat exhibited the shortest lag times prior to drug release and floating onset, the fastest increase in and highest maximum values of floating strength. The drug release was delayed efficiently within a time interval of 24 h by showing linear drug release characteristics. Poly(vinyl acetate) proved to be an appropriate excipient to ensure safe and reliable drug release. Floating strength measurements offered the possibility to quantify the floating ability of the developed systems and thus to compare different formulations more efficiently. Benchtop MRI studies allowed a deeper insight into drug release and floating mechanisms noninvasively and continuously.

Development and Characterization of Novel Floating-Mucoadhesive Tablets Bearing Venlafaxine Hydrochloride.

PubMed

Misra, Raghvendra; Bhardwaj, Peeyush

2016-01-01

The present investigation is concerned about the development of floating bioadhesive drug delivery system of venlafaxine hydrochloride which after oral administration exhibits a unique combination of floating and bioadhesion to prolong gastric residence time and increase drug bioavailability within the stomach. The floating bioadhesive tablets were prepared by the wet granulation method using different ratios of hydroxypropyl methyl cellulose (HPMC K4MCR) and Carbopol 934PNF as polymers. Sodium bicarbonate (NaHCO3) and citric acid were used as gas (CO2) generating agents. Tablets were characterized for floating properties, in vitro drug release, detachment force, and swelling index. The concentration of hydroxypropyl methyl cellulose and Carbopol 934PNF significantly affects the in vitro drug release, floating properties, detachment force, and swelling properties of the tablets. The optimized formulation showed the floating lag time 72 ± 2.49 seconds and duration of floating 24.50 ± 0.74 hr. The in vitro release studies and floating behavior were studied in simulated gastric fluid (SGF) at pH 1.2. Different drug release kinetics models were also applied. The in vitro drug release from tablets was sufficiently sustained (more than 18 hr) and the Fickian transports of the drug from the tablets were confirmed. The radiological evidence suggests that the tablets remained buoyant and altered position in the stomach of albino rabbit and mean gastric residence time was prolonged (more than > 6 hr).

Design, Development and Optimization of S (-) Atenolol Floating Sustained Release Matrix Tablets Using Surface Response Methodology

PubMed Central

Gunjal, P. T.; Shinde, M. B.; Gharge, V. S.; Pimple, S. V.; Gurjar, M. K.; Shah, M. N.

2015-01-01

The objective of this present investigation was to develop and formulate floating sustained release matrix tablets of s (-) atenolol, by using different polymer combinations and filler, to optimize by using surface response methodology for different drug release variables and to evaluate the drug release pattern of the optimized product. Floating sustained release matrix tablets of various combinations were prepared with cellulose-based polymers: Hydroxypropyl methylcellulose, sodium bicarbonate as a gas generating agent, polyvinyl pyrrolidone as a binder and lactose monohydrate as filler. The 32 full factorial design was employed to investigate the effect of formulation variables on different properties of tablets applicable to floating lag time, buoyancy time, % drug release in 1 and 6 h (D1 h,D6 h) and time required to 90% drug release (t90%). Significance of result was analyzed using analysis of non variance and P < 0.05 was considered statistically significant. S (-) atenolol floating sustained release matrix tablets followed the Higuchi drug release kinetics that indicates the release of drug follows anomalous (non-Fickian) diffusion mechanism. The developed floating sustained release matrix tablet of improved efficacy can perform therapeutically better than a conventional tablet. PMID:26798171

Design, Development and Optimization of S (-) Atenolol Floating Sustained Release Matrix Tablets Using Surface Response Methodology.

PubMed

Gunjal, P T; Shinde, M B; Gharge, V S; Pimple, S V; Gurjar, M K; Shah, M N

2015-01-01

The objective of this present investigation was to develop and formulate floating sustained release matrix tablets of s (-) atenolol, by using different polymer combinations and filler, to optimize by using surface response methodology for different drug release variables and to evaluate the drug release pattern of the optimized product. Floating sustained release matrix tablets of various combinations were prepared with cellulose-based polymers: Hydroxypropyl methylcellulose, sodium bicarbonate as a gas generating agent, polyvinyl pyrrolidone as a binder and lactose monohydrate as filler. The 3(2) full factorial design was employed to investigate the effect of formulation variables on different properties of tablets applicable to floating lag time, buoyancy time, % drug release in 1 and 6 h (D1 h,D6 h) and time required to 90% drug release (t90%). Significance of result was analyzed using analysis of non variance and P < 0.05 was considered statistically significant. S (-) atenolol floating sustained release matrix tablets followed the Higuchi drug release kinetics that indicates the release of drug follows anomalous (non-Fickian) diffusion mechanism. The developed floating sustained release matrix tablet of improved efficacy can perform therapeutically better than a conventional tablet.

Formulation and evaluation of non-effervescent floating tablets of losartan potassium.

PubMed

Getyala, Anil; Gangadharappa, H V; Prasad, M Sarat Chandra; Reddy, M Praveen Kumar; Kumar, T M Pramod

2013-10-01

The aim of the work is to modify the solubility and bioavailability of Losartan potassium, by employing noneffervescent floating drug delivery (tablet dosage forms). Non-effervescent systems are a type of floating drug delivery systems, that have been used to boost the gastric residence and the floatation time in the gastro intestinal tract. The study included formulation of floating tablets using polymers like Chitosan and Karaya gum as matrix forming agents. Accurel(®) MP 1000 was used as floating agent. The tablets were prepared by direct compression technique. FTIR, DSC studies conformed that there was no incompatibility between the polymer and the drug. Tablet preformulation parameters were within the Pharmacopoeial limit. Tablet showed zero lag time, contisnuance of buoyancy for >12 h. The tablet showed good in vitro release. Drug release was through swelling and abided by the gellation mechanism. In vivo X-ray studies depicted that tablets continued to float in the GIT for 12 h. Accelerated stability showed that, tablets were stable for over 6 month. Thus the prepared non-effervescent floating tablet of Losartan potassium can be used for the treatment of hypertension for more than 12 h with single dose administration.

Influence of different types of low substituted hydroxypropyl cellulose on tableting, disintegration, and floating behaviour of floating drug delivery systems

PubMed Central

Diós, Péter; Pernecker, Tivadar; Nagy, Sándor; Pál, Szilárd; Dévay, Attila

2014-01-01

The object of the present study is to evaluate the effect of application of low-substituted hydroxypropyl cellulose (L-HPC) 11 and B1 as excipients promoting floating in gastroretentive tablets. Directly compressed tablets were formed based on experimental design. Face-centred central composite design was applied with two factors and 3 levels, where amount of sodium alginate (X1) and L-HPC (X2) were the numerical factors. Applied types of L-HPCs and their 1:1 mixture were included in a categorical factor (X3). Studied parameters were floating lag time, floating time, floating force, swelling behaviour of tablets and dissolution of paracetamol, which was used as a model active substance. Due to their physical character, L-HPCs had different water uptake and flowability. Lower flowability and lower water uptake was observed after 60 min at L-HPC 11 compared to L-HPC B1. Shorter floating times were detected at L-HPC 11 and L-HPC mixtures with 0.5% content of sodium alginate, whereas alginate was the only significant factor. Evaluating results of drug release and swelling studies on floating tablets revealed correlation, which can serve to help to understand the mechanism of action of L-HPCs in the field development of gastroretentive dosage forms. PMID:26702261

Influence of hydroxypropyl methylcellulose on drug release pattern of a gastroretentive floating drug delivery system using a 3(2) full factorial design.

PubMed

Swain, Kalpana; Pattnaik, Satyanarayan; Mallick, Subrata; Chowdary, Korla Appana

2009-01-01

In the present investigation, controlled release gastroretentive floating drug delivery system of theophylline was developed employing response surface methodology. A 3(2) randomized full factorial design was developed to study the effect of formulation variables like various viscosity grades and contents of hydroxypropyl methylcellulose (HPMC) and their interactions on response variables. The floating lag time for all nine experimental trial batches were less than 2 min and floatation time of more than 12 h. Theophylline release from the polymeric matrix system followed non-Fickian anomalous transport. Multiple regression analysis revealed that both viscosity and content of HPMC had statistically significant influence on all dependent variables but the effect of these variables found to be nonlinear above certain threshold values.

Controlled release floating multiparticulates of metoprolol succinate by hot melt extrusion.

PubMed

Malode, Vilas N; Paradkar, Anant; Devarajan, Padma V

2015-08-01

We present hot melt extrusion (HME) for the design of floating multiparticulates. Metoprolol succinate was selected as the model drug. Our foremost objective was to optimize the components Eudragit(®) RS PO, polyethylene oxide (PEO) and hydroxypropyl methylcellulose (HPMC) to balance both buoyancy and controlled release. Gas generated by sodium bicarbonate in acidic medium was trapped in the polymer matrix to enable floating. Eudragit(®) RS PO and PEO with sodium bicarbonate resulted in multiparticulates which exhibited rapid flotation within 3 min but inadequate total floating time (TFT) of 3h. Addition of HPMC to the matrix did not affect floating lag time (FLT), moreover TFT increased to more than 12h with controlled release of metoprolol succinate. Floating multiparticulates exhibited t50% of 5.24h and t90% of 10.12h. XRD and DSC analysis revealed crystalline state of drug while FTIR suggested nonexistence of chemical interaction between the drug and the other excipients. The assay, FLT, TFT and the drug release of the multiparticulates were unchanged when stored at 40°C/75%RH for 3 months confirming stability. We present floating multiparticulates by HME which could be extrapolated to a range of other drugs. Our approach hence presents platform technology for floating multiparticulates. Copyright © 2015 Elsevier B.V. All rights reserved.

A modified emulsion gelation technique to improve buoyancy of hydrogel tablets for floating drug delivery systems.

PubMed

Yom-Tov, Ortal; Seliktar, Dror; Bianco-Peled, Havazelet

2015-10-01

The use of buoyant or floating hydrogel tablets is of particular interest in the sustained release of drugs to the stomach. They have an ability to slow the release rates of drugs by prolonging their absorption window in the upper part of the gastrointestinal (GI) tract. In this study we synthesized bioactive hydrogels that have sustainable release rates for drugs in the stomach based on a hydrogel preparation technique that employs emulsifying surfactants. The emulsion gelation technique, which encapsulates oil droplets within the hydrogels during crosslinking, was used to decrease their specific gravity in aqueous environments, resulting in floating drug release depots. Properties such as swelling, buoyancy, density and drug release were manipulated by changing the polymer concentrations, surfactant percentages and the oil:polymer ratios. The relationship between these properties and the hydrogel's floating lag time was documented. The potential for this material to be used as a floating drug delivery system was demonstrated. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of Multiple-Unit Floating Drug Delivery System of Clarithromycin: Formulation, in vitro Dissolution by Modified Dissolution Apparatus, in vivo Radiographic Studies in Human Volunteers.

PubMed

Reddy, Arun B; Reddy, Narendar D

2017-07-01

Clarithromycin (CM), a broad spectrum macrolide antibiotic used to eradicate H. pylori in peptic ulcer. Clarithromycin (CM) is well absorbed from the gastrointestinal tract, but has a bioavailability of 50% due to rapid biodegradation. The aim of this investigation was to increase the gastric residence time, and to control the drug release of clarithromycin by formulating into multiple unit floating mini-tablets. Floating tablets were prepared by using direct compression method with HPMC K 4 M and Polyox WSR 1105 as release retarded polymers and sodium bicarbonate as gas generating agent. The prepared mini-tablets were evaluated for thickness, weight variation, friability, hardness, drug content, in vitro buoyancy, swelling studies, in vitro dissolution studies by using modified Rossett-Rice test and in vivo radiographic studies in healthy human volunteers in fasting conditions. DSC analysis revealed that no interaction between drug and excipients. All the physical parameters of the tablets were within the acceptable limits. The optimized formulation (F6) had showed controlled drug release of 99.16±3.22% in 12 h, by zero-order release kinetics, along with floating lag time of 9.5±1.28 s and total floating time of 12±0.14 h. X-ray imaging studies revealed that in vivo gastric residence time of clarithromycin floating mini-tablet in the stomach was about 3.5 h. The results demonstrated that the developed floating mini-tablets of clarithromycin caused significant enhancement in gastric retention time along with sustained effect and increased oral bioavailability. © Georg Thieme Verlag KG Stuttgart · New York.

Optimization and evaluation of clarithromycin floating tablets using experimental mixture design.

PubMed

Uğurlu, Timucin; Karaçiçek, Uğur; Rayaman, Erkan

2014-01-01

The purpose of the study was to prepare and evaluate clarithromycin (CLA) floating tablets using experimental mixture design for treatment of Helicobacter pylori provided by prolonged gastric residence time and controlled plasma level. Ten different formulations were generated based on different molecular weight of hypromellose (HPMC K100, K4M, K15M) by using simplex lattice design (a sub-class of mixture design) with Minitab 16 software. Sodium bicarbonate and anhydrous citric acid were used as gas generating agents. Tablets were prepared by wet granulation technique. All of the process variables were fixed. Results of cumulative drug release at 8th h (CDR 8th) were statistically analyzed to get optimized formulation (OF). Optimized formulation, which gave floating lag time lower than 15 s and total floating time more than 10 h, was analyzed and compared with target for CDR 8th (80%). A good agreement was shown between predicted and actual values of CDR 8th with a variation lower than 1%. The activity of clarithromycin contained optimizedformula against H. pylori were quantified using well diffusion agar assay. Diameters of inhibition zones vs. log10 clarithromycin concentrations were plotted in order to obtain a standard curve and clarithromycin activity.

Floating gastroretentive drug delivery systems: Comparison of experimental and simulated dissolution profiles and floatation behavior.

PubMed

Eberle, Veronika A; Schoelkopf, Joachim; Gane, Patrick A C; Alles, Rainer; Huwyler, Jörg; Puchkov, Maxim

2014-07-16

Gastroretentive drug delivery systems (GRDDS) play an important role in the delivery of drug substances to the upper part of the gastrointestinal tract; they offer a possibility to overcome the limited gastric residence time of conventional dosage forms. The aim of the study was to understand drug-release and floatation mechanisms of a floating GRDDS based on functionalized calcium carbonate (FCC). The inherently low apparent density of the excipient (approx. 0.6 g/cm(3)) enabled a mechanism of floatation. The higher specific surface of FCC (approx. 70 m(2)) allowed sufficient hardness of resulting compacts. The floating mechanism of GRDDS was simulated in silico under simulated acidic and neutral conditions, and the results were compared to those obtained in vitro. United States Pharmacopeia (USP) dissolution methods are of limited usefulness for evaluating floating behavior and drug release of floating dosage forms. Therefore, we developed a custom-built stomach model to simultaneously analyze floating characteristics and drug release. In silico dissolution and floatation profiles of the FCC-based tablet were simulated using a three-dimensional cellular automata-based model. In simulated gastric fluid, the FCC-based tablets showed instant floatation. The compacts stayed afloat during the measurement in 0.1 N HCl and eroded completely while releasing the model drug substance. When water was used as dissolution medium, the tablets had no floating lag time and sank down during the measurement, resulting in a change of release kinetics. Floating dosage forms based on FCC appear promising. It was possible to manufacture floating tablets featuring a density of less than unity and sufficient hardness for further processing. In silico dissolution simulation offered a possibility to understand floating behavior and drug-release mechanism. Copyright © 2014 Elsevier B.V. All rights reserved.

Polyamine-Induced Rapid Root Abscission in Azolla pinnata

PubMed Central

Gurung, Sushma; Cohen, Michael F.; Fukuto, Jon; Yamasaki, Hideo

2012-01-01

Floating ferns of the genus Azolla detach their roots under stress conditions, a unique adaptive response termed rapid root abscission. We found that Azolla pinnata plants exhibited dose-dependent rapid root abscission in response to the polyamines spermidine and spermine after a substantial time lag (>20 min). The duration of the time lag decreased in response to high pH and high temperature whereas high light intensity increased the time lag and markedly lowered the rate of abscission. The oxidation products of polyamines, 1,3-diaminopropane, β-alanine and hydrogen peroxide all failed to initiate root abscission, and hydroxyethyl hydrazine, an inhibitor of polyamine oxidase, did not inhibit spermine-induced root abscission. Exposure of A. pinnata to the polyamines did not result in detectable release of NO and did not affect nitrite-dependent NO production. The finding of polyamine-induced rapid root abscission provides a facile assay for further study of the mode of action of polyamines in plant stress responses. PMID:22997568

Polyamine-Induced Rapid Root Abscission in Azolla pinnata.

PubMed

Gurung, Sushma; Cohen, Michael F; Fukuto, Jon; Yamasaki, Hideo

2012-01-01

Floating ferns of the genus Azolla detach their roots under stress conditions, a unique adaptive response termed rapid root abscission. We found that Azolla pinnata plants exhibited dose-dependent rapid root abscission in response to the polyamines spermidine and spermine after a substantial time lag (>20 min). The duration of the time lag decreased in response to high pH and high temperature whereas high light intensity increased the time lag and markedly lowered the rate of abscission. The oxidation products of polyamines, 1,3-diaminopropane, β-alanine and hydrogen peroxide all failed to initiate root abscission, and hydroxyethyl hydrazine, an inhibitor of polyamine oxidase, did not inhibit spermine-induced root abscission. Exposure of A. pinnata to the polyamines did not result in detectable release of NO and did not affect nitrite-dependent NO production. The finding of polyamine-induced rapid root abscission provides a facile assay for further study of the mode of action of polyamines in plant stress responses.

A novel automated alternating current biosusceptometry method to characterization of controlled-release magnetic floating tablets of metronidazole.

PubMed

Ferrari, Priscileila Colerato; dos Santos Grossklauss, Dany Bruno Borella; Alvarez, Matheus; Paixão, Fabiano Carlos; Andreis, Uilian; Crispim, Alexandre Giordano; de Castro, Ana Dóris; Evangelista, Raul Cesar; de Arruda Miranda, José Ricardo

2014-08-01

Alternating Current Biosusceptometry is a magnetically method used to characterize drug delivery systems. This work presents a system composed by an automated ACB sensor to acquire magnetic images of floating tablets. The purpose of this study was to use an automated Alternating Current Biosusceptometry (ACB) to characterize magnetic floating tablets for controlled drug delivery. Floating tablets were prepared with hydroxypropyl methylcellulose (HPMC) as hydrophilic gel material, sodium bicarbonate as gas-generating agent and ferrite as magnetic marker. ACB was used to characterize the floating lag time and the tablet hydration rate, by quantification of the magnetic images to magnetic area. Besides the buoyancy, the floating tablets were evaluated for weight uniformity, hardness, swelling and in vitro drug release. The optimized tablets were prepared with equal amounts of HPMC and ferrite, and began to float within 4 min, maintaining the flotation during more than 24 h. The data of all physical parameters lied within the pharmacopeial limits. Drug release at 24 h was about 40%. The ACB results showed that this study provided a new approach for in vitro investigation of controlled-release dosage forms. Moreover, using automated ACB will also be possible to test these parameters in humans allowing to establish an in vitro.in vivo correlation (IVIVC).

Application of ethyl cellulose, microcrystalline cellulose and octadecanol for wax based floating solid dispersion pellets.

PubMed

Yan, Hong-Xiang; Zhang, Shuang-Shuang; He, Jian-Hua; Liu, Jian-Ping

2016-09-05

The present study aimed to develop and optimize the wax based floating sustained-release dispersion pellets for a weakly acidic hydrophilic drug protocatechuic acid to achieve prolonged gastric residence time and improved bioavailability. This low-density drug delivery system consisted of octadecanol/microcrystalline cellulose mixture matrix pellet cores prepared by extrusion-spheronization technique, coated with drug/ethyl cellulose 100cp solid dispersion using single-step fluid-bed coating method. The formulation-optimized pellets could maintain excellent floating state without lag time and sustain the drug release efficiently for 12h based on non-Fickian transport mechanism. Observed by SEM, the optimized pellet was the dispersion-layered spherical structure containing a compact inner core. DSC, XRD and FTIR analysis revealed drug was uniformly dispersed in the amorphous molecule form and had no significant physicochemical interactions with the polymer dispersion carrier. The stability study of the resultant pellets further proved the rationality and integrity of the developed formulation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comparative evaluation of single and bilayered lamotrigine floating tablets

PubMed Central

Lakshmi, PK; Sridhar, M; Shruthi, B

2013-01-01

Aim: The purpose of this study was to prepare lamotrigine (LM) bilayered and single layered floating tablets and to compare their release profiles. Materials and Methods: LM floating tablets were prepared by direct compression method. Drug, hydroxy propyl methyl cellulose K4M, lactose monohydrate and polyvinylpyrrolidone K30 constitute controlled release layer components and floating layer components includes polymers and sodium bicarbonate. The prepared tablets were evaluated for physicochemical parameters such as hardness, friability, weight variation, thickness, floating lag time (FLT), floating time, in vitro buoyancy study, in vitro release studies. The drug-polymer interaction was studied by fourier transform infrared and differential scanning calorimetry. Results and Discussion: The FLT of all the formulations were within the prescribed limits (<3 min). When ethyl cellulose was used as floating layer component, tablets showed good buoyancy effect but eroded within 6-8 h. Hence it was replaced with hydroxypropyl cellulose -M hydrophilic polymer, which showed good FLT and floating duration for 16 h. Formulation LFC4 was found to be optimized with dissolution profile of zero order kinetics showing fickian diffusion. A comparative study of bilayered and single layered tablets of LM showed a highest similarity factor of 83.03, difference factor of 2.74 and t-test (P < 0.05) indicates that there is no significant difference between them. Conclusion: Though bilayered tablet possess many advantages, single layered tablet would be economical, cost-effective and reproducible for large scale production in the industry. However, the results of present study demonstrated that the in vitro development of bilayered gastro retentive floating tablets with controlled drug release profile for LM is feasible. PMID:24167788

Study of controlled-release floating tablets of dipyridamole using the dry-coated method.

PubMed

Chen, Kai; Wen, Haoyang; Yang, Feifei; Yu, Yibin; Gai, Xiumei; Wang, Haiying; Li, Pingfei; Pan, Weisan; Yang, Xinggang

2018-01-01

Dipyridamole (DIP), having a short biological half-life, has a narrow absorption window and is primarily absorbed in the stomach. So, the purpose of this study was to prepare controlled-release floating (CRF) tablets of dipyridamole by the dry-coated method. The influence of agents with different viscosity, hydroxypropylmethylcellulose (HPMC) and polyvinylpyrollidon K30 (PVP K30) in the core tablet and low-viscosity HPMC and PVP K30 in the coating layer on drug release, were investigated. Then, a study with a three-factor, three-level orthogonal experimental design was used to optimize the formulation of the CRF tablets. After data processing, the optimized formulation was found to be: 80 mg HPMC K4M in the core tablet, 80 mg HPMC E15 in core tablet and 40 mg PVP K30 in the coating layer. Moreover, an in vitro buoyancy study showed that the optimized formulation had an excellent floating ability and could immediately float without a lag time and this lasted more than 12 h. Furthermore, an in vivo gamma scintigraphic study showed that the gastric residence time of the CRF tablet was about 8 h.

Design and evaluation of hydrophobic coated buoyant core as floating drug delivery system for sustained release of cisapride

PubMed Central

Jacob, Shery; Nair, Anroop B; Patil, Pandurang N

2010-01-01

An inert hydrophobic buoyant coated–core was developed as floating drug delivery system (FDDS) for sustained release of cisapride using direct compression technology. Core contained low density, porous ethyl cellulose, which was coated with an impermeable, insoluble hydrophobic coating polymer such as rosin. It was further seal coated with low viscosity hydroxypropyl methyl cellulose (HPMC E15) to minimize moisture permeation and better adhesion with an outer drug layer. It was found that stable buoyant core was sufficient to float the tablet more than 8 h without the aid of sodium bicarbonate and citric acid. Sustained release of cisapride was achieved with HPMC K4M in the outer drug layer. The floating lag time required for these novel FDDS was found to be zero, however it is likely that the porosity or density of the core is critical for floatability of these tablets. The in vitro release pattern of these tablets in simulated gastric fluid showed the constant and controlled release for prolonged time. It can be concluded that the hydrophobic coated buoyant core could be used as FDDS for gastroretentive delivery system of cisapride or other suitable drugs. PMID:24825997

Development of a gastroretentive pulsatile drug delivery platform.

PubMed

Thitinan, Sumalee; McConville, Jason T

2012-04-01

To develop a novel gastroretentive pulsatile drug delivery platform by combining the advantages of floating dosage forms for the stomach and pulsatile drug delivery systems. A gastric fluid impermeable capsule body was used as a vessel to contain one or more drug layer(s) as well as one or more lag-time controlling layer(s). A controlled amount of air was sealed in the innermost portion of the capsule body to reduce the overall density of the drug delivery platform, enabling gastric floatation. An optimal mass fill inside the gastric fluid impermeable capsule body enabled buoyancy in a vertical orientation to provide a constant surface area for controlled erosion of the lag-time controlling layer. The lag-time controlling layer consisted of a swellable polymer, which rapidly formed a gel to seal the mouth of capsule body and act as a barrier to gastric fluid ingress. By varying the composition of the lag-time controlling layer, it was possible to selectively program the onset of the pulsatile delivery of a drug. This new delivery platform offers a new method of delivery for a variety of suitable drugs targeted in chronopharmaceutical therapy. This strategy could ultimately improve drug efficacy and patient compliance, and reduce harmful side effects by scaling back doses of drug administered. © 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

Formulation and evaluation of novel coated floating tablets of bergenin and cetirizine dihydrochloride for gastric delivery.

PubMed

He, Shuang; Li, Feng; Zhou, Dan; Du, Junrong; Huang, Yuan

2012-10-01

A novel coated gastric floating drug-delivery system (GFDDS) of bergenin (BN) and cetirizine dihydrochloride (CET) was developed. First, the pharmacodynamic studies were performed and the results revealed that the new compounds of bergenin/cetirizine dihydrochloride had comparative efficacy as commercial products (bergenin/chlorphenamine maleate) but with fewer side effects on central nervous system (CNS). Subsequently, bergenin was formulated as an extended-release core tablet while cetirizine dihydrochloride was incorporated into the gastric coating film for immediate release. The formulation of GFDDS was optimized by CET content uniformity test, in vitro buoyancy and drug release. Herein, the effects of sodium bicarbonate (effervescent), hydroxypropyl methylcellulose (HPMC, matrix polymer) and coating weight gain were investigated respectively. The optimized GFDDS exhibited good floating properties (buoyancy lag time < 2 min; floating duration > 10 h) and satisfactory drug-release profiles (immediate release of CET in 10 min and sustained release of BN for 12 h). In vivo gamma scintigraphy proved that the optimized GFDDS could retain in the stomach with a prolonged gastric retention time (GRT) of 5 h, and the coating layer showed no side effect for gastric retention. The novel coated gastric floating drug-delivery system offers a new approach to enhance BN's absorption at its absorption site and the efficacy of both CET and BN.

Statistical optimization and fabrication of a press coated pulsatile dosage form to treat nocturnal acid breakthrough.

PubMed

Agarwal, Vaibhav; Bansal, Mayank

2013-08-01

Present work focuses on the use of mimosa seed gum to develop a drug delivery system making combined use of floating and pulsatile principles, for the chrono-prevention of nocturnal acid breakthrough. The desired aim was achieved by fabricating a floating delivery system bearing time - lagged coating of Mimosa pudica seed polymer for the programmed release of Famotidine. Response Surface Methodology was the statistical tool that was employed for experiment designing, mathematical model generation and optimization study. A 3(2) full factorial design was used in designing the experiment.% weight ratio of mimosa gum to hydroxy propyl methyl cellulose in the coating combination and the coating weight were the independent variables, whereas the lag time and the cumulative % drug release in 360 minutes were the observed responses. Results revealed that both the coating composition and the coating weight significantly affected the release of drug from the dosage form. The optimized formulation prepared according to the computer generated software, Design-Expert(®) deciphered response which were in close proximity with the experimental responses, thus confirming the robustness as well as accuracy of the predicted model for the utilization of natural polymer like mimosa seed gum for the chronotherapeutic treatment of nocturnal acid breakthrough.

Design and evaluation of effervescent floating tablets based on hydroxyethyl cellulose and sodium alginate using pentoxifylline as a model drug

PubMed Central

Rahim, Safwan Abdel; Carter, Paul A; Elkordy, Amal Ali

2015-01-01

The aim of this work was to design and evaluate effervescent floating gastro-retentive drug delivery matrix tablets with sustained-release behavior using a binary mixture of hydroxyethyl cellulose and sodium alginate. Pentoxifylline was used as a highly water-soluble, short half-life model drug with a high density. The floating capacity, swelling, and drug release behaviors of drug-loaded matrix tablets were evaluated in 0.1 N HCl (pH 1.2) at 37°C±0.5°C. Release data were analyzed by fitting the power law model of Korsmeyer–Peppas. The effect of different formulation variables was investigated, such as wet granulation, sodium bicarbonate gas-forming agent level, and tablet hardness properties. Statistical analysis was applied by paired sample t-test and one-way analysis of variance depending on the type of data to determine significant effect of different parameters. All prepared tablets through wet granulation showed acceptable physicochemical properties and their drug release profiles followed non-Fickian diffusion. They could float on the surface of dissolution medium and sustain drug release over 24 hours. Tablets prepared with 20% w/w sodium bicarbonate at 50–54 N hardness were promising with respect to their floating lag time, floating duration, swelling ability, and sustained drug release profile. PMID:25848220

Risk based approach for design and optimization of stomach specific delivery of rifampicin.

PubMed

Vora, Chintan; Patadia, Riddhish; Mittal, Karan; Mashru, Rajashree

2013-10-15

The research envisaged focuses on risk management approach for better recognizing the risks, ways to mitigate them and propose a control strategy for the development of rifampicin gastroretentive tablets. Risk assessment using failure mode and effects analysis (FMEA) was done to depict the effects of specific failure modes related to respective formulation/process variable. A Box-Behnken design was used to investigate the effect of amount of sodium bicarbonate (X1), pore former HPMC (X2) and glyceryl behenate (X3) on percent drug release at 1st hour (Q1), 4th hour (Q4), 8th hour (Q8) and floating lag time (min). Main effects and interaction plots were generated to study effects of variables. Selection of the optimized formulation was done using desirability function and overlay contour plots. The optimized formulation exhibited Q1 of 20.9%, Q4 of 59.1%, Q8 of 94.8% and floating lag time of 4.0 min. Akaike information criteria and Model selection criteria revealed that the model was best described by Korsmeyer-Peppas power law. The residual plots demonstrated no existence of non-normality, skewness or outliers. The composite desirability for optimized formulation computed using equations and software were 0.84 and 0.86 respectively. FTIR, DSC and PXRD studies ruled out drug polymer interaction due to thermal treatment. Copyright © 2013 Elsevier B.V. All rights reserved.

Design and Optimization of Floating Drug Delivery System of Acyclovir

PubMed Central

Kharia, A. A.; Hiremath, S. N.; Singhai, A. K.; Omray, L. K.; Jain, S. K.

2010-01-01

The purpose of the present work was to design and optimize floating drug delivery systems of acyclovir using psyllium husk and hydroxypropylmethylcellulose K4M as the polymers and sodium bicarbonate as a gas generating agent. The tablets were prepared by wet granulation method. A 32 full factorial design was used for optimization of drug release profile. The amount of psyllium husk (X1) and hydroxypropylmethylcellulose K4M (X2) were selected as independent variables. The times required for 50% (t50%) and 70% (t70%) drug dissolution were selected as dependent variables. All the designed nine batches of formulations were evaluated for hardness, friability, weight variation, drug content uniformity, swelling index, in vitro buoyancy, and in vitro drug release profile. All formulations had floating lag time below 3 min and constantly floated on dissolution medium for more than 24 h. Validity of the developed polynomial equation was verified by designing two check point formulations (C1 and C2). The closeness of predicted and observed values for t50% and t70% indicates validity of derived equations for the dependent variables. These studies indicated that the proper balance between psyllium husk and hydroxypropylmethylcellulose K4M can produce a drug dissolution profile similar to the predicted dissolution profile. The optimized formulations followed Higuchi's kinetics while the drug release mechanism was found to be anomalous type, controlled by diffusion through the swollen matrix. PMID:21694992

Design and optimization of floating drug delivery system of acyclovir.

PubMed

Kharia, A A; Hiremath, S N; Singhai, A K; Omray, L K; Jain, S K

2010-09-01

The purpose of the present work was to design and optimize floating drug delivery systems of acyclovir using psyllium husk and hydroxypropylmethylcellulose K4M as the polymers and sodium bicarbonate as a gas generating agent. The tablets were prepared by wet granulation method. A 3(2) full factorial design was used for optimization of drug release profile. The amount of psyllium husk (X1) and hydroxypropylmethylcellulose K4M (X2) were selected as independent variables. The times required for 50% (t(50%)) and 70% (t(70%)) drug dissolution were selected as dependent variables. All the designed nine batches of formulations were evaluated for hardness, friability, weight variation, drug content uniformity, swelling index, in vitro buoyancy, and in vitro drug release profile. All formulations had floating lag time below 3 min and constantly floated on dissolution medium for more than 24 h. Validity of the developed polynomial equation was verified by designing two check point formulations (C1 and C2). The closeness of predicted and observed values for t(50%) and t(70%) indicates validity of derived equations for the dependent variables. These studies indicated that the proper balance between psyllium husk and hydroxypropylmethylcellulose K4M can produce a drug dissolution profile similar to the predicted dissolution profile. The optimized formulations followed Higuchi's kinetics while the drug release mechanism was found to be anomalous type, controlled by diffusion through the swollen matrix.

Formulation and evaluation of different floating tablets containing metronidazole to target stomach.

PubMed

Loh, Zhiao C; Elkordy, Amal A

2015-01-01

The purpose of this study is to formulate and develop tablets dosage form containing Metronidazole which has swelling and floating properties as a gastroretentive controlled-release drug delivery system to improve drug bioavailability. Fifteen different formulations of effervescence-forming floating systems were designed using HPMC K15M, xanthan gum, co-povidone, Eudragit® RL PO, pluronic® F-127 and/or polypropylene foam powder as swelling agents and sodium bicarbonate with/ without citric acid as gas-forming agents at different compositions. Six out of these 15 formulations which have satisfactory tablet floating behaviour were further studied with the incorporation of Metronidazole. The tablets were evaluated based on tablet physicochemical properties, floating behaviour, swelling ability and drug dissolution studies which were carried out using 0.1M HCl at 37°C for 8 hours. Furthermore, evaluation of the powder mixtures using Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC) and scanning electron microscope (SEM) were investigated. Most of the tablets show good physicochemical properties except for F11 which contains pluronic® F-127 as its release-retarding matrix-forming polymer. Other formulations show high swelling capacity, ability to float for at least 8 hours in vitro and have sustained drug release characteristics. Data obtained indicated that F3 which contains HPMC (12.5%w/w), xanthan gum (25%w/w), co-povidone (12.5%w/w) and sodium bicarbonate (31.7%w/w) is a suitable formulation with short floating lag time, good floating behaviour and sustained drug release for at least 8 hours in vitro with a zero order kinetic. Combinations of HPMC K15M and xanthan gum as swelling agents show synergistic effect in retarding drug release and are suitable in providing the most sustained drug release system.

Formulation and evaluation of floating tablet of H2-receptor antagonist.

PubMed

Kesarla, Rajesh S; Vora, Pratik Ashwinbhai; Sridhar, B K; Patel, Gunvant; Omri, Abdelwahab

2015-01-01

Conventional sustained dosage form of ranitidine hydrochloride (HCl) does not prevent frequent administration due to its degradation in colonic media and limited absorption in the upper part of GIT. Ranitidine HCl floating tablet was formulated with sublimation method to overcome the stated problem. Compatibility study for screening potential excipients was carried out using Fourier transform infrared spectroscopy (FT-IR) and differential scanning chromatography (DSC). Selected excipients were further evaluated for optimizing the formulation. Preliminary screening of binder, polymer and sublimating material was based on hardness and drug release, drug release with release kinetics and floating lag time with total floatation time, respectively. Selected excipients were subjected to 3(2) factorial design with polymer and sublimating material as independent factors. Matrix tablets were obtained by using 16/32" flat-faced beveled edges punches followed by sublimation. FT-IR and DSC indicated no significant incompatibility with selected excipients. Klucel-LF, POLYOX WSR N 60 K and l-menthol were selected as binder, polymer and sublimating material, respectively, for factorial design batches after preliminary screening. From the factorial design batches, optimum concentration to release the drug within 12 h was found to be 420 mg of POLYOX and 40 mg of l-menthol. Stability studies indicated the formulation as stable. Ranitidine HCl matrix floating tablets were formulated to release 90% of drug in stomach within 12 h. Hence, release of the drug could be sustained within narrow absorption site. Moreover, the dosage form was found to be floating within a fraction of second independent of the pH of media ensuring a robust formulation.

In vivo gastric residence and gastroprotective effect of floating gastroretentive tablet of DA-9601, an extract of Artemisia asiatica, in beagle dogs

PubMed Central

Kim, Jeong Soo; Cha, Kwang Ho; Kang, Seung Yeob; Won, Donghan; Jang, Sun Woo; Son, Miwon; Son, Moon Ho; Choi, Ho Jung; Lee, Young Won; Kang, Myung Joo

2016-01-01

Objective DA-9601, an extract of Artemisia asiatica containing eupatilin and jaceosidin as active compounds, has been prescribed to treat gastritis in Asia. In recent times, sustained-release, floating gastroretentive (GR) tablets of DA-9601 are available on the market. In the present study, the physical properties and in vitro drug release profile, in vivo gastric residence time, and gastroprotective effect of GR tablet were compared to those of immediate release (IR) tablets of DA-9601. Method In vitro buoyancy behavior (floating lag time and duration) and release profile of eupatilin were assessed in acidic medium. The in vivo intragastric behaviors of the barium sulfate-loaded IR and GR tablets were evaluated in beagle dogs by radiographic studies. Local gastroprotective effect was compared in an experimentally induced gastric lesion in beagle dogs after oral administration of IR (three times per day) or GR (twice daily) tablets for 15 days. Results Upon contact with gastric juice, a low-density floating tablet (apparent density of 0.93 g/cm3) was buoyant on the medium and was upheld for 14 hours, providing sustained drug release profile, whereas the IR tablet disintegrated within 10 minutes, showing complete drug release within 2 hours. In vivo radiographic studies showed that the GR tablet was retained for >4 hours in the stomach. Both DA-9601 formulations remarkably alleviated gastric mucosal injury compared to placebo group, when observed by gastric endoscopy. Conclusion Twice-daily GR tablets exhibited a prolonged gastric residence time and a remarkable mucosal restoration effect in animal models. Therefore, the GR system of DA-9601 could be a substitute dosage form for the treatment of gastritis, while reducing the dosing frequency and thus improving patient compliance. PMID:27354765

In vivo gastric residence and gastroprotective effect of floating gastroretentive tablet of DA-9601, an extract of Artemisia asiatica, in beagle dogs.

PubMed

Kim, Jeong Soo; Cha, Kwang Ho; Kang, Seung Yeob; Won, Donghan; Jang, Sun Woo; Son, Miwon; Son, Moon Ho; Choi, Ho Jung; Lee, Young Won; Kang, Myung Joo

2016-01-01

DA-9601, an extract of Artemisia asiatica containing eupatilin and jaceosidin as active compounds, has been prescribed to treat gastritis in Asia. In recent times, sustained-release, floating gastroretentive (GR) tablets of DA-9601 are available on the market. In the present study, the physical properties and in vitro drug release profile, in vivo gastric residence time, and gastroprotective effect of GR tablet were compared to those of immediate release (IR) tablets of DA-9601. In vitro buoyancy behavior (floating lag time and duration) and release profile of eupatilin were assessed in acidic medium. The in vivo intragastric behaviors of the barium sulfate-loaded IR and GR tablets were evaluated in beagle dogs by radiographic studies. Local gastroprotective effect was compared in an experimentally induced gastric lesion in beagle dogs after oral administration of IR (three times per day) or GR (twice daily) tablets for 15 days. Upon contact with gastric juice, a low-density floating tablet (apparent density of 0.93 g/cm(3)) was buoyant on the medium and was upheld for 14 hours, providing sustained drug release profile, whereas the IR tablet disintegrated within 10 minutes, showing complete drug release within 2 hours. In vivo radiographic studies showed that the GR tablet was retained for >4 hours in the stomach. Both DA-9601 formulations remarkably alleviated gastric mucosal injury compared to placebo group, when observed by gastric endoscopy. Twice-daily GR tablets exhibited a prolonged gastric residence time and a remarkable mucosal restoration effect in animal models. Therefore, the GR system of DA-9601 could be a substitute dosage form for the treatment of gastritis, while reducing the dosing frequency and thus improving patient compliance.

Development of a Novel Floating In-situ Gelling System for Stomach Specific Drug Delivery of the Narrow Absorption Window Drug Baclofen.

PubMed

R Jivani, Rishad; N Patel, Chhagan; M Patel, Dashrath; P Jivani, Nurudin

2010-01-01

The present study deals with development of a floating in-situ gel of the narrow absorption window drug baclofen. Sodium alginate-based in-situ gelling systems were prepared by dissolving various concentrations of sodium alginate in deionized water, to which varying concentrations of drug and calcium bicarbonate were added. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used to check the presence of any interaction between the drug and the excipients. A 3(2) full factorial design was used for optimization. The concentrations of sodium alginate (X1) and calcium bicarbonate (X2) were selected as the independent variables. The amount of the drug released after 1 h (Q1) and 10 h (Q10) and the viscosity of the solution were selected as the dependent variables. The gels were studied for their viscosity, in-vitro buoyancy and drug release. Contour plots were drawn for each dependent variable and check-point batches were prepared in order to get desirable release profiles. The drug release profiles were fitted into different kinetic models. The floating lag time and floating time found to be 2 min and 12 h respectively. A decreasing trend in drug release was observed with increasing concentrations of CaCO3. The computed values of Q1 and Q10 for the check-point batch were 25% and 86% respectively, compared to the experimental values of 27.1% and 88.34%. The similarity factor (f 2) for the check-point batch being 80.25 showed that the two dissolution profiles were similar. The drug release from the in-situ gel follows the Higuchi model, which indicates a diffusion-controlled release. A stomach specific in-situ gel of baclofen could be prepared using floating mechanism to increase the residence time of the drug in stomach and thereby increase the absorption.

Gastroretentive Ranitidine Hydrochloride Tablets with Combined Floating and Bioadhesive Properties: Factorial Design Analysis, In Vitro Evaluation and In Vivo Abdominal X-Ray Imaging.

PubMed

Abduljabbar, Hana N; Badr-Eldin, Shaimaa M; Aldawsari, Hibah M

2015-01-01

Ranitidine HCl is an H2-antagonist that suffers from low oral bioavailability of 50%. The site-specific absorption from the upper part of the small intestine and the colonic metabolism of the drug could partially contribute to its reduced bioavailability. To surmount these drawbacks, this work aimed at the formulation of Ranitidine HCl gastroretentive floating-biaodhesive tablets. A 3(2) factorial design was applied to assess the effects of matrix former (HPMC K100M): drug ratio, and the release retardant (Carbopol 971) amount on the characteristics of the tablets prepared using direct compression technique. The prepared tablets were thoroughly evaluated for physical properties, floating, swelling, bioadhesive and in vitro release behaviors. Statistical analysis of the results revealed significant effects for both formulation variables on the swelling index, maximum detachment force and cumulative percent drug released after 6 hours. In addition, the matrix- former: drug ratio showed a statistically significant effect on the floating lag time. Kinetic analysis of the release data indicated Higuchi diffusion kinetics and anomalous transport mechanism for all formulations. Scanning electron micrographs of the selected tablet formulation; F8, revealed intact surface without any perforations or channels in the dry state, while polymer expansion (relaxation) with some perforated areas were observed on the surface of the tablets after 12 hours dissolution in 0.1 N HCl. Furthermore, in vivo abdominal x-ray imaging showed good floating behavior of the selected formulation; F8, for up to 6 hours with appropriate bioadhesive property. In conclusion, the selected ranitidine HCl floating-bioadhesive tablets could be regarded as a promising gastroretentive drug delivery system that could deliver the drug at a controlled rate.

Formulation and evaluation of atenolol floating bioadhesive system using optimized polymer blends

PubMed Central

Siddam, Haritha; Kotla, Niranjan G.; Maddiboyina, Balaji; Singh, Sima; Sunnapu, Omprakash; Kumar, Anil; Sharma, Dinesh

2016-01-01

Introduction: Oral sustained release gastro retentive dosage forms offer several advantages for drugs having absorption from the upper gastrointestinal tract to improve the bioavailability of medications which have narrow absorption window. The aim of the study was to develop a floating bioadhesive drug delivery system exhibiting a unique combination of floatation and bioadhesion to prolong the residence in the stomach using atenolol as a model drug. Methods: Prior to compression, polymeric blend(s) were evaluated for flow properties. The tablets were prepared by direct compression method using bioadhesive polymer like Carbopol 934P and hydrophilic polymers like HPMC K4M, HPMC K15M, and HPMC K100M. The prepared tablets were evaluated for physical characteristics, bioadhesive strength, buoyancy lag time, swelling index and in vitro drug release studies. Results: The mean bioadhesive strength was found to be in the range of 16.2 to 52.1 gm. The optimized blend (F11) showed 92.3% drug releases after 24 hrs. Whilst, increase in concentration of carbopol 934P, bioadhesive strength and swelling index was increased with slow release. The n values of optimized formulations were found in the range of 0.631-0.719 indicating non-fickian anomalous type transport mechanism. Conclusion: The study aided in developing an ideal once-a-day gastro retentive floating drug delivery system with improved floating, swelling and bioadhesive characteristics with better bioavailability. PMID:27051631

Formulation and in vitro evaluation of Hydrodynamically balanced system for theophylline delivery.

PubMed

Nayak, Amit Kumar; Malakar, Jadupati

2011-06-01

The objective of the present study was to formulate hydrodynamically balanced systems (HBSs) of theophylline as single unit capsules. They were formulated by physical blending of theophylline with hydroxypropyl methyl cellulose, polyethylene oxide, polyvinyl pyrrolidone, ethyl cellulose, liquid paraffin, and lactose in different ratios. These theophylline HBS capsules were evaluated for weight uniformity, drug content uniformity, in vitro floating behavior and drug release in simulated gastric fluids (pH 1.2). All these formulated HBS capsules containing theophylline were floated well over 6 hours with no floating lag time, and also showed sustained in vitro drug release in simulated gastric fluid over 6 hours. The theophylline release from these capsules was more sustained with the addition of release modifiers (ethyl cellulose and liquid paraffin). The drug release pattern from these capsules was correlated well with first order model (F-1 to F-5) and Korsmeyer-Peppas model (F-6 and F-7) with the non-Fickian (anomalous) diffusion mechanism. These experimental results clearly indicated that these theophylline HBS capsules were able to remain buoyant in the gastric juice for longer period, which may improve oral bioavailability of theophylline.

Application of ion exchange resin in floating drug delivery system.

PubMed

Upadhye, Abhijeet A; Ambike, Anshuman A; Mahadik, Kakasaheb R; Paradkar, Anant

2008-10-01

The purpose of this study was to explore the application of low-density ion exchange resin (IER) Tulsion(R) 344, for floating drug delivery system (FDDS), and study the effect of its particle size on rate of complexation, water uptake, drug release, and in situ complex formation. Batch method was used for the preparation of complexes, which were characterized by physical methods. Tablet containing resin with high degree of crosslinking showed buoyancy lag time (BLT) of 5-8 min. Decreasing the particle size of resin showed decrease in water uptake and drug release, with no significant effect on the rate of complexation and in situ complex formation for both preformed complexes (PCs) and physical mixtures (PMs). Thus, low-density and high degree of crosslinking of resin and water uptake may be the governing factor for controlling the initial release of tablet containing PMs but not in situ complex formation. However, further sustained release may be due to in situ complex formation.

Development and evaluation of in situ gel of pregabalin

PubMed Central

Madan, Jyotsana R; Adokar, Bhushan R; Dua, Kamal

2015-01-01

Aim and Background: Pregabalin (PRG), an analog of gamma-aminobutyric acid, reduces the release of many neurotransmitters, including glutamate, and noradrenaline. It is used for the treatment of epilepsy; simple and complex partial convulsion. The present research work aims to ensure a high drug absorption by retarding the advancement of PRG formulation through the gastrointestinal tract. The work aims to design a controlled release PRG formulation which is administered as liquid and further gels in the stomach and floats in gastric juice. Materials and Methods: In situ gelling formulations were prepared using sodium alginate, calcium chloride, sodium citrate, hydroxypropyl methylcellulose (HPMC) K100M, and sodium bicarbonate. The prepared formulations were evaluated for solution viscosity, drug content, in vitro gelling studies, gel strength, and in vitro drug release. The final formulation was optimized using a 32 full factorial design. Results: The formulation containing 2.5% w/v sodium alginate and 0.2% w/v calcium chloride were considered optimum since it showed minimum floating lag time (18 s), optimum viscosity (287.3 cps), and gel strength (4087.17 dyne/cm2). The optimized formulation follows Korsmeyer-Peppas kinetic model with n value 0.3767 representing Fickian diffusion mechanism of drug release. Conclusion: Floating in situ gelling system of PRG can be formulated using sodium alginate as a gelling polymer and calcium chloride as a complexing agent to control the drug release for about 12 h for the treatment of epilepsy. PMID:26682193

Decadally resolved Lateglacial radiocarbon evidence from New Zealand kauri

NASA Astrophysics Data System (ADS)

Hogg, Alan; Southon, John; Turney, Chris; Palmer, Jonathan; Bronk Ramsey, Christopher; Fenwick, Pavla; Boswijk, Gretel; Büntgen, Ulf; Friedrich, Michael; Helle, Gerhard; Hughen, Konrad; Jones, Richard; Kromer, Bernd; Noronha, Alexandra; Reinig, Frederick; Reynard, Linda; Staff, Richard; Wacker, Lukas

2017-04-01

The Last Glacial-Interglacial Transition (LGIT; 15,000 - 11,000 cal BP) was characterised by complex spatiotemporal patterns of climate change, with numerous studies requiring accurate chronological control to decipher leads from lags in global palaeoclimatic, -environmental and archaeological records. However, close scrutiny of the few available tree-ring chronologies and radiocarbon-dated sequences composing the IntCal13 radiocarbon (14C) calibration curve, indicates significant weakness in 14C calibration across key periods of the LGIT. Here, we present a decadally-resolved atmospheric 14C record derived from New Zealand kauri spanning Greenland Stadial 1 (GS-1; 12,900 - 11,650 cal BP). Two floating kauri 14C time series, curve-matched to IntCal13, serve as a radiocarbon backbone through GS-1. Floating Northern Hemisphere (NH) 14C datasets are matched against the new kauri data, forming a robust NH 14C time series to 14,200 cal BP. Our results show that IntCal13 is questionable from 12,200 - 11,900 cal BP and the 10,400 BP 14C plateau is approximately five decades too short. By precisely aligning Southern and Northern Hemisphere tree-ring 14C records with marine 14C sequences, we document two relatively short periods of North Atlantic Meridional Overturning Circulation (AMOC) collapse during GS-1. Hence, sustained North Atlantic cooling across GS-1 was not driven by a prolonged AMOC reduction but was probably due to an equatorward migration of the Polar Front.

Floating-pulsatile release multiparticulate system for chronopharmacotherapy: effect of some hydrophobic additives on the buoyancy and release behavior of particles.

PubMed

Maghsoodi, M

2014-01-01

A blend of floating and pulsatile principles of a drug delivery system would have the advantage that a drug can be released in the upper gastrointestinal (GI) tract after a lag period, which is anticipated for chronotherapy. In this study, microballoons were prepared by an emulsion solvent diffusion technique using Eudragit S100, and hydrophobic additive (magnesium stearate, stearic acid or talc) for time- and site-specific drug release of piroxicam. The effect of hydrophobic additives on the production yield of floating microparticles, buoyant ability for 8 h, release of drug in simulated GI fluids (simulated gastric fluid [SGF] and simulated intestinal fluid [SIF]), mean particle size, apparent particle density, encapsulation efficiency of drug and physical state of incorporated drug were studied. Both production yield and buoyancy of the microballoons were affected by additives in the following order: magnesium stearate, stearic acid>free-additive>talc. The observed difference in yield and the buoyancy of the microballoons could be attributed to the hydrophobic character of the additives and the shell rigidity of the obtained microballoons. Incorporation of hydrophobic additives in the microballoons was found to impart the desired release properties to the microballoons by providing a 2-phase release pattern with initial slow release (5-6%) through 8 h in SGF followed by rapid pulse release (>92%) in SIF through 15 min. The microballoons co-formulated with magnesium stearate or stearic acid, combining excellent buoyancy and suitable drug release pattern of piroxicam, could be useful in chronopharmacotherapy in arthritis. © Georg Thieme Verlag KG Stuttgart · New York.

Novel swellable polymer of orchidaceae family for gastroretentive drug delivery of famotidine

PubMed Central

Razavi, Mahboubeh; Nyamathulla, Shaik; Karimian, Hamed; Noordin, Mohamed Ibrahim

2014-01-01

This study aimed to develop hydrophilic, gastroretentive matrix tablets of famotidine with good floating and swelling properties. A novel gastroretentive drug delivery formulation was designed using salep, also known as salepi, a flour obtained from grinding dried palmate tubers of Orchis morio var mascula (Orchidaceae family). The main polysaccharide content of salep is glucomannan, highly soluble in cold and hot water, which forms a viscous solution. Salep was characterized for physicochemical properties, thermal stability, chemical interaction, and surface morphology using X-ray diffraction analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy. Ten different formulations (S1–S10) were prepared using famotidine to salep ratios from 1:0.5 to 1:5. Results demonstrated that all formulations were able to sustain the drug release for more than 24 hours. The S5 formulation, with a famotidine to salep ratio of 1:2.5, had the shortest floating lag time of 35 seconds and 100% drug release within 24 hours. The dissolution data were fitted into popular mathematical models to assess the mechanism of drug release. S5 showed Zero order release (R=0.9746) with Higuchi diffusion (R=0.9428). We conclude that salep, a novel polymer, can be used in controlled release formulations to sustain release for 24 hours, due to inherent swelling and gelling properties. PMID:25246773

Optimization and evaluation of gastroretentive ranitidine HCl microspheres by using design expert software.

PubMed

Hooda, Aashima; Nanda, Arun; Jain, Manish; Kumar, Vikash; Rathee, Permender

2012-12-01

The current study involves the development and optimization of their drug entrapment and ex vivo bioadhesion of multiunit chitosan based floating system containing Ranitidine HCl by ionotropic gelation method for gastroretentive delivery. Chitosan being cationic, non-toxic, biocompatible, biodegradable and bioadhesive is frequently used as a material for drug delivery systems and used to transport a drug to an acidic environment where it enhances the transport of polar drugs across epithelial surfaces. The effect of various process variables like drug polymer ratio, concentration of sodium tripolyphosphate and stirring speed on various physiochemical properties like drug entrapment efficiency, particle size and bioadhesion was optimized using central composite design and analyzed using response surface methodology. The observed responses were coincided well with the predicted values given by the optimization technique. The optimized microspheres showed drug entrapment efficiency of 74.73%, particle size 707.26 μm and bioadhesion 71.68% in simulated gastric fluid (pH 1.2) after 8 h with floating lag time 40s. The average size of all the dried microspheres ranged from 608.24 to 720.80 μm. The drug entrapment efficiency of microspheres ranged from 41.67% to 87.58% and bioadhesion ranged from 62% to 86%. Accelerated stability study was performed on optimized formulation as per ICH guidelines and no significant change was found in drug content on storage. Copyright © 2012 Elsevier B.V. All rights reserved.

Process techniques of charge transfer time reduction for high speed CMOS image sensors

NASA Astrophysics Data System (ADS)

Zhongxiang, Cao; Quanliang, Li; Ye, Han; Qi, Qin; Peng, Feng; Liyuan, Liu; Nanjian, Wu

2014-11-01

This paper proposes pixel process techniques to reduce the charge transfer time in high speed CMOS image sensors. These techniques increase the lateral conductivity of the photo-generated carriers in a pinned photodiode (PPD) and the voltage difference between the PPD and the floating diffusion (FD) node by controlling and optimizing the N doping concentration in the PPD and the threshold voltage of the reset transistor, respectively. The techniques shorten the charge transfer time from the PPD diode to the FD node effectively. The proposed process techniques do not need extra masks and do not cause harm to the fill factor. A sub array of 32 × 64 pixels was designed and implemented in the 0.18 μm CIS process with five implantation conditions splitting the N region in the PPD. The simulation and measured results demonstrate that the charge transfer time can be decreased by using the proposed techniques. Comparing the charge transfer time of the pixel with the different implantation conditions of the N region, the charge transfer time of 0.32 μs is achieved and 31% of image lag was reduced by using the proposed process techniques.

Bifurcated method and apparatus for floating point addition with decreased latency time

DOEpatents

Farmwald, Paul M.

1987-01-01

Apparatus for decreasing the latency time associated with floating point addition and subtraction in a computer, using a novel bifurcated, pre-normalization/post-normalization approach that distinguishes between differences of floating point exponents.

Development of sustained release floating drug delivery system for norfloxacin: in vitro and in vivo evaluation.

PubMed

Guguloth, Mohan; Bomma, Ramesh; Veerabrahma, Kishan

2011-01-01

Norfloxacin is a drug with an absorption window. Its oral bioavailability is 30-40% and is a case for improvement by appropriate formulation design. In our previous study, gastroretentive floating tablets for norfloxacin were developed employing three different polymers such as HPMC K4M, HPMC K100M, and xanthan gum. The purpose of this investigation is to further improve and evaluate the in vitro and in vivo performance of the prepared floating tablets by inclusion of citric acid as an acidifier, which is also useful in a fed state. The prepared tablets were characterized and found to exhibit satisfactory physico-chemical characteristics. The effects of citric acid at different concentrations on drug release and floating properties were studied. All the prepared batches showed good in vitro buoyancy. It was observed that the tablets remained buoyant for 24 h. The best formulation (F4c), consisting of 1.5% citric acid and 18% HPMC K4M, was selected based on in vitro characteristics and used in vivo radiographic studies by incorporating barium sulphate. These studies revealed that the tablets remained in the stomach for 205 ± 8.4 min in fasting human volunteers. In vivo studies were carried out for the best formulation in eight healthy male human volunteers, and the pharmacokinetic parameters of the developed formulation were compared with marketed conventional (Norbid) tablets. Based on the in vivo performance in a two-way, crossover study design in healthy subjects, the developed floating tablets showed superior bioavailability than the Norbid tablets. The increased bioavailability of developed formulation was found to be 16.27%. Norfloxacin is a broad-spectrum antibiotic used to treat bacterial infections such as respiratory and urinary tract infections. Conventional norfloxacin tablets show incomplete drug absorption resulting in lower bioavailabilty. Norfloxacin is better absorbed in the stomach. The dosage forms that remain in the stomach are referred to as gastroretentive drug delivery systems. Gastroretentive floating tablets of norfloxcin were developed by employing three different polymers, which prolonged the drug release from the dosage forms. Tablet floatation was achieved by an effervescent mechanism. Citric acid at different concentrations was used in formulations to provide an acidic microenvironment. The prepared tablets were characterized for hardness, weight variation, thickness, friability, floating lag time, and dissolution. Around 12 tablet formulations were prepared as a continuation of the previous work. The best formulation (F4c) was selected based on in vitro characteristics and used in vivo radiographic studies by incorporating barium sulphate as a radio-opaque agent. The tablets remained in the stomach for about 205 ± 8.4 min. Bioavailability studies were conducted in healthy male human volunteers, and the pharmacokinetic parameters of the best formulation were compared with that of the marketed conventional (Norbid) tablet. The increased bioavailability of the developed formulation was found to be 16.27%.

Nanoflare vs Footpoint Heating : Observational Signatures

NASA Technical Reports Server (NTRS)

Winebarger, Amy; Alexander, Caroline; Lionello, Roberto; Linker, Jon; Mikic, Zoran; Downs, Cooper

2015-01-01

Time lag analysis shows very long time lags between all channel pairs. Impulsive heating cannot address these long time lags. 3D Simulations of footpoint heating shows a similar pattern of time lags (magnitude and distribution) to observations. Time lags and relative peak intensities may be able to differentiate between TNE and impulsive heating solutions. Adding a high temperature channel (like XRT Be-­thin) may improve diagnostics.

Effects of Fatigue on Driving Safety: A Comparison of Brake Reaction Times in Night Float and Postcall Physicians in Training.

PubMed

Talusan, Paul G; Long, Theodore; Halim, Andrea; Guliani, Laura; Carroll, Nicole; Reach, John

2014-12-01

Concerns about duty hour and resident safety have fostered discussion about postshift fatigue and driving impairment. We assessed how converting to a night float schedule for overnight coverage affected driving safety for trainees. Brake reaction times were measured for internal medicine and orthopaedic surgery resident volunteers after a traditional 28-hour call shift and after a night float shift. We conducted matched paired t tests of preshift and postshift reaction time means. Participants also completed the Epworth Sleepiness Scale pre- and postshift. From June to July 2013, we enrolled 58 interns and residents (28 orthopaedic surgery, 30 internal medicine). We included 24 (41%) trainees on night float rotations and 34 (59%) trainees on traditional 28-hour call shifts. For all residents on night float rotations, there was no significant difference pre- and postshift. An increase in reaction times was noted among trainees on 28-hour call rotations. This included no effect on reaction times for internal medicine trainees pre- and postshift, and an increase in reaction times for orthopaedic trainees. For both night float and traditional call groups, there were significant increases in the Epworth Sleepiness Scale. Trainees on traditional 28-hour call rotations had significantly worse postshift brake reaction times, whereas trainees on night float rotations had no difference. Orthopaedic trainees had significant differences in brake reaction times after a traditional call shift.

Effects of repeated snowboard exercise in virtual reality with time lags of visual scene behind body rotation on head stability and subjective slalom run performance in healthy young subjects.

PubMed

Wada, Yoshiro; Nishiike, Suetaka; Kitahara, Tadashi; Yamanaka, Toshiaki; Imai, Takao; Ito, Taeko; Sato, Go; Matsuda, Kazunori; Kitamura, Yoshiaki; Takeda, Noriaki

2016-11-01

After repeated snowboard exercises in the virtual reality (VR) world with increasing time lags in trials 3-8, it is suggested that the adaptation to repeated visual-vestibulosomatosensory conflict in the VR world improved dynamic posture control and motor performance in the real world without the development of motion sickness. The VR technology was used and the effects of repeated snowboard exercise examined in the VR world with time lags between visual scene and body rotation on the head stability and slalom run performance during exercise in healthy subjects. Forty-two healthy young subjects participated in the study. After trials 1 and 2 of snowboard exercise in the VR world without time lag, trials 3-8 were conducted with 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 s time lags of the visual scene that the computer creates behind board rotation, respectively. Finally, trial 9 was conducted without time lag. Head linear accelerations and subjective slalom run performance were evaluated. The standard deviations of head linear accelerations in inter-aural direction were significantly increased in trial 8, with a time lag of 0.6 s, but significantly decreased in trial 9 without a time lag, compared with those in trial 2 without a time lag. The subjective scores of slalom run performance were significantly decreased in trial 8, with a time lag of 0.6 s, but significantly increased in trial 9 without a time lag, compared with those in trial 2 without a time lag. Motion sickness was not induced in any subjects.

Long-Term Observations of Ocean Biogeochemistry with Nitrate and Oxygen Sensors in Apex Profiling Floats

NASA Astrophysics Data System (ADS)

Johnson, K. S.; Coletti, L.; Jannasch, H.; Martz, T.; Swift, D.; Riser, S.

2008-12-01

Long-term, autonomous observations of ocean biogeochemical cycles are now feasible with chemical sensors in profiling floats. These sensors will enable decadal-scale observations of trends in global ocean biogeochemical cycles. Here, we focus on measurements on nitrate and dissolved oxygen. The ISUS (In Situ Ultraviolet Spectrophotometer) optical nitrate sensor has been adapted to operate in a Webb Research, Apex profiling float. The Apex float is of the type used in the Argo array and is designed for multi-year, expendable deployments in the ocean. Floats park at 1000 m depth and make 60 nitrate and oxygen measurements at depth intervals ranging from 50 m below 400 m to 5 m in the upper 100 m as they profile to the surface. All data are transmitted to shore using the Iridium telemetry system and they are available on the Internet in near-real time. Floats equipped with ISUS and an Aanderaa oxygen sensor are capable of making 280 vertical profiles from 1000 m. At a 5 day cycle time, the floats should have nearly a four year endurance. Three floats have now been deployed at the Hawaii Ocean Time series station (HOT), Ocean Station Papa (OSP) in the Gulf of Alaska and at 50 South, 30 East in the Southern Ocean. Two additional floats are designated for deployment at the Bermuda Atlantic Time Series station (BATS) and in the Drake Passage. The HOT float has made 56 profiles over 260 days and should continue operating for 3 more years. Nitrate concentrations are in excellent agreement with the long-term mean observed at HOT. No significant long-term drift in sensor response has occurred. A variety of features have been observed in the HOT nitrate data that are linked to contemporaneous changes in oxygen production and mesoscale dynamics. The impacts of these features will be briefly described. The Southern Ocean float has operated for 200 days and is now observing reinjection of nitrate into surface waters as winter mixing occurs(surface nitrate > 24 micromolar). We expect that the OSP and Southern Ocean floats will provide a quantitative measurement of the timing and magnitude of the spring bloom via the drawdown of surface nitrate. We are funded through NSF and NOPP to continue float deployments at HOT, BATS, OSP and the Southern Ocean for the next 3 years and to refine the sensor so it can be offered as a commercial option for all float users. New sensors in development for float deployments include a stable ISFET pH sensor.

Dual-mechanism gastroretentive drug delivery system loaded with an amorphous solid dispersion prepared by hot-melt extrusion.

PubMed

Vo, Anh Q; Feng, Xin; Pimparade, Manjeet; Ye, Xinyou; Kim, Dong Wuk; Martin, Scott T; Repka, Michael A

2017-05-01

In the present study, we aimed to prepare a gastroretentive drug delivery system that would be both highly resistant to gastric emptying via multiple mechanisms and would also potentially induce in situ supersaturation. The bioadhesive floating pellets, loaded with an amorphous solid dispersion, were prepared in a single step of hot-melt extrusion technology. Hydroxypropyl cellulose (Klucel™ MF) and hypromellose (Benecel™ K15M) were used as matrix-forming polymers, and felodipine was used as the model drug. The foam pellets were fabricated based on the expansion of CO 2 , which was generated from sodium bicarbonate during the melt-extrusion process. A 2 n full factorial experimental design was utilized to investigate the effects of formulation compositions to the pellet properties. The melt-extrusion process transformed the crystalline felodipine into an amorphous state that was dispersed and "frozen" in the polymer matrix. All formulations showed high porosity and were able to float immediately, without lag time, on top of gastric fluid, and maintained their buoyancy over 12h. The pellet-specific floating force, which could be as high as 4800μN/g, increased significantly during the first hour, and was relatively stable until 9h. The sodium bicarbonate percentage was found to be most significantly effect to the floating force. The ex vivo bioadhesion force of the pellets to porcine stomach mucosa was approximately 5mN/pellet, which was more than five times higher than the gravitation force of the pellet saturated with water. Drug release was well controlled up to 12h in the sink condition of 0.5% sodium lauryl sulphate in 0.1N HCl. The dissolution at 1, 3, 5, and 8h were 5-12%, 25-45%, 55-80%, and ≥75% respectively for all 11 formulations. In biorelevant dissolution medium, a supersaturated solution was formed, and the concentration was maintained at around 2μg/mL, approximately 10-folds higher than that of the pure felodipine. All input factors significantly affected dissolution in the first 3h, but afterwards, only drug load and hypromellose (HPMC) content had significant effects. The prepared drug delivery system has great potential in overcoming low and fluctuating bioavailability of poorly soluble drugs. Felodipine (PubChem CID: 3333); hypromellose (PubChem CID: 57503849), hydroxypropyl cellulose (PubChem CID: 71306830), sodium bicarbonate (PubChem CID: 516892); sodium carbonate (PubChem CID: 10340). Copyright © 2017 Elsevier B.V. All rights reserved.

Lag Times and Peak Coefficients for Rural Watersheds in Kansas

DOT National Transportation Integrated Search

1999-10-01

Lag time is an essential input to the most common synthetic unit-hydrograph models. The lag time for an ungaged stream must be estimated from the physical characteristics of the stream and its watershed. In this study, a lag-time formula for small ru...

Effects of Fatigue on Driving Safety: A Comparison of Brake Reaction Times in Night Float and Postcall Physicians in Training

PubMed Central

Talusan, Paul G.; Long, Theodore; Halim, Andrea; Guliani, Laura; Carroll, Nicole; Reach, John

2014-01-01

Background Concerns about duty hour and resident safety have fostered discussion about postshift fatigue and driving impairment. Objective We assessed how converting to a night float schedule for overnight coverage affected driving safety for trainees. Methods Brake reaction times were measured for internal medicine and orthopaedic surgery resident volunteers after a traditional 28-hour call shift and after a night float shift. We conducted matched paired t tests of preshift and postshift reaction time means. Participants also completed the Epworth Sleepiness Scale pre- and postshift. Results From June to July 2013, we enrolled 58 interns and residents (28 orthopaedic surgery, 30 internal medicine). We included 24 (41%) trainees on night float rotations and 34 (59%) trainees on traditional 28-hour call shifts. For all residents on night float rotations, there was no significant difference pre- and postshift. An increase in reaction times was noted among trainees on 28-hour call rotations. This included no effect on reaction times for internal medicine trainees pre- and postshift, and an increase in reaction times for orthopaedic trainees. For both night float and traditional call groups, there were significant increases in the Epworth Sleepiness Scale. Conclusions Trainees on traditional 28-hour call rotations had significantly worse postshift brake reaction times, whereas trainees on night float rotations had no difference. Orthopaedic trainees had significant differences in brake reaction times after a traditional call shift. PMID:26140113

pH responsive alginate polymeric rafts for controlled drug release by using box behnken response surface design

PubMed Central

Abbas, Ghulam; Hanif, Muhammad; Khan, Mahtab Ahmad

2017-01-01

Abstract Aim of the present work was to develop alginate raft forming tablets for controlled release pantoprazole sodium sesquihydrate (PSS). Box behnken design was used to optimize 15 formulations with three independent and three dependent variables. Physical tests of all formulations were within pharmacopoeial limits. Raft was characterized by their strength, thickness, resilience, acid neutralizing capacity, floating lag time and total floating time. Raft strength, thickness and resilience of optimized formulation AR9 were 7.43 ± 0.019 g, 5.8 ± 0.245 cm and greater than 480 min, respectively. Buffering and neutralizing capacity were 11.2 ± 1.01 and 6.5 ± 0.56 meq, respectively. Dissolution studies were performed by using simulated gastric fluid pH 1.2 and cumulative percentage release of optimized formulation AR9 was found 98%. First order release kinetics were followed and non-fickian diffusion was observed as value of n was greater than 0.45 in korsmeyer-peppas model. PSS, polymers, tablets and rafts were further characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). FTIR spectra of PSS, polymers and raft of optimized formulation AR9 showed peaks at 3223.09, 1688.17, 1586.67, 1302.64 and 1027.74 cm−1 due to –OH stretching, ester carbonyl group (C=O) stretching, existence of water and carboxylic group in raft, C–N stretching and –OH bending vibration showed no interaction between them. XRD showed diffraction lines indicates crystalline nature of PSS. DSC thermogram showed endothermic peaks at 250 °C for PSS. The developed raft was suitable for controlled release delivery of PSS. PMID:29491774

47 CFR 52.103 - Lag times.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 3 2010-10-01 2010-10-01 false Lag times. 52.103 Section 52.103... Free Numbers § 52.103 Lag times. (a) Definitions. As used in this section, the following definitions... and an exchange carrier intercept recording is being provided. (3) Lag Time. The interval between a...

47 CFR 52.103 - Lag times.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 3 2012-10-01 2012-10-01 false Lag times. 52.103 Section 52.103... Free Numbers § 52.103 Lag times. (a) Definitions. As used in this section, the following definitions... and an exchange carrier intercept recording is being provided. (3) Lag Time. The interval between a...

47 CFR 52.103 - Lag times.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 3 2011-10-01 2011-10-01 false Lag times. 52.103 Section 52.103... Free Numbers § 52.103 Lag times. (a) Definitions. As used in this section, the following definitions... and an exchange carrier intercept recording is being provided. (3) Lag Time. The interval between a...

47 CFR 52.103 - Lag times.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 3 2013-10-01 2013-10-01 false Lag times. 52.103 Section 52.103... Free Numbers § 52.103 Lag times. (a) Definitions. As used in this section, the following definitions... and an exchange carrier intercept recording is being provided. (3) Lag Time. The interval between a...

Estimation of watershed lag times and times of concentration for the Kansas City Area : technical summary.

DOT National Transportation Integrated Search

2016-04-01

The new lag-time equation for the Kansas City area performs better than the 2001 KU-KDOT equation for urban lag time, which was developed from a study of 14 gaged watersheds in Johnson County (McEnroe & Zhao, 2001). The main advantage of the new lag-...

[Complexity and its integrative effects of the time lags of environment factors affecting Larix gmelinii stem sap flow].

PubMed

Wang, Hui-Mei; Sun, Wei; Zu, Yuan-Gang; Wang, Wen-Jie

2011-12-01

Based on the one-year (2005) observations with a frequency of half hour on the stem sap flow of Larix gmelinii plantation trees planted in 1969 and the related environmental factors air humidity (RH), air temperature (T(air)), photosynthetic components active radiation (PAR), soil temperature (T(soil)), and soil moisture (TDR), principal analysis (PCA) and correction analysis were made on the time lag effect of the stem flow in different seasons (26 days of each season) and in a year via dislocation analysis, with the complexity and its integrative effects of the time lags of environment factors affecting the stem sap flow approached. The results showed that in different seasons and for different environmental factors, the time lag effect varied obviously. In general, the time lag of PAR was 0.5-1 hour ahead of sap flow, that of T(air) and RH was 0-2 hours ahead of or behind the sap flow, and the time lags of T(soil) and TDR were much longer or sometimes undetectable. Because of the complexity of the time lags, no evident improvements were observed in the linear correlations (R2, slope, and intercept) when the time lags based on short-term (20 days) data were used to correct the time lags based on whole year data. However, obvious improvements were found in the standardized and non-standardized correlation coefficients in stepwise multiple regressions, i.e., the time lag corrections could improve the effects of RH, but decreased the effects of PAR, T(air), and T(soil). PCA could be used to simplify the complexity. The first and the second principal components could stand for over 75% information of all the environmental factors in different seasons and in whole year. The time lags of both the first and the second principal components were 1-1.5 hours in advance of the sap flow, except in winter (no time lag effect).

Effective Iterated Greedy Algorithm for Flow-Shop Scheduling Problems with Time lags

NASA Astrophysics Data System (ADS)

ZHAO, Ning; YE, Song; LI, Kaidian; CHEN, Siyu

2017-05-01

Flow shop scheduling problem with time lags is a practical scheduling problem and attracts many studies. Permutation problem(PFSP with time lags) is concentrated but non-permutation problem(non-PFSP with time lags) seems to be neglected. With the aim to minimize the makespan and satisfy time lag constraints, efficient algorithms corresponding to PFSP and non-PFSP problems are proposed, which consist of iterated greedy algorithm for permutation(IGTLP) and iterated greedy algorithm for non-permutation (IGTLNP). The proposed algorithms are verified using well-known simple and complex instances of permutation and non-permutation problems with various time lag ranges. The permutation results indicate that the proposed IGTLP can reach near optimal solution within nearly 11% computational time of traditional GA approach. The non-permutation results indicate that the proposed IG can reach nearly same solution within less than 1% computational time compared with traditional GA approach. The proposed research combines PFSP and non-PFSP together with minimal and maximal time lag consideration, which provides an interesting viewpoint for industrial implementation.

Application of a movable active vibration control system on a floating raft

NASA Astrophysics Data System (ADS)

Wang, Zhen; Mak, Cheuk Ming

2018-02-01

This paper presents a theoretical study of an inertial actuator connected to an accelerometer by a local feedback loop for active vibration control on a floating raft. On the criterion of the minimum power transmission from the vibratory machines to the flexible foundation in the floating raft, the best mounting positions for the inertial actuator on the intermediate mass of the floating raft are investigated. Simulation results indicate that the best mounting positions for the inertial actuator vary with frequency. To control time-varying excitations of vibratory machines on a floating raft effectively, an automatic control system based on real-time measurement of a cost function and automatically searching the best mounting position of the inertial actuator is proposed. To the best of our knowledge, it is the first time that an automatic control system is proposed to move an actuator automatically for controlling a time-varying excitation.

Statistical properties of Fourier-based time-lag estimates

NASA Astrophysics Data System (ADS)

Epitropakis, A.; Papadakis, I. E.

2016-06-01

Context. The study of X-ray time-lag spectra in active galactic nuclei (AGN) is currently an active research area, since it has the potential to illuminate the physics and geometry of the innermost region (I.e. close to the putative super-massive black hole) in these objects. To obtain reliable information from these studies, the statistical properties of time-lags estimated from data must be known as accurately as possible. Aims: We investigated the statistical properties of Fourier-based time-lag estimates (I.e. based on the cross-periodogram), using evenly sampled time series with no missing points. Our aim is to provide practical "guidelines" on estimating time-lags that are minimally biased (I.e. whose mean is close to their intrinsic value) and have known errors. Methods: Our investigation is based on both analytical work and extensive numerical simulations. The latter consisted of generating artificial time series with various signal-to-noise ratios and sampling patterns/durations similar to those offered by AGN observations with present and past X-ray satellites. We also considered a range of different model time-lag spectra commonly assumed in X-ray analyses of compact accreting systems. Results: Discrete sampling, binning and finite light curve duration cause the mean of the time-lag estimates to have a smaller magnitude than their intrinsic values. Smoothing (I.e. binning over consecutive frequencies) of the cross-periodogram can add extra bias at low frequencies. The use of light curves with low signal-to-noise ratio reduces the intrinsic coherence, and can introduce a bias to the sample coherence, time-lag estimates, and their predicted error. Conclusions: Our results have direct implications for X-ray time-lag studies in AGN, but can also be applied to similar studies in other research fields. We find that: a) time-lags should be estimated at frequencies lower than ≈ 1/2 the Nyquist frequency to minimise the effects of discrete binning of the observed time series; b) smoothing of the cross-periodogram should be avoided, as this may introduce significant bias to the time-lag estimates, which can be taken into account by assuming a model cross-spectrum (and not just a model time-lag spectrum); c) time-lags should be estimated by dividing observed time series into a number, say m, of shorter data segments and averaging the resulting cross-periodograms; d) if the data segments have a duration ≳ 20 ks, the time-lag bias is ≲15% of its intrinsic value for the model cross-spectra and power-spectra considered in this work. This bias should be estimated in practise (by considering possible intrinsic cross-spectra that may be applicable to the time-lag spectra at hand) to assess the reliability of any time-lag analysis; e) the effects of experimental noise can be minimised by only estimating time-lags in the frequency range where the sample coherence is larger than 1.2/(1 + 0.2m). In this range, the amplitude of noise variations caused by measurement errors is smaller than the amplitude of the signal's intrinsic variations. As long as m ≳ 20, time-lags estimated by averaging over individual data segments have analytical error estimates that are within 95% of the true scatter around their mean, and their distribution is similar, albeit not identical, to a Gaussian.

Signatures of Steady Heating in Time Lag Analysis of Coronal Emission

NASA Technical Reports Server (NTRS)

Viall, Nicholeen M.; Klimchuk, James A.

2016-01-01

Among the multitude of methods used to investigate coronal heating, the time lag method of Viall Klimchuk is becoming increasingly prevalent as an analysis technique that is complementary to those that are traditionally used.The time lag method cross correlates light curves at a given spatial location obtained in spectral bands that sample different temperature plasmas. It has been used most extensively with data from the Atmospheric Imaging Assembly on the Solar Dynamics Observatory. We have previously applied the time lag method to entire active regions and surrounding the quiet Sun and created maps of the results. We find that the majority of time lags are consistent with the cooling of coronal plasma that has been impulsively heated. Additionally, a significant fraction of the map area has a time lag of zero. This does not indicate a lack of variability. Rather, strong variability must be present, and it must occur in phase between the different channels. We have previously shown that these zero time lags are consistent with the transition region response to coronal nanoflares, although other explanations are possible. A common misconception is that the zero time lag indicates steady emission resulting from steady heating. Using simulated and observed light curves, we demonstrate here that highly correlated light curves at zero time lag are not compatible with equilibrium solutions. Such light curves can only be created by evolution

The effect of premilking udder preparation on Holstein cows milked 3 times daily.

PubMed

Watters, R D; Schuring, N; Erb, H N; Schukken, Y H; Galton, D M

2012-03-01

Premilking udder preparation (including forestripping and duration of lag time-the time between first tactile stimulation and attachment of milking unit) might influence milking measures such as milking unit on-time, incidence of bimodality, and milk flow rates in Holstein cows milked 3 times daily. Holstein cows (n=786) from an 1,800-cow commercial dairy herd were enrolled under a restricted randomized design to determine the effect of 9 different premilking routines. Lag times were 0, 60, 90, 120, and 240s and included forestripping or no forestripping for a total of 9 treatments (no forestripping for 0 lag time); the study was conducted from February to November 2008. All cow-treatment combinations were compared with the control: predipping plus forestripping and drying with 90s of lag time. Cows were initially assigned to 1 of 3 treatments for a period of 7d and upon completion of the first 7-d period were reassigned to a different treatment until all treatments had been completed. From one treatment period to the next, cows had to switch stimulation method with no restriction on lag time. Cows did not receive all treatments during the duration of the trial. Early- to mid-lactation cows (EML; 17-167 DIM) and late-lactation cows (LL; 174-428 DIM) were housed in 2 different pens. Milk yield was significantly different between dip + forestrip and dip+dry for 2 of the treatments for EML cows compared with dip + forestrip and 90 s of lag-time (DF90); however, this was not thought to be due to treatment because the significant lag times were very different (60 and 240 s) and neither was an extreme value. Milk yield did not differ with treatment for the LL cows. Milking unit on-time did not differ when comparing all treatments for EML with treatment DF90; however, an increase in milking unit on-time occurred when lag time was 60s or less for LL cows. The highest incidence of bimodal milk curves was when lag time = 0 and this was independent of stage of lactation; a lag time of 240 s had the second-highest incidence of bimodal milk curves for EML and LL cows. Milk harvested in the first 2 min was lower for lag times of 0 and 240 s when compared with DF90. Increasing the lag time for all cows appeared to improve overall milking time efficiency (although lag time had no effect on EML cows). Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Effect of lag time distribution on the lag phase of bacterial growth - a Monte Carlo analysis

USDA-ARS?s Scientific Manuscript database

The objective of this study is to use Monte Carlo simulation to evaluate the effect of lag time distribution of individual bacterial cells incubated under isothermal conditions on the development of lag phase. The growth of bacterial cells of the same initial concentration and mean lag phase durati...

Exploring lag times between monthly atmospheric deposition and stream chemistry in Appalachian forests using cross-correlation

NASA Astrophysics Data System (ADS)

DeWalle, David R.; Boyer, Elizabeth W.; Buda, Anthony R.

2016-12-01

Forecasts of ecosystem changes due to variations in atmospheric emissions policies require a fundamental understanding of lag times between changes in chemical inputs and watershed response. Impacts of changes in atmospheric deposition in the United States have been documented using national and regional long-term environmental monitoring programs beginning several decades ago. Consequently, time series of weekly NADP atmospheric wet deposition and monthly EPA-Long Term Monitoring stream chemistry now exist for much of the Northeast which may provide insights into lag times. In this study of Appalachian forest basins, we estimated lag times for S, N and Cl by cross-correlating monthly data from four pairs of stream and deposition monitoring sites during the period from 1978 to 2012. A systems or impulse response function approach to cross-correlation was used to estimate lag times where the input deposition time series was pre-whitened using regression modeling and the stream response time series was filtered using the deposition regression model prior to cross-correlation. Cross-correlations for S were greatest at annual intervals over a relatively well-defined range of lags with the maximum correlations occurring at mean lags of 48 months. Chloride results were similar but more erratic with a mean lag of 57 months. Few high-correlation lags for N were indicated. Given the growing availability of atmospheric deposition and surface water chemistry monitoring data and our results for four Appalachian basins, further testing of cross-correlation as a method of estimating lag times on other basins appears justified.

Why does lag affect the durability of memory-based automaticity: loss of memory strength or interference?

PubMed

Wilkins, Nicolas J; Rawson, Katherine A

2013-10-01

In Rickard, Lau, and Pashler's (2008) investigation of the lag effect on memory-based automaticity, response times were faster and proportion of trials retrieved was higher at the end of practice for short lag items than for long lag items. However, during testing after a delay, response times were slower and proportion of trials retrieved was lower for short lag items than for long lag items. The current study investigated the extent to which the lag effect on the durability of memory-based automaticity is due to interference or to the loss of memory strength with time. Participants repeatedly practiced alphabet subtraction items in short lag and long lag conditions. After practice, half of the participants were immediately tested and the other half were tested after a 7-day delay. Results indicate that the lag effect on the durability of memory-based automaticity is primarily due to interference. We discuss potential modification of current memory-based processing theories to account for these effects. © 2013.

Improvements in floating point addition/subtraction operations

DOEpatents

Farmwald, P.M.

1984-02-24

Apparatus is described for decreasing the latency time associated with floating point addition and subtraction in a computer, using a novel bifurcated, pre-normalization/post-normalization approach that distinguishes between differences of floating point exponents.

Floating Collection in an Academic Library: An Audacious Experiment That Succeeded

ERIC Educational Resources Information Center

Coopey, Barbara; Eshbach, Barbara; Notartomas, Trish

2016-01-01

Can a floating collection thrive in a large multicampus academic research library? Floating collections have been successful in public libraries for some time, but it is uncommon for academic libraries and unheard of for a large academic library system. This article will discuss the investigation into the feasibility of a floating collection at…

AN INVESTIGATION OF TIME LAG MAPS USING THREE-DIMENSIONAL SIMULATIONS OF HIGHLY STRATIFIED HEATING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winebarger, Amy R.; Lionello, Roberto; Downs, Cooper

2016-11-10

The location and frequency of coronal energy release provide a significant constraint on the coronal heating mechanism. The evolution of the intensity observed in coronal structures found from time lag analysis of Atmospheric Imaging Assembly (AIA) data has been used to argue that heating must occur sporadically. Recently, we have demonstrated that quasi-steady, highly stratified (footpoint) heating can produce results qualitatively consistent with the evolution of observed coronal structures. The goals of this paper are to demonstrate that time lag analysis of 3D simulations of footpoint heating are qualitatively consistent with time lag analysis of observations and to use themore » 3D simulations to further understand whether time lag analysis is a useful tool in defining the evolution of coronal structures. We find the time lag maps generated from simulated data are consistent with the observed time lag maps. We next investigate several example points. In some cases, the calculated time lag reflects the evolution of a unique loop along the line of sight, though there may be additional evolving structures along the line of sight. We confirm that using the multi-peak AIA channels can produce time lags that are difficult to interpret. We suggest using a different high temperature channel, such as an X-ray channel. Finally, we find that multiple evolving structures along the line of sight can produce time lags that do not represent the physical properties of any structure along the line of sight, although the cross-correlation coefficient of the lightcurves is high. Considering the projected geometry of the loops may reduce some of the line-of-sight confusion.« less

Electronic trigger for capacitive touchscreen and extension of ISO 15781 standard time lag measurements to smartphones

NASA Astrophysics Data System (ADS)

Bucher, François-Xavier; Cao, Frédéric; Viard, Clément; Guichard, Frédéric

2014-03-01

We present in this paper a novel capacitive device that stimulates the touchscreen interface of a smartphone (or of any imaging device equipped with a capacitive touchscreen) and synchronizes triggering with the DxO LED Universal Timer to measure shooting time lag and shutter lag according to ISO 15781:2013. The device and protocol extend the time lag measurement beyond the standard by including negative shutter lag, a phenomenon that is more and more commonly found in smartphones. The device is computer-controlled, and this feature, combined with measurement algorithms, makes it possible to automatize a large series of captures so as to provide more refined statistical analyses when, for example, the shutter lag of "zero shutter lag" devices is limited by the frame time as our measurements confirm.

SUPERGRANULES AS PROBES OF THE SUN'S MERIDIONAL CIRCULATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hathaway, David H., E-mail: david.hathaway@nasa.gov

2012-11-20

Recent analysis revealed that supergranules (convection cells seen at the Sun's surface) are advected by the zonal flows at depths equal to the widths of the cells themselves. Here we probe the structure of the meridional circulation by cross-correlating maps of the Doppler velocity signal using a series of successively longer time lags between maps. We find that the poleward meridional flow decreases in amplitude with time lag and reverses direction to become an equatorward return flow at time lags >24 hr. These cross-correlation results are dominated by larger and deeper cells at longer time lags. (The smaller cells havemore » shorter lifetimes and do not contribute to the correlated signal at longer time lags.) We determine the characteristic cell size associated with each time lag by comparing the equatorial zonal flows measured at different time lags with the zonal flows associated with different cell sizes from a Fourier analysis. This association gives a characteristic cell size of {approx}50 Mm at a 24 hr time lag. This indicates that the poleward meridional flow returns equatorward at depths >50 Mm-just below the base of the surface shear layer. A substantial and highly significant equatorward flow (4.6 {+-} 0.4 m s{sup -1}) is found at a time lag of 28 hr corresponding to a depth of {approx}70 Mm. This represents one of the first positive detections of the Sun's meridional return flow and illustrates the power of using supergranules to probe the Sun's internal dynamics.« less

Investigating critical effects of variegated lubricants, glidants and hydrophilic additives on lag time of press coated ethylcellulose tablets.

PubMed

Patadia, Riddhish; Vora, Chintan; Mittal, Karan; Mashru, Rajashree

2016-01-01

The research envisaged focuses on vital impacts of variegated lubricants, glidants and hydrophilic additives on lag time of press coated ethylcellulose (EC) tablets using prednisone as a model drug. Several lubricants and glidants such as magnesium stearate, colloidal SiO2, sodium stearyl fumarate, talc, stearic acid, polyethylene glycol (6000) and glyceryl behenate were investigated to understand their effects on lag time by changing their concentrations in outer coat. Further, the effects of hydrophilic additives on lag time were examined for hydroxypropylmethylcellulose (E5), hydroxypropylcellulose (EF and SSL), povidone (K30), copovidone, polyethylene glycol (4000), lactose and mannitol. In vitro drug release testing revealed that each selected lubricant/glidant, if present even at concentration of 0.25% w/w, significantly reduced the lag time of press coated tablets. Specifically, colloidal SiO2 and/or magnesium stearate were detrimental while other lubricants/glidants were relatively less injurious. Among hydrophilic additives, freely water soluble fillers had utmost influence in lag time, whereas, comparatively less impact was observed with polymeric binders. Concisely, glidant and lubricant should be chosen to have minimal impact on lag time and further judicious selection of hydrophilic additives should be exercised for modulating lag time of pulsatile release formulations.

A semi-floating gate memory based on van der Waals heterostructures for quasi-non-volatile applications

NASA Astrophysics Data System (ADS)

Liu, Chunsen; Yan, Xiao; Song, Xiongfei; Ding, Shijin; Zhang, David Wei; Zhou, Peng

2018-05-01

As conventional circuits based on field-effect transistors are approaching their physical limits due to quantum phenomena, semi-floating gate transistors have emerged as an alternative ultrafast and silicon-compatible technology. Here, we show a quasi-non-volatile memory featuring a semi-floating gate architecture with band-engineered van der Waals heterostructures. This two-dimensional semi-floating gate memory demonstrates 156 times longer refresh time with respect to that of dynamic random access memory and ultrahigh-speed writing operations on nanosecond timescales. The semi-floating gate architecture greatly enhances the writing operation performance and is approximately 106 times faster than other memories based on two-dimensional materials. The demonstrated characteristics suggest that the quasi-non-volatile memory has the potential to bridge the gap between volatile and non-volatile memory technologies and decrease the power consumption required for frequent refresh operations, enabling a high-speed and low-power random access memory.

Merging altimeter data with Argo profiles to improve observation of tropical Pacific thermocline circulation and ENSO

NASA Astrophysics Data System (ADS)

Zhang, D.; Lee, T.; Wang, F.; McPhaden, M. J.; Kessler, W. S.

2016-12-01

Meridional thermocline currents play an important role in the recharge and discharge of tropical Pacific warm water during the development and transition of ENSO cycles. Previous analyses have shown large variations of the equatorward meridional thermocline convergence/divergence on ENSO and decadal time scales in the interior ocean. The total convergence/divergence is however unknown due to the lack of long term observation in the western boundary currents. Numerical modelling studies suggested a tendency of compensation between the interior and western boundary currents, but the exact compensation is model dependent. While Argo floats provide reasonable data coverage in the interior ocean, few floats are in the western boundary currents. Recent multi-mission satellite altimeter data and advanced processing techniques have resulted in higher resolution sea surface height anomaly (SSHA) products with better accuracy closer to the coasts. This study utilizes the statistical relationship between Argo dynamic height profiles and altimeter SSHA to calculate geostrophic thermocline currents in both the interior ocean and the western boundary of the tropical Pacific. The derived thermocline currents in the western boundary are validated by a 3.5-year moored Acoustic Doppler Current Profiler (ADCP) measurement in the Mindanao Current and by a series of glider surveys (Davis et al. 2012) in the Solomon Sea. The meridional transport timeseries of the interior and western boundary currents in the thermocline show different lead-lag relationships to the Nino 3.4 index. Results will be discussed in the context of recent 2014-2015 El Nino development and the potential contribution to the Tropical Pacific Observing System (TPOS).

Gamma scintigraphic study of the hydrodynamically balanced matrix tablets of Metformin HCl in rabbits

PubMed Central

Razavi, Mahboubeh; Karimian, Hamed; Yeong, Chai Hong; Sarji, Sazilah Ahmad; Chung, Lip Yong; Nyamathulla, Shaik; Noordin, Mohamed Ibrahim

2015-01-01

The purpose of this study is to evaluate the in vitro and in vivo performance of gastro-retentive matrix tablets having Metformin HCl as model drug and combination of natural polymers. A total of 16 formulations were prepared by a wet granulation method using xanthan, tamarind seed powder, tamarind kernel powder and salep as the gel-forming agents and sodium bicarbonate as a gas-forming agent. All the formulations were evaluated for compendial and non-compendial tests and in vitro study was carried out on a USP-II dissolution apparatus at a paddle speed of 50 rpm. MOX2 formulation, composed of salep and xanthan in the ratio of 4:1 with 96.9% release, was considered as the optimum formulation with more than 90% release in 12 hours and short floating lag time. In vivo study was carried out using gamma scintigraphy in New Zealand White rabbits, optimized formulation was incorporated with 10 mg of 153Sm for labeling MOX2 formulation. The radioactive samarium oxide was used as the marker to trace transit of the tablets in the gastrointestinal tract. The in vivo data also supported retention of MOX2 formulation in the gastric region for 12 hours and were different from the control formulation without a gas and gel forming agent. It was concluded that the prepared floating gastro-retentive matrix tablets had a sustained-release effect in vitro and in vivo, gamma scintigraphy played an important role in locating the oral transit and the drug-release pattern. PMID:26124637

Formulation, in vitro evaluation and study of variables on tri-layered gastro-retentive delivery system of diltiazem HCl.

PubMed

Raut Desai, Shilpa; Rohera, Bhagwan D

2014-03-01

Tri-layered floating tablets using only one grade of polyethylene oxide (PEO) would enable easy manufacturing, reproducibility and controlled release for highly soluble drugs. To evaluate the potential of PEO as a sole polymer for the controlled release and to study the effect of formulation variables on release and gastric retention of highly soluble Diltiazem hydrochloride (DTZ). Tablets were compressed with middle layer consisting of drug and polymer while outer layers consisted of polymer with sodium bicarbonate. Design of formulation to obtain 12 h, zero-order release and rapid floatation was done by varying the grades, quantity of PEO and sodium bicarbonate. Dissolution data were fitted in drug release models and swelling/erosion studies were undertaken to verify the drug release mechanism. Effect of formulation variables and tablet surface morphology using scanning electron microscopy were studied. The optimized formula passed the criteria of USP dissolution test I and exhibited floating lag-time of 3-4 min. Drug release was faster from low molecular weight (MW) PEO as compared to high MW. With an increase in the amount of sodium bicarbonate, faster buoyancy was achieved due to the increased CO2 gas formation. Drug release followed zero-order and gave a good fit to the Korsmeyer-Peppas model, which suggested that drug release was due to diffusion through polymer swelling. Zero-order, controlled release profile with the desired buoyancy can be achieved by using optimum formula quantities of sodium bicarbonate and polymer. The tri-layered system shows promising delivery of DTZ, and possibly other water-soluble drugs.

14 CFR 25.529 - Hull and main float landing conditions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... stern landings, the limit water reaction load factors are those computed under § 25.527. In addition— (1... upward component and a side component equal, respectively, to 0.75 and 0.25 tan β times the resultant... upward load at the step of each float of 0.75 and a side load of 0.25 tan β at one float times the step...

14 CFR 25.529 - Hull and main float landing conditions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... stern landings, the limit water reaction load factors are those computed under § 25.527. In addition— (1... upward component and a side component equal, respectively, to 0.75 and 0.25 tan β times the resultant... upward load at the step of each float of 0.75 and a side load of 0.25 tan β at one float times the step...

Vegetation, substrate and hydrology in floating marshes in the Mississippi river delta plain wetlands, USA

USGS Publications Warehouse

Sasser, C.E.; Gosselink, J.G.; Swenson, E.M.; Swarzenski, C.M.; Leibowitz, N.C.

1996-01-01

In the 1940s extensive floating marshes (locally called 'flotant') were reported and mapped in coastal wetlands of the Mississippi River Delta Plain. These floating marshes included large areas of Panicum hemitomon-dominated freshwater marshes, and Spartina patens/Scirpus olneyi brackish marshes. Today these marshes appear to be quite different in extent and type. We describe five floating habitats and one non-floating, quaking habitat based on differences in buoyancy dynamics (timing and degree of floating), substrate characteristics, and dominant vegetation. All floating marshes have low bulk density, organic substrates. Nearly all are fresh marshes. Panicum hemitomon floating marshes presently occur within the general regions that were reported in the 1940's by O'Neil, but are reduced in extent. Some of the former Panicum hemitomon marshes have been replaced by seasonally or variably floating marshes dominated, or co-dominated by Sagittaria lancifolia or Eleocharis baldwinii. ?? 1996 Kluwer Academic Publishers.

Individual cell lag time distributions of Cronobacter (Enterobacter sakazakii) and impact of pooling samples on its detection in powdered infant formula.

PubMed

Miled, Rabeb Bennour; Guillier, Laurent; Neves, Sandra; Augustin, Jean-Christophe; Colin, Pierre; Besse, Nathalie Gnanou

2011-06-01

Cells of six strains of Cronobacter were subjected to dry stress and stored for 2.5 months at ambient temperature. The individual cell lag time distributions of recovered cells were characterized at 25 °C and 37 °C in non-selective broth. The individual cell lag times were deduced from the times taken by cultures from individual cells to reach an optical density threshold. In parallel, growth curves for each strain at high contamination levels were determined in the same growth conditions. In general, the extreme value type II distribution with a shape parameter fixed to 5 (EVIIb) was the most effective at describing the 12 observed distributions of individual cell lag times. Recently, a model for characterizing individual cell lag time distribution from population growth parameters was developed for other food-borne pathogenic bacteria such as Listeria monocytogenes. We confirmed this model's applicability to Cronobacter by comparing the mean and the standard deviation of individual cell lag times to populational lag times observed with high initial concentration experiments. We also validated the model in realistic conditions by studying growth in powdered infant formula decimally diluted in Buffered Peptone Water, which represents the first enrichment step of the standard detection method for Cronobacter. Individual lag times and the pooling of samples significantly affect detection performances. Copyright © 2010 Elsevier Ltd. All rights reserved.

Estimation of watershed lag times and times of concentration for the Kansas City Area.

DOT National Transportation Integrated Search

2016-04-01

Lag time (TL) and time of concentration (TC) are two related measures of how quickly a stream responds to : runoff-producing rainfall over its watershed. In this report, a general relationship for lag time is derived from the : Manning equation for f...

Analysis of Quasi-periodic Oscillations and Time Lag in Ultraluminous X-Ray Sources with XMM-Newton

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zi-Jian; Xiao, Guang-Cheng; Zhang, Shu

We investigated the power density spectrum (PDS) and time lag of ultraluminous X-ray sources (ULXs) observed by XMM-Newton . We determined the PDSs for each ULX and found that five of them show intrinsic variability due to obvious quasi-periodic oscillations (QPOs) of mHz–1 Hz, consistent with previous reports. We further investigated these five ULXs to determine their possible time lag. The ULX QPOs exhibit a soft time lag that is linearly related to the QPO frequency. We discuss the likelihood of the ULX QPOs being type-C QPO analogs, and the time lag models. The ULXs might harbor intermediate-mass black holesmore » if their QPOs are type-C QPO analogs. We suggest that the soft lag and the linearity may be due to reverberation.« less

A generalized expression for lag-time in the gas-phase permeation of hollow tubes

NASA Technical Reports Server (NTRS)

Shah, K. K.; Nelson, H. G.; Johnson, D. L.; Hamaker, F. M.

1975-01-01

A generalized expression for the nonsteady-state parameter, lag-time, has been obtained from Fick's second law for gas-phase transport through hollow, cylindrical membranes. This generalized expression is simplified for three limiting cases of practical interest: (1) diffusion controlled transport, (2) phase boundary reaction control at the inlet surface, and (3) phase boundary reaction control at the outlet surface. In all three cases the lag-time expressions were found to be inversely proportional only to the diffusion coefficient and functionally dependent on the membrane radii. Finally, the lag-time expressions were applied to experimentally obtained lag-time data for alpha-phase titanium and alpha-phase iron.

Technical Note: Intrafractional changes in time lag relationship between anterior-posterior external and superior-inferior internal motion signals in abdominal tumor sites.

PubMed

Regmi, Rajesh; Lovelock, D Michael; Zhang, Pengpeng; Pham, Hai; Xiong, Jianping; Yorke, Ellen D; Goodman, Karyn A; Wu, Abraham J; Mageras, Gig S

2015-06-01

To investigate constancy, within a treatment session, of the time lag relationship between implanted markers in abdominal tumors and an external motion surrogate. Six gastroesophageal junction and three pancreatic cancer patients (IRB-approved protocol) received two cone-beam CTs (CBCT), one before and one after treatment. Time between scans was less than 30 min. Each patient had at least one implanted fiducial marker near the tumor. In all scans, abdominal displacement (Varian RPM) was recorded as the external motion signal. Purpose-built software tracked fiducials, representing internal signal, in CBCT projection images. Time lag between superior-inferior (SI) internal and anterior-posterior external signals was found by maximizing the correlation coefficient in each breathing cycle and averaging over all cycles. Time-lag-induced discrepancy between internal SI position and that predicted from the external signal (external prediction error) was also calculated. Mean ± standard deviation time lag, over all scans and patients, was 0.10 ± 0.07 s (range 0.01-0.36 s). External signal lagged the internal in 17/18 scans. Change in time lag between pre- and post-treatment CBCT was 0.06 ± 0.07 s (range 0.01-0.22 s), corresponding to 3.1% ± 3.7% (range 0.6%-10.8%) of gate width (range 1.6-3.1 s). In only one patient, change in time lag exceeded 10% of the gate width. External prediction error over all scans of all patients varied from 0.1 ± 0.1 to 1.6 ± 0.4 mm. Time lag between internal motion along SI and external signals is small compared to the treatment gate width of abdominal patients examined in this study. Change in time lag within a treatment session, inferred from pre- to post-treatment measurements is also small, suggesting that a single measurement of time lag at the session start is adequate. These findings require confirmation in a larger number of patients.

Technical Note: Intrafractional changes in time lag relationship between anterior–posterior external and superior–inferior internal motion signals in abdominal tumor sites

PubMed Central

Regmi, Rajesh; Lovelock, D. Michael; Zhang, Pengpeng; Pham, Hai; Xiong, Jianping; Yorke, Ellen D.; Goodman, Karyn A.; Wu, Abraham J.; Mageras, Gig S.

2015-01-01

Purpose: To investigate constancy, within a treatment session, of the time lag relationship between implanted markers in abdominal tumors and an external motion surrogate. Methods: Six gastroesophageal junction and three pancreatic cancer patients (IRB-approved protocol) received two cone-beam CTs (CBCT), one before and one after treatment. Time between scans was less than 30 min. Each patient had at least one implanted fiducial marker near the tumor. In all scans, abdominal displacement (Varian RPM) was recorded as the external motion signal. Purpose-built software tracked fiducials, representing internal signal, in CBCT projection images. Time lag between superior–inferior (SI) internal and anterior–posterior external signals was found by maximizing the correlation coefficient in each breathing cycle and averaging over all cycles. Time-lag-induced discrepancy between internal SI position and that predicted from the external signal (external prediction error) was also calculated. Results: Mean ± standard deviation time lag, over all scans and patients, was 0.10 ± 0.07 s (range 0.01–0.36 s). External signal lagged the internal in 17/18 scans. Change in time lag between pre- and post-treatment CBCT was 0.06 ± 0.07 s (range 0.01–0.22 s), corresponding to 3.1% ± 3.7% (range 0.6%–10.8%) of gate width (range 1.6–3.1 s). In only one patient, change in time lag exceeded 10% of the gate width. External prediction error over all scans of all patients varied from 0.1 ± 0.1 to 1.6 ± 0.4 mm. Conclusions: Time lag between internal motion along SI and external signals is small compared to the treatment gate width of abdominal patients examined in this study. Change in time lag within a treatment session, inferred from pre- to post-treatment measurements is also small, suggesting that a single measurement of time lag at the session start is adequate. These findings require confirmation in a larger number of patients. PMID:26127033

Fungal mycelia show lag time before re-growth on endogenous carbon.

PubMed

Pollack, Judith K; Li, Zheng Jian; Marten, Mark R

2008-06-15

Nutrient starvation is a common occurrence for filamentous fungi. To better understand the effects of starvation, we used a parallel plate flow chamber to study individual fungal mycelia when subjected to a step change in glucose concentration. We report the presence of a finite "lag time" in starved mycelia during which they ceased to grow/extend while switching from growth on exogenous carbon to re-growth on endogenous carbon. This lag time precedes other morphological or physiological changes such as change in growth rate (50-70% reduction), vacuolation (up to 16%), and decreased hyphal diameter (almost 50% reduction). Data suggests that during lag time, vacuolar degradation produces sufficient endogenous carbon to support survival and restart hyphal extension. Lag time is inversely related to the size of the mycelium at the time of starvation, which suggests a critical flow of endogenous carbon to the apical tip. We present a mathematical model consistent with our experimental observations that relate lag time, area, and flow of endogenous carbon. (c) 2008 Wiley Periodicals, Inc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Regmi, Rajesh; Lovelock, D. Michael; Zhang, Pengpeng

Purpose: To investigate constancy, within a treatment session, of the time lag relationship between implanted markers in abdominal tumors and an external motion surrogate. Methods: Six gastroesophageal junction and three pancreatic cancer patients (IRB-approved protocol) received two cone-beam CTs (CBCT), one before and one after treatment. Time between scans was less than 30 min. Each patient had at least one implanted fiducial marker near the tumor. In all scans, abdominal displacement (Varian RPM) was recorded as the external motion signal. Purpose-built software tracked fiducials, representing internal signal, in CBCT projection images. Time lag between superior–inferior (SI) internal and anterior–posterior externalmore » signals was found by maximizing the correlation coefficient in each breathing cycle and averaging over all cycles. Time-lag-induced discrepancy between internal SI position and that predicted from the external signal (external prediction error) was also calculated. Results: Mean ± standard deviation time lag, over all scans and patients, was 0.10 ± 0.07 s (range 0.01–0.36 s). External signal lagged the internal in 17/18 scans. Change in time lag between pre- and post-treatment CBCT was 0.06 ± 0.07 s (range 0.01–0.22 s), corresponding to 3.1% ± 3.7% (range 0.6%–10.8%) of gate width (range 1.6–3.1 s). In only one patient, change in time lag exceeded 10% of the gate width. External prediction error over all scans of all patients varied from 0.1 ± 0.1 to 1.6 ± 0.4 mm. Conclusions: Time lag between internal motion along SI and external signals is small compared to the treatment gate width of abdominal patients examined in this study. Change in time lag within a treatment session, inferred from pre- to post-treatment measurements is also small, suggesting that a single measurement of time lag at the session start is adequate. These findings require confirmation in a larger number of patients.« less

Temporal evolution of photon energy emitted from two-component advective flows: origin of time lag

NASA Astrophysics Data System (ADS)

Chatterjee, Arka; Chakrabarti, Sandip K.; Ghosh, Himadri

2017-12-01

X-ray time lag of black hole candidates contains important information regarding the emission geometry. Recently, study of time lags from observational data revealed very intriguing properties. To investigate the real cause of this lag behavior with energy and spectral states, we study photon paths inside a two-component advective flow (TCAF) which appears to be a satisfactory model to explain the spectral and timing properties. We employ the Monte Carlo simulation technique to carry out the Comptonization process. We use a relativistic thick disk in Schwarzschild geometry as the CENtrifugal pressure supported BOundary Layer (CENBOL) which is the Compton cloud. In TCAF, this is the post-shock region of the advective component. Keplerian disk on the equatorial plane which is truncated at the inner edge i.e. at the outer boundary of the CENBOL, acts as the soft photon source. Ray-tracing code is employed to track the photons to a distantly located observer. We compute the cumulative time taken by a photon during Comptonization, reflection and following the curved geometry on the way to the observer. Time lags between various hard and soft bands have been calculated. We study the variation of time lags with accretion rates, CENBOL size and inclination angle. Time lags for different energy channels are plotted for different inclination angles. The general trend of variation of time lag with QPO frequency and energy as observed in satellite data is reproduced.

AN INTEGRATED MODEL FOR THE PRODUCTION OF X-RAY TIME LAGS AND QUIESCENT SPECTRA FROM HOMOGENEOUS AND INHOMOGENEOUS BLACK HOLE ACCRETION CORONAE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kroon, John J.; Becker, Peter A., E-mail: jkroon@gmu.edu, E-mail: pbecker@gmu.edu

2016-04-20

Many accreting black holes manifest time lags during outbursts, in which the hard Fourier component typically lags behind the soft component. Despite decades of observations of this phenomenon, the underlying physical explanation for the time lags has remained elusive, although there are suggestions that Compton reverberation plays an important role. However, the lack of analytical solutions has hindered the interpretation of the available data. In this paper, we investigate the generation of X-ray time lags in Compton scattering coronae using a new mathematical approach based on analysis of the Fourier-transformed transport equation. By solving this equation, we obtain the Fouriermore » transform of the radiation Green’s function, which allows us to calculate the exact dependence of the time lags on the Fourier frequency, for both homogeneous and inhomogeneous coronal clouds. We use the new formalism to explore a variety of injection scenarios, including both monochromatic and broadband (bremsstrahlung) seed photon injection. We show that our model can successfully reproduce both the observed time lags and the time-averaged (quiescent) X-ray spectra for Cyg X-1 and GX 339-04, using a single set of coronal parameters for each source. The time lags are the result of impulsive bremsstrahlung injection occurring near the outer edge of the corona, while the time-averaged spectra are the result of continual distributed injection of soft photons throughout the cloud.« less

Investigating effects of hydroxypropyl methylcellulose (HPMC) molecular weight grades on lag time of press-coated ethylcellulose tablets.

PubMed

Patadia, Riddhish; Vora, Chintan; Mittal, Karan; Mashru, Rajashree

2016-11-01

The research undertaken exemplifies the effects of hydroxypropyl methylcellulose (HPMC) molecular weight (MW) grades of on lag time of press-coated ethylcellulose (EC) tablets. The formulation comprised an immediate release core (containing prednisone as a model drug) surrounded by compression coating with variegated EC-HPMC blends. Five selected HPMC grades (E5, E15, E50, K100LV and K4M) were explored at three different concentrations (10% w/w, 20% w/w and 30% w/w in outer coat) to understand their effects on lag time and drug release. In vitro drug release testing demonstrated that, with increase in concentration of E5 and E15, up to 30% w/w, the mean lag time decreased progressively; whereas with remaining grades, the mean lag time initially decreased up to 20% w/w level and thereafter increased for 30% w/w level. Importantly, with increase in HPMC concentration in the outer coat, the variability in lag time (%RSD; n = 6) was decreased for each of E5, E15 and E50, whereas increased for K100LV and K4M. In general, the variability in lag time was increased with increase in HPMC MW at studied concentration levels. Markedly, tablets with 30% w/w K4M in outer coat exhibited slight premature release (before the rupture of outer coat) along with high variability in lag time. Overall, the study concluded that low MW HPMCs (E5, E15 and E50) were found rather efficient than higher MW HPMCs for developing robust EC-based press-coated pulsatile release formulations where precise lag time followed by sharp burst release is desired.

Hydrophilic excipients modulate the time lag of time-controlled disintegrating press-coated tablets.

PubMed

Lin, Shan-Yang; Li, Mei-Jane; Lin, Kung-Hsu

2004-08-16

An oral press-coated tablet was developed by means of direct compression to achieve the time-controlled disintegrating or rupturing function with a distinct predetermined lag time. This press-coated tablet containing sodium diclofenac in the inner core was formulated with an outer shell by different weight ratios of hydrophobic polymer of micronized ethylcellulose (EC) powder and hydrophilic excipients such as spray-dried lactose (SDL) or hydroxypropyl methylcellulose (HPMC). The effect of the formulation of an outer shell comprising both hydrophobic polymer and hydrophilic excipients on the time lag of drug release was investigated. The release profile of the press-coated tablet exhibited a time period without drug release (time lag) followed by a rapid and complete release phase, in which the outer shell ruptured or broke into 2 halves. The lag phase was markedly dependent on the weight ratios of EC/SDL or EC/HPMC in the outer shell. Different time lags of the press-coated tablets from 1.0 to 16.3 hours could be modulated by changing the type and amount of the excipients. A semilogarithmic plot of the time lag of the tablet against the weight ratios of EC/SDL or EC/HPMC in the outer shell demonstrated a good linear relationship, with r = 0.976 and r = 0.982, respectively. The predetermined time lag prior to the drug release from a press-coated tablet prepared by using a micronized EC as a retarding coating shell can be adequately scheduled with the addition of hydrophilic excipients according to the time or site requirements.

Effects of timber harvesting on the lag time of Caspar Creek watershed

Treesearch

Karen Hardison Sendek

1985-01-01

Abstract - Hydrograph lag time was analyzed to determine changes after road construction and after selective, tractor-yarded logging in a Caspar Creek watershed, Mendocino County, California. The paired watershed technique was used. Hydrograph lag time for each storm was the time separation between the midpoint of precipitation and the time coordinate of the runoff...

Assessment of the abnormal growth of floating macrophytes in Winam Gulf (Kenya) by using MODIS imagery time series

NASA Astrophysics Data System (ADS)

Fusilli, L.; Collins, M. O.; Laneve, G.; Palombo, A.; Pignatti, S.; Santini, F.

2013-02-01

The objective of this research study is to assess the capability of time-series of MODIS imagery to provide information suitable for enhancing the understanding of the temporal cycles shown by the abnormal growth of the floating macrophytes in order to support monitoring and management action of Lake Victoria water resources. The proliferation of invasive plants and aquatic weeds is of growing concern. Starting from 1989, Lake Victoria has been interested by the high infestation of water hyacinth with significant socio-economic impact on riparian populations. In this paper, we describe an approach based on the time-series of MODIS to derive the temporal behaviour, the abundance and distribution of the floating macrophytes in the Winam Gulf (Kenyan portion of the Lake Victoria) and its possible links to the concentrations of the main water constituencies. To this end, we consider the NDVI values computed from the MODIS imagery time-series from 2000 to 2009 to identify the floating macrophytes cover and an appropriate bio-optical model to retrieve, by means of an inverse procedure, the concentrations of chlorophyll a, coloured dissolved organic matter and total suspended solid. The maps of the floating vegetation based on the NDVI values allow us to assess the spatial and temporal dynamics of the weeds with high time resolution. A floating vegetation index (FVI) has been introduced for describing the weeds pollution level. The results of the analysis show a consistent temporal relation between the water constituent concentrations within the Winam Gulf and the FVI, especially in the proximity of the greatest proliferation of floating vegetation in the last 10 years that occurred between the second half of 2006 and the first half of 2007.The adopted approach will be useful to implement an automatic system for monitoring and predicting the floating macrophytes proliferation in Lake Victoria.

Time-lag properties of corona streamer discharges between impulse sphere and dc needle electrodes under atmospheric air conditions.

PubMed

Okano, Daisuke

2013-02-01

In this study of corona streamer discharges from an impulse generator using a dc power supply, the relationship of the discharge time-lag with the dc bias voltage between the sphere-to-needle electrodes under atmospheric conditions is investigated. Devices utilizing corona discharges have been used to purify air or water, destroy bacteria, and to remove undesirable substances, and in order to achieve fast response times and high power efficiencies in such devices, it is important to minimize the time-lag of the corona discharge. Our experimental results show that (a) the discharge path of a negatively biased needle electrode will be straighter than that of a positively biased needle and (b) the discharge threshold voltage in both the positive and the negative needle electrodes is nearly equal to 33 kV. By expressing the discharge voltage as a power function of time-lag, the extent of corona generation can be quantitatively specified using the exponent of this power function. The observed behavior of a corona streamer discharge between the negative spherical and the positive needle electrodes indicates that the largest power exponent is associated with the shortest time-lag, owing to the reduction in the statistical time-lag in the absence of a formative time-lag.

A FOURIER-TRANSFORMED BREMSSTRAHLUNG FLASH MODEL FOR THE PRODUCTION OF X-RAY TIME LAGS IN ACCRETING BLACK HOLE SOURCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kroon, John J.; Becker, Peter A., E-mail: jkroon@gmu.edu, E-mail: pbecker@gmu.edu

Accreting black hole sources show a wide variety of rapid time variability, including the manifestation of time lags during X-ray transients, in which a delay (phase shift) is observed between the Fourier components of the hard and soft spectra. Despite a large body of observational evidence for time lags, no fundamental physical explanation for the origin of this phenomenon has been presented. We develop a new theoretical model for the production of X-ray time lags based on an exact analytical solution for the Fourier transform describing the diffusion and Comptonization of seed photons propagating through a spherical corona. The resultingmore » Green's function can be convolved with any source distribution to compute the associated Fourier transform and time lags, hence allowing us to explore a wide variety of injection scenarios. We show that thermal Comptonization is able to self-consistently explain both the X-ray time lags and the steady-state (quiescent) X-ray spectrum observed in the low-hard state of Cyg X-1. The reprocessing of bremsstrahlung seed photons produces X-ray time lags that diminish with increasing Fourier frequency, in agreement with the observations for a wide range of sources.« less

Time-lag properties of corona streamer discharges between impulse sphere and dc needle electrodes under atmospheric air conditions

NASA Astrophysics Data System (ADS)

Okano, Daisuke

2013-02-01

In this study of corona streamer discharges from an impulse generator using a dc power supply, the relationship of the discharge time-lag with the dc bias voltage between the sphere-to-needle electrodes under atmospheric conditions is investigated. Devices utilizing corona discharges have been used to purify air or water, destroy bacteria, and to remove undesirable substances, and in order to achieve fast response times and high power efficiencies in such devices, it is important to minimize the time-lag of the corona discharge. Our experimental results show that (a) the discharge path of a negatively biased needle electrode will be straighter than that of a positively biased needle and (b) the discharge threshold voltage in both the positive and the negative needle electrodes is nearly equal to 33 kV. By expressing the discharge voltage as a power function of time-lag, the extent of corona generation can be quantitatively specified using the exponent of this power function. The observed behavior of a corona streamer discharge between the negative spherical and the positive needle electrodes indicates that the largest power exponent is associated with the shortest time-lag, owing to the reduction in the statistical time-lag in the absence of a formative time-lag.

Studies on applicability of press-coated tablets using hydroxypropylcellulose (HPC) in the outer shell for timed-release preparations.

PubMed

Fukui, E; Uemura, K; Kobayashi, M

2000-08-10

Press-coated tablets, containing diltiazem hydrochloride (DIL) in the core tablet and coated with hydroxypropylcellulose (HPC) as the outer shell, were examined for applicability as timed-release tablets with a predetermined lag time and subsequent rapid drug release phase. Various types of press-coated tablets were prepared using a rotary tabletting machine and their DIL dissolution behavior was evaluated by the JP paddle method. The results indicated that tablets with the timed-release function could be prepared, and that the lag times were prolonged as the viscosity of HPC and the amount of the outer shell were increased. The lag times could be controlled widely by the above method, however, the compression load had little effect. Two different kinds of timed-release press-coated tablets that showed lag times of 3 and 6 h in the in vitro test (denoted PCT(L3) and PCT(L6), respectively) were administered to beagle dogs. DIL was first detected in the plasma more than 3 h after administration, and both tablets showed timed-release. The lag times showed a good agreement between the in vivo and in vitro tests in PCT(L3). However, the in vivo lag times were about 4 h in PCT(L6) and were much shorter than the in vitro lag time. The dissolution test was performed at different paddle rotation speeds, and good agreement was obtained between the in vivo and in vitro lag times at 150 rpm. This suggested that the effects of gastrointestinal peristalsis and contraction should also be taken into consideration for the further development of drug delivery systems.

X-ray short-time lags in the Fe-K energy band produced by scattering clouds in active galactic nuclei

NASA Astrophysics Data System (ADS)

Mizumoto, Misaki; Done, Chris; Hagino, Kouichi; Ebisawa, Ken; Tsujimoto, Masahiro; Odaka, Hirokazu

2018-07-01

X-rays illuminating the accretion disc in active galactic nuclei give rise to an iron K line and its associated reflection spectrum that are lagged behind the continuum variability by the light-travel time from the source to the disc. The measured lag time-scales in the iron band can be as short as ˜Rg/c, where Rg is the gravitational radius, which is often interpreted as evidence for a very small continuum source close to the event horizon of a rapidly spinning black hole. However, the short lags can also be produced by reflection from more distant material, because the primary photons with no time-delay dilute the time-lags caused by the reprocessed photons. We perform a Monte Carlo simulation to calculate the dilution effect in the X-ray reverberation lags from a half-shell of neutral material placed at 100 Rg from the central source. This gives lags of ˜2 Rg/c, but the iron line is a distinctly narrow feature in the lag-energy plot, whereas the data often show a broader line. We show that both the short lag and the line broadening can be reproduced, if the scattering material is outflowing at ˜0.1c. The velocity structure in the wind can also give shifts in the line profile in the lag-energy plot calculated at different frequencies. Hence we propose that the observed broad iron reverberation lags and shifts in profile as a function of frequency of variability can arise from a disc wind at fairly large distances from the X-ray source.

Effect of environmental factors on the kinetics of insulin fibril formation: elucidation of the molecular mechanism.

PubMed

Nielsen, L; Khurana, R; Coats, A; Frokjaer, S; Brange, J; Vyas, S; Uversky, V N; Fink, A L

2001-05-22

In the search for the molecular mechanism of insulin fibrillation, the kinetics of insulin fibril formation were studied under different conditions using the fluorescent dye thioflavin T (ThT). The effect of insulin concentration, agitation, pH, ionic strength, anions, seeding, and addition of 1-anilinonaphthalene-8-sulfonic acid (ANS), urea, TMAO, sucrose, and ThT on the kinetics of fibrillation was investigated. The kinetics of the fibrillation process could be described by the lag time for formation of stable nuclei (nucleation) and the apparent rate constant for the growth of fibrils (elongation). The addition of seeds eliminated the lag phase. An increase in insulin concentration resulted in shorter lag times and faster growth of fibrils. Shorter lag times and faster growth of fibrils were seen at acidic pH versus neutral pH, whereas an increase in ionic strength resulted in shorter lag times and slower growth of fibrils. There was no clear correlation between the rate of fibril elongation and ionic strength. Agitation during fibril formation attenuated the effects of insulin concentration and ionic strength on both lag times and fibril growth. The addition of ANS increased the lag time and decreased the apparent growth rate for insulin fibril formation. The ANS-induced inhibition appears to reflect the formation of amorphous aggregates. The denaturant, urea, decreased the lag time, whereas the stabilizers, trimethylamine N-oxide dihydrate (TMAO) and sucrose, increased the lag times. The results indicated that both nucleation and fibril growth were controlled by hydrophobic and electrostatic interactions. A kinetic model, involving the association of monomeric partially folded intermediates, whose concentration is stimulated by the air-water interface, leading to formation of the critical nucleus and thence fibrils, is proposed.

Design and in vitro evaluation of multiparticulate floating drug delivery system of zolpidem tartarate.

PubMed

Amrutkar, P P; Chaudhari, P D; Patil, S B

2012-01-01

Zolpidem tartarate is a non-benzodiazepine, sedative-hypnotic, which finds its major use in various types of insomnia. The present work relates to development of multiparticulate floating drug delivery system based on gas generation technique to prolong the gastric residence time and to increase the overall bioavailability. Modified release dosage form of zolpidem tartarate adapted to release over a predetermined time period, according to biphasic profile of dissolution, where the first phase is immediate release phase for inducing the sleep and the second phase is modified release phase for maintaining the sleep up to 10 h. The system consists of zolpidem tartarate layered pellets coated with effervescent layer and polymeric membrane. The floating ability and in vitro drug release of the system were dependent on amount of the effervescent agent (sodium bicarbonate) layered onto the drug layered pellets, and coating level of the polymeric membrane (Eudragit(®) NE 30D). The system could float completely within 5 min and maintain the floating over a period of 10 h. The multiparticulate floating delivery system of zolpidem tartarate with rapid floating and modified drug release was obtained. Copyright © 2011 Elsevier B.V. All rights reserved.

40 CFR 60.112b - Standard for volatile organic compounds (VOC).

Code of Federal Regulations, 2010 CFR

2010-07-01

... for Volatile Organic Liquid Storage Vessels (Including Petroleum Liquid Storage Vessels) for Which... specifications: (i) The internal floating roof shall rest or float on the liquid surface (but not necessarily in... be floating on the liquid surface at all times, except during initial fill and during those intervals...

40 CFR 60.112b - Standard for volatile organic compounds (VOC).

Code of Federal Regulations, 2012 CFR

2012-07-01

... for Volatile Organic Liquid Storage Vessels (Including Petroleum Liquid Storage Vessels) for Which... specifications: (i) The internal floating roof shall rest or float on the liquid surface (but not necessarily in... be floating on the liquid surface at all times, except during initial fill and during those intervals...

40 CFR 60.112b - Standard for volatile organic compounds (VOC).

Code of Federal Regulations, 2014 CFR

2014-07-01

... for Volatile Organic Liquid Storage Vessels (Including Petroleum Liquid Storage Vessels) for Which... specifications: (i) The internal floating roof shall rest or float on the liquid surface (but not necessarily in... be floating on the liquid surface at all times, except during initial fill and during those intervals...

40 CFR 60.112b - Standard for volatile organic compounds (VOC).

Code of Federal Regulations, 2013 CFR

2013-07-01

... for Volatile Organic Liquid Storage Vessels (Including Petroleum Liquid Storage Vessels) for Which... specifications: (i) The internal floating roof shall rest or float on the liquid surface (but not necessarily in... be floating on the liquid surface at all times, except during initial fill and during those intervals...

40 CFR 60.112b - Standard for volatile organic compounds (VOC).

Code of Federal Regulations, 2011 CFR

2011-07-01

... for Volatile Organic Liquid Storage Vessels (Including Petroleum Liquid Storage Vessels) for Which... specifications: (i) The internal floating roof shall rest or float on the liquid surface (but not necessarily in... be floating on the liquid surface at all times, except during initial fill and during those intervals...

Variability of Tropical Cyclone Heat Potential and Barrier layers in the South Indian Ocean

NASA Astrophysics Data System (ADS)

Mawren, D.; Reason, C. J. C.

2016-02-01

This study investigates the influence of Tropical Cyclone Heat Potential (TCHP) as well as salinity stratification during the passage of intense tropical cyclones. Using in-situ observations, reanalysis data and ocean model simulations, this study indicates that TC intensification is affected by high TCHP values and deep barrier layers. TCHP computed from 1/5° resolution regional ocean model (ROMS) agrees well with that derived from Argo float data and SODA which extends over a longer period (1950-2010). Time series of TCHP in the South Indian Ocean shows strongest interannual variability during 1997-1998, 2003, 2007 and is relatively highly correlated at 1 month lag with ENSO (r = 0.67, significant at 95 %). The interannual variability of barrier layer thickness (BLT) was analyzed over the Seychelles-Chagos thermocline ridge (SCTR) and high-amplitude fluctuations in BLT appear to overlay with large positive TCHP values. Analysis also shows that both BLT and TCHP are modulated by the westward propagating Rossby waves. A case study of Category 5 Tropical cyclone BANSI that developed over and east of Madagascar during 11-18 Jan 2015 is presented.

Spatial and temporal dynamics of deep percolation, lag time and recharge in an irrigated semi-arid region

NASA Astrophysics Data System (ADS)

Nazarieh, F.; Ansari, H.; Ziaei, A. N.; Izady, A.; Davari, K.; Brunner, P.

2018-05-01

The time required for deep percolating water to reach the water table can be considerable in areas with a thick vadose zone. Sustainable groundwater management, therefore, has to consider the spatial and temporal dynamics of groundwater recharge. The key parameters that control the lag time have been widely examined in soil physics using small-scale lysimeters and modeling studies. However, only a small number of studies have analyzed how deep-percolation rates affect groundwater recharge dynamics over large spatial scales. This study examined how the parameters influencing lag time affect groundwater recharge in a semi-arid catchment under irrigation (in northeastern Iran) using a numerical modeling approach. Flow simulations were performed by the MODFLOW-NWT code with the Vadose-Zone Flow (UZF) Package. Calibration of the groundwater model was based on data from 48 observation wells. Flow simulations showed that lag times vary from 1 to more than 100 months. A sensitivity analysis demonstrated that during drought conditions, the lag time was highly sensitive to the rate of deep percolation. The study illustrated two critical points: (1) the importance of providing estimates of the lag time as a basis for sustainable groundwater management, and (2) lag time not only depends on factors such as soil hydraulic conductivity or vadose zone depth but also depends on the deep-percolation rates and the antecedent soil-moisture condition. Therefore, estimates of the lag time have to be associated with specific percolation rates, in addition to depth to groundwater and soil properties.

X-ray time lags in PG 1211+143

NASA Astrophysics Data System (ADS)

Lobban, A. P.; Vaughan, S.; Pounds, K.; Reeves, J. N.

2018-05-01

We investigate the X-ray time lags of a recent ˜630 ks XMM-Newton observation of PG 1211+143. We find well-correlated variations across the XMM-Newton EPIC bandpass, with the first detection of a hard lag in this source with a mean time delay of up to ˜3 ks at the lowest frequencies. We find that the energy-dependence of the low-frequency hard lag scales approximately linearly with log(E) when averaged over all orbits, consistent with the propagating fluctuations model. However, we find that the low-frequency lag behaviour becomes more complex on time-scales longer than a single orbit, suggestive of additional modes of variability. We also detect a high-frequency soft lag at ˜10-4 Hz with the magnitude of the delay peaking at ≲ 0.8 ks, consistent with previous observations, which we discuss in terms of small-scale reverberation.

Detecting PM2.5's Correlations between Neighboring Cities Using a Time-Lagged Cross-Correlation Coefficient.

PubMed

Wang, Fang; Wang, Lin; Chen, Yuming

2017-08-31

In order to investigate the time-dependent cross-correlations of fine particulate (PM2.5) series among neighboring cities in Northern China, in this paper, we propose a new cross-correlation coefficient, the time-lagged q-L dependent height crosscorrelation coefficient (denoted by p q (τ, L)), which incorporates the time-lag factor and the fluctuation amplitude information into the analogous height cross-correlation analysis coefficient. Numerical tests are performed to illustrate that the newly proposed coefficient ρ q (τ, L) can be used to detect cross-correlations between two series with time lags and to identify different range of fluctuations at which two series possess cross-correlations. Applying the new coefficient to analyze the time-dependent cross-correlations of PM2.5 series between Beijing and the three neighboring cities of Tianjin, Zhangjiakou, and Baoding, we find that time lags between the PM2.5 series with larger fluctuations are longer than those between PM2.5 series withsmaller fluctuations. Our analysis also shows that cross-correlations between the PM2.5 series of two neighboring cities are significant and the time lags between two PM2.5 series of neighboring cities are significantly non-zero. These findings providenew scientific support on the view that air pollution in neighboring cities can affect one another not simultaneously but with a time lag.

PHYSIOLOGICAL DYNAMICS OF SIPHONOPHORES FROM DEEP SCATTERING LAYERS.

DTIC Science & Technology

Effects of siphonophores on sound propagation in the sea were studied by determining the size of gas bubbles they contain and produce, and the times...volumes, and rates involved in these processes. Major findings were: (1) gases contained in fresh siphonophore floats are generally close to...constants for siphonophore floats are close to those for chitin; (4) calculated energy requirements for countering hydrostatic pressures indicate that float refilling times are probably no more than a few hours. (Author)

Quantifying the effect of water activity and storage temperature on single spore lag times of three moulds isolated from spoiled bakery products.

PubMed

Dagnas, Stéphane; Gougouli, Maria; Onno, Bernard; Koutsoumanis, Konstantinos P; Membré, Jeanne-Marie

2017-01-02

The inhibitory effect of water activity (a w ) and storage temperature on single spore lag times of Aspergillus niger, Eurotium repens (Aspergillus pseudoglaucus) and Penicillium corylophilum strains isolated from spoiled bakery products, was quantified. A full factorial design was set up for each strain. Data were collected at levels of a w varying from 0.80 to 0.98 and temperature from 15 to 35°C. Experiments were performed on malt agar, at pH5.5. When growth was observed, ca 20 individual growth kinetics per condition were recorded up to 35days. Radius of the colony vs time was then fitted with the Buchanan primary model. For each experimental condition, a lag time variability was observed, it was characterized by its mean, standard deviation (sd) and 5 th percentile, after a Normal distribution fit. As the environmental conditions became stressful (e.g. storage temperature and a w lower), mean and sd of single spore lag time distribution increased, indicating longer lag times and higher variability. The relationship between mean and sd followed a monotonous but not linear pattern, identical whatever the species. Next, secondary models were deployed to estimate the cardinal values (minimal, optimal and maximal temperatures, minimal water activity where no growth is observed anymore) for the three species. That enabled to confirm the observation made based on raw data analysis: concerning the temperature effect, A. niger behaviour was significantly different from E. repens and P. corylophilum: T opt of 37.4°C (standard deviation 1.4°C) instead of 27.1°C (1.4°C) and 25.2°C (1.2°C), respectively. Concerning the a w effect, from the three mould species, E. repens was the species able to grow at the lowest a w (aw min estimated to 0.74 (0.02)). Finally, results obtained with single spores were compared to findings from a previous study carried out at the population level (Dagnas et al., 2014). For short lag times (≤5days), there was no difference between lag time of the population (ca 2000 spores inoculated in one spot) and mean (nor 5 th percentile) of single spore lag time distribution. In contrast, when lag time was longer, i.e. under more stressful conditions, there was a discrepancy between individual and population lag times (population lag times shorter than 5 th percentiles of single spore lag time distribution), confirming a stochastic process. Finally, the temperature cardinal values estimated with single spores were found to be similar to those obtained at the population level, whatever the species. All these findings will be used to describe better mould spore lag time variability and then to predict more accurately bakery product shelf-life. Copyright © 2016 Elsevier B.V. All rights reserved.

Do subjective symptoms predict our perception of jet-lag?

PubMed

Waterhouse, J; Edwards, B; Nevill, A; Atkinson, G; Reilly, T; Davies, P; Godfrey, R

2000-10-01

A total of 39 subjects were studied after a flight from the UK to either Sydney or Brisbane (10 time-zones to the east). Subjects varied widely in their age, their athletic ability, whether or not they were taking melatonin, and in their objectives when in Australia. For the first 6 days after arrival, subjects scored their jet-lag five times per day and other subjective variables up to five times per day, using visual analogue scales. For jet-lag, the scale was labelled 0 = no jet-lag to 10 = very bad jet-lag; the extremes of the other scales were labelled - 5 and + 5, indicating marked changes compared with normal, and the centrepoint was labelled 0 indicating 'normal'. Mean daily values for jet-lag and fatigue were initially high (+ 3.65 +/- 0.35 and + 1.55 +/- 0.22 on day 1, respectively) and fell progressively on subsequent days, but were still raised significantly (p < 0.05) on day 5 (fatigue) or day 6 (jet-lag). In addition, times of waking were earlier on all days. By contrast, falls in concentration and motivation, and rises in irritability and nocturnal wakings, had recovered by day 4 or earlier, and bowel activity was less frequent, with harder stools, on days 1 and 2 only. Also, on day 1, there was a decrease in the ease of getting to sleep (- 1.33 +/- 0.55), but this changed to an increase from day 2 onwards (for example, + 0.75 +/- 0.25 on day 6). Stepwise regression analysis was used to investigate predictors of jet-lag. The severity of jet-lag at all the times that were measured was strongly predicted by fatigue ratings made at the same time. Its severity at 08:00 h was predicted by an earlier time of waking, by feeling less alert 30 min after waking and, marginally, by the number of waking episodes. Jet-lag at 12:00 and 16:00 h was strongly predicted by a fall of concentration at these times; jet-lag at mealtimes (12:00, 16:00 and 20:00 h) was predicted by the amount of feeling bloated. Such results complicate an exact interpretation that can be placed on an assessment of a global term such as jet-lag, particularly if the assessment is made only once per day.

Time-lag effects of global vegetation responses to climate change.

PubMed

Wu, Donghai; Zhao, Xiang; Liang, Shunlin; Zhou, Tao; Huang, Kaicheng; Tang, Bijian; Zhao, Wenqian

2015-09-01

Climate conditions significantly affect vegetation growth in terrestrial ecosystems. Due to the spatial heterogeneity of ecosystems, the vegetation responses to climate vary considerably with the diverse spatial patterns and the time-lag effects, which are the most important mechanism of climate-vegetation interactive effects. Extensive studies focused on large-scale vegetation-climate interactions use the simultaneous meteorological and vegetation indicators to develop models; however, the time-lag effects are less considered, which tends to increase uncertainty. In this study, we aim to quantitatively determine the time-lag effects of global vegetation responses to different climatic factors using the GIMMS3g NDVI time series and the CRU temperature, precipitation, and solar radiation datasets. First, this study analyzed the time-lag effects of global vegetation responses to different climatic factors. Then, a multiple linear regression model and partial correlation model were established to statistically analyze the roles of different climatic factors on vegetation responses, from which the primary climate-driving factors for different vegetation types were determined. The results showed that (i) both the time-lag effects of the vegetation responses and the major climate-driving factors that significantly affect vegetation growth varied significantly at the global scale, which was related to the diverse vegetation and climate characteristics; (ii) regarding the time-lag effects, the climatic factors explained 64% variation of the global vegetation growth, which was 11% relatively higher than the model ignoring the time-lag effects; (iii) for the area with a significant change trend (for the period 1982-2008) in the global GIMMS3g NDVI (P < 0.05), the primary driving factor was temperature; and (iv) at the regional scale, the variation in vegetation growth was also related to human activities and natural disturbances. Considering the time-lag effects is quite important for better predicting and evaluating the vegetation dynamics under the background of global climate change. © 2015 John Wiley & Sons Ltd.

The impact of the night float system on internal medicine residency programs.

PubMed

Trontell, M C; Carson, J L; Taragin, M I; Duff, A

1991-01-01

To study the design, method of implementation, perceived benefits, and problems associated with a night float system. Self-administered questionnaire completed by program directors, which included both structured and open-ended questions. The answers reflect resident and student opinions as well as those of the program directors, since program directors regularly obtain feedback from these groups. The 442 accredited internal medicine residency programs listed in the 1988-89 Directory of Graduate Medical Education Programs. Of the 442 programs, 79% responded, and 30% had experience with a night float system. The most frequent methods for initiating a night float system included: decreasing elective time (42.3%), hiring more residents (26.9%), creating a non-teaching service (12.5%), and reallocating housestaff time (9.6%). Positive effects cited include decreased fatigue, improved housestaff morale, improved recruiting, and better attitude toward internal medicine training. The quality of medical care was considered the same or better by most programs using it. The most commonly cited problems were decreased continuity of care, inadequate teaching of the night float team, and miscommunication. Residency programs using a night float system usually observe a positive effect on housestaff morale, recruitment, and working hours and no detrimental effect on the quality of patient care. Miscommunication and inadequate learning experience for the night float team are important potential problems. This survey suggests that the night float represents one solution to reducing resident working hours.

Constraining Anisotropic Lorentz Violation via the Spectral-lag Transition of GRB 160625B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, Jun-Jie; Wu, Xue-Feng; Shao, Lang

Violations of Lorentz invariance can lead to an energy-dependent vacuum dispersion of light, which results in arrival-time differences of photons with different energies arising from a given transient source. In this work, direction-dependent dispersion constraints are obtained on nonbirefringent Lorentz-violating effects using the observed spectral lags of the gamma-ray burst GRB 160625B. This burst has unusually large high-energy photon statistics, so we can obtain constraints from the true spectral time lags of bunches of high-energy photons rather than from the rough time lag of a single highest-energy photon. Also, GRB 160625B is the only burst to date having a well-definedmore » transition from positive lags to negative lags, providing a unique opportunity to distinguish Lorentz-violating effects from any source-intrinsic time lag in the emission of photons of different energy bands. Our results place comparatively robust two-sided constraints on a variety of isotropic and anisotropic coefficients for Lorentz violation, including the first bounds on Lorentz-violating effects from operators of mass dimension 10 in the photon sector.« less

Review: the environmental status and implications of the nitrate time lag in Europe and North America

NASA Astrophysics Data System (ADS)

Vero, Sara E.; Basu, Nandita B.; Van Meter, Kimberly; Richards, Karl G.; Mellander, Per-Erik; Healy, Mark G.; Fenton, Owen

2018-02-01

The efficacy of water quality policies aiming to reduce or prevent nitrate contamination of waterbodies may be constrained by the inherent delay or "time lag" of water and solute transport through unsaturated (soil) and saturated (groundwater) pathways. These delays must be quantified in order to establish realistic deadlines, thresholds and policy expectations, and to design effective best management practices. The objective of this review is to synthesise the current state of research on nitrate-related time lags in both the European and North American environmental and legislative contexts. The durations of time lags have been found to differ according to climatic, pedological, landscape and management scenarios. Elucidation of these driving factors at a watershed scale is essential where water quality is impaired or at risk. Finally, the existence of time lags is increasingly being acknowledged at a policy level and incorporated into the development of environmental legislation. However, the full impact of these time lags is not yet fully understood or appreciated, and continued outreach and education in scientific, public and policy venues is still required.

On floats and float tests

NASA Technical Reports Server (NTRS)

Seewald, Friedrich

1931-01-01

The principal source of information on float resistance is the model test. In view of the insuperable difficulties opposing any attempt at theoretical treatment of the resistance problem, particularly at attitudes which tend toward satisfactory take-off, such as the transitory stage to planing, the towing test is and will remain the primary method for some time.

75 FR 4897 - Self-Regulatory Organizations; Notice of Filing and Immediate Effectiveness of Proposed Rule...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-29

... $100 million public float requirement to those companies, unless there is only very limited trading...-held shares (``public float'') of $40 million at the time of listing. All other companies must have a... value of the company's offering to demonstrate the company's compliance with the applicable public float...

The Weighted-Average Lagged Ensemble.

PubMed

DelSole, T; Trenary, L; Tippett, M K

2017-11-01

A lagged ensemble is an ensemble of forecasts from the same model initialized at different times but verifying at the same time. The skill of a lagged ensemble mean can be improved by assigning weights to different forecasts in such a way as to maximize skill. If the forecasts are bias corrected, then an unbiased weighted lagged ensemble requires the weights to sum to one. Such a scheme is called a weighted-average lagged ensemble. In the limit of uncorrelated errors, the optimal weights are positive and decay monotonically with lead time, so that the least skillful forecasts have the least weight. In more realistic applications, the optimal weights do not always behave this way. This paper presents a series of analytic examples designed to illuminate conditions under which the weights of an optimal weighted-average lagged ensemble become negative or depend nonmonotonically on lead time. It is shown that negative weights are most likely to occur when the errors grow rapidly and are highly correlated across lead time. The weights are most likely to behave nonmonotonically when the mean square error is approximately constant over the range forecasts included in the lagged ensemble. An extreme example of the latter behavior is presented in which the optimal weights vanish everywhere except at the shortest and longest lead times.

Current Status of Biomedical Book Reviewing: Part II. Time Lag in Biomedical Book Reviewing

PubMed Central

Chen, Ching-Chih

1974-01-01

This part of the study explores the effectiveness of the review media in terms of speed of reviewing, comprehensiveness of review treatment, and authority. The time lags for the fifty-four journals varied widely, the mean ranging from 5.8 months to forty-two months. The time lags for all 3,347 reviews varied even more widely, ranging from less than a month to 108 months after a book was off the press. The 3,347 reviews had a mean time lag of 10.43 months and a standard deviation of 6.63 months. PMID:4826480

How to induce multiple delays in coupled chaotic oscillators?

NASA Astrophysics Data System (ADS)

Bhowmick, Sourav K.; Ghosh, Dibakar; Roy, Prodyot K.; Kurths, Jürgen; Dana, Syamal K.

2013-12-01

Lag synchronization is a basic phenomenon in mismatched coupled systems, delay coupled systems, and time-delayed systems. It is characterized by a lag configuration that identifies a unique time shift between all pairs of similar state variables of the coupled systems. In this report, an attempt is made how to induce multiple lag configurations in coupled systems when different pairs of state variables attain different time shift. A design of coupling is presented to realize this multiple lag synchronization. Numerical illustration is given using examples of the Rössler system and the slow-fast Hindmarsh-Rose neuron model. The multiple lag scenario is physically realized in an electronic circuit of two Sprott systems.

Structure and Fabrication of a Microscale Flow-Rate/Skin Friction Sensor

NASA Technical Reports Server (NTRS)

Chandrasekharan, Vijay (Inventor); Sells, Jeremy (Inventor); Sheplak, Mark (Inventor); Arnold, David P. (Inventor)

2014-01-01

A floating element shear sensor and method for fabricating the same are provided. According to an embodiment, a microelectromechanical systems (MEMS)-based capacitive floating element shear stress sensor is provided that can achieve time-resolved turbulence measurement. In one embodiment, a differential capacitive transduction scheme is used for shear stress measurement. The floating element structure for the differential capacitive transduction scheme incorporates inter digitated comb fingers forming differential capacitors, which provide electrical output proportional to the floating element deflection.

X-ray short-time lags in the Fe-K energy band produced by scattering clouds in active galactic nuclei

NASA Astrophysics Data System (ADS)

Mizumoto, Misaki; Done, Chris; Hagino, Kouichi; Ebisawa, Ken; Tsujimoto, Masahiro; Odaka, Hirokazu

2018-05-01

X-rays illuminating the accretion disc in active galactic nuclei give rise to an iron K line and its associated reflection spectrum which are lagged behind the continuum variability by the light-travel time from the source to the disc. The measured lag timescales in the iron band can be as short as ˜Rg/c, where Rg is the gravitational radius, which is often interpreted as evidence for a very small continuum source close to the event horizon of a rapidly spinning black hole. However, the short lags can also be produced by reflection from more distant material, because the primary photons with no time-delay dilute the time-lags caused by the reprocessed photons. We perform a Monte-Carlo simulation to calculate the dilution effect in the X-ray reverberation lags from a half-shell of neutral material placed at 100 Rg from the central source. This gives lags of ˜2 Rg/c, but the iron line is a distinctly narrow feature in the lag-energy plot, whereas the data often show a broader line. We show that both the short lag and the line broadening can be reproduced if the scattering material is outflowing at ˜0.1c. The velocity structure in the wind can also give shifts in the line profile in the lag-energy plot calculated at different frequencies. Hence we propose that the observed broad iron reverberation lags and shifts in profile as a function of frequency of variability can arise from a disc wind at fairly large distances from the X-ray source.

A Time Lag Analysis of Temporal Relations between Motivation, Academic Achievement, and Two Cognitive Abilities

ERIC Educational Resources Information Center

Greene, Monica R.; Pasnak, Robert; Romero, Sandy L.

2009-01-01

Research Findings: The present study employed a time lag design to assess temporal relationships between motivation, academic achievement, and cognitive development. Eighty-one children from 2 preschool programs were measured twice, with an 11-week time lag, on 2 measures of motivation (marble drop task, bean bag toss task), 2 measures of…

Expert Systems on Multiprocessor Architectures. Volume 4. Technical Reports

DTIC Science & Technology

1991-06-01

Floated-Current-Time0 -> The time that this function is called in user time uflts, expressed as a floating point number. Halt- Poligono Arrests the...default a statistics file will be printed out, if it can be. To prevent this make No-Statistics true. Unhalt- Poligono Unarrests the process in which the

Development of a novel drug delivery system, time-controlled explosion system (TES). IV. In vivo drug release behavior.

PubMed

Ueda, S; Ibuki, R; Kawamura, A; Murata, S; Takahashi, T; Kimura, S; Hata, T

1994-01-01

Time-Controlled Explosion System (TES) has the time-controlled drug release property with a pre-designed lag time. The drug release from the system is initiated by destruction of the membrane. In this study, metoprolol tartrate was used as a model drug. After five types of TES with different in vitro lag times were orally administrated to dogs, plasma metoprolol concentration was monitored. There existed a good correlation between in vitro and in vivo lag time, while the extent of absorbed metoprolol decreased with prolongation of lag time. Next, the in vivo drug release behavior was directly investigated using five different colored TES with a lag time of two hours. Each TES was consecutively administrated to the fasted dogs at predetermined intervals. The amount of metoprolol released was monitored by recovering the administered TES from the gastrointestinal trace. The in vivo release profile corresponded with the in vitro one. It is demonstrated that TES can release the drug in in vivo conditions similarly to in vitro. Based on these results, the decrease of the absorption is suggested to be caused by increased hepatic first-pass metabolism of the drug due to the retarded release rate with longer lag time.

Preparation and investigation of novel gastro-floating tablets with 3D extrusion-based printing.

PubMed

Li, Qijun; Guan, Xiaoying; Cui, Mengsuo; Zhu, Zhihong; Chen, Kai; Wen, Haoyang; Jia, Danyang; Hou, Jian; Xu, Wenting; Yang, Xinggang; Pan, Weisan

2018-01-15

Three dimensional (3D) extrusion-based printing is a paste-based rapid prototyping process, which is capable of building complex 3D structures. The aim of this study was to explore the feasibility of 3D extrusion-based printing as a pharmaceutical manufacture technique for the fabrication of gastro-floating tablets. Novel low-density lattice internal structure gastro-floating tablets of dipyridamole were developed to prolong the gastric residence time in order to improve drug release rate and consequently, improve bioavailability and therapeutic efficacy. Excipients commonly employed in the pharmaceutical study could be efficiently applied in the room temperature 3D extrusion-based printing process. The tablets were designed with three kinds of infill percentage and prepared by hydroxypropyl methylcellulose (HPMC K4M) and hydroxypropyl methylcellulose (HPMC E15) as hydrophilic matrices and microcrystalline cellulose (MCC PH101) as extrusion molding agent. In vitro evaluation of the 3D printed gastro-floating tablets was performed by determining mechanical properties, content uniformity, and weight variation. Furthermore, re-floating ability, floating duration time, and drug release behavior were also evaluated. Dissolution profiles revealed the relationship between infill percentage and drug release behavior. The results of this study revealed the potential of 3D extrusion-based printing to fabricate gastro-floating tablets with more than 8h floating process with traditional pharmaceutical excipients and lattice internal structure design. Copyright © 2017. Published by Elsevier B.V.

Time lag between immigration and tuberculosis rates in immigrants in the Netherlands: a time-series analysis.

PubMed

van Aart, C; Boshuizen, H; Dekkers, A; Korthals Altes, H

2017-05-01

In low-incidence countries, most tuberculosis (TB) cases are foreign-born. We explored the temporal relationship between immigration and TB in first-generation immigrants between 1995 and 2012 to assess whether immigration can be a predictor for TB in immigrants from high-incidence countries. We obtained monthly data on immigrant TB cases and immigration for the three countries of origin most frequently represented among TB cases in the Netherlands: Morocco, Somalia and Turkey. The best-fit seasonal autoregressive integrated moving average (SARIMA) model to the immigration time-series was used to prewhiten the TB time series. The cross-correlation function (CCF) was then computed on the residual time series to detect time lags between immigration and TB rates. We identified a 17-month lag between Somali immigration and Somali immigrant TB cases, but no time lag for immigrants from Morocco and Turkey. The absence of a lag in the Moroccan and Turkish population may be attributed to the relatively low TB prevalence in the countries of origin and an increased likelihood of reactivation TB in an ageing immigrant population. Understanding the time lag between Somali immigration and TB disease would benefit from a closer epidemiological analysis of cohorts of Somali cases diagnosed within the first years after entry.

Non steady-state descriptions of drug permeation through stratum corneum. I. The biphasic brick-and-mortar model.

PubMed

Heisig, M; Lieckfeldt, R; Wittum, G; Mazurkevich, G; Lee, G

1996-03-01

The diffusion equation should be solved for the non-steady-state problem of drug diffusion within a two-dimensional, biphasic stratum corneum membrane having homogeneous lipid and corneocyte phases. A numerical method was developed for a brick-and-mortar SC-geometry, enabling an explicit solution for time-dependent drug concentration within both phases. The lag time and permeability were calculated. It is shown how the barrier property of this model membrane depends on relative phase permeability, corneocyte alignment, and corneocyte-lipid partition coefficient. Additionally, the time-dependent drug concentration profiles within the membrane can be observed during the lag and steady-state phases. The model SC-membrane predicts, from purely morphological principles, lag times and permeabilities that are in good agreement with experimental values. The long lag times and very small permeabilities reported for human SC can only be predicted for a highly-staggered corneocyte geometry and corneocytes that are 1000 times less permeable than the lipid phase. Although the former conclusion is reasonable, the latter is questionable. The elongated, flattened corneocyte shape renders lag time and permeability insensitive to large changes in their alignment within the SC. Corneocyte/lipid partitioning is found to be fundamentally different to SC/donor partitioning, since increasing drug lipophilicity always reduces both lag time and permeability.

Consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates.

PubMed

Vero, S E; Ibrahim, T G; Creamer, R E; Grant, J; Healy, M G; Henry, T; Kramers, G; Richards, K G; Fenton, O

2014-12-01

The true efficacy of a programme of agricultural mitigation measures within a catchment to improve water quality can be determined only after a certain hydrologic time lag period (subsequent to implementation) has elapsed. As the biophysical response to policy is not synchronous, accurate estimates of total time lag (unsaturated and saturated) become critical to manage the expectations of policy makers. The estimation of the vertical unsaturated zone component of time lag is vital as it indicates early trends (initial breakthrough), bulk (centre of mass) and total (Exit) travel times. Typically, estimation of time lag through the unsaturated zone is poor, due to the lack of site specific soil physical data, or by assuming saturated conditions. Numerical models (e.g. Hydrus 1D) enable estimates of time lag with varied levels of input data. The current study examines the consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates using simulated and actual soil profiles. Results indicated that: greater temporal resolution (from daily to hourly) of meteorological data was more critical as the saturated hydraulic conductivity of the soil decreased; high clay content soils failed to converge reflecting prevalence of lateral component as a contaminant pathway; elucidation of soil hydraulic properties was influenced by the complexity of soil physical data employed (textural menu, ROSETTA, full and partial soil water characteristic curves), which consequently affected time lag ranges; as the importance of the unsaturated zone increases with respect to total travel times the requirements for high complexity/resolution input data become greater. The methodology presented herein demonstrates that decisions made regarding input data and landscape position will have consequences for the estimated range of vertical travel times. Insufficiencies or inaccuracies regarding such input data can therefore mislead policy makers regarding the achievability of water quality targets. Copyright © 2014 Elsevier B.V. All rights reserved.

Are floating algal mats a refuge from hypoxia for estuarine invertebrates?

PubMed Central

Knysh, Kyle M.; Theriault, Emma F.; Pater, Christina C.; Courtenay, Simon C.; van den Heuvel, Michael R.

2017-01-01

Eutrophic aquatic habitats are characterized by the proliferation of vegetation leading to a large standing biomass that upon decomposition may create hypoxic (low-oxygen) conditions. This is indeed the case in nutrient impacted estuaries of Prince Edward Island, Canada, where macroalgae, from the genus Ulva, form submerged ephemeral mats. Hydrological forces and gases released from photosynthesis and decomposition lead to these mats occasionally floating to the water’s surface, henceforth termed floating mats. Here, we explore the hypothesis that floating mats are refugia during periods of sustained hypoxia/anoxia and examine how the invertebrate community responds to it. Floating mats were not always present, so in the first year (2013) sampling was attempted monthly and limited to when both floating and submerged mats occurred. In the subsequent year sampling was weekly, but at only one estuary due to logistical constraints from increased sampling frequency, and was not limited to when both mat types occurred. Water temperature, salinity, and pH were monitored bi-weekly with dissolved oxygen concentration measured hourly. The floating and submerged assemblages shared many of the same taxa but were statistically distinct communities; submerged mats tended to have a greater proportion of benthic animals and floating mats had more mobile invertebrates and insects. In 2014, sampling happened to occur in the weeks before the onset of anoxia, during 113 consecutive hours of sustained anoxia, and for four weeks after normoxic conditions returned. The invertebrate community on floating mats appeared to be unaffected by anoxia, indicating that these mats may be refugia during times of oxygen stress. Conversely, there was a dramatic decrease in animal abundances that remained depressed on submerged mats for two weeks. Cluster analysis revealed that the submerged mat communities from before the onset of anoxia and four weeks after anoxia were highly similar to each other, indicating recovery. When mobile animals were considered alone, there was an exponential relationship between the percentage of animals on floating mats, relative to the total number on both mat types, and hypoxia. The occupation of floating mats by invertebrates at all times, and their dominance there during hypoxia/anoxia, provides support for the hypothesis that floating mats are refugia. PMID:28348927

A Race Against Time: Time Lags in Terrestrial-Aquatic Linkages

NASA Astrophysics Data System (ADS)

Basu, N. B.

2017-12-01

Unprecedented decreases in atmospheric nitrogen (N) deposition together with increases in agricultural N-use efficiency have led to decreases in net anthropogenic N inputs in many eastern U.S. and Canadian watersheds as well as in Europe. Despite such decreases, N concentrations in streams and rivers continue to increase, and problems of coastal eutrophication remain acute. Such a mismatch between N inputs and outputs can arise due to legacy N accumulation and subsequent lag times between implementation of conservation measures and improvements in water quality. In the present study, we quantified such lag times by pairing long-term N input trajectories with stream N concentration data in multiple watersheds in North America. Results show significant nonlinearity between N inputs and outputs, with a strong hysteresis effect indicative of decadal-scale lag times. Lag times were found to be negatively correlated with both tile drainage and watershed slope, with tile drainage being a dominant control in fall and watershed slope being significant during the spring snowmelt period. Quantification of such lags will be crucial to policy-makers as they struggle to set appropriate goals for water quality improvement in human-impacted watersheds.

Relation between germination and mycelium growth of individual fungal spores.

PubMed

Gougouli, Maria; Koutsoumanis, Konstantinos P

2013-02-15

The relation between germination time and lag time of mycelium growth of individual spores was studied by combining microscopic and macroscopic techniques. The radial growth of a large number (100-200) of Penicillium expansum and Aspergillus niger mycelia originating from single spores was monitored macroscopically at isothermal conditions ranging from 0 to 30°C and 10 to 41.5°C, respectively. The radial growth curve for each mycelium was fitted to a linear model for the estimation of mycelium lag time. The results showed that the lag time varied significantly among single spores. The cumulative frequency distributions of the lag times were fitted to the modified Gompertz model and compared with the respective distributions for the germination time, which were obtained microscopically. The distributions of the measured mycelium lag time were found to be similar to the germination time distributions under the same conditions but shifted in time with the lag times showing a significant delay compared to germination times. A numerical comparison was also performed based on the distribution parameters λ(m) and λ(g), which indicate the time required from the spores to start the germination process and the completion of the lag phase, respectively. The relative differences %(λ(m)-λ(g))/λ(m) were not found to be significantly affected by temperatures tested with mean values of 72.5±5.1 and 60.7±2.1 for P. expansum for A. niger, respectively. In order to investigate the source of the above difference, a time-lapse microscopy method was developed providing videos with the behavior of single fungal spore from germination until mycelium formation. The distances of the apexes of the first germ tubes that emerged from the swollen spore were measured in each frame of the videos and these data were expressed as a function of time. The results showed that in the early hyphal development, the measured radii appear to increase exponentially, until a certain time, where growth becomes linear. The two phases of hyphal development can explain the difference between germination and lag time. Since the lag time is estimated from the extrapolation of the regression line of the linear part of the graph only, its value is significantly higher than the germination time, t(G). The relation of germination and lag time was further investigated by comparing their temperature dependence using the Cardinal Model with Inflection. The estimated values of the cardinal parameters (T(min), T(opt), and T(max)) for 1/λ(g) were found to be very close to the respective values for 1/λ(m), indicating similar temperature dependence between them. Copyright © 2012 Elsevier B.V. All rights reserved.

On the design of a radix-10 online floating-point multiplier

NASA Astrophysics Data System (ADS)

McIlhenny, Robert D.; Ercegovac, Milos D.

2009-08-01

This paper describes an approach to design and implement a radix-10 online floating-point multiplier. An online approach is considered because it offers computational flexibility not available with conventional arithmetic. The design was coded in VHDL and compiled, synthesized, and mapped onto a Virtex 5 FPGA to measure cost in terms of LUTs (look-up-tables) as well as the cycle time and total latency. The routing delay which was not optimized is the major component in the cycle time. For a rough estimate of the cost/latency characteristics, our design was compared to a standard radix-2 floating-point multiplier of equivalent precision. The results demonstrate that even an unoptimized radix-10 online design is an attractive implementation alternative for FPGA floating-point multiplication.

Calibration of Watershed Lag Time Equation for Philippine Hydrology using RADARSAT Digital Elevation Models

NASA Astrophysics Data System (ADS)

Cipriano, F. R.; Lagmay, A. M. A.; Horritt, M.; Mendoza, J.; Sabio, G.; Punay, K. N.; Taniza, H. J.; Uichanco, C.

2015-12-01

Widespread flooding is a major problem in the Philippines. The country experiences heavy amount of rainfall throughout the year and several areas are prone to flood hazards because of its unique topography. Human casualties and destruction of infrastructure are just some of the damages caused by flooding and the Philippine government has undertaken various efforts to mitigate these hazards. One of the solutions was to create flood hazard maps of different floodplains and use them to predict the possible catastrophic results of different rain scenarios. To produce these maps with accurate output, different input parameters were needed and one of those is calculating hydrological components from topographical data. This paper presents how a calibrated lag time (TL) equation was obtained using measurable catchment parameters. Lag time is an essential input in flood mapping and is defined as the duration between the peak rainfall and peak discharge of the watershed. The lag time equation involves three measurable parameters, namely, watershed length (L), maximum potential retention (S) derived from the curve number, and watershed slope (Y), all of which were available from RADARSAT Digital Elevation Models (DEM). This approach was based on a similar method developed by CH2M Hill and Horritt for Taiwan, which has a similar set of meteorological and hydrological parameters with the Philippines. Rainfall data from fourteen water level sensors covering 67 storms from all the regions in the country were used to estimate the actual lag time. These sensors were chosen by using a screening process that considers the distance of the sensors from the sea, the availability of recorded data, and the catchment size. The actual lag time values were plotted against the values obtained from the Natural Resource Conservation Management handbook lag time equation. Regression analysis was used to obtain the final calibrated equation that would be used to calculate the lag time specifically for rivers in the Philippine setting. The calculated lag time values could then be used as a parameter for modeling different flood scenarios in the country.

Improving precipitation forecast with hybrid 3DVar and time-lagged ensembles in a heavy rainfall event

NASA Astrophysics Data System (ADS)

Wang, Yuanbing; Min, Jinzhong; Chen, Yaodeng; Huang, Xiang-Yu; Zeng, Mingjian; Li, Xin

2017-01-01

This study evaluates the performance of three-dimensional variational (3DVar) and a hybrid data assimilation system using time-lagged ensembles in a heavy rainfall event. The time-lagged ensembles are constructed by sampling from a moving time window of 3 h along a model trajectory, which is economical and easy to implement. The proposed hybrid data assimilation system introduces flow-dependent error covariance derived from time-lagged ensemble into variational cost function without significantly increasing computational cost. Single observation tests are performed to document characteristic of the hybrid system. The sensitivity of precipitation forecasts to ensemble covariance weight and localization scale is investigated. Additionally, the TLEn-Var is evaluated and compared to the ETKF(ensemble transformed Kalman filter)-based hybrid assimilation within a continuously cycling framework, through which new hybrid analyses are produced every 3 h over 10 days. The 24 h accumulated precipitation, moisture, wind are analyzed between 3DVar and the hybrid assimilation using time-lagged ensembles. Results show that model states and precipitation forecast skill are improved by the hybrid assimilation using time-lagged ensembles compared with 3DVar. Simulation of the precipitable water and structure of the wind are also improved. Cyclonic wind increments are generated near the rainfall center, leading to an improved precipitation forecast. This study indicates that the hybrid data assimilation using time-lagged ensembles seems like a viable alternative or supplement in the complex models for some weather service agencies that have limited computing resources to conduct large size of ensembles.

Floating marine litter as a raft for drifting voyages for Planes minutus (Crustacea: Decapoda: Grapsidae) and Liocarcinus navigator (Crustacea: Decapoda: Polybiidae).

PubMed

Tutman, P; Kapiris, K; Kirinčić, M; Pallaoro, A

2017-07-15

The Columbus crab Planes minutus and Arch-fronted swimming crab Liocarcinus navigator, within their distribution ranges in the Mediterranean, were found rafted on plastic macro-litter floating on the open south Adriatic. While P. minutus was recorded from inanimate flotsam outside of the Mediterranean, L. navigator is herein reported for the first time on floating marine litter. The role of floating litter as habitat or as a dispersal agent for marine invertebrates has received quite attention however, records of decapod crabs drifting on litter has been relatively sparse. Our results suggests that vast quantities of floating debris, comprised primarily of non-biodegradable plastic polymers, probably will augment natural floating substrates in the marine environment, potentially facilitating the spread of invasive species. The dispersion of rafting crabs through floating debris should be investigated given the high potential ecological risk of invasion by exotic species due to the increase in waste production (ecological risk assessment). Copyright © 2017 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Yan-Fei; Green, Paul J.; Pancoast, Anna

We study the time lags between the continuum emission of quasars at different wavelengths, based on more than four years of multi-band ( g , r , i , z ) light curves in the Pan-STARRS Medium Deep Fields. As photons from different bands emerge from different radial ranges in the accretion disk, the lags constrain the sizes of the accretion disks. We select 240 quasars with redshifts of z ≈ 1 or z ≈ 0.3 that are relatively emission-line free. The light curves are sampled from day to month timescales, which makes it possible to detect lags on themore » scale of the light crossing time of the accretion disks. With the code JAVELIN , we detect typical lags of several days in the rest frame between the g band and the riz bands. The detected lags are ∼2–3 times larger than the light crossing time estimated from the standard thin disk model, consistent with the recently measured lag in NGC 5548 and microlensing measurements of quasars. The lags in our sample are found to increase with increasing luminosity. Furthermore, the increase in lags going from g − r to g − i and then to g − z is slower than predicted in the thin disk model, particularly for high-luminosity quasars. The radial temperature profile in the disk must be different from what is assumed. We also find evidence that the lags decrease with increasing line ratios between ultraviolet Fe ii lines and Mg ii, which may point to changes in the accretion disk structure at higher metallicity.« less

AIR POLLUTION EPIDEMIOLOGY: CAN INFORMATION BE OBTAINED FROM THE VARIATIONS IN SIGNIFICANCE AND RISK AS A FUNCTION OF DAYS AFTER EXPOSURE (LAG STRUCTURE)?

EPA Science Inventory

Determine if analysis of lag structure from time series epidemiology, using gases, particles, and source factor time series, can contribute to understanding the relationships among various air pollution indicators. Methods: Analyze lag structure from an epidemiologic study of ca...

Protein Z efficiently depletes thrombin generation in disseminated intravascular coagulation with poor prognosis.

PubMed

Lee, Nuri; Kim, Ji-Eun; Gu, Ja-Yoon; Yoo, Hyun Ju; Kim, Inho; Yoon, Sung-Soo; Park, Seonyang; Han, Kyou-Sup; Kim, Hyun Kyung

2016-01-01

Disseminated intravascular coagulation (DIC) is characterized by consumption of coagulation factors and anticoagulants. Thrombin generation assay (TGA) gives useful information about global hemostatic status. We developed a new TGA system that anticoagulant addition can deplete thrombin generation in plasma, which may reflect defective anticoagulant system in DIC. TGAs were measured on the calibrated automated thrombogram with and without thrombomodulin or protein Z in 152 patients who were suspected of having DIC, yielding four parameters including lag time, endogenous thrombin potential, peak thrombin and time-to-peak in each experiment. Nonsurvivors showed significantly prolonged lag time and time-to-peak in TGA-protein Z system, which was performed with added protein Z. In multivariate Cox regression analysis, lag time and time-to-peak in TGA system were significant independent prognostic factors. In TGA-protein Z system, lag time and time-to-peak were revealed as independent prognostic factors of DIC. Protein Z addition could potentiate its anticoagulant effect in DIC with poor prognosis, suggesting the presence of defective protein Z system. The prolonged lag time and time-to-peak in both TGA and TGA-protein Z systems are expected to be used as independent prognostic factors of DIC.

[Time lag effect between poplar' s sap flow velocity and microclimate factors in agroforestry system in West Liaoning Province].

PubMed

Di, Sun; Guan, De-xin; Yuan, Feng-hui; Wang, An-zhi; Wu, Jia-bing

2010-11-01

By using Granier's thermal dissipation probe, the sap flow velocity of the poplars in agroforestry system in west Liaoning was continuously measured, and the microclimate factors were measured synchronously. Dislocation contrast method was applied to analyze the sap flow velocity and corresponding air temperature, air humidity, net radiation, and vapor pressure deficit to discuss the time lag effect between poplar' s sap flow velocity and microclimate factors on sunny days. It was found that the poplar's sap flow velocity advanced of air temperature, air humidity, and vapor pressure deficit, and lagged behind net radiation. The sap flow velocity in June, July, August, and September was advanced of 70, 30, 50, and 90 min to air temperature, of 80, 30, 40, and 90 min to air humidity, and of 90, 50, 70, and 120 min to vapor pressure deficit, but lagged behind 10, 10, 40, and 40 min to net radiation, respectively. The time lag time of net radiation was shorter than that of air temperature, air humidity, and vapor pressure. The regression analysis showed that in the cases the time lag effect was contained and not, the determination coefficients between comprehensive microclimate factor and poplar's sap flow velocity were 0.903 and 0.855, respectively, indicating that when the time lag effect was contained, the determination coefficient was ascended by 2.04%, and thus, the simulation accuracy of poplar's sap flow velocity was improved.

Circulation patterns in the deep Subtropical Northeast Atlantic with ARGO data

NASA Astrophysics Data System (ADS)

Calheiros, Tomas; Bashmachnikov, Igor

2014-05-01

In this work we study the dominant circulation patterns in the Subtropical Northeast Atlantic using ARGO data [25-45o N, 5-35o W]. The data were obtained from the Coriolis operational data center (ftp://ftp.ifremer.fr) for the years 1999-2013. During this period of time in the study there were available area 376 floats with 15062 float-months of total time. The floats were launched in the depths range between 300 and 2000 m, but most of the floats were concentrated at 1000 m (2000 float-months) and 1500 m (3400 float-months). In the upper 400-m layer there were also about 1000 float-months, but their number and distribution did not allow analysis of the mean currents over the study region. For each float position Lagrangian current velocity was computed as the difference between the position when the buoy started sinking to the reference depth and the consequent position of surfacing of the float, divided by the respective time interval. This allowed reducing the noise related with sea-surface drift of the buoys during the data-transmission periods. Mean Eulerian velocity and its error were computed in each of the 2ox2o square. Whenever in a 2ox2o square more than 150 observations of the Lagrangian velocity were available, the square was split into 4 smaller 1ox1o squares, in each of which the mean Eulerian velocities and their errors were estimated. Eulerian currents at 1000 m, as well as at 1500 m depth formed an overall anticyclonic circulation pattern in the study region. The modal velocity of all buoys at 1000 m level was 4 cm/s with an error of the mean of 1.8 cm/s. The modal velocity of all buoys at 1500m was 3 cm/s with an error of the mean of 1.4 cm/s. The southwestward flows near the Madeira Island and further westwards flow along the zonal band of 25-30o N at 1500 m depth well corresponded to the extension of the deep fraction of the Mediterranean Water salt tong.

Stability and chaotification of vibration isolation floating raft systems with time-delayed feedback control.

PubMed

Li, Y L; Xu, D L; Fu, Y M; Zhou, J X

2011-09-01

This paper presents a systematic study on the stability of a two-dimensional vibration isolation floating raft system with a time-delayed feedback control. Based on the generalized Sturm criterion, the critical control gain for the delay-independent stability region and critical time delays for the stability switches are derived. The critical conditions can provide a theoretical guidance of chaotification design for line spectra reduction. Numerical simulations verify the correctness of the approach. Bifurcation analyses reveal that chaotification is more likely to occur in unstable region defined by these critical conditions, and the stiffness of the floating raft and mass ratio are the sensitive parameters to reduce critical control gain.

A Comparison of Several Methods of Measuring Ignition Lag in a Compression-ignition Engine

NASA Technical Reports Server (NTRS)

Spanogle, J A

1934-01-01

The ignition lag of a fuel oil in the combustion chamber of a high speed compression-ignition engine was measured by three different methods. The start of injection of the fuel as observed with a Stoborama was taken as the start of the period of ignition lag in all cases. The end of the period of ignition lag was determined by observation of the appearance of incandescence in the combustion chamber, by inspection of a pressure-time card for evidence of pressure rise, and by analysis of the indicator card for evidence of the combustion of a small but definite quantity of fuel. A comparison of the values for ignition lags obtained by these three methods indicates that the appearance of incandescence is later than other evidences of the start of combustion, that visual inspection of a pressure-time diagram gives consistent and usable values with a minimum requirement of time and/or apparatus, and that analysis of the indicator card is not worth while for ignition lag alone.

A comparison of alternative variants of the lead and lag time TTO.

PubMed

Devlin, Nancy; Buckingham, Ken; Shah, Koonal; Tsuchiya, Aki; Tilling, Carl; Wilkinson, Grahame; van Hout, Ben

2013-05-01

'Lead Time' TTO improves upon conventional TTO by providing a uniform method for eliciting positive and negative values. This research investigates (i) the values generated from different combinations of time in poor health and in full health; and the order in which these appear (lead vs. lag); (ii) whether values concur with participants' views about states; (iii) methods for handling extreme preferences. n = 208 participants valued five EQ-5D states, using two of four variants. Combinations of lead time and health state duration were: 10 years and 20 years; 5 years and 1 year; 5 years and 10 years; and a health state duration of 5 years with a lag time of 10 years. Longer lead times capture more preferences, but may involve a framing effect. Lag time results in less non-trading for mild states, and less time being traded for severe states. Negative values broadly agree with participants' stated opinion that the state is worse than dead. The values are sensitive to the ratio of lead time to duration of poor health, and the order in which these appear (lead vs. lag). It is feasible to handle extreme preferences though challenges remain. Copyright © 2012 John Wiley & Sons, Ltd.

Time lags between crown and basal sap flows in tropical lianas and co-occurring trees.

PubMed

Chen, Ya-Jun; Bongers, Frans; Tomlinson, Kyle; Fan, Ze-Xin; Lin, Hua; Zhang, Shu-Bin; Zheng, Yu-Long; Li, Yang-Ping; Cao, Kun-Fang; Zhang, Jiao-Lin

2016-06-01

Water storage in the stems of woody plants contributes to their responses to short-term water shortages. To estimate the contribution of water storage to the daily water budget of trees, time lags of sap flow between different positions of trunk are used as a proxy of stem water storage. In lianas, another large group of woody species, it has rarely been studied whether stored water functions in their daily water use, despite their increasing roles in the carbon and water dynamics of tropical forests caused by their increasing abundance. We hypothesized that lianas would exhibit large time lags due to their extremely long stems, wide vessels and large volume of parenchyma in the stem. We examined time lags in sap flow, diel changes of stem volumetric water content (VWC) and biophysical properties of sapwood of 19 lianas and 26 co-occurring trees from 27 species in 4 forests (karst, tropical seasonal, flood plain and savanna) during a wet season. The plants varied in height/length from <5 to >60 m. The results showed that lianas had significantly higher saturated water content (SWC) and much lower wood density than trees. Seven of 19 liana individuals had no time lags; in contrast, only 3 of 26 tree individuals had no time lags. In general, lianas had shorter time lags than trees in our data set, but this difference was not significant for our most conservative analyses. Across trees and lianas, time lag duration increased with diurnal maximum changeable VWC but was independent of the body size, path length, wood density and SWC. The results suggest that in most lianas, internal stem water storage contributes little to daily water budget, while trees may rely more on stored water in the stem. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Transport and time lag of chlorofluorocarbon gases in the unsaturated zone, Rabis Creek, Denmark

USGS Publications Warehouse

Engesgaard, Peter; Højberg, Anker L.; Hinsby, Klaus; Jensen, Karsten H.; Laier, Troels; Larsen, Flemming; Busenberg, Eurybiades; Plummer, Niel

2004-01-01

Transport of chlorofluorocarbon (CFC) gases through the unsaturated zone to the water table is affected by gas diffusion, air–water exchange (solubility), sorption to the soil matrix, advective–dispersive transport in the water phase, and, in some cases, anaerobic degradation. In deep unsaturated zones, this may lead to a time lag between entry of gases at the land surface and recharge to groundwater. Data from a Danish field site were used to investigate how time lag is affected by variations in water content and to explore the use of simple analytical solutions to calculate time lag. Numerical simulations demonstrate that either degradation or sorption of CFC-11 takes place, whereas CFC-12 and CFC-113 are nonreactive. Water flow did not appreciably affect transport. An analytical solution for the period with a linear increase in atmospheric CFC concentrations (approximately early 1970s to early 1990s) was used to calculate CFC profiles and time lags. We compared the analytical results with numerical simulations. The time lags in the 15-m-deep unsaturated zone increase from 4.2 to between 5.2 and 6.1 yr and from 3.4 to 3.9 yr for CFC-11 and CFC-12, respectively, when simulations change from use of an exponential to a linear increase in atmospheric concentrations. The CFC concentrations at the water table before the early 1990s can be estimated by displacing the atmospheric input function by these fixed time lags. A sensitivity study demonstrates conditions under which a time lag in the unsaturated zone becomes important. The most critical parameter is the tortuosity coefficient. The analytical approach is valid for the low range of tortuosity coefficients (τ = 0.1–0.4) and unsaturated zones greater than approximately 20 m in thickness. In these cases the CFC distribution may still be from either the exponential or linear phase. In other cases, the use of numerical models, as described in our work and elsewhere, is an option.

Numerical study on aerodynamic damping of floating vertical axis wind turbines

NASA Astrophysics Data System (ADS)

Cheng, Zhengshun; Aagaard Madsen, Helge; Gao, Zhen; Moan, Torgeir

2016-09-01

Harvesting offshore wind energy resources using floating vertical axis wind turbines (VAWTs) has attracted an increasing interest in recent years. Due to its potential impact on fatigue damage, the aerodynamic damping should be considered in the preliminary design of a floating VAWT based on the frequency domain method. However, currently the study on aerodynamic damping of floating VAWTs is very limited. Due to the essential difference in aerodynamic load characteristics, the aerodynamic damping of a floating VAWT could be different from that of a floating horizontal axis wind turbine (HAWT). In this study, the aerodynamic damping of floating VAWTs was studied in a fully coupled manner, and its influential factors and its effects on the motions, especially the pitch motion, were demonstrated. Three straight-bladed floating VAWTs with identical solidity and with a blade number varying from two to four were considered. The aerodynamic damping under steady and turbulent wind conditions were estimated using fully coupled aero-hydro-servo-elastic time domain simulations. It is found that the aerodynamic damping ratio of the considered floating VAWTs ranges from 1.8% to 5.3%. Moreover, the aerodynamic damping is almost independent of the rotor azimuth angle, and is to some extent sensitive to the blade number.

14 CFR 23.529 - Hull and main float landing conditions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... landing. For symmetrical step, bow, and stern landings, the limit water reaction load factors are those....25 tan β times the resultant load in the corresponding symmetrical landing condition; and (2) The... at one float times the step landing load reached under § 23.527. The side load is directed inboard...

14 CFR 23.529 - Hull and main float landing conditions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... landing. For symmetrical step, bow, and stern landings, the limit water reaction load factors are those....25 tan β times the resultant load in the corresponding symmetrical landing condition; and (2) The... at one float times the step landing load reached under § 23.527. The side load is directed inboard...

Floating-to-Fixed-Point Conversion for Digital Signal Processors

NASA Astrophysics Data System (ADS)

Menard, Daniel; Chillet, Daniel; Sentieys, Olivier

2006-12-01

Digital signal processing applications are specified with floating-point data types but they are usually implemented in embedded systems with fixed-point arithmetic to minimise cost and power consumption. Thus, methodologies which establish automatically the fixed-point specification are required to reduce the application time-to-market. In this paper, a new methodology for the floating-to-fixed point conversion is proposed for software implementations. The aim of our approach is to determine the fixed-point specification which minimises the code execution time for a given accuracy constraint. Compared to previous methodologies, our approach takes into account the DSP architecture to optimise the fixed-point formats and the floating-to-fixed-point conversion process is coupled with the code generation process. The fixed-point data types and the position of the scaling operations are optimised to reduce the code execution time. To evaluate the fixed-point computation accuracy, an analytical approach is used to reduce the optimisation time compared to the existing methods based on simulation. The methodology stages are described and several experiment results are presented to underline the efficiency of this approach.

Module assemblage technology for floating systems: in vitro flotation and in vivo gastro-retention.

PubMed

Strusi, Orazio Luca; Sonvico, Fabio; Bettini, Ruggero; Santi, Patrizia; Colombo, Gaia; Barata, Pedro; Oliveira, Ana; Santos, Delfim; Colombo, Paolo

2008-07-14

The aim of this research was to study, in vitro by resultant-weight measurement and in vivo by gamma-scintigraphy experiments in humans, the floatation behavior of systems obtained by modules assembled in void configuration. The assembled system technology allowed the manufacturing of a system characterized by the presence of an internal void space that provided an apparent density lower than water. The gastro-retention times of floating assembled systems were determined in comparison with non-floating systems having the same mass and composition. In vitro the floatation of the system started immediately after immersion in water and lasted for more than 5 h. The in vivo studies confirmed that the in vitro floating ability of void configuration was maintained also in the human stomach where the system stayed for periods of time ranging from 2.5 to 5.0 h, depending on the food regimen and the sex of the subject. Reiterate eating and drinking further prolonged the stomach residence time.

Homozygous diploid deletion strains of Saccharomyces cerevisiae that determine lag phase and dehydration tolerance.

PubMed

D'Elia, Riccardo; Allen, Patricia L; Johanson, Kelly; Nickerson, Cheryl A; Hammond, Timothy G

2005-06-01

This study identifies genes that determine length of lag phase, using the model eukaryotic organism, Saccharomyces cerevisiae. We report growth of a yeast deletion series following variations in the lag phase induced by variable storage times after drying-down yeast on filters. Using a homozygous diploid deletion pool, lag times ranging from 0 h to 90 h were associated with increased drop-out of mitochondrial genes and increased survival of nuclear genes. Simple linear regression (R2 analysis) shows that there are over 500 genes for which > 70% of the variation can be explained by lag alone. In the genes with a positive correlation, such that the gene abundance increases with lag and hence the deletion strain is suitable for survival during prolonged storage, there is a strong predominance of nucleonic genes. In the genes with a negative correlation, such that the gene abundance decreases with lag and hence the strain may be critical for getting yeast out of the lag phase, there is a strong predominance of glycoproteins and transmembrane proteins. This study identifies yeast deletion strains with survival advantage on prolonged storage and amplifies our understanding of the genes critical for getting out of the lag phase.

Homozygous diploid deletion strains of Saccharomyces cerevisiae that determine lag phase and dehydration tolerance

NASA Technical Reports Server (NTRS)

D'Elia, Riccardo; Allen, Patricia L.; Johanson, Kelly; Nickerson, Cheryl A.; Hammond, Timothy G.

2005-01-01

This study identifies genes that determine length of lag phase, using the model eukaryotic organism, Saccharomyces cerevisiae. We report growth of a yeast deletion series following variations in the lag phase induced by variable storage times after drying-down yeast on filters. Using a homozygous diploid deletion pool, lag times ranging from 0 h to 90 h were associated with increased drop-out of mitochondrial genes and increased survival of nuclear genes. Simple linear regression (R2 analysis) shows that there are over 500 genes for which > 70% of the variation can be explained by lag alone. In the genes with a positive correlation, such that the gene abundance increases with lag and hence the deletion strain is suitable for survival during prolonged storage, there is a strong predominance of nucleonic genes. In the genes with a negative correlation, such that the gene abundance decreases with lag and hence the strain may be critical for getting yeast out of the lag phase, there is a strong predominance of glycoproteins and transmembrane proteins. This study identifies yeast deletion strains with survival advantage on prolonged storage and amplifies our understanding of the genes critical for getting out of the lag phase.

An improved measurement system for FOG pure lag time with no changing of FOG work status

NASA Astrophysics Data System (ADS)

Chen, X.; Yang, J. H.; Zhou, Y. L.; Shu, X. W.

2018-05-01

The minimum pure lag time is an important factor for characterizing the dynamic performance of fiber optical gyroscope. It is defined as the time duration from the reception of velocity-shock signal to the output of corresponding fiber-optic gyroscope data. Many engineering projects have required for this index specifically, so the measurement of the minimum pure lag time is highly demanded. In typically measurement system, the work status of tested FOG has to be changed. In this work, a FOG pure lag time measurement system without changing the work status of the FOG has been demonstrated. During the operation of this test system, the impact structure generated a shock towards the FOG, and the pure lag time was measured through data processing analysis. The design scheme and test principle have been researched and analyzed in detail. And a prototype has been developed and used for experiment successfully. This measurement system can realize a measurement accuracy of better than ±3 μs and a system resolution of 108.6ns.

Systematic review: association of shift length, protected sleep time, and night float with patient care, residents' health, and education.

PubMed

Reed, Darcy A; Fletcher, Kathlyn E; Arora, Vineet M

2010-12-21

The Accreditation Council for Graduate Medical Education's new duty-hour standards limit interns' shifts to 16 hours and night float to 6 consecutive nights. Protected sleep time (that is, "nap") is strongly encouraged. As duty-hour reforms are implemented, examination of the quality and outcomes of the relevant literature is important. To systematically review the literature examining shift length, protected sleep time, and night float. MEDLINE, PREMEDLINE, and EMBASE from January 1989 through May 2010. Studies examined the associations of shift length, protected sleep time, or night float with patient care, resident health, and education outcomes among residents in practice settings. Study quality was measured by using the validated Medical Education Research Study Quality Instrument and the U.S. Preventive Services Task Force criteria. Two investigators independently rated study quality, and interrater agreement was calculated. Sixty-four studies met inclusion criteria. Most studies used single-group cross-sectional (19 studies [29.7%]) or pre-post (41 studies [64.1%]) designs, and 4 (6.3%) were randomized, controlled trials. Five studies (7.8%) were multi-institutional. Twenty-four of 33 (72.7%) studies examining shift length reported that shorter shifts were associated with decreased medical errors, motor vehicle crashes, and percutaneous injuries. Only 2 studies assessed protected sleep time and reported that residents' adherence to naps was poor. Night floats described in 33 studies involved 5 to 7 consecutive nights. Most studies used single-institution, observational designs. Publication bias is likely but difficult to assess in this methodologically weak and heterogeneous body of evidence. For the limited outcomes measured, most studies supported reducing shift length but did not adequately address the optimal shift duration. Studies had numerous methodological limitations and unclear generalizability for most outcomes. Specific recommendations about shift length, protected sleep time, and night float should acknowledge the limitations of this evidence. Accreditation Council for Graduate Medical Education.

A study of the cross-correlation and time lag in black hole X-ray binary XTE J1859+226

NASA Astrophysics Data System (ADS)

Pei, Songpeng; Ding, Guoqiang; Li, Zhibing; Lei, Yajuan; Yuen, Rai; Qu, Jinlu

2017-07-01

With Rossi X-ray Timing Explorer (RXTE) data, we systematically study the cross-correlation and time lag in all spectral states of black hole X-ray binary (BHXB) XTE J1859+226 in detail during its entire 1999-2000 outburst that lasted for 166 days. Anti-correlations and positive correlations and their respective soft and hard X-ray lags are only detected in the first 100 days of the outburst when the luminosity is high. This suggests that the cross-correlations may be related to high luminosity. Positive correlations are detected in every state of XTE J1859+226, viz., hard state, hard-intermediate state (HIMS), soft-intermediate state (SIMS) and soft state. However, anti-correlations are only detected in HIMS and SIMS, anti-correlated hard lags are only detected in SIMS, while anti-correlated soft lags are detected in both HIMS and SIMS. Moreover, the ratio of the observations with anti-correlated soft lags to hard lags detected in XTE J1859+226 is significantly different from that in neutron star low-mass X-ray binaries (NS LMXBs). So far, anti-correlations are never detected in the soft state of BHXBs but detected in every branch or state of NS LMXBs. This may be due to the origin of soft seed photons in BHXBs is confined to the accretion disk and, for NS LMXBs, from both accretion disk and the surface of the NS. We notice that the timescale of anti-correlated time lags detected in XTE J1859+226 is similar with that of other BHXBs and NS LMXBs. We suggest that anti-correlated soft lag detected in BHXB may result from fluctuation in the accretion disk as well as NS LMXB.

A review of sensors, samplers and methods for marine biological observations.

NASA Astrophysics Data System (ADS)

Simmons, S. E.; Chavez, F.; Pearlman, J.; Working Group, T B S

2016-02-01

Physical scientists now have Argo floats, gliders and AUVs to supplement satellites to provide a 3-D view of the time-varying global ocean temperature and salinity structure. Biogeochemists are catching up with evolving sensors for nitrate, optical properties, oxygen and pH that can now be added to these autonomous systems. Biologists are still lagging, although some promising sensor systems based on but not limited to acoustic, chemical, genomic or imaging techniques, that can sense from microbes to whales, are on the horizon. These techniques can not only be applied in situ but also on samples returned to the laboratory using the autonomous systems. The number of samples is limiting, requiring adaptive and smart systems. Given the importance of biology to ocean health and the future earth, and the present reliance on humans and ships for observing species and abundance it is paramount that new biological sensor systems be developed. This abstract will review recent efforts to identify core biological variables for the US Integrated Ocean Observing System and address new sensors and innovations for observing these variables, particularly focused on availability and maturity of sensors. The relevance of this work in a global context will also be touched on.

A Lagging Model for Describing Drawdown Induced by a Constant-Rate Pumping in a Leaky Confined Aquifer

NASA Astrophysics Data System (ADS)

Lin, Ye-Chen; Yeh, Hund-Der

2017-10-01

This study proposes a generalized Darcy's law with considering phase lags in both the water flux and drawdown gradient to develop a lagging flow model for describing drawdown induced by constant-rate pumping (CRP) in a leaky confined aquifer. The present model has a mathematical formulation similar to the dual-porosity model. The Laplace-domain solution of the model with the effect of wellbore storage is derived by the Laplace transform method. The time-domain solution for the case of neglecting the wellbore storage and well radius is developed by the use of Laplace transform and Weber transform. The results of sensitivity analysis based on the solution indicate that the drawdown is very sensitive to the change in each of the transmissivity and storativity. Also, a study for the lagging effect on the drawdown indicates that its influence is significant associated with the lag times. The present solution is also employed to analyze a data set taken from a CRP test conducted in a fractured aquifer in South Dakota, USA. The results show the prediction of this new solution with considering the phase lags has very good fit to the field data, especially at early pumping time. In addition, the phase lags seem to have a scale effect as indicated in the results. In other words, the lagging behavior is positively correlated with the observed distance in the Madison aquifer.

Impact of anti-tacking agents on properties of gas-entrapped membrane and effervescent floating tablets.

PubMed

Kriangkrai, Worawut; Puttipipatkhachorn, Satit; Sriamornsak, Pornsak; Pongjanyakul, Thaned; Sungthongjeen, Srisagul

2014-12-01

Tackiness caused by the gas-entrapped membrane (Eudragit(®)RL 30D) was usually observed during storage of the effervescent floating tablets, leading to failure in floatation and sustained release. In this work, common anti-tacking agents (glyceryl monostearate (GMS) and talc) were used to solve this tackiness problem. The impact of anti-tacking agent on the properties of free films and corresponding floating tablets was investigated. GMS was more effective than talc in reducing tackiness of the film. Addition and increasing amount of anti-tacking agents lowered the film mechanical strength, but the coating films were still strong and flexible enough to resist the generated gas pressure inside the floating tablet. Wettability and water vapor permeability of the film decreased with increasing level of anti-tacking agents as a result of their hydrophobicity. No interaction between anti-tacking agents and polymer was observed as confirmed by Fourier transform infrared spectroscopy, powder X-ray diffractometry, and differential scanning calorimetry studies. Increasing amount of anti-tacking agents decreased time to float and tended to retard drug release of the floating tablets. Floating properties and drug release were also influenced by type of anti-tacking agents. The obtained floating tablets still possessed good floating properties and controlled drug release even though anti-tacking agent had some effects. The results demonstrated that the tackiness problem of the floating tablets could be solved by incorporating anti-tacking agent into the gas-entrapped membrane.

High-throughput Analysis of Ultrasonication-forced Amyloid Fibrillation Reveals the Mechanism Underlying the Large Fluctuation in the Lag Time*

PubMed Central

Umemoto, Ayaka; Yagi, Hisashi; So, Masatomo; Goto, Yuji

2014-01-01

Amyloid fibrils form in supersaturated solutions of precursor proteins by a nucleation and growth mechanism characterized by a lag time. Although the lag time provides a clue to understanding the complexity of nucleation events, its long period and low reproducibility have been obstacles for exact analysis. Ultrasonication is known to effectively break supersaturation and force fibrillation. By constructing a Handai amyloid burst inducer, which combines a water bath-type ultrasonicator and a microplate reader, we examined the ultrasonication-forced fibrillation of several proteins, with a focus on the fluctuation in the lag time. Amyloid fibrillation of hen egg white lysozyme was examined at pH 2.0 in the presence of 1.0–5.0 M guanidine hydrochloride (GdnHCl), in which the dominant species varied from the native to denatured conformations. Although fibrillation occurred at various concentrations of GdnHCl, the lag time varied largely, with a minimum being observed at ∼3.0 m, the concentration at which GdnHCl-dependent denaturation ended. The coefficient of variation of the lag time did not depend significantly on the GdnHCl concentration and was 2-fold larger than that of the ultrasonication-dependent oxidation of iodide, a simple model reaction. These results suggest that the large fluctuation observed in the lag time for amyloid fibrillation originated from a process associated with a common amyloidogenic intermediate, which may have been a relatively compact denatured conformation. We also suggest that the Handai amyloid burst inducer system will be useful for studying the mechanism of crystallization of proteins because proteins form crystals by the same mechanism as amyloid fibrils under supersaturation. PMID:25118286

Response variables for evaluation of the effectiveness of conservation corridors.

PubMed

Gregory, Andrew J; Beier, Paul

2014-06-01

Many studies have evaluated effectiveness of corridors by measuring species presence in and movement through small structural corridors. However, few studies have assessed whether these response variables are adequate for assessing whether the conservation goals of the corridors have been achieved or considered the costs or lag times involved in measuring the response variables. We examined 4 response variables-presence of the focal species in the corridor, interpatch movement via the corridor, gene flow, and patch occupancy--with respect to 3 criteria--relevance to conservation goals, lag time (fewest generations at which a positive response to the corridor might be evident with a particular variable), and the cost of a study when applying a particular variable. The presence variable had the least relevance to conservation goals, no lag time advantage compared with interpatch movement, and only a moderate cost advantage over interpatch movement or gene flow. Movement of individual animals between patches was the most appropriate response variable for a corridor intended to provide seasonal migration, but it was not an appropriate response variable for corridor dwellers, and for passage species it was only moderately relevant to the goals of gene flow, demographic rescue, and recolonization. Response variables related to gene flow provided a good trade-off among cost, relevance to conservation goals, and lag time. Nonetheless, the lag time of 10-20 generations means that evaluation of conservation corridors cannot occur until a few decades after a corridor has been established. Response variables related to occupancy were most relevant to conservation goals, but the lag time and costs to detect corridor effects on occupancy were much greater than the lag time and costs to detect corridor effects on gene flow. © 2014 Society for Conservation Biology.

How much does the time lag between wildlife field-data collection and LiDAR-data acquisition matter for studies of animal distributions? A case study using bird communities

Treesearch

Kerri T. Vierling; Charles E. Swift; Andrew T. Hudak; Jody C. Vogeler; Lee A. Vierling

2014-01-01

Vegetation structure quantified by light detection and ranging (LiDAR) can improve understanding of wildlife occupancy and species-richness patterns. However, there is often a time lag between the collection of LiDAR data and wildlife data. We investigated whether a time lag between the LiDAR acquisition and field-data acquisition affected mapped wildlife distributions...

[Are simple time lags responsible for cyclic variation of population density? : A comparison of laboratory population dynamics of Brachionus calyciflorus pallas (rotatoria) with computer simulations].

PubMed

Halbach, Udo; Burkhardt, Heinz Jürgen

1972-09-01

Laboratory populations of the rotifer Brachionus calyciflorus were cultured at different temperatures (25, 20, 15°C) but otherwise at constant conditions. The population densities showed relatively constant oscillations (Figs. 1 to 3A-C). Amplitudes and frequencies of the oscillations were positively correlated with temperature (Table 1). A test was made, whether the logistic growth function with simple time lag is able to describe the population curves. There are strong similarities between the simulations (Figs. 1-3E) and the real population dynamics if minor adjustments of the empirically determined parameters are made. There-fore it is suggested that time lags are responsible for the observed oscillations. However, the actual time lags probably do not act in the simple manner of the model, because birth and death rates react with different time lags, and both parameters are dependent on individual age and population density. A more complex model, which incorporates these modifications, should lead to a more realistic description of the observed oscillations.

Projective-anticipating, projective, and projective-lag synchronization of time-delayed chaotic systems on random networks.

PubMed

Feng, Cun-Fang; Xu, Xin-Jian; Wang, Sheng-Jun; Wang, Ying-Hai

2008-06-01

We study projective-anticipating, projective, and projective-lag synchronization of time-delayed chaotic systems on random networks. We relax some limitations of previous work, where projective-anticipating and projective-lag synchronization can be achieved only on two coupled chaotic systems. In this paper, we realize projective-anticipating and projective-lag synchronization on complex dynamical networks composed of a large number of interconnected components. At the same time, although previous work studied projective synchronization on complex dynamical networks, the dynamics of the nodes are coupled partially linear chaotic systems. In this paper, the dynamics of the nodes of the complex networks are time-delayed chaotic systems without the limitation of the partial linearity. Based on the Lyapunov stability theory, we suggest a generic method to achieve the projective-anticipating, projective, and projective-lag synchronization of time-delayed chaotic systems on random dynamical networks, and we find both its existence and sufficient stability conditions. The validity of the proposed method is demonstrated and verified by examining specific examples using Ikeda and Mackey-Glass systems on Erdos-Renyi networks.

Performance of FORTRAN floating-point operations on the Flex/32 multicomputer

NASA Technical Reports Server (NTRS)

Crockett, Thomas W.

1987-01-01

A series of experiments has been run to examine the floating-point performance of FORTRAN programs on the Flex/32 (Trademark) computer. The experiments are described, and the timing results are presented. The time required to execute a floating-point operation is found to vary considerbaly depending on a number of factors. One factor of particular interest from an algorithm design standpoint is the difference in speed between common memory accesses and local memory accesses. Common memory accesses were found to be slower, and guidelines are given for determinig when it may be cost effective to copy data from common to local memory.

To lag or not to lag? How to compare indices of stock markets that operate on different times

NASA Astrophysics Data System (ADS)

Sandoval, Leonidas

2014-06-01

Financial markets worldwide do not have the same working hours. As a consequence, the study of correlation or causality between financial market indices becomes dependent on whether we should use all indices on the same day or lagged indices in computations of correlation matrices. The answer this article proposes is that we should consider both, by representing original and lagged indices in the same network. We then obtain a better understanding of how indices that operate on different hours relate to each other. We use a diverse range of 79 stock market indices from around the world and study their correlation structure, the eigenvalues and eigenvectors of their correlations under different time periods and volatility, as well as the differences between the working hours of the stock exchanges in order to analyze the possible time zone effects and suggest ways to remove them. We also analyze the enlarged correlation matrix obtained from original and lagged indices and examine a network structure derived from it, thus showing connections between lagged and original indices that could not be well represented before.

First measurements with Argo flots in the Southern Baltic Sea

NASA Astrophysics Data System (ADS)

Walczowski, Waldemar; Goszczko, Ilona; Wieczorek, Piotr; Merchel, Malgorzata; Rak, Daniel

2017-04-01

The Argo programme is one of the most important elements of the ocean observing system. Currently almost 4000 Argo floats profile global oceans and deliver real time data. Originally Argo floats were developed for open ocean observations. Therefore a standard float can dive up to 2000 m and deep Argo floats are under development. However in the last years the shallow shelf seas become also interesting for Argo users. Institute of Oceanology Polish Academy of Sciences (IOPAN) participates in the Euro-Argo research infrastructure, the European contribution to Argo system. A legal and governance framework (Euro-Argo ERIC) was set up in May 2014. For a few years IOPAN has deployed floats mostly in the Nordic Seas and the European Arctic region. In the end of 2016 the first Polish Argo float was deployed in the Southern Baltic Sea. Building on the successful experience with Argo floats deployed by the Finnish oceanographers in the Bothnian Sea and Gotland Basin, the IOPAN float was launched in the Bornholm Deep during the fall cruise of IOPAN research vessel Oceania. The standard APEX float equipped with 2-way Iridium communication was used and different modes of operation, required for the specific conditions in the shallow and low saline Baltic Sea, were tested. Settings for the Baltic float are different than for the oceanic mode and were frequently changed during the mission to find the optimum solution. Changing the float parking depth during the mission allows for the limited control of the float drift direction. Results of a high resolution numerical forecast model for the Baltic Sea proved to be a valuable tool for determining the parking depth of the float in the different flow regimes. Trajectory and drift velocity of the Argo float deployed in the Southern Baltic depended strongly on the atmospheric forcing (in particular wind speed and direction), what was clearly manifested during the 'Axel' storm passing over the deployment area in January 2017. The first deployment showed clearly that Argo floats can be a useful tool for the Baltic Sea monitoring as the important element of a more complex, multidisciplinary observing system.

A new approach in gastroretentive drug delivery system using cholestyramine.

PubMed

Umamaheshwari, R B; Jain, Subheet; Jain, N K

2003-01-01

We prepared cellulose acetate butyrate (CAB)-coated cholestyramine microcapsules as a intragastric floating drug delivery system endowed with floating ability due to the carbon dioxide generation when exposed to the gastric fluid. The microcapsules also have a mucoadhesive property. Ion-exchange resin particles can be loaded with bicarbonate followed by acetohydroxamic acid (AHA) and coated with CAB by emulsion solvent evaporation method. The drug concentration was monitored to maintain the floating property and minimum effective concentration. The effect of CAB: drug-resin ratio (2:1, 4:1, 6:1 w/w) on the particle size, floating time, and drug release was determined. Cholestyramine microcapsules were characterized for shape, surface characteristics, and size distribution; cholestyramine/acetohydroxamic acid interactions inside microcapsules were investigated by X-ray diffractometry. The buoyancy time of CAB-coated formulations was better than that of uncoated resin particles. Also, a longer floating time was observed with a higher polymer:drug resin complex ratio (6:1). With increasing coating thickness the particle size was increased but drug release rate was decreased. The drug release rate was higher in simulated gastric fluid (SGF) than in simulated intestinal fluid (SIF). The in vivo mucoadhesion studies were performed with rhodamine-isothiocyanate (RITC) by fluorescent probe method. The amount of CAB-coated cholestyramine microcapsules that remained in the stomach was slightly lower than that of uncoated resin particles. Cholestyramine microcapsules were distributed throughout the stomach and exhibited prolonged gastric residence via mucoadhesion. These results suggest that CAB-coated microcapsules could be a floating as well as a mucoadhesive drug delivery system. Thus, it has promise in the treatment of Helicobacter pylori.

Intersection delay estimation from floating car data via principal curves: a case study on Beijing's road network

NASA Astrophysics Data System (ADS)

Liu, Xiliang; Lu, Feng; Zhang, Hengcai; Qiu, Peiyuan

2013-06-01

It is a pressing task to estimate the real-time travel time on road networks reliably in big cities, even though floating car data has been widely used to reflect the real traffic. Currently floating car data are mainly used to estimate the real-time traffic conditions on road segments, and has done little for turn delay estimation. However, turn delays on road intersections contribute significantly to the overall travel time on road networks in modern cities. In this paper, we present a technical framework to calculate the turn delays on road networks with float car data. First, the original floating car data collected with GPS equipped taxies was cleaned and matched to a street map with a distributed system based on Hadoop and MongoDB. Secondly, the refined trajectory data set was distributed among 96 time intervals (from 0: 00 to 23: 59). All of the intersections where the trajectories passed were connected with the trajectory segments, and constituted an experiment sample, while the intersections on arterial streets were specially selected to form another experiment sample. Thirdly, a principal curve-based algorithm was presented to estimate the turn delays at the given intersections. The algorithm argued is not only statistically fitted the real traffic conditions, but also is insensitive to data sparseness and missing data problems, which currently are almost inevitable with the widely used floating car data collecting technology. We adopted the floating car data collected from March to June in Beijing city in 2011, which contains more than 2.6 million trajectories generated from about 20000 GPS-equipped taxicabs and accounts for about 600 GB in data volume. The result shows the principal curve based algorithm we presented takes precedence over traditional methods, such as mean and median based approaches, and holds a higher estimation accuracy (about 10%-15% higher in RMSE), as well as reflecting the changing trend of traffic congestion. With the estimation result for the travel delay at intersections, we analyzed the spatio-temporal distribution of turn delays in three time scenarios (0: 00-0: 15, 8: 15-8: 30 and 12: 00-12: 15). It indicates that during one's single trip in Beijing, average 60% of the travel time on the road networks is wasted on the intersections, and this situation is even worse in daytime. Although the 400 main intersections take only 2.7% of all the intersections, they occupy about 18% travel time.

Observations of Transient ISS Floating Potential Variations During High Voltage Solar Array Operations

NASA Technical Reports Server (NTRS)

Willis, Emily M.; Minow, Joseph I.; Parker, Linda N.; Pour, Maria Z. A.; Swenson, Charles; Nishikawa, Ken-ichi; Krause, Linda Habash

2016-01-01

The International Space Station (ISS) continues to be a world-class space research laboratory after over 15 years of operations, and it has proven to be a fantastic resource for observing spacecraft floating potential variations related to high voltage solar array operations in Low Earth Orbit (LEO). Measurements of the ionospheric electron density and temperature along the ISS orbit and variations in the ISS floating potential are obtained from the Floating Potential Measurement Unit (FPMU). In particular, rapid variations in ISS floating potential during solar array operations on time scales of tens of milliseconds can be recorded due to the 128 Hz sample rate of the Floating Potential Probe (FPP) pro- viding interesting insight into high voltage solar array interaction with the space plasma environment. Comparing the FPMU data with the ISS operations timeline and solar array data provides a means for correlating some of the more complex and interesting transient floating potential variations with mission operations. These complex variations are not reproduced by current models and require further study to understand the underlying physical processes. In this paper we present some of the floating potential transients observed over the past few years along with the relevant space environment parameters and solar array operations data.

[Further study on possibility of diffusion of Oncomelania hupensis with water in river channels of the east route of South-to-North Water Diversion Project].

PubMed

Huang, Yi-Xin; Hang, De-Rong; Tang, Hong-Ping; Sun, Dao-Kuan; Zhou, Can-Hua; Gao, Jin-Bin; Zheng, Bo; Hu, Gui-Quan; Li, Qian; Huang, Yong-Jun; She, Guang-Song; Ren, Zhi-Yuan

2014-12-01

To study the drifting law of floats and potential risks of Oncomelania hupensis diffusion in the water diversion rivers of the east route of South-to-North Water Diversion Project. The O. hupensis snails in the river channels were monitored by the salvage method and snail luring method with rice straw curtains, and the diffusion possibility of snails along with water was assessed through the drift test of floats with GPS. In the flood seasons from 2006 to 2013, totally 8 338.0 kg of floats were salvaged, and 2 100 rice straw curtains were put into water in the Li Canal and Jinbao shipping channel, but no Oncomelania snails were found. The drift test of floats with GPS before water diversion showed that the flow velocity on water surface (northbound) was 0.45 m/s, the average drift velocity of the floats was 0.56 - 0.60 m/s, and the average drift distances each time were 999.70 - 1 995.50 m in the Gaoshui River section, while there were no obvious drift in Jinbao shipping channel section. During the water diversion period, the flow velocity on water surface (northbound) was 0.45 m/s, the average drift velocity of the floats was 0.35 - 0.41m/s, and the average drift distances each time were 1 248.06 -1 289.44 m in the Gaoshui River, while in Jinbao shipping channel section, the flow velocity on water surface was 0.28 m/s, the average drift velocity of the floats was 0.25 - 0.27 m/s, and the average drift distances each time were 477.76 - 496.38 m. The drift test showed that the floats gradually closed to the river bank as affected by water flow, wind direction and ship waves, when blocked by the reeds, water plants or other obstacles, and they would stopped and could not continue to drift without outside help. There are no Oncomelania snails found in the river channels of the east route of South-to-North Water Diversion Project. The drifting distance of the floating debris along with the water is restricted by the flow rate and shore environment.

Catchment Legacies and Time Lags: A Parsimonious Watershed Model to Predict the Effects of Legacy Storage on Nitrogen Export

PubMed Central

Van Meter, Kimberly J.; Basu, Nandita B.

2015-01-01

Nutrient legacies in anthropogenic landscapes, accumulated over decades of fertilizer application, lead to time lags between implementation of conservation measures and improvements in water quality. Quantification of such time lags has remained difficult, however, due to an incomplete understanding of controls on nutrient depletion trajectories after changes in land-use or management practices. In this study, we have developed a parsimonious watershed model for quantifying catchment-scale time lags based on both soil nutrient accumulations (biogeochemical legacy) and groundwater travel time distributions (hydrologic legacy). The model accurately predicted the time lags observed in an Iowa watershed that had undergone a 41% conversion of area from row crop to native prairie. We explored the time scales of change for stream nutrient concentrations as a function of both natural and anthropogenic controls, from topography to spatial patterns of land-use change. Our results demonstrate that the existence of biogeochemical nutrient legacies increases time lags beyond those due to hydrologic legacy alone. In addition, we show that the maximum concentration reduction benefits vary according to the spatial pattern of intervention, with preferential conversion of land parcels having the shortest catchment-scale travel times providing proportionally greater concentration reductions as well as faster response times. In contrast, a random pattern of conversion results in a 1:1 relationship between percent land conversion and percent concentration reduction, irrespective of denitrification rates within the landscape. Our modeling framework allows for the quantification of tradeoffs between costs associated with implementation of conservation measures and the time needed to see the desired concentration reductions, making it of great value to decision makers regarding optimal implementation of watershed conservation measures. PMID:25985290

Catchment legacies and time lags: a parsimonious watershed model to predict the effects of legacy storage on nitrogen export.

PubMed

Van Meter, Kimberly J; Basu, Nandita B

2015-01-01

Nutrient legacies in anthropogenic landscapes, accumulated over decades of fertilizer application, lead to time lags between implementation of conservation measures and improvements in water quality. Quantification of such time lags has remained difficult, however, due to an incomplete understanding of controls on nutrient depletion trajectories after changes in land-use or management practices. In this study, we have developed a parsimonious watershed model for quantifying catchment-scale time lags based on both soil nutrient accumulations (biogeochemical legacy) and groundwater travel time distributions (hydrologic legacy). The model accurately predicted the time lags observed in an Iowa watershed that had undergone a 41% conversion of area from row crop to native prairie. We explored the time scales of change for stream nutrient concentrations as a function of both natural and anthropogenic controls, from topography to spatial patterns of land-use change. Our results demonstrate that the existence of biogeochemical nutrient legacies increases time lags beyond those due to hydrologic legacy alone. In addition, we show that the maximum concentration reduction benefits vary according to the spatial pattern of intervention, with preferential conversion of land parcels having the shortest catchment-scale travel times providing proportionally greater concentration reductions as well as faster response times. In contrast, a random pattern of conversion results in a 1:1 relationship between percent land conversion and percent concentration reduction, irrespective of denitrification rates within the landscape. Our modeling framework allows for the quantification of tradeoffs between costs associated with implementation of conservation measures and the time needed to see the desired concentration reductions, making it of great value to decision makers regarding optimal implementation of watershed conservation measures.

Reentrainment of the circadian pacemaker during jet lag: East-west asymmetry and the effects of north-south travel.

PubMed

Diekman, Casey O; Bose, Amitabha

2018-01-21

The normal alignment of circadian rhythms with the 24-h light-dark cycle is disrupted after rapid travel between home and destination time zones, leading to sleep problems, indigestion, and other symptoms collectively known as jet lag. Using mathematical and computational analysis, we study the process of reentrainment to the light-dark cycle of the destination time zone in a model of the human circadian pacemaker. We calculate the reentrainment time for travel between any two points on the globe at any time of the day and year. We construct one-dimensional entrainment maps to explain several properties of jet lag, such as why most people experience worse jet lag after traveling east than west. We show that this east-west asymmetry depends on the endogenous period of the traveler's circadian clock as well as daylength. Thus the critical factor is not simply whether the endogenous period is greater than or less than 24 h as is commonly assumed. We show that the unstable fixed point of an entrainment map determines whether a traveler reentrains through phase advances or phase delays, providing an understanding of the threshold that separates orthodromic and antidromic modes of reentrainment. Contrary to the conventional wisdom that jet lag only occurs after east-west travel across multiple time zones, we predict that the change in daylength encountered during north-south travel can cause jet lag even when no time zones are crossed. Our techniques could be used to provide advice to travelers on how to minimize jet lag on trips involving multiple destinations and a combination of transmeridian and translatitudinal travel. Copyright © 2017 Elsevier Ltd. All rights reserved.

Technical Note: High temporal resolution characterization of gating response time.

PubMed

Wiersma, Rodney D; McCabe, Bradley P; Belcher, Andrew H; Jensen, Patrick J; Smith, Brett; Aydogan, Bulent

2016-06-01

Low temporal latency between a gating ON/OFF signal and the LINAC beam ON/OFF during respiratory gating is critical for patient safety. Here the authors describe a novel method to precisely measure gating lag times at high temporal resolutions. A respiratory gating simulator with an oscillating platform was modified to include a linear potentiometer for position measurement. A photon diode was placed at linear accelerator isocenter for beam output measurement. The output signals of the potentiometer and diode were recorded simultaneously at 2500 Hz with an analog to digital converter for four different commercial respiratory gating systems. The ON and OFF of the beam signal were located and compared to the expected gating window for both phase and position based gating and the temporal lag times extracted. For phase based gating, a real-time position management (RPM) infrared marker tracking system with a single camera and a RPM system with a stereoscopic camera were measured to have mean gate ON/OFF lag times of 98/90 and 86/44 ms, respectively. For position based gating, an AlignRT 3D surface system and a Calypso magnetic fiducial tracking system were measured to have mean gate ON/OFF lag times of 356/529 and 209/60 ms, respectively. Temporal resolution of the method was high enough to allow characterization of individual gate cycles and was primary limited by the sampling speed of the data recording device. Significant variation of mean gate ON/OFF lag time was found between different gating systems. For certain gating devices, individual gating cycle lag times can vary significantly.

Technical Note: High temporal resolution characterization of gating response time

PubMed Central

Wiersma, Rodney D.; McCabe, Bradley P.; Belcher, Andrew H.; Jensen, Patrick J.; Smith, Brett; Aydogan, Bulent

2016-01-01

Purpose: Low temporal latency between a gating ON/OFF signal and the LINAC beam ON/OFF during respiratory gating is critical for patient safety. Here the authors describe a novel method to precisely measure gating lag times at high temporal resolutions. Methods: A respiratory gating simulator with an oscillating platform was modified to include a linear potentiometer for position measurement. A photon diode was placed at linear accelerator isocenter for beam output measurement. The output signals of the potentiometer and diode were recorded simultaneously at 2500 Hz with an analog to digital converter for four different commercial respiratory gating systems. The ON and OFF of the beam signal were located and compared to the expected gating window for both phase and position based gating and the temporal lag times extracted. Results: For phase based gating, a real-time position management (RPM) infrared marker tracking system with a single camera and a RPM system with a stereoscopic camera were measured to have mean gate ON/OFF lag times of 98/90 and 86/44 ms, respectively. For position based gating, an AlignRT 3D surface system and a Calypso magnetic fiducial tracking system were measured to have mean gate ON/OFF lag times of 356/529 and 209/60 ms, respectively. Conclusions: Temporal resolution of the method was high enough to allow characterization of individual gate cycles and was primary limited by the sampling speed of the data recording device. Significant variation of mean gate ON/OFF lag time was found between different gating systems. For certain gating devices, individual gating cycle lag times can vary significantly. PMID:27277028

Recent Shift in Climate Relationship Enables Prediction of the Timing of Bird Breeding

PubMed Central

Bellamy, Paul E.; Hill, Ross A.; Ferns, Peter N.

2016-01-01

Large-scale climate processes influence many aspects of ecology including breeding phenology, reproductive success and survival across a wide range of taxa. Some effects are direct, for example, in temperate-zone birds, ambient temperature is an important cue enabling breeding effort to coincide with maximum food availability, and earlier breeding in response to warmer springs has been documented in many species. In other cases, time-lags of up to several years in ecological responses have been reported, with effects mediated through biotic mechanisms such as growth rates or abundance of food supplies. Here we use 23 years of data for a temperate woodland bird species, the great tit (Parus major), breeding in deciduous woodland in eastern England to demonstrate a time-lagged linear relationship between the on-set of egg laying and the winter index of the North Atlantic Oscillation such that timing can be predicted from the winter index for the previous year. Thus the timing of bird breeding (and, by inference, the timing of spring events in general) can be predicted one year in advance. We also show that the relationship with the winter index appears to arise through an abiotic time-lag with local spring warmth in our study area. Examining this link between local conditions and larger-scale processes in the longer-term showed that, in the past, significant relationships with the immediately preceding winter index were more common than those with the time-lagged index, and especially so from the late 1930s to the early 1970s. However, from the mid 1970s onwards, the time-lagged relationship has become the most significant, suggesting a recent change in climate patterns. The strength of the current time-lagged relationship suggests that it might have relevance for other temperature-dependent ecological relationships. PMID:27182711

Automatic detection of Floating Ice at Antarctic Continental Margin from Remotely Sensed Image with Object-oriented Matching

NASA Astrophysics Data System (ADS)

Zhao, Z.

2011-12-01

Changes in ice sheet and floating ices around that have great significance for global change research. In the context of global warming, rapidly changing of Antarctic continental margin, caving of ice shelves, movement of iceberg are all closely related to climate change and ocean circulation. Using automatic change detection technology to rapid positioning the melting Region of Polar ice sheet and the location of ice drift would not only strong support for Global Change Research but also lay the foundation for establishing early warning mechanism for melting of the polar ice and Ice displacement. This paper proposed an automatic change detection method using object-based segmentation technology. The process includes three parts: ice extraction using image segmentation, object-baed ice tracking, change detection based on similarity matching. An approach based on similarity matching of eigenvector is proposed in this paper, which used area, perimeter, Hausdorff distance, contour, shape and other information of each ice-object. Different time of LANDSAT ETM+ data, Chinese environment disaster satellite HJ1B date, MODIS 1B date are used to detect changes of Floating ice at Antarctic continental margin respectively. We select different time of ETM+ data(January 7, 2003 and January 16, 2003) with the area around Antarctic continental margin near the Lazarev Bay, which is from 70.27454853 degrees south latitude, longitude 12.38573410 degrees to 71.44474167 degrees south latitude, longitude 10.39252222 degrees,included 11628 sq km of Antarctic continental margin area, as a sample. Then we can obtain the area of floating ices reduced 371km2, and the number of them reduced 402 during the time. In addition, the changes of all the floating ices around the margin region of Antarctic within 1200 km are detected using MODIS 1B data. During the time from January 1, 2008 to January 7, 2008, the floating ice area decreased by 21644732 km2, and the number of them reduced by 83080. The results show that the object-based information extraction algorithm can obtain more precise details of a single object, while the change detection method based on similarity matching can effectively tracking the change of floating ice.

Patterns of Activity in A Global Model of A Solar Active Region

NASA Technical Reports Server (NTRS)

Bradshaw, S. J.; Viall, N. M.

2016-01-01

In this work we investigate the global activity patterns predicted from a model active region heated by distributions of nanoflares that have a range of frequencies. What differs is the average frequency of the distributions. The activity patterns are manifested in time lag maps of narrow-band instrument channel pairs. We combine hydrodynamic and forward modeling codes with a magnetic field extrapolation to create a model active region and apply the time lag method to synthetic observations. Our aim is not to reproduce a particular set of observations in detail, but to recover some typical properties and patterns observed in active regions. Our key findings are the following. (1) Cooling dominates the time lag signature and the time lags between the channel pairs are generally consistent with observed values. (2) Shorter coronal loops in the core cool more quickly than longer loops at the periphery. (3) All channel pairs show zero time lag when the line of sight passes through coronal loop footpoints. (4) There is strong evidence that plasma must be re-energized on a timescale comparable to the cooling timescale to reproduce the observed coronal activity, but it is likely that a relatively broad spectrum of heating frequencies are operating across active regions. (5) Due to their highly dynamic nature, we find nanoflare trains produce zero time lags along entire flux tubes in our model active region that are seen between the same channel pairs in observed active regions.

Improving energy efficiency in handheld biometric applications

NASA Astrophysics Data System (ADS)

Hoyle, David C.; Gale, John W.; Schultz, Robert C.; Rakvic, Ryan N.; Ives, Robert W.

2012-06-01

With improved smartphone and tablet technology, it is becoming increasingly feasible to implement powerful biometric recognition algorithms on portable devices. Typical iris recognition algorithms, such as Ridge Energy Direction (RED), utilize two-dimensional convolution in their implementation. This paper explores the energy consumption implications of 12 different methods of implementing two-dimensional convolution on a portable device. Typically, convolution is implemented using floating point operations. If a given algorithm implemented integer convolution vice floating point convolution, it could drastically reduce the energy consumed by the processor. The 12 methods compared include 4 major categories: Integer C, Integer Java, Floating Point C, and Floating Point Java. Each major category is further divided into 3 implementations: variable size looped convolution, static size looped convolution, and unrolled looped convolution. All testing was performed using the HTC Thunderbolt with energy measured directly using a Tektronix TDS5104B Digital Phosphor oscilloscope. Results indicate that energy savings as high as 75% are possible by using Integer C versus Floating Point C. Considering the relative proportion of processing time that convolution is responsible for in a typical algorithm, the savings in energy would likely result in significantly greater time between battery charges.

Air-Deployable Profiling Floats for Tropical Cyclone Research

NASA Astrophysics Data System (ADS)

Jayne, S. R.; Robbins, P.; Owens, B.; Ekholm, A.; Dufour, J. E.; Sanabia, E.

2016-02-01

The development of a smaller profiling float that can be launched from Hurricane Hunter aircraft offers the opportunity to monitor the upper-ocean thermal structure over a time span of many months. These Argo-type profiling floats can be deployed in advance of, or during, a tropical cyclone from any aircraft equipped with an A-sized (AXBT) launch tube, or from the stern ramp of a C-130. The floats have the same dimensions as an AXBT and weigh about 8.5 kg. Upon deployment, the floats parachute to the surface, detach and automatically begin their programmed mission. The recorded temperature data is averaged over 1-meter bins that are reported back via the Iridium satellite phone network, which is then automatically processed and posted to the GTS. The floats are also reprogrammable via the 2-way communication afforded by Iridium. We report on the results of deployments during the 2014 and 2015 hurricane seasons. Unique observations of the ocean response from Hurricane Ignacio are particularly noteworthy and will be presented. Further plans for continued development of floats include measuring salinity (from an inductive conductivity sensor) and observations of the surface wave field (measured by an onboard accelerometer) will also be described.

Eddy-covariance data with low signal-to-noise ratio: time-lag determination, uncertainties and limit of detection

NASA Astrophysics Data System (ADS)

Langford, B.; Acton, W.; Ammann, C.; Valach, A.; Nemitz, E.

2015-10-01

All eddy-covariance flux measurements are associated with random uncertainties which are a combination of sampling error due to natural variability in turbulence and sensor noise. The former is the principal error for systems where the signal-to-noise ratio of the analyser is high, as is usually the case when measuring fluxes of heat, CO2 or H2O. Where signal is limited, which is often the case for measurements of other trace gases and aerosols, instrument uncertainties dominate. Here, we are applying a consistent approach based on auto- and cross-covariance functions to quantify the total random flux error and the random error due to instrument noise separately. As with previous approaches, the random error quantification assumes that the time lag between wind and concentration measurement is known. However, if combined with commonly used automated methods that identify the individual time lag by looking for the maximum in the cross-covariance function of the two entities, analyser noise additionally leads to a systematic bias in the fluxes. Combining data sets from several analysers and using simulations, we show that the method of time-lag determination becomes increasingly important as the magnitude of the instrument error approaches that of the sampling error. The flux bias can be particularly significant for disjunct data, whereas using a prescribed time lag eliminates these effects (provided the time lag does not fluctuate unduly over time). We also demonstrate that when sampling at higher elevations, where low frequency turbulence dominates and covariance peaks are broader, both the probability and magnitude of bias are magnified. We show that the statistical significance of noisy flux data can be increased (limit of detection can be decreased) by appropriate averaging of individual fluxes, but only if systematic biases are avoided by using a prescribed time lag. Finally, we make recommendations for the analysis and reporting of data with low signal-to-noise and their associated errors.

Eddy-covariance data with low signal-to-noise ratio: time-lag determination, uncertainties and limit of detection

NASA Astrophysics Data System (ADS)

Langford, B.; Acton, W.; Ammann, C.; Valach, A.; Nemitz, E.

2015-03-01

All eddy-covariance flux measurements are associated with random uncertainties which are a combination of sampling error due to natural variability in turbulence and sensor noise. The former is the principal error for systems where the signal-to-noise ratio of the analyser is high, as is usually the case when measuring fluxes of heat, CO2 or H2O. Where signal is limited, which is often the case for measurements of other trace gases and aerosols, instrument uncertainties dominate. We are here applying a consistent approach based on auto- and cross-covariance functions to quantifying the total random flux error and the random error due to instrument noise separately. As with previous approaches, the random error quantification assumes that the time-lag between wind and concentration measurement is known. However, if combined with commonly used automated methods that identify the individual time-lag by looking for the maximum in the cross-covariance function of the two entities, analyser noise additionally leads to a systematic bias in the fluxes. Combining datasets from several analysers and using simulations we show that the method of time-lag determination becomes increasingly important as the magnitude of the instrument error approaches that of the sampling error. The flux bias can be particularly significant for disjunct data, whereas using a prescribed time-lag eliminates these effects (provided the time-lag does not fluctuate unduly over time). We also demonstrate that when sampling at higher elevations, where low frequency turbulence dominates and covariance peaks are broader, both the probability and magnitude of bias are magnified. We show that the statistical significance of noisy flux data can be increased (limit of detection can be decreased) by appropriate averaging of individual fluxes, but only if systematic biases are avoided by using a prescribed time-lag. Finally, we make recommendations for the analysis and reporting of data with low signal-to-noise and their associated errors.

Stratification by cyanobacteria in lakes: a dynamic buoyancy model indicates size limitations met by Planktothrix rubescens filaments.

PubMed

Walsby, Anthony E

2005-11-01

The ability of the Planktothrix rubescens to stratify in Lake Zürich is related to the size and shape of the cyanobacterial filaments. Detailed measurements made in the lake are used in a dynamic computer model of buoyancy regulation to investigate the vertical movements of filaments tracking the depth at which the irradiance would support neutral buoyancy. The movement of the filament lags behind the constantly changing target depth owing to (a) the time taken for the filament to respond to the irradiance by changing its density and (b) the time it takes to move by sinking down or floating up through the water column. The model simulates the stratification depth over a 5-month period of the summer from the continuous measurements of irradiance and weekly measurements of light attenuation and temperature, without any further adjustment over the period. Models using filaments of the size observed in Lake Zürich explain several details of the observed depth changes: smaller planktonic cyanobacteria (e.g. Limnothrix sp.) are unable to migrate fast enough and larger ones (e.g. Anabaena spp.) will overshoot and become entrained in the epilimnion. The model can be used to simulate recruitment of Planktothrix filaments from different depths after vernal stratification. Recruitment of filaments from depths down to 45 m will contribute to the metalimnetic population increase in early July.

Gastroretentive extended-release floating granules prepared using a novel fluidized hot melt granulation (FHMG) technique.

PubMed

Zhai, H; Jones, D S; McCoy, C P; Madi, A M; Tian, Y; Andrews, G P

2014-10-06

The objective of this work was to investigate the feasibility of using a novel granulation technique, namely, fluidized hot melt granulation (FHMG), to prepare gastroretentive extended-release floating granules. In this study we have utilized FHMG, a solvent free process in which granulation is achieved with the aid of low melting point materials, using Compritol 888 ATO and Gelucire 50/13 as meltable binders, in place of conventional liquid binders. The physicochemical properties, morphology, floating properties, and drug release of the manufactured granules were investigated. Granules prepared by this method were spherical in shape and showed good flowability. The floating granules exhibited sustained release exceeding 10 h. Granule buoyancy (floating time and strength) and drug release properties were significantly influenced by formulation variables such as excipient type and concentration, and the physical characteristics (particle size, hydrophilicity) of the excipients. Drug release rate was increased by increasing the concentration of hydroxypropyl cellulose (HPC) and Gelucire 50/13, or by decreasing the particle size of HPC. Floating strength was improved through the incorporation of sodium bicarbonate and citric acid. Furthermore, floating strength was influenced by the concentration of HPC within the formulation. Granules prepared in this way show good physical characteristics, floating ability, and drug release properties when placed in simulated gastric fluid. Moreover, the drug release and floating properties can be controlled by modification of the ratio or physical characteristics of the excipients used in the formulation.

Short-term effects of floods on Japanese encephalitis in Nanchong, China, 2007-2012: A time-stratified case-crossover study.

PubMed

Zhang, Feifei; Liu, Zhidong; Zhang, Caixia; Jiang, Baofa

2016-09-01

This time-stratified case-crossover study aimed to quantify the impact of floods on daily Japanese encephalitis (JE) cases from 2007 to 2012 in Nanchong city of Sichuan Province, China. Using conditional logistic regression analysis, we calculated the odds ratios (ORs) and 95% confidence intervals (CIs) at different lagged days, adjusting for daily average temperature (AT) and daily average relative humidity (ARH). A total of 370 JE cases were notified during the study period, with the median patient age being 4.2years. The seasonal pattern of JE cases clustered in July and August during the study period. Floods were significantly associated with an increased number of JE cases from lag 23 to lag 24, with the strongest lag effect at lag 23 (OR=2.00, 95% CI: 1.14-3.52). Similarly, AT and ARH were positively associated with daily JE cases from lag 0 to lag 8 and from lag 0 to lag 9, respectively. Floods, with AT and ARH, can be used to forecast JE outbreaks in the study area. Based on the results of this study, recommendations include undertaking control measures before the number of cases increases, especially for regions with similar geographic, climatic, and socio-economic conditions as those in the study area. Copyright © 2016 Elsevier B.V. All rights reserved.

Free float and stochastic volatility: the experience of a small open economy

NASA Astrophysics Data System (ADS)

Selçuk, Faruk

2004-11-01

Following a dramatic collapse of a fixed exchange rate based inflation stabilization program, Turkey moved into a free floating exchange rate system in February 2001. In this paper, an asymmetric stochastic volatility model of the foreign exchange rate in Turkey is estimated for the floating period. It is shown that there is a positive relation between the exchange return and its volatility. Particularly, an increase in the return at time t results in an increase in volatility at time t+1. However, the effect is asymmetric: a decrease in the exchange rate return at time t causes a relatively less decrease in volatility at time t+1. The results imply that a central bank with a volatility smoothing policy would be biased in viewing the shocks to the exchange rate in favor of appreciation. The bias would increase if the bank is also following an inflation targeting policy.

The Measurement of Pressure Through Tubes in Pressure Distribution Tests

NASA Technical Reports Server (NTRS)

Hemke, Paul E

1928-01-01

The tests described in this report were made to determine the error caused by using small tubes to connect orifices on the surface of aircraft to central pressure capsules in making pressure distribution tests. Aluminum tubes of 3/16-inch inside diameter were used to determine this error. Lengths from 20 feet to 226 feet and pressures whose maxima varied from 2 inches to 140 inches of water were used. Single-pressure impulses for which the time of rise of pressure from zero to a maximum varied from 0.25 second to 3 seconds were investigated. The results show that the pressure recorded at the capsule on the far end of the tube lags behind the pressure at the orifice end and experiences also a change in magnitude. For the values used in these tests the time lag and pressure change vary principally with the time of rise of pressure from zero to a maximum and the tube length. Curves are constructed showing the time lag and pressure change. Empirical formulas are also given for computing the time lag. Analysis of pressure distribution tests made on airplanes in flight shows that the recorded pressures are slightly higher than the pressures at the orifice and that the time lag is negligible. The apparent increase in pressure is usually within the experimental error, but in the case of the modern pursuit type of airplane the pressure increase may be 5 per cent. For pressure-distribution tests on airships the analysis shows that the time lag and pressure change may be neglected.

Time-lagged response of the Antarctic atmosphere to tropical MJO convection

NASA Astrophysics Data System (ADS)

Henderson, G. R.; Barrett, B.

2017-12-01

Intraseasonal tropical climate variability has important implications on mid- and high- latitude climate, and in recent studies has been shown to modulate a number of weather processes in the Northern Hemisphere, such as snow depth, sea ice concentration, precipitation, atmospheric rivers, and air temperature. In such studies, the leading mode of tropical intraseasonal variability, the Madden-Julian Oscillation (MJO), has tended to lag tropical convection by approximately 7 days. However, no such consensus exists when considering the relationship and lag between the MJO and the Antarctic atmosphere. This study builds on previous work by further examining the time-lagged response of Southern Hemisphere tropospheric circulation to tropical MJO forcing, with specific focus on the latitude belt associated with the Antarctic Oscillation, during the months of June (Austral winter) and December (Austral summer) using NCEP-DOE Reanalysis 2 data for the years 1970-2016. Principal findings indicate that the time lag with strongest height anomalies depends on both the location of the MJO convection (e.g., the MJO phase) and the season, and that the lagged height anomalies in the Antarctic atmosphere are fairly consistent across different vertical levels and latitudinal bands. In addition, certain MJO phases in December displayed lagged height anomalies indicative of blocking-type atmospheric patterns, with an approximate wavenumber of 4, whereas in June most phases were associated with progressive height anomaly centers displaying a wavenumber-3 type pattern.

Oceanic and atmospheric conditions associated with the pentad rainfall over the southeastern peninsular India during the North-East Indian Monsoon season

NASA Astrophysics Data System (ADS)

Shanmugasundaram, Jothiganesh; Lee, Eungul

2018-03-01

The association of North-East Indian Monsoon rainfall (NEIMR) over the southeastern peninsular India with the oceanic and atmospheric conditions over the adjacent ocean regions at pentad time step (five days period) was investigated during the months of October to December for the period 1985-2014. The non-parametric correlation and composite analyses were carried out for the simultaneous and lagged time steps (up to four lags) of oceanic and atmospheric variables with pentad NEIMR. The results indicated that NEIMR was significantly correlated: 1) positively with both sea surface temperature (SST) led by 1-4 pentads (lag 1-4 time steps) and latent heat flux (LHF) during the simultaneous, lag 1 and 2 time steps over the equatorial western Indian Ocean, 2) positively with SST but negatively with LHF (less heat flux from ocean to atmosphere) during the same and all the lagged time steps over the Bay of Bengal. Consistently, during the wet NEIMR pentads over the southeastern peninsular India, SST significantly increased over the Bay of Bengal during all the time steps and the equatorial western Indian Ocean during the lag 2-4 time steps, while the LHF decreased over the Bay of Bengal (all time steps) and increased over the Indian Ocean (same, lag 1 and 2). The investigation on ocean-atmospheric interaction revealed that the enhanced LHF over the equatorial western Indian Ocean was related to increased atmospheric moisture demand and increased wind speed, whereas the reduced LHF over the Bay of Bengal was associated with decreased atmospheric moisture demand and decreased wind speed. The vertically integrated moisture flux and moisture transport vectors from 1000 to 850 hPa exhibited that the moisture was carried away from the equatorial western Indian Ocean to the strong moisture convergence regions of the Bay of Bengal during the same and lag 1 time steps of wet NEIMR pentads. Further, the moisture over the Bay of Bengal was transported to the southeastern peninsular India through stronger cyclonic circulations, which were confirmed by the moisture transport vectors and positive vorticity. The identified ocean and atmosphere processes, associated with the wet NEIMR conditions, could be a valuable scientific input for enhancing the rainfall predictability, which has a huge socioeconomic value to agriculture and water resource management sectors in the southeastern peninsular India.

A comparison of methods for estimating open-water evaporation in small wetlands

USGS Publications Warehouse

Masoner, Jason R.; Stannard, David I.

2010-01-01

We compared evaporation measurements from a floating pan, land pan, chamber, and the Priestley-Taylor (PT) equation. Floating pan, land pan, and meteorological data were collected from June 6 to July 21, 2005, at a small wetland in the Canadian River alluvium in central Oklahoma, USA. Evaporation measured with the floating pan compared favorably to 12 h chamber measurements. Differences between chamber and floating pan rates ranged from −0.2 to 0.3 mm, mean of 0.1 mm. The difference between chamber and land pan rates ranged from 0.8 to 2.0 mm, mean of 1.5 mm. The mean chamber-to-floating pan ratio was 0.97 and the mean chamber-to-land pan ratio was 0.73. The chamber-to-floating pan ratio of 0.97 indicates the use of a floating pan to measure evaporation in small limited-fetch water bodies is an appropriate and accurate method for the site investigated. One-sided Paired t-Tests indicate daily floating pan rates were significantly less than land pan and PT rates. A two-sided Paired t-Test indicated there was no significant difference between land pan and PT values. The PT equation tends to overestimate evaporation during times when the air is of low drying power and tends to underestimate as drying power increases.

Combined GPS/GLONASS Precise Point Positioning with Fixed GPS Ambiguities

PubMed Central

Pan, Lin; Cai, Changsheng; Santerre, Rock; Zhu, Jianjun

2014-01-01

Precise point positioning (PPP) technology is mostly implemented with an ambiguity-float solution. Its performance may be further improved by performing ambiguity-fixed resolution. Currently, the PPP integer ambiguity resolutions (IARs) are mainly based on GPS-only measurements. The integration of GPS and GLONASS can speed up the convergence and increase the accuracy of float ambiguity estimates, which contributes to enhancing the success rate and reliability of fixing ambiguities. This paper presents an approach of combined GPS/GLONASS PPP with fixed GPS ambiguities (GGPPP-FGA) in which GPS ambiguities are fixed into integers, while all GLONASS ambiguities are kept as float values. An improved minimum constellation method (MCM) is proposed to enhance the efficiency of GPS ambiguity fixing. Datasets from 20 globally distributed stations on two consecutive days are employed to investigate the performance of the GGPPP-FGA, including the positioning accuracy, convergence time and the time to first fix (TTFF). All datasets are processed for a time span of three hours in three scenarios, i.e., the GPS ambiguity-float solution, the GPS ambiguity-fixed resolution and the GGPPP-FGA resolution. The results indicate that the performance of the GPS ambiguity-fixed resolutions is significantly better than that of the GPS ambiguity-float solutions. In addition, the GGPPP-FGA improves the positioning accuracy by 38%, 25% and 44% and reduces the convergence time by 36%, 36% and 29% in the east, north and up coordinate components over the GPS-only ambiguity-fixed resolutions, respectively. Moreover, the TTFF is reduced by 27% after adding GLONASS observations. Wilcoxon rank sum tests and chi-square two-sample tests are made to examine the significance of the improvement on the positioning accuracy, convergence time and TTFF. PMID:25237901

Technical Note: High temporal resolution characterization of gating response time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiersma, Rodney D., E-mail: rwiersma@uchicago.edu; McCabe, Bradley P.; Belcher, Andrew H.

2016-06-15

Purpose: Low temporal latency between a gating ON/OFF signal and the LINAC beam ON/OFF during respiratory gating is critical for patient safety. Here the authors describe a novel method to precisely measure gating lag times at high temporal resolutions. Methods: A respiratory gating simulator with an oscillating platform was modified to include a linear potentiometer for position measurement. A photon diode was placed at linear accelerator isocenter for beam output measurement. The output signals of the potentiometer and diode were recorded simultaneously at 2500 Hz with an analog to digital converter for four different commercial respiratory gating systems. The ONmore » and OFF of the beam signal were located and compared to the expected gating window for both phase and position based gating and the temporal lag times extracted. Results: For phase based gating, a real-time position management (RPM) infrared marker tracking system with a single camera and a RPM system with a stereoscopic camera were measured to have mean gate ON/OFF lag times of 98/90 and 86/44 ms, respectively. For position based gating, an AlignRT 3D surface system and a Calypso magnetic fiducial tracking system were measured to have mean gate ON/OFF lag times of 356/529 and 209/60 ms, respectively. Conclusions: Temporal resolution of the method was high enough to allow characterization of individual gate cycles and was primary limited by the sampling speed of the data recording device. Significant variation of mean gate ON/OFF lag time was found between different gating systems. For certain gating devices, individual gating cycle lag times can vary significantly.« less

Theory for Transitions Between Exponential and Stationary Phases: Universal Laws for Lag Time

NASA Astrophysics Data System (ADS)

Himeoka, Yusuke; Kaneko, Kunihiko

2017-04-01

The quantitative characterization of bacterial growth has attracted substantial attention since Monod's pioneering study. Theoretical and experimental works have uncovered several laws for describing the exponential growth phase, in which the number of cells grows exponentially. However, microorganism growth also exhibits lag, stationary, and death phases under starvation conditions, in which cell growth is highly suppressed, for which quantitative laws or theories are markedly underdeveloped. In fact, the models commonly adopted for the exponential phase that consist of autocatalytic chemical components, including ribosomes, can only show exponential growth or decay in a population; thus, phases that halt growth are not realized. Here, we propose a simple, coarse-grained cell model that includes an extra class of macromolecular components in addition to the autocatalytic active components that facilitate cellular growth. These extra components form a complex with the active components to inhibit the catalytic process. Depending on the nutrient condition, the model exhibits typical transitions among the lag, exponential, stationary, and death phases. Furthermore, the lag time needed for growth recovery after starvation follows the square root of the starvation time and is inversely related to the maximal growth rate. This is in agreement with experimental observations, in which the length of time of cell starvation is memorized in the slow accumulation of molecules. Moreover, the lag time distributed among cells is skewed with a long time tail. If the starvation time is longer, an exponential tail appears, which is also consistent with experimental data. Our theory further predicts a strong dependence of lag time on the speed of substrate depletion, which can be tested experimentally. The present model and theoretical analysis provide universal growth laws beyond the exponential phase, offering insight into how cells halt growth without entering the death phase.

Lagged effects of family-supportive organization perceptions and supervision in relation to generalized work-related resources.

PubMed

Matthews, Russell A; Toumbeva, Tatiana H

2015-07-01

In the present study, grounded in organizational support and social exchange theory, the dynamic lagged interplay between family supportive supervision (FSS), family supportive organization perceptions (FSOP), perceived organizational support (POS), and leader-member exchange (LMX) was examined. Data were collected from 435 respondents over 3 time points with 6-week lags between assessments. Consistent with theory, FSS had a significant lagged effect on FSOP, whereas the reverse relationship was not supported. Interestingly, contrary to conservation of resources theory, we did not find significant lagged effects between POS and FSOP. Results further indicated that LMX and FSS were reciprocally related over time, suggesting the potential for a dynamic, mutually beneficial exchange relationship between subordinates and supervisors. Theoretical implications and considerations for research and practice are discussed. (PsycINFO Database Record (c) 2015 APA, all rights reserved).

P-channel differential multiple-time programmable memory cells by laterally coupled floating metal gate fin field-effect transistors

NASA Astrophysics Data System (ADS)

Wang, Tai-Min; Chien, Wei-Yu; Hsu, Chia-Ling; Lin, Chrong Jung; King, Ya-Chin

2018-04-01

In this paper, we present a new differential p-channel multiple-time programmable (MTP) memory cell that is fully compatible with advanced 16 nm CMOS fin field-effect transistors (FinFET) logic processes. This differential MTP cell stores complementary data in floating gates coupled by a slot contact structure, which make different read currents possible on a single cell. In nanoscale CMOS FinFET logic processes, the gate dielectric layer becomes too thin to retain charges inside floating gates for nonvolatile data storage. By using a differential architecture, the sensing window of the cell can be extended and maintained by an advanced blanket boost scheme. The charge retention problem in floating gate cells can be improved by periodic restoring lost charges when significant read window narrowing occurs. In addition to high programming efficiency, this p-channel MTP cells also exhibit good cycling endurance as well as disturbance immunity. The blanket boost scheme can remedy the charge loss problem under thin gate dielectrics.

Dynamic characteristics of heart rate control by the autonomic nervous system in rats.

PubMed

Mizuno, Masaki; Kawada, Toru; Kamiya, Atsunori; Miyamoto, Tadayoshi; Shimizu, Shuji; Shishido, Toshiaki; Smith, Scott A; Sugimachi, Masaru

2010-09-01

We estimated the transfer function of autonomic heart rate (HR) control by using random binary sympathetic or vagal nerve stimulation in anaesthetized rats. The transfer function from sympathetic stimulation to HR response approximated a second-order, low-pass filter with a lag time (gain, 4.29 +/- 1.55 beats min(1) Hz(1); natural frequency, 0.07 +/- 0.03 Hz; damping coefficient, 1.96 +/- 0.64; and lag time, 0.73 +/- 0.12 s). The transfer function from vagal stimulation to HR response approximated a first-order, low-pass filter with a lag time (gain, 8.84 +/- 4.51 beats min(1) Hz(1); corner frequency, 0.12 +/- 0.06 Hz; and lag time, 0.12 +/- 0.08 s). These results suggest that the dynamic characteristics of HR control by the autonomic nervous system in rats are similar to those of larger mammals.

The Causal Connection Between Disc and Power-Law Variability in Hard State Black Hole X-Ray Binaries

NASA Technical Reports Server (NTRS)

Uttley, P.; Wilkinson, T.; Cassatella, P.; Wilms, J.; Pottschimdt, K.; Hanke, M.; Boeck, M.

2010-01-01

We use the XMM-Newton EPIC-pn instrument in timing mode to extend spectral time-lag studies of hard state black hole X-ray binaries into the soft X-ray band. \\Ve show that variations of the disc blackbody emission substantially lead variations in the power-law emission, by tenths of a second on variability time-scales of seconds or longer. The large lags cannot be explained by Compton scattering but are consistent with time-delays due to viscous propagation of mass accretion fluctuations in the disc. However, on time-scales less than a second the disc lags the power-law variations by a few ms, consistent with the disc variations being dominated by X-ray heating by the power-law, with the short lag corresponding to the light-travel time between the power-law emitting region and the disc. Our results indicate that instabilities in the accretion disc are responsible for continuum variability on time-scales of seconds or longer and probably also on shorter time-scales.

LAG-3 Represents a Marker of CD4+ T Cells with Regulatory Activity in Patients with Bone Fracture.

PubMed

Wang, Jun; Ti, Yunfan; Wang, Yicun; Guo, Guodong; Jiang, Hui; Chang, Menghan; Qian, Hongbo; Zhao, Jianning; Sun, Guojing

2018-04-19

The lymphocyte activation gene 3 (LAG-3) is a CD4 homolog with binding affinity to MHC class II molecules. It is thought that LAG-3 exerts a bimodal function, such that co-ligation of LAG-3 and CD3 could deliver an inhibitory signal in conventional T cells, whereas, on regulatory T cells, LAG-3 expression could promote their inhibitory function. In this study, we investigated the role of LAG-3 expression on CD4 + T cells in patients with long bone fracture. We found that LAG-3 + cells represented approximately 13% of peripheral blood CD4 + T cells on average. Compared to LAG-3 - CD4 + T cells, LAG-3 + CD4 + T cells presented significantly higher Foxp3 and CTLA-4 expression. Directly ex vivo or with TCR stimulation, LAG-3 + CD4 + T cells expressed significantly higher levels of IL-10 and TGF-β than LAG-3 - CD4 + T cells. Interestingly, blocking the LAG-3-MHC class II interaction actually increased the IL-10 expression by LAG-3 + CD4 + T cells. The frequency of LAG-3 + CD4 + T cell was positively correlated with restoration of healthy bone function in long bone fracture patients. These results together suggested that LAG-3 is a marker of CD4 + T cells with regulatory function; at the same time, LAG-3 might have limited the full suppressive potential of Treg cells.

Competition between Primary Nucleation and Autocatalysis in Amyloid Fibril Self-Assembly

PubMed Central

Eden, Kym; Morris, Ryan; Gillam, Jay; MacPhee, Cait E.; Allen, Rosalind J.

2015-01-01

Kinetic measurements of the self-assembly of proteins into amyloid fibrils are often used to make inferences about molecular mechanisms. In particular, the lag time—the quiescent period before aggregates are detected—is often found to scale with the protein concentration as a power law, whose exponent has been used to infer the presence or absence of autocatalytic growth processes such as fibril fragmentation. Here we show that experimental data for lag time versus protein concentration can show signs of kinks: clear changes in scaling exponent, indicating changes in the dominant molecular mechanism determining the lag time. Classical models for the kinetics of fibril assembly suggest that at least two mechanisms are at play during the lag time: primary nucleation and autocatalytic growth. Using computer simulations and theoretical calculations, we investigate whether the competition between these two processes can account for the kinks which we observe in our and others’ experimental data. We derive theoretical conditions for the crossover between nucleation-dominated and growth-dominated regimes, and analyze their dependence on system volume and autocatalysis mechanism. Comparing these predictions to the data, we find that the experimentally observed kinks cannot be explained by a simple crossover between nucleation-dominated and autocatalytic growth regimes. Our results show that existing kinetic models fail to explain detailed features of lag time versus concentration curves, suggesting that new mechanistic understanding is needed. More broadly, our work demonstrates that care is needed in interpreting lag-time scaling exponents from protein assembly data. PMID:25650930

SPECTRAL-TIMING ANALYSIS OF THE LOWER kHz QPO IN THE LOW-MASS X-RAY BINARY AQUILA X-1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Troyer, Jon S.; Cackett, Edward M., E-mail: jon.troyer@wayne.edu

2017-01-10

Spectral-timing products of kilohertz quasi-periodic oscillations (kHz QPOs) in low-mass X-ray binary (LMXB) systems, including energy- and frequency-dependent lags, have been analyzed previously in 4U 1608-52, 4U 1636-53, and 4U 1728-34. Here, we study the spectral-timing properties of the lower kHz QPO of the neutron star LMXB Aquila X-1 for the first time. We compute broadband energy lags as well as energy-dependent lags and the covariance spectrum using data from the Rossi X-ray Timing Explorer . We find characteristics similar to those of previously studied systems, including soft lags of ∼30 μ s between the 3.0–8.0 keV and 8.0–20.0 keVmore » energy bands at the average QPO frequency. We also find lags that show a nearly monotonic trend with energy, with the highest-energy photons arriving first. The covariance spectrum of the lower kHz QPO is well fit by a thermal Comptonization model, though we find a seed photon temperature higher than that of the mean spectrum, which was also seen in Peille et al. and indicates the possibility of a composite boundary layer emitting region. Lastly, we see in one set of observations an Fe K component in the covariance spectrum at 2.4- σ confidence, which may raise questions about the role of reverberation in the production of lags.« less

Identifying some determinants of "jet lag" and its symptoms: a study of athletes and other travellers.

PubMed

Waterhouse, J; Edwards, B; Nevill, A; Carvalho, S; Atkinson, G; Buckley, P; Reilly, T; Godfrey, R; Ramsay, R

2002-02-01

Travelling across multiple time zones disrupts normal circadian rhythms and induces "jet lag". Possible effects of this on training and performance in athletes were concerns before the Sydney Olympic Games. To identify some determinants of jet lag and its symptoms. A mixture of athletes, their coaches, and academics attending a conference (n = 85) was studied during their flights from the United Kingdom to Australia (two flights with a one hour stopover in Singapore), and for the first six days in Australia. Subjects differed in age, sex, chronotype, flexibility of sleeping habits, feelings of languor, fitness, time of arrival in Australia, and whether or not they had previous experience of travel to Australia. These variables and whether the body clock adjusted to new local time by phase advance or delay were tested as predictors for jet lag and some of its symptoms by stepwise multiple regression analyses. The amount of sleep in the first flight was significantly greater in those who had left the United Kingdom in the evening than the morning (medians of 5.5 hours and 1.5 hours respectively; p = 0.0002, Mann-Whitney), whereas there was no significant difference on the second flight (2.5 hours v 2.8 hours; p = 0.72). Only the severity of jet lag and assessments of sleep and fatigue were commonly predicted significantly (p<0.05) by regression analysis, and then by only some of the variables. Thus increasing age and a later time of arrival in Australia were associated with less jet lag and fatigue, and previous experience of travel to Australia was associated with an earlier time of getting to sleep. Subjects who had adjusted by phase advance suffered worse jet lag during the 5th and 6th days in Australia. These results indicate the importance of an appropriate choice of itinerary and lifestyle for reducing the negative effects of jet lag in athletes and others who wish to perform optimally in the new time zone.

Effect of Repetition Lag on Priming of Unfamiliar Visual Objects in Young and Older Adults

PubMed Central

Gordon, Leamarie T.; Soldan, Anja; Thomas, Ayanna K.; Stern, Yaakov

2013-01-01

Across three experiments, we examined the effect of repetition lag on priming of unfamiliar visual objects in healthy young and older adults. Multiple levels of lag were examined, ranging from short (one to four intervening stimuli) to long (50+ intervening stimuli). In each experiment, subjects viewed a series of new and repeated line drawings of objects and decided whether they depicted structurally possible or impossible figures. Experiment 1 and 2 found similar levels of priming in young and older adults at short and medium lags. At the longer repetition lags (∼20+ intervening stimuli), older adults showed less overall priming, as measured by reaction time facilitation, than young adults. This indicates that older adults can rapidly encode unfamiliar three-dimensional objects to support priming at shorter lags; however, they cannot maintain these representations over longer intervals. In addition to repetition lag, we also explored the relationship between priming and cognitive reserve, as measured by education and verbal intelligence. In the older adults, higher levels of cognitive reserve were associated with greater reaction time priming, suggesting that cognitive reserve may mediate the relationship between aging and priming. PMID:23276220

Drift trajectories of a floating human body simulated in a hydraulic model of Puget Sound.

PubMed

Ebbesmeyer, C C; Haglund, W D

1994-01-01

After a young man jumped off a 221-foot (67 meters) high bridge, the drift of the body that beached 20 miles (32 km) away at Alki Point in Seattle, Washington was simulated with a hydraulic model. Simulations for the appropriate time period were performed using a small floating bead to represent the body in the hydraulic model at the University of Washington. Bead movements were videotaped and transferred to Computer Aided Drafting (AutoCAD) charts on a personal computer. Because of strong tidal currents in the narrow passage under the bridge (The Narrows near Tacoma, WA), small changes in the time of the jump (+/- 30 minutes) made large differences in the distance the body traveled (30 miles; 48 km). Hydraulic and other types of oceanographic models may be located by contacting technical experts known as physical oceanographers at local universities, and can be utilized to demonstrate trajectories of floating objects and the time required to arrive at selected locations. Potential applications for forensic death investigators include: to be able to set geographic and time limits for searches; determine potential origin of remains found floating or beached; and confirm and correlate information regarding entry into the water and sightings of remains.

A Self-Powered Fast-Sampling Profiling Float in support of a Mesoscale Ocean Observing System in the Western North Pacific

NASA Astrophysics Data System (ADS)

Valdez, T.; Chao, Y.; Davis, R. E.; Jones, J.

2012-12-01

This talk will describe a new self-powered profiling float that can perform fast sampling over the upper ocean for long durations in support of a mesoscale ocean observing system in the Western North Pacific. The current state-of-the-art profiling floats can provide several hundreds profiles for the upper ocean every ten days. To quantify the role of the upper ocean in modulating the development of Typhoons requires at least an order of magnitude reduction for the sampling interval. With today's profiling float and battery technology, a fast sampling of one day or even a few hours will reduce the typical lifetime of profiling floats from years to months. Interactions between the ocean and typhoons often involves mesoscale eddies and fronts, which require a dense array of floats to reveal the 3-dimensional structure. To measure the mesoscale ocean over a large area like the Western North Pacific therefore requires a new technology that enables fast sampling and long duration at the same time. Harvesting the ocean renewable energy associated with the vertical temperature differentials has the potential to power profiling floats with fast sampling over long durations. Results from the development and deployment of a prototype self-powered profiling float (known as SOLO-TREC) will be presented. With eight hours sampling in the upper 500 meters, the upper ocean temperature and salinity reveal pronounced high frequency variations. Plans to use the SOLO-TREC technology in support of a dense array of fast sampling profiling floats in the Western North Pacific will be discussed.

Time-dependent Electron Acceleration in Blazar Transients: X-Ray Time Lags and Spectral Formation

NASA Astrophysics Data System (ADS)

Lewis, Tiffany R.; Becker, Peter A.; Finke, Justin D.

2016-06-01

Electromagnetic radiation from blazar jets often displays strong variability, extending from radio to γ-ray frequencies. In a few cases, this variability has been characterized using Fourier time lags, such as those detected in the X-rays from Mrk 421 using BeppoSAX. The lack of a theoretical framework to interpret the data has motivated us to develop a new model for the formation of the X-ray spectrum and the time lags in blazar jets based on a transport equation including terms describing stochastic Fermi acceleration, synchrotron losses, shock acceleration, adiabatic expansion, and spatial diffusion. We derive the exact solution for the Fourier transform of the electron distribution and use it to compute the Fourier transform of the synchrotron radiation spectrum and the associated X-ray time lags. The same theoretical framework is also used to compute the peak flare X-ray spectrum, assuming that a steady-state electron distribution is achieved during the peak of the flare. The model parameters are constrained by comparing the theoretical predictions with the observational data for Mrk 421. The resulting integrated model yields, for the first time, a complete first-principles physical explanation for both the formation of the observed time lags and the shape of the peak flare X-ray spectrum. It also yields direct estimates of the strength of the shock and the stochastic magnetohydrodynamical wave acceleration components in the Mrk 421 jet.

Unified random access memory (URAM) by integration of a nanocrystal floating gate for nonvolatile memory and a partially depleted floating body for capacitorless 1T-DRAM

NASA Astrophysics Data System (ADS)

Ryu, Seong-Wan; Han, Jin-Woo; Kim, Chung-Jin; Kim, Sungho; Choi, Yang-Kyu

2009-03-01

This paper describes a unified memory (URAM) that utilizes a nanocrystal SOI MOSFET for multi-functional applications of both nonvolatile memory (NVM) and capacitorless 1T-DRAM. By using a discrete storage node (Ag nanocrystal) as the floating gate of the NVM, high defect immunity and 2-bit/cell operation were achieved. The embedded nanocrystal NVM also showed 1T-DRAM operation (program/erase time = 100 ns) characteristics, which were realized by storing holes in the floating body of the SOI MOSFET, without requiring an external capacitor. Three-bit/cell operation was accomplished for different applications - 2-bits for nonvolatility and 1-bit for fast operation.

Time Lags between Exanthematous Illness Attributed to Zika Virus, Guillain-Barré Syndrome, and Microcephaly, Salvador, Brazil

PubMed Central

Paploski, Igor A.D.; Prates, Ana Paula P.B.; Cardoso, Cristiane W.; Kikuti, Mariana; Silva, Monaise M. O.; Waller, Lance A.; Reis, Mitermayer G.; Kitron, Uriel

2016-01-01

Zika virus infection emerged as a public health emergency after increasing evidence for its association with neurologic disorders and congenital malformations. In Salvador, Brazil, outbreaks of acute exanthematous illness (AEI) attributed to Zika virus, Guillain-Barré syndrome (GBS), and microcephaly occurred in 2015. We investigated temporal correlations and time lags between these outbreaks to identify a common link between them by using epidemic curves and time series cross-correlations. Number of GBS cases peaked after a lag of 5–9 weeks from the AEI peak. Number of suspected cases of microcephaly peaked after a lag of 30–33 weeks from the AEI peak, which corresponded to time of potential infections of pregnant mothers during the first trimester. These findings support the association of GBS and microcephaly with Zika virus infection and provide evidence for a temporal relationship between timing of arboviral infection of pregnant women during the first trimester and birth outcome. PMID:27144515

Lag and anticipating synchronization without time-delay coupling.

PubMed

Corron, Ned J; Blakely, Jonathan N; Pethel, Shawn D

2005-06-01

We describe a new method for achieving approximate lag and anticipating synchronization in unidirectionally coupled chaotic oscillators. The method uses a specific parameter mismatch between the drive and response that is a first-order approximation to true time-delay coupling. As a result, an adjustable lag or anticipation effect can be achieved without the need for a variable delay line, making the method simpler and more economical to implement in many physical systems. We present a stability analysis, demonstrate the method numerically, and report experimental observation of the effect in radio-frequency electronic oscillators. In the circuit experiments, both lag and anticipation are controlled by tuning a single capacitor in the response oscillator.

Software Aspects of IEEE Floating-Point Computations for Numerical Applications in High Energy Physics

ScienceCinema

Arnold, Jeffrey

2018-05-14

Floating-point computations are at the heart of much of the computing done in high energy physics. The correctness, speed and accuracy of these computations are of paramount importance. The lack of any of these characteristics can mean the difference between new, exciting physics and an embarrassing correction. This talk will examine practical aspects of IEEE 754-2008 floating-point arithmetic as encountered in HEP applications. After describing the basic features of IEEE floating-point arithmetic, the presentation will cover: common hardware implementations (SSE, x87) techniques for improving the accuracy of summation, multiplication and data interchange compiler options for gcc and icc affecting floating-point operations hazards to be avoided. About the speaker: Jeffrey M Arnold is a Senior Software Engineer in the Intel Compiler and Languages group at Intel Corporation. He has been part of the Digital->Compaq->Intel compiler organization for nearly 20 years; part of that time, he worked on both low- and high-level math libraries. Prior to that, he was in the VMS Engineering organization at Digital Equipment Corporation. In the late 1980s, Jeff spent 2½ years at CERN as part of the CERN/Digital Joint Project. In 2008, he returned to CERN to spent 10 weeks working with CERN/openlab. Since that time, he has returned to CERN multiple times to teach at openlab workshops and consult with various LHC experiments. Jeff received his Ph.D. in physics from Case Western Reserve University.

Eddy Seeding in the Labrador Sea: a Submerged Autonomous Launching Platform (SALP) Application

NASA Astrophysics Data System (ADS)

Furey, Heather H.; Femke de Jong, M.; Bower, Amy S.

2013-04-01

A simplified Submerged Autonomous Launch Platform (SALP) was used to release profiling floats into warm-core Irminger Rings (IRs) in order to investigate their vertical structure and evolution in the Labrador Sea from September 2007 - September 2009. IRs are thought to play an important role in restratification after convection in the Labrador Sea. The SALP is designed to release surface drifters or subsurface floats serially from a traditional ocean mooring, using real-time ocean measurements as criteria for launch. The original prototype instrument used properties measured at multiple depths, with information relayed to the SALP controller via acoustic modems. In our application, two SALP carousels were attached at 500 meters onto a heavily-instrumented deep water mooring, in the path of recently-shed IRs off the west Greenland shelf. A release algorithm was designed to use temperature and pressure measured at the SALP depth only to release one or two APEX profiling drifters each time an IR passed the mooring, using limited historical observations to set release thresholds. Mechanically and electronically, the SALP worked well: out of eleven releases, there was only one malfunction when a float was caught in the cage after the burn-wire had triggered. However, getting floats trapped in eddies met with limited success due to problems with the release algorithm and float ballasting. Out of seven floats launched from the platform using oceanographic criteria, four were released during warm water events that were not related to passing IRs. Also, after float release, it took on average about 2.6 days for the APEX to adjust from its initial ballast depth, about 600 meters, to its park point of 300 meters, leaving the float below the trapped core of water in the IRs. The other mooring instruments (at depths of 100 to 3000 m), revealed that 12 IRs passed by the mooring in the 2-year monitoring period. With this independent information, we were able to assess and improve the release algorithm, still based on ocean conditions measured only at one depth. We found that much better performance could have been achieved with an algorithm that detected IRs based on a temperature difference from a long-term running mean rather than a fixed temperature threshold. This highlights the challenge of designing an appropriate release strategy with limited a priori information on the amplitude and time scales of the background variability.

Air pollutants and atmospheric pressure increased risk of ED visit for spontaneous pneumothorax.

PubMed

Park, Joo Hyung; Lee, Sun Hwa; Yun, Seong Jong; Ryu, Seokyong; Choi, Seung Woon; Kim, Hye Jin; Kang, Tae Kyung; Oh, Sung Chan; Cho, Suk Jin

2018-04-14

To investigate the impact of short-term exposure to air pollutants and meteorological variation on ED visits for primary spontaneous pneumothorax (PSP). We retrospectively identified PSP cases that presented at the ED of our tertiary center between January 2015 and September 2016. We classified the days into three types: no PSP day (0 case/day), sporadic days (1-2 cases/day), and cluster days (PSP, ≥3 cases/day). Association between the daily incidence of PSP with air pollutants and meteorological data were determined using Poisson generalized-linear-model to calculate incidence rate ratio (IRRs) and the use of time-series (lag-1 [the cumulative air pollution level on the previous day of PSP], lag-2 [two days ago], and lag-3 [three days ago]). Using multivariate logistic regression analysis, O 3 (p = 0.010), NO 2 (p = 0.047), particulate matters (PM) 10 (p = 0.021), and PM 2.5 (p = 0.008) were significant factors of PSP occurrence. When the concentration of O 3 , NO 2 , PM 10 , and PM 2.5 were increased, PSP IRRs increased approximately 15, 16, 3, and 5-fold, respectively. With the time-series analyses, atmospheric pressure in lag-3 was significantly lower and in lag-2, was significantly higher in PSP days compared with no PSP days. Among air pollutant concentrations, O 3 in lag-1 (p = 0.017) and lag-2 (p = 0.038), NO 2 in lag-1 (p = 0.015) and lag-2 (p = 0.009), PM 10 in lag-1 (p = 0.012), and PM 2.5 in lag-1 (p = 0.021) and lag-2 (p = 0.032) were significantly different between no PSP and PSP days. Increased concentrations of air pollutants and abrupt change in atmospheric pressure were significantly associated with increased IRR of PSP. Copyright © 2018 Elsevier Inc. All rights reserved.

Hamiltonian model and dynamic analyses for a hydro-turbine governing system with fractional item and time-lag

NASA Astrophysics Data System (ADS)

Xu, Beibei; Chen, Diyi; Zhang, Hao; Wang, Feifei; Zhang, Xinguang; Wu, Yonghong

2017-06-01

This paper focus on a Hamiltonian mathematical modeling for a hydro-turbine governing system including fractional item and time-lag. With regards to hydraulic pressure servo system, a universal dynamical model is proposed, taking into account the viscoelastic properties and low-temperature impact toughness of constitutive materials as well as the occurrence of time-lag in the signal transmissions. The Hamiltonian model of the hydro-turbine governing system is presented using the method of orthogonal decomposition. Furthermore, a novel Hamiltonian function that provides more detailed energy information is presented, since the choice of the Hamiltonian function is the key issue by putting the whole dynamical system to the theory framework of the generalized Hamiltonian system. From the numerical experiments based on a real large hydropower station, we prove that the Hamiltonian function can describe the energy variation of the hydro-turbine suitably during operation. Moreover, the effect of the fractional α and the time-lag τ on the dynamic variables of the hydro-turbine governing system are explored and their change laws identified, respectively. The physical meaning between fractional calculus and time-lag are also discussed in nature. All of the above theories and numerical results are expected to provide a robust background for the safe operation and control of large hydropower stations.

40 CFR 61.271 - Emission standard.

Code of Federal Regulations, 2010 CFR

2010-07-01

... provide a projection below the liquid surface. Except for automatic bleeder vents, rim space vents, roof... floating roof means a cover that rests on the liquid surface (but not necessarily in complete contact with... floating on the liquid surface at all times, except during initial fill and during those intervals when the...

40 CFR 61.271 - Emission standard.

Code of Federal Regulations, 2014 CFR

2014-07-01

... provide a projection below the liquid surface. Except for automatic bleeder vents, rim space vents, roof... floating roof means a cover that rests on the liquid surface (but not necessarily in complete contact with... floating on the liquid surface at all times, except during initial fill and during those intervals when the...

Drug Lag and Key Regulatory Barriers in the Emerging Markets

PubMed Central

Wileman, Harriet; Mishra, Arun

2010-01-01

There have been numerous investigations targeted at identifying whether a drug lag exists in the mature markets of the US, EU and Japan. This work focuses on the emerging markets because of the potential they hold for the future of the pharmaceutical industry as a consequence of rapid economic and political development. The aims of this work are to ascertain whether a drug lag exists in the emerging markets and how it has changed over time from the 1960s to the 2000s. It will also highlight key regulatory barriers which may contribute to drug lag. The date of the marketing authorisation (MA) approval by the US Food and Drug Administration (FDA) was used as a reference point. A comparison against the company database regarding emerging market specific approval enabled the difference in time and thus the drug lag for that particular market to be calculated. This work concludes that the overall relative drug lag in the emerging markets has decreased over time and that there are seven key regulatory barriers which need to be targeted in order to make further improvements; ‘Western Approval’, local clinical development (LCD), Certificate of Pharmaceutical Product (CPP), Good Manufacturing Practice (GMP), pricing approval, document authentication and harmonisation. PMID:21829782

Long-Term Outcome and Complications Following Prophylactic Laparoscopic-Assisted Gastropexy in Dogs.

PubMed

Loy Son, Natasha K; Singh, Ameet; Amsellem, Pierre; Kilkenny, Jessica; Brisson, Brigitte A; Oblak, Michelle L; Ogilvie, Adam T

2016-11-01

To characterize the short- and long-term outcome (>12 months), complications, and owner satisfaction following prophylactic laparoscopic-assisted gastropexy (LAG) in dogs. Retrospective study. Client-owned dogs (n = 49). Dogs that underwent prophylactic LAG at 2 veterinary academic hospitals were studied. Surgical time, anesthesia time, concurrent intra- and extra-abdominal procedures, and intraoperative and postoperative complications were recorded following review of medical records. Veterinarian and/or owner follow-up was obtained to determine outcome and satisfaction with LAG. Five of 49 dogs (10%) experienced complications related to abdominal access during LAG. Four percent (2/49) of dogs experienced an intraoperative complication. Follow-up information was available for 89% of dogs (44/49). Four dogs died of causes unrelated to LAG or gastric dilatation volvulus (GDV) in the follow-up period. Two dogs experienced major postoperative complications requiring additional veterinary intervention. Thirty percent (13 dogs) experienced a minor postoperative self-limiting wound-related complication. Median follow-up time was 698 days (range, 411-1825). No dogs experienced GDV. One hundred percent of dog owners were satisfied with LAG, would repeat the procedure in a future pet, and would recommend the procedure to a friend or family member. LAG was an effective procedure for prevention of GDV and was associated with high client satisfaction in this cohort of dogs. A moderate rate of postoperative wound complications occurred that were minor and self-limiting in nature. © Copyright 2016 by The American College of Veterinary Surgeons.

WindWaveFloat (WWF): Final Scientific Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alla Weinstein; Roddier, Dominique; Banister, Kevin

2012-03-30

Principle Power Inc. and National Renewable Energy Lab (NREL) have completed a contract to assess the technical and economic feasibility of integrating wave energy converters into the WindFloat, resulting in a new concept called the WindWaveFloat (WWF). The concentration of several devices on one platform could offer a potential for both economic and operational advantages. Wind and wave energy converters can share the electrical cable and power transfer equipment to transport the electricity to shore. Access to multiple generation devices could be simplified, resulting in cost saving at the operational level. Overall capital costs may also be reduced, provided thatmore » the design of the foundation can be adapted to multiple devices with minimum modifications. Finally, the WindWaveFloat confers the ability to increase energy production from individual floating support structures, potentially leading to a reduction in levelized energy costs, an increase in the overall capacity factor, and greater stability of the electrical power delivered to the grid. The research conducted under this grant investigated the integration of several wave energy device types into the WindFloat platform. Several of the resulting system designs demonstrated technical feasibility, but the size and design constraints of the wave energy converters (technical and economic) make the WindWaveFloat concept economically unfeasible at this time. Not enough additional generation could be produced to make the additional expense associated with wave energy conversion integration into the WindFloat worthwhile.« less

Wind tunnel research comparing lateral control devices, particularly at high angles of attack XI : various floating tip ailerons on both rectangular and tapered wings

NASA Technical Reports Server (NTRS)

Weick, Fred E; Harris, Thomas A

1933-01-01

Discussed here are a series of systematic tests being conducted to compare different lateral control devices with particular reference to their effectiveness at high angles of attack. The present tests were made with six different forms of floating tip ailerons of symmetrical section. The tests showed the effect of the various ailerons on the general performance characteristics of the wing, and on the lateral controllability and stability characteristics. In addition, the hinge moments were measured for the most interesting cases. The results are compared with those for a rectangular wing with ordinary ailerons and also with those for a rectangular wing having full-chord floating tip ailerons. Practically all the floating tip ailerons gave satisfactory rolling moments at all angles of attack and at the same time gave no adverse yawing moments of appreciable magnitude. The general performance characteristics with the floating tip ailerons, however, were relatively poor, especially the rate of climb. None of the floating tip ailerons entirely eliminated the auto rotational moments at angles of attack above the stall, but all of them gave lower moments than a plain wing. Some of the floating ailerons fluttered if given sufficiently large deflection, but this could have been eliminated by moving the hinge axis of the ailerons forward. Considering all points including hinge moments, the floating tip ailerons on the wing with 5:1 taper are probably the best of those which were tested.

Monthly ENSO Forecast Skill and Lagged Ensemble Size

PubMed Central

DelSole, T.; Tippett, M.K.; Pegion, K.

2018-01-01

Abstract The mean square error (MSE) of a lagged ensemble of monthly forecasts of the Niño 3.4 index from the Climate Forecast System (CFSv2) is examined with respect to ensemble size and configuration. Although the real‐time forecast is initialized 4 times per day, it is possible to infer the MSE for arbitrary initialization frequency and for burst ensembles by fitting error covariances to a parametric model and then extrapolating to arbitrary ensemble size and initialization frequency. Applying this method to real‐time forecasts, we find that the MSE consistently reaches a minimum for a lagged ensemble size between one and eight days, when four initializations per day are included. This ensemble size is consistent with the 8–10 day lagged ensemble configuration used operationally. Interestingly, the skill of both ensemble configurations is close to the estimated skill of the infinite ensemble. The skill of the weighted, lagged, and burst ensembles are found to be comparable. Certain unphysical features of the estimated error growth were tracked down to problems with the climatology and data discontinuities. PMID:29937973

Monthly ENSO Forecast Skill and Lagged Ensemble Size

NASA Astrophysics Data System (ADS)

Trenary, L.; DelSole, T.; Tippett, M. K.; Pegion, K.

2018-04-01

The mean square error (MSE) of a lagged ensemble of monthly forecasts of the Niño 3.4 index from the Climate Forecast System (CFSv2) is examined with respect to ensemble size and configuration. Although the real-time forecast is initialized 4 times per day, it is possible to infer the MSE for arbitrary initialization frequency and for burst ensembles by fitting error covariances to a parametric model and then extrapolating to arbitrary ensemble size and initialization frequency. Applying this method to real-time forecasts, we find that the MSE consistently reaches a minimum for a lagged ensemble size between one and eight days, when four initializations per day are included. This ensemble size is consistent with the 8-10 day lagged ensemble configuration used operationally. Interestingly, the skill of both ensemble configurations is close to the estimated skill of the infinite ensemble. The skill of the weighted, lagged, and burst ensembles are found to be comparable. Certain unphysical features of the estimated error growth were tracked down to problems with the climatology and data discontinuities.

Mutagenic analysis of the nucleation propensity of oxidized Alzheimer's beta-amyloid peptide.

PubMed

Christopeit, Tony; Hortschansky, Peter; Schroeckh, Volker; Gührs, Karlheinz; Zandomeneghi, Giorgia; Fändrich, Marcus

2005-08-01

The formation of polypeptide aggregates represents a nucleated polymerization reaction in which an initial nucleation event (lag phase) is followed by the extension of newly formed nuclei into larger aggregates, including fibrils (growth phase). The efficiencies of these reactions relate to the lag time (lag phase) and to the rate of aggregation (growth phase), which can be determined from experimental aggregation curves. Here we present a mutagenic analysis in which we replace valine 18 of the Alzheimer's Abeta (1-40) peptide with 17 different amino acids and determine its effect on the lag time, and therefore, on the propensity of nucleation. Comparison with various physico-chemical properties shows that nucleation is affected in a predictable manner depending on the beta-sheet propensity and hydrophobicity of residue 18. In addition, we observe a direct proportionality between the lag time and the rate of aggregation. These data imply that the two reactions, nucleation and polymerization, are governed by very similar physicochemical principles and that they involve the formation of the same types of noncovalent interactions.

SOFT LAGS IN NEUTRON STAR kHz QUASI-PERIODIC OSCILLATIONS: EVIDENCE FOR REVERBERATION?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barret, Didier, E-mail: didier.barret@irap.omp.eu; CNRS, Institut de Recherche en Astrophysique et Planetologie, 9 Av. colonel Roche, BP 44346, F-31028 Toulouse cedex 4

2013-06-10

High frequency soft reverberation lags have now been detected from stellar mass and supermassive black holes. Their interpretation involves reflection of a hard source of photons onto an accretion disk, producing a delayed reflected emission, with a time lag consistent with the light travel time between the irradiating source and the disk. Independently of the location of the clock, the kHz quasi-periodic oscillation (QPO) emission is thought to arise from the neutron star boundary layer. Here, we search for the signature of reverberation of the kHz QPO emission, by measuring the soft lags and the lag energy spectrum of themore » lower kHz QPOs from 4U1608-522. Soft lags, ranging from {approx}15 to {approx}40 {mu}s, between the 3-8 keV and 8-30 keV modulated emissions are detected between 565 and 890 Hz. The soft lags are not constant with frequency and show a smooth decrease between 680 Hz and 890 Hz. The broad band X-ray spectrum is modeled as the sum of a disk and a thermal Comptonized component, plus a broad iron line, expected from reflection. The spectral parameters follow a smooth relationship with the QPO frequency, in particular the fitted inner disk radius decreases steadily with frequency. Both the bump around the iron line in the lag energy spectrum and the consistency between the lag changes and the inferred changes of the inner disk radius, from either spectral fitting or the QPO frequency, suggest that the soft lags may indeed involve reverberation of the hard pulsating QPO source on the disk.« less

Sleep Disorders and Complementary Health Approaches : What the Science Says

MedlinePlus

... symptoms of jet lag and improve sleep following travel across multiple time zones. A 2009 Cochrane review supporting this recommendation ... oral melatonin for alleviating jet lag after air travel across several time zones, and concluded that melatonin is remarkably effective ...

A Falling Corona Model for the Anomalous Behavior of the Broad Emission Lines in NGC 5548

NASA Astrophysics Data System (ADS)

Sun, Mouyuan; Xue, Yongquan; Cai, Zhenyi; Guo, Hengxiao

2018-04-01

NGC 5548 has been intensively monitored by the AGN Space Telescope and Optical Reverberation Mapping collaboration. Approximately after half of the light curves, the correlation between the broad emission lines and the lag-corrected ultraviolet (UV) continua becomes weak. This anomalous behavior is accompanied by an increase of soft X-ray emission. We propose a simple model to understand this anomalous behavior, i.e., the corona might fall down, thereby increasing the covering fraction of the inner disk. Therefore, X-ray and extreme-UV emission suffer from spectral variations. The UV continua variations are driven by both X-ray and extreme-UV variations. Consequently, the spectral variability induced by the falling corona would dilute the correlation between the broad emission lines and the UV continua. Our model can explain many additional observational facts, including the dependence of the anomalous behavior on velocity and ionization energy. We also show that the time lag and correlation between the X-ray and the UV variations change as NGC 5548 displays the anomalous behavior. The time lag is dramatically longer than the expectation from disk reprocessing if the anomalous behavior is properly excluded. During the anomalous state, the time lag approaches the light-travel timescale of disk reprocessing albeit with a much weaker correlation. We speculate that the time lag in the normal state is caused by reprocessing of the broad line region gas. As NGC 5548 enters the abnormal state, the contribution of the broad line region gas is smaller; the time lag reflects disk reprocessing. We also discuss alternative scenarios.

TEMPORAL VARIABILITY FROM THE TWO-COMPONENT ADVECTIVE FLOW SOLUTION AND ITS OBSERVATIONAL EVIDENCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutta, Broja G.; Chakrabarti, Sandip K.

2016-09-10

In the propagating oscillatory shock model, the oscillation of the post-shock region, i.e., the Compton cloud, causes the observed low-frequency quasi-periodic oscillations (QPOs). The evolution of QPO frequency is explained by the systematic variation of the Compton cloud size, i.e., the steady radial movement of the shock front, which is triggered by the cooling of the post-shock region. Thus, analysis of the energy-dependent temporal properties in different variability timescales can diagnose the dynamics and geometry of accretion flows around black holes. We study these properties for the high-inclination black hole source XTE J1550-564 during its 1998 outburst and the low-inclinationmore » black hole source GX 339-4 during its 2006–07 outburst using RXTE /PCA data, and we find that they can satisfactorily explain the time lags associated with the QPOs from these systems. We find a smooth decrease of the time lag as a function of time in the rising phase of both sources. In the declining phase, the time lag increases with time. We find a systematic evolution of QPO frequency and hard lags in these outbursts. In XTE J1550-564, the lag changes from hard to soft (i.e., from a positive to a negative value) at a crossing frequency (ν {sub c}) of ∼3.4 Hz. We present possible mechanisms to explain the lag behavior of high and low-inclination sources within the framework of a single two-component advective flow model.« less

Partial dust obscuration in active galactic nuclei as a cause of broad-line profile and lag variability, and apparent accretion disc inhomogeneities

NASA Astrophysics Data System (ADS)

Gaskell, C. Martin; Harrington, Peter Z.

2018-04-01

The profiles of the broad emission lines of active galactic nuclei (AGNs) and the time delays in their response to changes in the ionizing continuum ("lags") give information about the structure and kinematics of the inner regions of AGNs. Line profiles are also our main way of estimating the masses of the supermassive black holes (SMBHs). However, the profiles often show ill-understood, asymmetric structure and velocity-dependent lags vary with time. Here we show that partial obscuration of the broad-line region (BLR) by outflowing, compact, dusty clumps produces asymmetries and velocity-dependent lags similar to those observed. Our model explains previously inexplicable changes in the ratios of the hydrogen lines with time and velocity, the lack of correlation of changes in line profiles with variability of the central engine, the velocity dependence of lags, and the change of lags with time. We propose that changes on timescales longer than the light-crossing time do not come from dynamical changes in the BLR, but are a natural result of the effect of outflowing dusty clumps driven by radiation pressure acting on the dust. The motion of these clumps offers an explanation of long-term changes in polarization. The effects of the dust complicate the study of the structure and kinematics of the BLR and the search for sub-parsec SMBH binaries. Partial obscuration of the accretion disc can also provide the local fluctuations in luminosity that can explain sizes deduced from microlensing.

Time-Lag in Responses of Birds to Atlantic Forest Fragmentation: Restoration Opportunity and Urgency.

PubMed

Uezu, Alexandre; Metzger, Jean Paul

2016-01-01

There are few opportunities to evaluate the relative importance of landscape structure and dynamics upon biodiversity, especially in highly fragmented tropical landscapes. Conservation strategies and species risk evaluations often rely exclusively on current aspects of landscape structure, although such limited assumptions are known to be misleading when time-lag responses occur. By relating bird functional-group richness to forest patch size and isolation in ten-year intervals (1956, 1965, 1978, 1984, 1993 and 2003), we revealed that birds with different sensitivity to fragmentation display contrasting responses to landscape dynamics in the Brazilian Atlantic Forest. For non-sensitive groups, there was no time-lag in response: the recent degree of isolation best explains their variation in richness, which likely relates to these species' flexibility to adapt to changes in landscape structure. However, for sensitive bird groups, the 1978 patch area was the best explanatory variable, providing evidence for a 25-year time-lag in response to habitat reduction. Time-lag was more likely in landscapes that encompass large patches, which can support temporarily the presence of some sensitive species, even when habitat cover is relatively low. These landscapes potentially support the most threatened populations and should be priorities for restoration efforts to avoid further species loss. Although time-lags provide an opportunity to counteract the negative consequences of fragmentation, it also reinforces the urgency of restoration actions. Fragmented landscapes will be depleted of biodiversity if landscape structure is only maintained, and not improved. The urgency of restoration action may be even higher in landscapes where habitat loss and fragmentation history is older and where no large fragment remained to act temporarily as a refuge.

Integration of animal behaviors under stresses with different time courses

PubMed Central

Zheng, Lun; Zheng, Xigeng

2014-01-01

We used animal models of “forced swim stress” and “chronic unpredictable stress”, and tried to reveal whether a passive coping style of high flotation behavior in forced swim stress predicts anhedonia behavior after chronic unpredictable stress, and whether the dopamine system regulates floating and anhedonia behaviors. Our results confirmed that depression-prone rats use “floating behavior” as a coping strategy in forced swim stress and more readily suffer from anhedonia during chronic unpredictable stress. Intraperitoneal injection or nucleus accumbens microinjection of the dopamine 2/3 receptor subtype agonist ropinirole reduced floating behaviors in depression-prone animals, but increased sucrose preference in rats showing anhedonia. These data indicate that floating behavior is a defensive mode that is preferred by susceptible individuals under conditions of acute stress. Simultaneously, these animals more readily experienced anhedonia under long-term stress; that is, they were more readily affected by depression. Our results suggest that dopamine 2/3 receptor subtypes in the nucleus accumbens play an important role in floating behaviors and anhedonia. PMID:25317159

Observation and modeling of compressional Pi 3 magnetic pulsations

NASA Technical Reports Server (NTRS)

Matsuoka, Hitoshi; Takahashi, K.; Yumoto, K.; Anderson, B. J.; Sibeck, D. G.

1995-01-01

Compressional magnetic pulsations with irregular waveforms and periods longer than 150 s (here termed Pi 3) have been studied by using data from Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer (AMPTE/CCE) and GOES 5 and 6 in the dayside magnetosphere and compared with signatures on the ground at low latitudes by using data from Kakioka station (L = 1.25). On the ground, the pulsations appear in the horizontal component. A study of 17 such concurrent events during a 2-month period in 1986 reveals the following pulsation characteristics. (1) The peak-to-peak amplitudes in space (delta B(sub T)) and on the ground (delta H) are comparable and are in the range of 0.5-7 nT. (2) On the ground the pulsations can be seen at all local times, even at midnight, while at geostationary orbit they are observed only on the dayside with a clear amplitude maximum at noon. (3) The pulsations on the ground lag those observed by CCE near local noon, and the lag increases as the local time separation between CCE and the ground station increases. The time lag is 1-2 min longer when the ground station is on the nightside than when it is on the dayside. (4) The time lag between pulsations observed at geostationary orbit and near noon by CCE varies systematically with local time and is about 2 min per 6 hours of local time separation. These observations indicate that some nightside pulsations in the Pi 3 band have dayside origins. The position dependence of the pulsation amplitude can be explained well by changes in the magnetopause current, which are in turn presumably caused by changes in the solar wind dynamic pressure. The time lags observed in space are consistent with signal propagation in the MHD fast mode, but the variation in space-ground time lags with ground station local time must be attributed to another mechanism.

Modelling growth of Penicillium expansum and Aspergillus niger at constant and fluctuating temperature conditions.

PubMed

Gougouli, Maria; Koutsoumanis, Konstantinos P

2010-06-15

The growth of Penicillium expansum and Aspergillus niger, isolated from yogurt production environment, was investigated on malt extract agar with pH=4.2 and a(w)=0.997, simulating yogurt, at isothermal conditions ranging from -1.3 to 35 degrees C and from 5 to 42.3 degrees C, respectively. The growth rate (mu) and (apparent) lag time (lambda) of the mycelium growth were modelled as a function of temperature using a Cardinal Model with Inflection (CMI). The results showed that the CMI can describe successfully the effect of temperature on fungal growth within the entire biokinetic range for both isolates. The estimated values of the CMI for mu were T(min)=-5.74 degrees C, T(max)=30.97 degrees C, T(opt)=22.08 degrees C and mu(opt)=0.221 mm/h for P. expansum and T(min)=10.13 degrees C, T(max)=43.13 degrees C, T(opt)=31.44 degrees C, and mu(opt)=0.840 mm/h for A. niger. The cardinal values for lambda were very close to the respective values for mu indicating similar temperature dependence of the growth rate and the lag time of the mycelium growth. The developed models were further validated under fluctuating temperature conditions using various dynamic temperature scenarios. The time-temperature conditions studied included single temperature shifts before or after the end of the lag time and continuous periodic temperature fluctuations. The prediction of growth at changing temperature was based on the assumption that after a temperature shift the growth rate is adopted instantaneously to the new temperature, while the lag time was predicted using a cumulative lag approach. The results showed that when the temperature shifts occurred before the end of the lag, they did not cause any significant additional lag and the observed total lag was very close to the cumulative lag predicted by the model. In experiments with temperature shifts after the end of the lag time, accurate predictions were obtained when the temperature profile included temperatures which were inside the region of growth, showing that the assumption that mu is adopted instantaneously to the current temperature is concrete. In contrast, for scenarios with temperatures close or outside the growth region the models overestimated growth, indicating that fungi were stressed by this type of temperature shifts. The present study provides useful data for understanding the behavior of P. expansum and A. niger at dynamic temperature conditions while the developed models can be used as effective tools in assessing the risk of fungal spoilage and predicting shelf life of foods. Copyright 2010. Published by Elsevier B.V.

Diverse Responses of Global Vegetation to Climate Changes: Spatial Patterns and Time-lag Effects

NASA Astrophysics Data System (ADS)

Wu, D.; Zhao, X.; Zhou, T.; Huang, K.; Xu, W.

2014-12-01

Global climate changes have enormous influences on vegetation growth, meanwhile, response of vegetation to climate express space diversity and time-lag effects, which account for spatial-temporal disparities of climate change and spatial heterogeneity of ecosystem. Revelation of this phenomenon will help us further understanding the impact of climate change on vegetation. Assessment and forecast of global environmental change can be also improved under further climate change. Here we present space diversity and time-lag effects patterns of global vegetation respond to three climate factors (temperature, precipitation and solar radiation) based on quantitative analysis of satellite data (NDVI) and Climate data (Climate Research Unit). We assessed the time-lag effects of global vegetation to main climate factors based on the great correlation fitness between NDVI and the three climate factors respectively among 0-12 months' temporal lags. On this basis, integrated response model of NDVI and the three climate factors was built to analyze contribution of different climate factors to vegetation growth with multiple regression model and partial correlation model. In the result, different vegetation types have distinct temporal lags to the three climate factors. For the precipitation, temporal lags of grasslands are the shortest while the evergreen broad-leaf forests are the longest, which means that grasslands are more sensitive to precipitation than evergreen broad-leaf forests. Analysis of different climate factors' contribution to vegetation reveal that vegetation are dominated by temperature in the high northern latitudes; they are mainly restricted by precipitation in arid and semi-arid areas (Australia, Western America); in humid areas of low and intermediate latitudes (Amazon, Eastern America), vegetation are mainly influenced by solar radiation. Our results reveal the time-lag effects and major driving factors of global vegetation growth and explain the spatiotemporal variations of global vegetation in last 30 years. Significantly, it is as well as in forecasting and assessing the influences of future climate change on the vegetation dynamics. This work was supported by the High Technology Research and Development Program of China (Grant NO.2013AA122801).

Programmable Off-The-Shelf cell-enabled GPS loggers optimized for retrieving after being used as a float in large river experiments.

NASA Astrophysics Data System (ADS)

Hut, Rolf; Bogaard, Thom

2017-04-01

Throwing something in a river and seeing how fast it floats downstream is the first thing that every hydrologists does when encountering a new river. Using a collection of floats allows estimation of gauge surface water velocity and dispersion characteristics. To use floats over long (hundreds of kilometers) stretches of river requires either a crew that keeps an eye on the floats (labor intensive) or having high-tech floats that upload their location on regular intervals, such that they can be retrieved at the end of the experiment. GPS floats with communication units have been custom build by scientists before. Connecting GPS units to GSM modems used to require deep knowledge on micro-electronics and network protocols. In this work we present a version that is build using only off-the-shelf electronics that require no deep knowledge of either micro electronics nor network protocols. The new cellular enabled Particle Electron development board made it possible to connect a Sparkfun OpenLog (SD-card based logger) to a GPS tracker with no soldering and little programming. Because scientist can program the device themselves, settings like sample time can be adapted to the needs of specific experiments and additional sensors can be easily added. When writing GPS location every minute to SD and reporting every fifteen minutes online, our logger can run for three days on a single 2200 mAh LiPo battery (provided with the Particle Electron). Cost of components for our logger is less than 150. The durability of our GPS loggers will be tested during a field campaign at the end of January 2017 where 15 floats will float down the Irrawaddy river over a length of more than 200 km, during two days.

Increased water temperature renders single-housed C57BL/6J mice susceptible to antidepressant treatment in the forced swim test.

PubMed

Bächli, Heidi; Steiner, Michel A; Habersetzer, Ursula; Wotjak, Carsten T

2008-02-11

To investigate genotype x environment interactions in the forced swim test, we tested the influence of water temperature (20 degrees C, 25 degrees C, 30 degrees C) on floating behaviour in single-housed male C57BL/6J and BALB/c mice. We observed a contrasting relationship between floating and water temperature between the two strains, with C57BL/6J floating more and BALB/c floating less with increasing water temperature, independent of the lightening conditions and the time point of testing during the animals' circadian rhythm. Both strains showed an inverse relationship between plasma corticosterone concentration and water temperature, indicating that the differences in stress coping are unrelated to different perception of the aversive encounter. Treatment with desipramine (20mg/kg, i.p.) caused a reduction in immobility time in C57BL/6J mice if the animals were tested at 30 degrees C water temperature, with no effect at 25 degrees C and no effects on forced swim stress-induced corticosterone secretion. The same treatment failed to affect floating behaviour in BALB/c at any temperature, but caused a decrease in plasma corticosterone levels. Taken together we demonstrate that an increase in water temperature in the forced swim test exerts opposite effects on floating behaviour in C57BL/6J and BALB/c and renders single-housed C57BL/6J mice, but not BALB/c mice, susceptible to antidepressant-like behavioral effects of desipramine.

Microclimate and architectural tectonic: vernacular floating house resilience in Seberang Ulu 1, Palembang

NASA Astrophysics Data System (ADS)

Puspitasari, P.; Kadri, T.; Indartoyo, I.; Kusumawati, L.

2018-01-01

This paper aims to describe the results of preliminary research on floating houses on the Musi River, Seberang Ulu 1, Palembang, focused on studying the influence of microclimates to the tectonics of Rumah Rakit (Floating House). The increase of water surface due to global warming will increase the need of using floating house typology in the future. The description of the inhabitants’ experiences on applying technics to create vernacular floating houses is considered as significant knowledge to develop advance technology on the basis of local characteristic. Vernacular floating houses resilience consists of natural experiences of inhabitants in adapting their daily activities to the characteristic of local climate. By using qualitative approach, the Rumah Rakit inhabitants’ verbal information in this article becomes the main aspect in exploring local knowledge. At the end, the conceptual model of vernacular Rumah Rakit in Seberang Ulu 1, Palembang is formulated, in terms of building architectural tectonic that is closely related to the local climate characteristic. The knowledge can be utilized in the context of rehabilitation or preservation of such architectural objects that are their existences tend to be extinct at this time.

Emergence and temporal structure of Lead-Lag correlations in collective stock dynamics

NASA Astrophysics Data System (ADS)

Xia, Lisi; You, Daming; Jiang, Xin; Chen, Wei

2018-07-01

Understanding the correlations among stock returns is crucial for reducing the risk of investment in stock markets. As an important stylized correlation, lead-lag effect plays a major role in analyzing market volatility and deriving trading strategies. Here, we explore historical lead-lag relationships among stocks in the Chinese stock market. Strongly positive lagged correlations can be empirically observed. We demonstrate this lead-lag phenomenon is not constant but temporally emerges during certain periods. By introducing moving time window method, we transform the lead-lag dynamics into a series of asymmetric lagged correlation matrices. Dynamic lead-lag structures are uncovered in the form of temporal network structures. We find that the size of lead-lag group experienced a rapid drop during the year 2012, which signaled a re-balance of the stock market. On the daily timescale, we find the lead-lag structure exhibits several persistent patterns, which can be characterized by the Jaccard matrix. We show significant market events can be distinguished in the Jaccard matrix diagram. Taken together, we study an integration of all the temporal networks and identify several leading stock sectors, which are in accordance with the common Chinese economic fundamentals.

Microbial detection method based on sensing molecular hydrogen

NASA Technical Reports Server (NTRS)

Wilkins, J. R.; Stoner, G. E.; Boykin, E. H.

1974-01-01

A simple method for detecting bacteria, based on the time of hydrogen evolution, was developed and tested against various members of the Enterobacteriaceae group. The test system consisted of (1) two electrodes, platinum and a reference electrode, (2) a buffer amplifier, and (3) a strip-chart recorder. Hydrogen evolution was measured by an increase in voltage in the negative (cathodic) direction. A linear relationship was established between inoculum size and the time hydrogen was detected (lag period). Lag times ranged from 1 h for 1 million cells/ml to 7 h for 1 cell/ml. For each 10-fold decrease in inoculum, length of the lag period increased 60 to 70 min. Based on the linear relationship between inoculum and lag period, these results indicate the potential application of the hydrogen-sensing method for rapidly detecting coliforms and other gas-producing microorganisms in a variety of clinical, food, and other samples.

Time lag and communication in changing unpopular norms.

PubMed

Gërxhani, Klarita; Bruggeman, Jeroen

2015-01-01

Humans often coordinate their social lives through norms. When a large majority of people are dissatisfied with an existing norm, it seems obvious that they will change it. Often, however, this does not occur. We investigate how a time lag between individual support of a norm change and the change itself hinders such change, related to the critical mass of supporters needed to effectuate the change, and the (im)possibility of communicating about it. To isolate these factors, we utilize a laboratory experiment. As predicted, we find unambiguous effects of time lag on precluding norm change; a higher threshold for a critical mass does so as well. Communication facilitates choosing superior norms but it does not necessarily lead to norm change when the uncertainty on whether there will be a norm change in the future is high. Communication seems to help coordination on actions at the present but not the future. Hence, the uncertainty driven by time lag makes individuals choose the status quo, here the unpopular norm.

Time Lag and Communication in Changing Unpopular Norms

PubMed Central

Gërxhani, Klarita; Bruggeman, Jeroen

2015-01-01

Humans often coordinate their social lives through norms. When a large majority of people are dissatisfied with an existing norm, it seems obvious that they will change it. Often, however, this does not occur. We investigate how a time lag between individual support of a norm change and the change itself hinders such change, related to the critical mass of supporters needed to effectuate the change, and the (im)possibility of communicating about it. To isolate these factors, we utilize a laboratory experiment. As predicted, we find unambiguous effects of time lag on precluding norm change; a higher threshold for a critical mass does so as well. Communication facilitates choosing superior norms but it does not necessarily lead to norm change when the uncertainty on whether there will be a norm change in the future is high. Communication seems to help coordination on actions at the present but not the future. Hence, the uncertainty driven by time lag makes individuals choose the status quo, here the unpopular norm. PMID:25880200

Calculation of power spectrums from digital time series with missing data points

NASA Technical Reports Server (NTRS)

Murray, C. W., Jr.

1980-01-01

Two algorithms are developed for calculating power spectrums from the autocorrelation function when there are missing data points in the time series. Both methods use an average sampling interval to compute lagged products. One method, the correlation function power spectrum, takes the discrete Fourier transform of the lagged products directly to obtain the spectrum, while the other, the modified Blackman-Tukey power spectrum, takes the Fourier transform of the mean lagged products. Both techniques require fewer calculations than other procedures since only 50% to 80% of the maximum lags need be calculated. The algorithms are compared with the Fourier transform power spectrum and two least squares procedures (all for an arbitrary data spacing). Examples are given showing recovery of frequency components from simulated periodic data where portions of the time series are missing and random noise has been added to both the time points and to values of the function. In addition the methods are compared using real data. All procedures performed equally well in detecting periodicities in the data.

[Studies on preparation of sustained-release Shuxiong formulation, a traditional Chinese medicine compound recipe, using time-controlled release techniques].

PubMed

Song, Hong-Tao; Zhang, Qian; Jiang, Peng; Guo, Tao; Chen, Da-Wei; He, Zhong-Gui

2006-09-01

To prepare a sustained-release formulation of traditional Chinese medicine compound recipe by adopting time-controlled release techniques. Shuxiong tablets were chosen as model drug. The prescription and technique of core tablets were formulated with selecting disintegrating time and swelling volume of core tablets in water as index. The time-controlled release tablets were prepared by adopting press-coated techniques, using PEG6000, HCO and EVA as coating materials. The influences of compositions, preparation process and dissolution conditions in vitro on the lag time (T(lag)) of drug release were investigated. The composition of core tablets was as follow: 30% of drug, 50% MCC and 20% CMS-Na. The T(lag) of time-controlled release tablets was altered remarkably by PEG6000 content of the outer layer, the amount of outer layer and hardness of tablet. The viscosity of dissolution media and basket rotation had less influence on the T(lag) but more on rate of drug release. The core tablets pressed with the optimized composition had preferable swelling and disintegrating properties. The shuxiong sustained-release formulations which contained core tablet and two kinds of time-controlled release tablets with 3 h and 6 h of T(lag) could release drug successively at 0 h, 3 h and 6 h in vitro. The technique made it possible that various components with extremely different physicochemical properties in these preparations could release synchronously.

TIME-DEPENDENT ELECTRON ACCELERATION IN BLAZAR TRANSIENTS: X-RAY TIME LAGS AND SPECTRAL FORMATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, Tiffany R.; Becker, Peter A.; Finke, Justin D., E-mail: pbecker@gmu.edu, E-mail: tlewis13@gmu.edu, E-mail: justin.finke@nrl.navy.mil

2016-06-20

Electromagnetic radiation from blazar jets often displays strong variability, extending from radio to γ -ray frequencies. In a few cases, this variability has been characterized using Fourier time lags, such as those detected in the X-rays from Mrk 421 using Beppo SAX. The lack of a theoretical framework to interpret the data has motivated us to develop a new model for the formation of the X-ray spectrum and the time lags in blazar jets based on a transport equation including terms describing stochastic Fermi acceleration, synchrotron losses, shock acceleration, adiabatic expansion, and spatial diffusion. We derive the exact solution formore » the Fourier transform of the electron distribution and use it to compute the Fourier transform of the synchrotron radiation spectrum and the associated X-ray time lags. The same theoretical framework is also used to compute the peak flare X-ray spectrum, assuming that a steady-state electron distribution is achieved during the peak of the flare. The model parameters are constrained by comparing the theoretical predictions with the observational data for Mrk 421. The resulting integrated model yields, for the first time, a complete first-principles physical explanation for both the formation of the observed time lags and the shape of the peak flare X-ray spectrum. It also yields direct estimates of the strength of the shock and the stochastic magnetohydrodynamical wave acceleration components in the Mrk 421 jet.« less

Cloud-to-ground lightning and surface rainfall in warm-season Florida thunderstorms

USGS Publications Warehouse

Gungle, B.; Krider, E.P.

2006-01-01

Relationships between cloud-to-ground (CG) lightning and surface rainfall have been examined in nine isolated, warm-season thunderstorms on the east coast of central Florida. CG flashes and the associated rain volumes were measured as a function of time in storm-centered reference frames that followed each storm over a network of rain gauges. Values of the storm-average rain volume per CG flash ranged from 0.70 ?? 104 to 6.4 ?? 104 m3/CG flash, with a mean (and standard deviation) of 2.6 ?? 104 ?? 2.1 ?? 104 m3/CG flash. Values of the rain volume concurrent with CG flashes ranged from 0.11 ?? 104 to 4.9 ?? 104 m3/CG flash with a mean of 2.1 ?? 104 ?? 2.0 ?? 104 m3/CG flash. The lag-time between the peak CG flash rate and the peak rainfall rate (using 5 min bins), and the results of a lag correlation analysis, show that surface rainfall tends to follow the lightning (positive lag) by up to 20 min in six storms. In one storm the rainfall preceded the lightning by 5 min, and two storms had nonsignificant lags. Values of the lagged rain volume concurrent with CG flashes ranged from 0.43 ?? 104 to 4.9 ?? 104 m3/CG flash, and the mean was 1.9 ?? 104 ?? 1.7 ?? 104 m3/CG flash. For the five storms that produced 12 or more flashes and had significant lags, a plot of the optimum lag time versus the total number of CG flashes shows a linear trend (R2 = 0.56). The number of storms is limited, but the lag results do indicate that large storms tend to have longer lags. A linear fit to the lagged rain volume vs. the number of concurrent CG flashes has a slope of 1.9 ?? 104 m3/CG flash (R2 = 0.83). We conclude that warm-season Florida thunderstorms produce a roughly constant rain volume per CG flash and that CG lightning can be used to estimate the location and intensity of convective rainfall in that weather regime. Copyright 2006 by the American Geophysical Union.

Response of spectral vegetation indices to soil moisture in grasslands and shrublands

USGS Publications Warehouse

Zhang, Li; Ji, Lei; Wylie, Bruce K.

2011-01-01

The relationships between satellite-derived vegetation indices (VIs) and soil moisture are complicated because of the time lag of the vegetation response to soil moisture. In this study, we used a distributed lag regression model to evaluate the lag responses of VIs to soil moisture for grasslands and shrublands at Soil Climate Analysis Network sites in the central and western United States. We examined the relationships between Moderate Resolution Imaging Spectroradiometer (MODIS)-derived VIs and soil moisture measurements. The Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) showed significant lag responses to soil moisture. The lag length varies from 8 to 56 days for NDVI and from 16 to 56 days for NDWI. However, the lag response of NDVI and NDWI to soil moisture varied among the sites. Our study suggests that the lag effect needs to be taken into consideration when the VIs are used to estimate soil moisture.

Simplifying the diagnosis of 4 common voiding conditions using uroflow/electromyography, electromyography lag time and voiding history.

PubMed

Van Batavia, Jason P; Combs, Andrew J; Hyun, Grace; Bayer, Agnes; Medina-Kreppein, Daisy; Schlussel, Richard N; Glassberg, Kenneth I

2011-10-01

Noninvasive uroflowmetry with simultaneous electromyography is useful to triage cases of lower urinary tract symptoms into 4 urodynamically defined conditions, especially when incorporating short and long electromyography lag times in the analysis. We determined the prevalence of these 4 conditions at a single referral institution and the usefulness of uroflowmetry with simultaneous electromyography and electromyography lag time to confirm the diagnosis, guide treatment and monitor response. We retrospectively reviewed the records of 100 consecutive normal children who presented with persistent lower urinary tract symptoms, underwent uroflowmetry with electromyography as part of the initial evaluation and were diagnosed with 1 of 4 conditions based on certain uroflowmetry/electromyography features. The conditions included 1) dysfunctional voiding--active pelvic floor electromyography during voiding with or without staccato flow, 2a) idiopathic detrusor overactivity disorder-A--a quiet pelvic floor during voiding and shortened lag time (less than 2 seconds), 2b) idiopathic detrusor overactivity disorder-B--a quiet pelvic floor with a normal lag time, 3) detrusor underutilization disorder--volitionally deferred voiding with expanded bladder capacity but a quiet pelvic floor, and 4) primary bladder neck dysfunction--prolonged lag time (greater than 6 seconds) and a depressed, right shifted uroflowmetry curve with a quiet pelvic floor during voiding. Treatment was tailored to the underlying condition in each patient. The group consisted of 50 males and 50 females with a mean age of 8 years (range 3 to 18). Dysfunctional voiding was more common in females (p <0.05) while idiopathic detrusor overactivity disorder-B and primary bladder neck dysfunction were more common in males (p <0.01). With treatment uroflowmetry parameters normalized for all types. Electromyography lag time increased in idiopathic detrusor overactivity disorder-A cases and decreased in primary bladder neck dysfunction cases. Noninvasive uroflowmetry with simultaneous electromyography offers an excellent alternative to invasive urodynamics to diagnose 4 urodynamically defined conditions. It identifies the most appropriate therapy for the specific condition and objectively monitors the treatment response. Copyright © 2011 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

THE LICK AGN MONITORING PROJECT: BROAD-LINE REGION RADII AND BLACK HOLE MASSES FROM REVERBERATION MAPPING OF Hbeta

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bentz, Misty C.; Walsh, Jonelle L.; Barth, Aaron J.

2009-11-01

We have recently completed a 64-night spectroscopic monitoring campaign at the Lick Observatory 3-m Shane telescope with the aim of measuring the masses of the black holes in 12 nearby (z < 0.05) Seyfert 1 galaxies with expected masses in the range approx10{sup 6}-10{sup 7} M {sub sun} and also the well-studied nearby active galactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including NGC 5548) showed optical variability of sufficient strength during the monitoring campaign to allow for a time lag to be measured between the continuum fluctuations and the response to these fluctuations in themore » broad Hbeta emission. We present here the light curves for all the objects in this sample and the subsequent Hbeta time lags for the nine objects where these measurements were possible. The Hbeta lag time is directly related to the size of the broad-line region (BLR) in AGNs, and by combining the Hbeta lag time with the measured width of the Hbeta emission line in the variable part of the spectrum, we determine the virial mass of the central supermassive black hole in these nine AGNs. The absolute calibration of the black hole masses is based on the normalization derived by Onken et al., which brings the masses determined by reverberation mapping into agreement with the local M {sub BH}-sigma{sub *}relationship for quiescent galaxies. We also examine the time lag response as a function of velocity across the Hbeta line profile for six of the AGNs. The analysis of four leads to rather ambiguous results with relatively flat time lags as a function of velocity. However, SBS 1116+583A exhibits a symmetric time lag response around the line center reminiscent of simple models for circularly orbiting BLR clouds, and Arp 151 shows an asymmetric profile that is most easily explained by a simple gravitational infall model. Further investigation will be necessary to fully understand the constraints placed on the physical models of the BLR by the velocity-resolved response in these objects.« less

Four-Year Cross-Lagged Associations between Physical and Mental Health in the Medical Outcomes Study.

ERIC Educational Resources Information Center

Hays, Ron D.; And Others

1994-01-01

Applied structural equation modeling to evaluation of cross-lagged panel models. Self-reports of physical and mental health at three time points spanning four-year interval were analyzed to illustrate cross-lagged analysis methodology. Data were analyzed from 856 patients with hypertension, diabetes, heart disease, or depression. Cross-lagged…

Using Tensor Completion Method to Achieving Better Coverage of Traffic State Estimation from Sparse Floating Car Data

PubMed Central

Ran, Bin; Song, Li; Cheng, Yang; Tan, Huachun

2016-01-01

Traffic state estimation from the floating car system is a challenging problem. The low penetration rate and random distribution make available floating car samples usually cover part space and time points of the road networks. To obtain a wide range of traffic state from the floating car system, many methods have been proposed to estimate the traffic state for the uncovered links. However, these methods cannot provide traffic state of the entire road networks. In this paper, the traffic state estimation is transformed to solve a missing data imputation problem, and the tensor completion framework is proposed to estimate missing traffic state. A tensor is constructed to model traffic state in which observed entries are directly derived from floating car system and unobserved traffic states are modeled as missing entries of constructed tensor. The constructed traffic state tensor can represent spatial and temporal correlations of traffic data and encode the multi-way properties of traffic state. The advantage of the proposed approach is that it can fully mine and utilize the multi-dimensional inherent correlations of traffic state. We tested the proposed approach on a well calibrated simulation network. Experimental results demonstrated that the proposed approach yield reliable traffic state estimation from very sparse floating car data, particularly when dealing with the floating car penetration rate is below 1%. PMID:27448326

Using Tensor Completion Method to Achieving Better Coverage of Traffic State Estimation from Sparse Floating Car Data.

PubMed

Ran, Bin; Song, Li; Zhang, Jian; Cheng, Yang; Tan, Huachun

2016-01-01

Traffic state estimation from the floating car system is a challenging problem. The low penetration rate and random distribution make available floating car samples usually cover part space and time points of the road networks. To obtain a wide range of traffic state from the floating car system, many methods have been proposed to estimate the traffic state for the uncovered links. However, these methods cannot provide traffic state of the entire road networks. In this paper, the traffic state estimation is transformed to solve a missing data imputation problem, and the tensor completion framework is proposed to estimate missing traffic state. A tensor is constructed to model traffic state in which observed entries are directly derived from floating car system and unobserved traffic states are modeled as missing entries of constructed tensor. The constructed traffic state tensor can represent spatial and temporal correlations of traffic data and encode the multi-way properties of traffic state. The advantage of the proposed approach is that it can fully mine and utilize the multi-dimensional inherent correlations of traffic state. We tested the proposed approach on a well calibrated simulation network. Experimental results demonstrated that the proposed approach yield reliable traffic state estimation from very sparse floating car data, particularly when dealing with the floating car penetration rate is below 1%.

Effects of pore forming agents on chitosan-graft-poly(N-vinylpyrrolidone) hydrogel properties for use as a matrix for floating drug delivery

NASA Astrophysics Data System (ADS)

Budianto, E.; Al-Shidqi, M. F.; Cahyana, A. H.

2017-07-01

Eradicating H. pylori-based infection by using conventional oral dosage form of amoxicillin trihydrate finds difficulties to overcome rapid gastric retention time. Encapsulating amoxicillin trihydrate in floating drug delivery system may solve the problem. In this research, the floating drug delivery system of amoxicillin trihydrate encapsulated in floating chitosan-graft-poly(N-vinyl pyrrolidone) hydrogels containing CaCO3 and NaHCO3 as pore forming agents has been successfully prepared. Pore forming agents used was varied with the ratio of 10 to 25% pore forming agents to total mass of the used materials. The hydrogel were characterizedusing FTIR spectrophotometer and stereo microscope. As pore forming agents compositions increased, the porosity (%) and floating properties increased but followed by decrease in drug entrapment efficiency. Most of the floating hydrogels possessed floating ability longer than 180 min and the highest porosity was found in hydrogel containing 25% NaHCO3. Hydrogel containing CaCO3 showed sustained drug release profile than hydrogel containing NaHCO3. However, the optimum formulation was achieved at composition of 10% NaHCO3 with 57% of drug entrapped within the hydrogel and 43% drug released. The results of these studies show that NaHCO3 is an effective pore forming agents for chitosan-graft-poly(N-vinyl pyrrolidone) hydrogel preparation as compare to CaCO3.

Limits on an energy dependence of the speed of light from a flare of the active galaxy PKS 2155-304.

PubMed

Aharonian, F; Akhperjanian, A G; Barres de Almeida, U; Bazer-Bachi, A R; Becherini, Y; Behera, B; Beilicke, M; Benbow, W; Bernlöhr, K; Boisson, C; Bochow, A; Borrel, V; Braun, I; Brion, E; Brucker, J; Brun, P; Bühler, R; Bulik, T; Büsching, I; Boutelier, T; Carrigan, S; Chadwick, P M; Charbonnier, A; Chaves, R C G; Chounet, L-M; Clapson, A C; Coignet, G; Costamante, L; Dalton, M; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubois, F; Dubus, G; Dyks, J; Egberts, K; Emmanoulopoulos, D; Espigat, P; Farnier, C; Feinstein, F; Fiasson, A; Förster, A; Fontaine, G; Füssling, M; Gabici, S; Gallant, Y A; Gérard, L; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Holleran, M; Hoppe, S; Horns, D; Jacholkowska, A; de Jager, O C; Jung, I; Katarzyński, K; Kaufmann, S; Kendziorra, E; Kerschhaggl, M; Khangulyan, D; Khélifi, B; Keogh, D; Komin, Nu; Kosack, K; Lamanna, G; Lenain, J-P; Lohse, T; Marandon, V; Martin, J M; Martineau-Huynh, O; Marcowith, A; Maurin, D; McComb, T J L; Medina, C; Moderski, R; Moulin, E; Naumann-Godo, M; de Naurois, M; Nedbal, D; Nekrassov, D; Niemiec, J; Nolan, S J; Ohm, S; Olive, J-F; de Oña Wilhelmi, E; Orford, K J; Osborne, J L; Ostrowski, M; Panter, M; Pedaletti, G; Pelletier, G; Petrucci, P-O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raubenheimer, B C; Raue, M; Rayner, S M; Renaud, M; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Ruppel, J; Sahakian, V; Santangelo, A; Schlickeiser, R; Schöck, F M; Schröder, R; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Skilton, J L; Sol, H; Spangler, D; Stawarz, Ł; Steenkamp, R; Stegmann, C; Superina, G; Tam, P H; Tavernet, J-P; Terrier, R; Tibolla, O; van Eldik, C; Vasileiadis, G; Venter, C; Vialle, J P; Vincent, P; Vivier, M; Völk, H J; Volpe, F; Wagner, S J; Ward, M; Zdziarski, A A; Zech, A

2008-10-24

In the past few decades, several models have predicted an energy dependence of the speed of light in the context of quantum gravity. For cosmological sources such as active galaxies, this minuscule effect can add up to measurable photon-energy dependent time lags. In this Letter a search for such time lags during the High Energy Stereoscopic System observations of the exceptional very high energy flare of the active galaxy PKS 2155-304 on 28 July 2006 is presented. Since no significant time lag is found, lower limits on the energy scale of speed of light modifications are derived.

Effectiveness of Circadian countermeasures in simulated transmeridian flight schedules

NASA Technical Reports Server (NTRS)

Moline, Margaret L.; Monk, Timothy H.

1989-01-01

The symptoms of jet-lag commonly afflict travelers who cross time zones. Insomnia during the new night, daytime fatigue, malaise, sleepiness, and gastrointestinal disturbances can occur for as long as 3 weeks after jet travel across even a few time zones. These symptoms are largely due to the slow rate of adjustment of the internal circadian timing system to the new time zone. Since business (or pleasure) can be seriously interrupted by such symptoms, it is important to determine ways to speed up the adjustment process to ameliorate the symptoms. Airline pilots have reported that they frequently nap to counter jet lag symptoms, and that they view this as a useful technique. Napping as a countermeasure would be attractive since it is practical and would take advantage of a naturally occurring phase of sleepiness after lunch. Napping also makes sense since insomnia is a common jet lag symptom. Thus, a laboratory simulation of jet lag was designed to test the ability of napping to increase the rate of adjustment following a time zone shift in a population of middle-aged men.

Throwing Pattern: Changes in Timing of Joint Lag According to Age between and within Skill Level

ERIC Educational Resources Information Center

Southard, Dan

2009-01-01

Accomplished throwers conserve angular momentum when distal joints of the throwing arm reach peak velocity at a later time than their proximal neighbors. The result is an increase in velocity of the most distal segment--the hand. Past research indicates that skill level varies by the number of joints experiencing distal timing lag (time to peak…

Hydrodynamic analysis of floating platform for special purposes under complex water environment

NASA Astrophysics Data System (ADS)

Ma, Guang-ying; Yao, Yun-long

2018-03-01

This article studied a new floating offshore platform for special purposes, which was assembled by standard floating modules. By using ANSYS AQWA software, the hydrodynamic model of the platform was established. The time history responses of the platform motions and the cable tension forces were calculate under complex water environments, such as wind, wave, current and mooring. The results showed that the tension of the four cables are far less than the breaking tension of the cable, so that the cable will not break. This study can be referenced by the relevant researchers and engineers.

Lipid tethering of breast tumor cells enables real-time imaging of free-floating cell dynamics and drug response

PubMed Central

Whipple, Rebecca A.; Zhang, Peipei; Sooklal, Elisabeth L.; Martin, Stuart S.; Jewell, Christopher M.

2016-01-01

Free-floating tumor cells located in the blood of cancer patients, known as circulating tumor cells (CTCs), have become key targets for studying metastasis. However, effective strategies to study the free-floating behavior of tumor cells in vitro have been a major barrier limiting the understanding of the functional properties of CTCs. Upon extracellular-matrix (ECM) detachment, breast tumor cells form tubulin-based protrusions known as microtentacles (McTNs) that play a role in the aggregation and re-attachment of tumor cells to increase their metastatic efficiency. In this study, we have designed a strategy to spatially immobilize ECM-detached tumor cells while maintaining their free-floating character. We use polyelectrolyte multilayers deposited on microfluidic substrates to prevent tumor cell adhesion and the addition of lipid moieties to tether tumor cells to these surfaces through interactions with the cell membranes. This coating remains optically clear, allowing capture of high-resolution images and videos of McTNs on viable free-floating cells. In addition, we show that tethering allows for the real-time analysis of McTN dynamics on individual tumor cells and in response to tubulin-targeting drugs. The ability to image detached tumor cells can vastly enhance our understanding of CTCs under conditions that better recapitulate the microenvironments they encounter during metastasis. PMID:26871289

Role of Lymphocyte Activation Gene-3 (Lag-3) in Conventional and Regulatory T Cell Function in Allogeneic Transplantation

PubMed Central

Sega, Emanuela I.; Leveson-Gower, Dennis B.; Florek, Mareike; Schneidawind, Dominik; Luong, Richard H.; Negrin, Robert S.

2014-01-01

Lag-3 has emerged as an important molecule in T cell biology. We investigated the role of Lag-3 in conventional T cell (Tcon) and regulatory T cell (Treg) function in murine GVHD with the hypothesis that Lag-3 engagement diminishes alloreactive T cell responses after bone marrow transplantation. We demonstrate that Lag-3 deficient Tcon (Lag-3−/− Tcon) induce significantly more severe GVHD than wild type (WT) Tcon and that the absence of Lag-3 on CD4 but not CD8 T cells is responsible for exacerbating GVHD. Lag-3−/− Tcon exhibited increased activation and proliferation as indicated by CFSE and bioluminescence imaging analyses and higher levels of activation markers such as CD69, CD107a, granzyme B, and Ki-67 as well as production of IL-10 and IFN-g early after transplantation. Lag-3−/− Tcon were less responsive to suppression by WT Treg as compared to WT Tcon. The absence of Lag-3, however, did not impair Treg function as both Lag-3−/− and WT Treg equally suppress the proliferation of Tcon in vitro and in vivo and protect against GVHD. Further, we demonstrate that allogeneic Treg acquire recipient MHC class II molecules through a process termed trogocytosis. As MHC class II is a ligand for Lag-3, we propose a novel suppression mechanism employed by Treg involving the acquisition of host MHC-II followed by the engagement of Lag-3 on T cells. These studies demonstrate for the first time the biologic function of Lag-3 expression on conventional and regulatory T cells in GVHD and identify Lag-3 as an important regulatory molecule involved in alloreactive T cell proliferation and activation after bone marrow transplantation. PMID:24475140

Catchment Legacies and Trajectories: Understanding Time Lags in Catchment Response as a Function of Hydrologic and Biogeochemical Controls

NASA Astrophysics Data System (ADS)

Basu, N. B.; Van Meter, K. J.

2012-12-01

Increased nutrient loads delivered from watersheds due to agricultural intensification, industrialization, and urbanization have contributed globally to the persistence of large hypoxic zones in inland and coastal waters. Watershed management practices targeting these non-point source pollutants often lead to little or no improvement in water quality, even after extensive implementation of conservation measures or Best Management Practices (BMPs). The lag time between implementation of a conservation measure and resultant water quality benefits has recently been recognized as an important factor in the "apparent" failure of these BMPs. When conservation measures are implemented without explicit consideration of the lag time and with expectations that they will lead to immediate benefits, the resulting failure to meet such expectations can discourage vital restoration efforts. It is therefore important to quantify the lag times associated with watershed management efforts a priori and to implement restoration strategies targeted specifically at minimizing lag times and maximizing restoration benefits. The focus of this research is to develop a framework for understanding the time lags between land-use changes and stream water quality benefits. We hypothesize that such time lags arise from nutrient legacies building over decades of fertilizer application. For nitrogen (N), one can conceptualize this as either hydrologic legacy, in the form of dissolved nitrate that is delayed due to slow groundwater transport, or as biogeochemical legacy, in the form of organic N, possibly in dissolved or readily mineralizable forms. Indeed, mass-balance studies across the Mississippi and Thames river basins indicate the possibility of missing N mass in these landscapes, with inputs being consistently greater than the outputs even when accounting for all possible pathways of nitrogen transformation. Historical soil data within the upper Mississippi River Basin (MRB) indicate that agriculture depletes organic N in surface soil, but leads to N accumulations deeper in the profile. Nitrogen accumulation estimates (approximately 2 million Mt/yr) based on the historical data are startlingly close to the deficit suggested by mass-balance studies of the MRB (3 million Mt/yr). Understanding the lag times associated with such biogeochemical legacies requires quantification of this accumulation as a function of landscape attributes, climate, and management controls, as well as the rate of mineralization of accumulated N after implementation of management practices. Understanding hydrologic legacy requires a partitioning of flow along various pathways (e.g., overland flow, tile flow, or groundwater pathways), and the distribution of travel times along the pathways. Based on this framework, we developed a coupled hydrologic and biogeochemical model to quantify these legacies and predict landscape recovery times as a function of natural and anthropogenic controls.

An integrated error estimation and lag-aware data assimilation scheme for real-time flood forecasting

USDA-ARS?s Scientific Manuscript database

The performance of conventional filtering methods can be degraded by ignoring the time lag between soil moisture and discharge response when discharge observations are assimilated into streamflow modelling. This has led to the ongoing development of more optimal ways to implement sequential data ass...

Evolution of Accretion Disc Geometry of GRS 1915+105 during its χ state as revealed by TCAF solution

NASA Astrophysics Data System (ADS)

Dutta, Broja G.; Pal, Partha Sarathi; Chakrabarti, Sandip K.

2018-06-01

The evolution of the C-type low frequency quasi-periodic oscillations (LFQPOs) and associated time lag in transient black hole sources as a function of time can be explained by variation of the Compton cloud size in a Two Component Advective Flow solution (TCAF). A similar study of a persistent source, GRS 1915+105, has not been attempted. We fit the evolution of QPOs with propagatory oscillating shock (POS) solution for two sets of so-called χ-state observations and find that the shock steadily recedes with almost constant velocity when QPO frequency is decreasing and the spectrum is hardening. The shock moves inward with a constant velocity v0 = 473.0 cm s-1 and v0 = 400.0 cm s-1 respectively in these two cases, when the QPO frequency is increasing and the spectrum softens. This behavior is similar to what was observed in XTE J1550-564 during the 1998 outburst. The time lag measured at the QPO frequency varies in a similar way as the size of the Compton cloud. Most interestingly, in both the cases, the lag switches sign (hard lag to soft lag) at a QPO frequency of ˜2.3 - 2.5 Hz irrespective of the energy of photons. We find, at very low frequencies <1 Hz, the Comptonizing Efficiency (CE) increases with QPO frequency and at higher QPO frequencies the trend is opposite. The time lags become mostly positive at all energies when CE is larger than ˜0.85% for both the sources.

THE SPECTRAL-TIMING PROPERTIES OF UPPER AND LOWER kHz QPOs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peille, Philippe; Barret, Didier; Uttley, Phil, E-mail: philippe.peille@irap.omp.eu

2015-10-01

Soft lags from the emission of the lower kilohertz quasi-periodic oscillations (kHz QPOs) of neutron star low-mass X-ray binaries have been reported from 4U1608-522 and 4U1636-536. Those lags hold prospects for constraining the origin of the QPO emission. In this paper, we investigate the spectral-timing properties of both the lower and upper kHz QPOs from the neutron star binary 4U1728-34, using the entire Rossi X-Ray Timing Explorer archive on this source. We show that the lag-energy spectra of the two QPOs are systematically different: while the lower kHz QPO shows soft lags, the upper kHz QPO shows either a flatmore » lag-energy spectrum or hard variations lagging softer variations. This suggests two different QPO-generation mechanisms. We also performed the first spectral deconvolution of the covariance spectra of both kHz QPOs. The QPO spectra are consistent with Comptonized blackbody emission, similar to the one found in the time-averaged spectrum, but with a higher seed-photon temperature, suggesting that a more compact inner region of the Comptonization layer (boundary/spreading layer, corona) is responsible for the QPO emission. Considering our results together with other recent findings, this leads us to the hypothesis that the lower kHz QPO signal is generated by coherent oscillations of the compact boundary layer region itself. The upper kHz QPO signal may then be linked to less-coherent accretion-rate variations produced in the inner accretion disk, and is then detected when they reach the boundary layer.« less

On the phase lag of turbulent dissipation in rotating tidal flows

NASA Astrophysics Data System (ADS)

Zhang, Qianjiang; Wu, Jiaxue

2018-03-01

Field observations of rotating tidal flows in a shallow tidally swept sea reveal that a notable phase lag of both shear production and turbulent dissipation increases with height above the seafloor. These vertical delays of turbulent quantities are approximately equivalent in magnitude to that of squared mean shear. The shear production approximately equals turbulent dissipation over the phase-lag column, and thus a main mechanism of phase lag of dissipation is mean shear, rather than vertical diffusion of turbulent kinetic energy. By relating the phase lag of dissipation to that of the mean shear, a simple formulation with constant eddy viscosity is developed to describe the phase lag in rotating tidal flows. An analytical solution indicates that the phase lag increases linearly with height subjected to a combined effect of tidal frequency, Coriolis parameter and eddy viscosity. The vertical diffusion of momentum associated with eddy viscosity produces the phase lag of squared mean shear, and resultant delay of turbulent quantities. Its magnitude is inhibited by Earth's rotation. Furthermore, a theoretical formulation of the phase lag with a parabolic eddy viscosity profile can be constructed. A first-order approximation of this formulation is still a linear function of height, and its magnitude is approximately 0.8 times that with constant viscosity. Finally, the theoretical solutions of phase lag with realistic viscosity can be satisfactorily justified by realistic phase lags of dissipation.

Determination of the Time-Space Magnetic Correlation Functions in the Solar Wind

NASA Astrophysics Data System (ADS)

Weygand, J. M.; Matthaeus, W. H.; Kivelson, M.; Dasso, S.

2013-12-01

Magnetic field data from many different intervals and 7 different solar wind spacecraft are employed to estimate the scale-dependent time decorrelation function in the interplanetary magnetic field in both the slow and fast solar wind. This estimation requires correlations varying with both space and time lags. The two point correlation function with no time lag is determined by correlating time series data from multiple spacecraft separated in space and for complete coverage of length scales relies on many intervals with different spacecraft spatial separations. In addition we employ single spacecraft time-lagged correlations, and two spacecraft time lagged correlations to access different spatial and temporal correlation data. Combining these data sets gives estimates of the scale-dependent time decorrelation function, which in principle tells us how rapidly time decorrelation occurs at a given wavelength. For static fields the scale-dependent time decorrelation function is trivially unity, but in turbulence the nonlinear cascade process induces time-decorrelation at a given length scale that occurs more rapidly with decreasing scale. The scale-dependent time decorrelation function is valuable input to theories as well as various applications such as scattering, transport, and study of predictability. It is also a fundamental element of formal turbulence theory. Our results are extension of the Eulerian correlation functions estimated in Matthaeus et al. [2010], Weygand et al [2012; 2013].

Ergodicity of Traffic Flow with Constant Penetration Rate for Traffic Monitoring via Floating Vehicle Technique

NASA Astrophysics Data System (ADS)

Gunawan, Fergyanto E.; Abbas, Bahtiar S.; Atmadja, Wiedjaja; Yoseph Chandra, Fajar; Agung, Alexander AS; Kusnandar, Erwin

2014-03-01

Traffic congestion in Asian megacities has become extremely worse, and any means to lessen the congestion level is urgently needed. Building an efficient mass transportation system is clearly necessary. However, implementing Intelligent Transportation Systems (ITS) have also been demonstrated effective in various advanced countries. Recently, the floating vehicle technique (FVT), an ITS implementation, has become cost effective to provide real-time traffic information with proliferation of the smartphones. Although many publications have discussed various issues related to the technique, none of them elaborates the discrepancy of a single floating car data (FCD) and the associated fleet data. This work addresses the issue based on an analysis of Sugiyama et al's experimental data. The results indicate that there is an optimum averaging time interval such that the estimated velocity by the FVT reasonably representing the traffic velocity.

Modeling eye gaze patterns in clinician-patient interaction with lag sequential analysis.

PubMed

Montague, Enid; Xu, Jie; Chen, Ping-Yu; Asan, Onur; Barrett, Bruce P; Chewning, Betty

2011-10-01

The aim of this study was to examine whether lag sequential analysis could be used to describe eye gaze orientation between clinicians and patients in the medical encounter. This topic is particularly important as new technologies are implemented into multiuser health care settings in which trust is critical and nonverbal cues are integral to achieving trust. This analysis method could lead to design guidelines for technologies and more effective assessments of interventions. Nonverbal communication patterns are important aspects of clinician-patient interactions and may affect patient outcomes. The eye gaze behaviors of clinicians and patients in 110 videotaped medical encounters were analyzed using the lag sequential method to identify significant behavior sequences. Lag sequential analysis included both event-based lag and time-based lag. Results from event-based lag analysis showed that the patient's gaze followed that of the clinician, whereas the clinician's gaze did not follow the patient's. Time-based sequential analysis showed that responses from the patient usually occurred within 2 s after the initial behavior of the clinician. Our data suggest that the clinician's gaze significantly affects the medical encounter but that the converse is not true. Findings from this research have implications for the design of clinical work systems and modeling interactions. Similar research methods could be used to identify different behavior patterns in clinical settings (physical layout, technology, etc.) to facilitate and evaluate clinical work system designs.

Modeling Eye Gaze Patterns in Clinician-Patient Interaction with Lag Sequential Analysis

PubMed Central

Montague, E; Xu, J; Asan, O; Chen, P; Chewning, B; Barrett, B

2011-01-01

Objective The aim of this study was to examine whether lag-sequential analysis could be used to describe eye gaze orientation between clinicians and patients in the medical encounter. This topic is particularly important as new technologies are implemented into multi-user health care settings where trust is critical and nonverbal cues are integral to achieving trust. This analysis method could lead to design guidelines for technologies and more effective assessments of interventions. Background Nonverbal communication patterns are important aspects of clinician-patient interactions and may impact patient outcomes. Method Eye gaze behaviors of clinicians and patients in 110-videotaped medical encounters were analyzed using the lag-sequential method to identify significant behavior sequences. Lag-sequential analysis included both event-based lag and time-based lag. Results Results from event-based lag analysis showed that the patients’ gaze followed that of clinicians, while clinicians did not follow patients. Time-based sequential analysis showed that responses from the patient usually occurred within two seconds after the initial behavior of the clinician. Conclusion Our data suggest that the clinician’s gaze significantly affects the medical encounter but not the converse. Application Findings from this research have implications for the design of clinical work systems and modeling interactions. Similar research methods could be used to identify different behavior patterns in clinical settings (physical layout, technology, etc.) to facilitate and evaluate clinical work system designs. PMID:22046723

A critique of the cross-lagged panel model.

PubMed

Hamaker, Ellen L; Kuiper, Rebecca M; Grasman, Raoul P P P

2015-03-01

The cross-lagged panel model (CLPM) is believed by many to overcome the problems associated with the use of cross-lagged correlations as a way to study causal influences in longitudinal panel data. The current article, however, shows that if stability of constructs is to some extent of a trait-like, time-invariant nature, the autoregressive relationships of the CLPM fail to adequately account for this. As a result, the lagged parameters that are obtained with the CLPM do not represent the actual within-person relationships over time, and this may lead to erroneous conclusions regarding the presence, predominance, and sign of causal influences. In this article we present an alternative model that separates the within-person process from stable between-person differences through the inclusion of random intercepts, and we discuss how this model is related to existing structural equation models that include cross-lagged relationships. We derive the analytical relationship between the cross-lagged parameters from the CLPM and the alternative model, and use simulations to demonstrate the spurious results that may arise when using the CLPM to analyze data that include stable, trait-like individual differences. We also present a modeling strategy to avoid this pitfall and illustrate this using an empirical data set. The implications for both existing and future cross-lagged panel research are discussed. (c) 2015 APA, all rights reserved).

The Lag-Luminosity Relation in the GRB Source-Frame: An Investigation with Swift BAT Bursts

NASA Technical Reports Server (NTRS)

Ukwatta, T. N.; Dhuga, K. S.; Stamatikos, M.; Dermer, C. D.; Sakamoto, T.; Sonbas, E.; Parke, W. C.; Maximon, L. C.; Linnemann, J. T.; Bhat, P. N.;

A way around the Nyquist lag

NASA Astrophysics Data System (ADS)

Penland, C.

2017-12-01

One way to test for the linearity of a multivariate system is to perform Linear Inverse Modeling (LIM) to a multivariate time series. LIM yields an estimated operator by combining a lagged covariance matrix with the contemporaneous covariance matrix. If the underlying dynamics is linear, the resulting dynamical description should not depend on the particular lag at which the lagged covariance matrix is estimated. This test is known as the "tau test." The tau test will be severely compromised if the lag at which the analysis is performed is approximately half the period of an internal oscillation frequency. In this case, the tau test will fail even though the dynamics are actually linear. Thus, until now, the tau test has only been possible for lags smaller than this "Nyquist lag." In this poster, we investigate the use of Hilbert transforms as a way to avoid the problems associated with Nyquist lags. By augmenting the data with dimensions orthogonal to those spanning the original system, information that would be inaccessible to LIM in its original form may be sampled.

Constant versus variable response signal delays in speed--accuracy trade-offs: effects of advance preparation for processing time.

PubMed

Miller, Jeff; Sproesser, Gudrun; Ulrich, Rolf

2008-07-01

In two experiments, we used response signals (RSs) to control processing time and trace out speed--accuracy trade-off(SAT) functions in a difficult perceptual discrimination task. Each experiment compared performance in blocks of trials with constant and, hence, temporally predictable RS lags against performance in blocks with variable, unpredictable RS lags. In both experiments, essentially equivalent SAT functions were observed with constant and variable RS lags. We conclude that there is little effect of advance preparation for a given processing time, suggesting that the discrimination mechanisms underlying SAT functions are driven solely by bottom-up information processing in perceptual discrimination tasks.

Floating tablets for controlled release of ofloxacin via compression coating of hydroxypropyl cellulose combined with effervescent agent.

PubMed

Qi, Xiaole; Chen, Haiyan; Rui, Yao; Yang, Fengjiao; Ma, Ning; Wu, Zhenghong

2015-07-15

To prolong the residence time of dosage forms within gastrointestinal trace until all drug released at desired rate was one of the real challenges for oral controlled-release drug delivery system. Herein, we developed a fine floating tablet via compression coating of hydrophilic polymer (hydroxypropyl cellulose) combined with effervescent agent (sodium bicarbonate) to achieve simultaneous control of release rate and location of ofloxacin. Sodium alginate was also added in the coating layer to regulate the drug release rate. The effects of the weight ratio of drug and the viscosity of HPC on the release profile were investigated. The optimized formulations were found to immediately float within 30s and remain lastingly buoyant over a period of 12 h in simulated gastric fluid (SGF, pH 1.2) without pepsin, indicating a satisfactory floating and zero-order drug release profile. In addition, the oral bioavailability experiment in New Zealand rabbits showed that, the relative bioavailability of the ofloxacin after administrated of floating tablets was 172.19%, compared to marketed common release tablets TaiLiBiTuo(®). These results demonstrated that those controlled-released floating tables would be a promising gastro-retentive delivery system for drugs acting in stomach. Copyright © 2015 Elsevier B.V. All rights reserved.

Weathering of field-collected floating and stranded Macondo oils during and shortly after the Deepwater Horizon oil spill.

PubMed

Stout, Scott A; Payne, James R; Emsbo-Mattingly, Stephen D; Baker, Gregory

2016-04-15

Chemical analysis of large populations of floating (n=62) and stranded (n=1174) Macondo oils collected from the northern Gulf of Mexico sea surface and shorelines during or within seven weeks of the end of the Deepwater Horizon oil spill demonstrates the range, rates, and processes affecting surface oil weathering. Oil collected immediately upon reaching the sea surface had already lost most mass below n-C8 from dissolution of soluble aliphatics, monoaromatics, and naphthalenes during the oil's ascent with further reductions extending up to n-C13 due to the onset of evaporation. With additional time, weathering of the floating and stranded oils advanced with total PAH (TPAH50) depletions averaging 69±23% for floating oils and 94±3% for stranded oils caused by the combined effects of evaporation, dissolution, and photo-oxidation, the latter of which also reduced triaromatic steroid biomarkers. Biodegradation was not evident among the coalesced floating oils studied, but had commenced in some stranded oils. Copyright © 2016 Elsevier Ltd. All rights reserved.

Development and calibration of an air-floating six-axis force measurement platform using self-calibration

NASA Astrophysics Data System (ADS)

Huang, Bin; Wang, Xiaomeng; Li, Chengwei; Yi, Jiajing; Lu, Rongsheng; Tao, Jiayue

2016-09-01

This paper describes the design, working principle, as well as calibration of an air-floating six-axis force measurement platform, where the floating plate and nozzles were connected without contact, preventing inter-dimensional coupling and increasing precision significantly. The measurement repeatability error of the force size in the platform is less than 0.2% full scale (FS), which is significantly better than the precision of 1% FS in the six-axis force sensors on the current market. We overcame the difficulties of weight loading device in high-precision calibration by proposing a self-calibration method based on the floating plate gravity and met the calibration precision requirement of 0.02% FS. This study has general implications for the development and calibration of high-precision multi-axis force sensors. In particular, the air-floating six-axis force measurement platform could be applied to the calibration of some special sensors such as flexible tactile sensors and may be used as a micro-nano mechanical assembly platform for real-time assembly force testing.

Cross-sectional study on their reproductive health status of 604 female floating residents in Beijing.

PubMed

Wang, Y; An, L; Zhang, X B; Wang, S X

1999-03-01

The rapid increases in the numbers of female labor migrants ("floating residents") in cities such as Beijing have created challenges for China's reproductive health care system. An exploratory study conducted in Beijing in 1996 of 507 floating workers engaged in household management work (average age, 27.4 years) sought to gain information to facilitate the design of reproductive health services for this group. The women had resided in Beijing for an average of 3.7 years, generally with their families. 84% were married, at a mean age of 21.87 years; married women had an average of 1.43 live births, 42% of which had occurred in Beijing. 25% did not receive any prenatal care and 60% did not know whom to consult about maternal-child health care problems. Contraceptive prevalence was 81.1% among floating workers compared with 97% among a comparison group of nonmigrant agricultural and textile workers. Most floating workers were unaware of any contraceptive methods other than the one they were using (generally the IUD or female sterilization). Finally, only 8.4% could cite symptoms of sexually transmitted diseases and 33.9% had not heard of AIDS. Laboratory examinations revealed a 29.3% prevalence of reproductive tract infections among female floating residents. bacterial vaginitis (11.6%) and Mycoplasma infection (6.7%) were most prevalent. These findings confirm that female floating residents remain in Beijing a long time and have a serious unmet need for targeted reproductive health care services.

The Lag-Luminosity Relation in the GRB Source Frame: An Investigation with Swift BAT Bursts

NASA Technical Reports Server (NTRS)

Ukwatta, T. N.; Dhuga, K. S.; Stamatikos, M.; Dermer, C. D.; Sakamoto, T.; Sonbas, E.; Parke, W. C.; Maximon, L. C.; Linnemann, J. T.; Bhat, P. N.;

The effect of rising vs. falling glucose level on amperometric glucose sensor lag and accuracy in Type 1 diabetes.

PubMed

Ward, W K; Engle, J M; Branigan, D; El Youssef, J; Massoud, R G; Castle, J R

2012-08-01

Because declining glucose levels should be detected quickly in persons with Type 1 diabetes, a lag between blood glucose and subcutaneous sensor glucose can be problematic. It is unclear whether the magnitude of sensor lag is lower during falling glucose than during rising glucose. Initially, we analysed 95 data segments during which glucose changed and during which very frequent reference blood glucose monitoring was performed. However, to minimize confounding effects of noise and calibration error, we excluded data segments in which there was substantial sensor error. After these exclusions, and combination of data from duplicate sensors, there were 72 analysable data segments (36 for rising glucose, 36 for falling). We measured lag in two ways: (1) the time delay at the vertical mid-point of the glucose change (regression delay); and (2) determination of the optimal time shift required to minimize the difference between glucose sensor signals and blood glucose values drawn concurrently. Using the regression delay method, the mean sensor lag for rising vs. falling glucose segments was 8.9 min (95%CI 6.1-11.6) vs. 1.5 min (95%CI -2.6 to 5.5, P<0.005). Using the time shift optimization method, results were similar, with a lag that was higher for rising than for falling segments [8.3 (95%CI 5.8-10.7) vs. 1.5 min (95% CI -2.2 to 5.2), P<0.001]. Commensurate with the lag results, sensor accuracy was greater during falling than during rising glucose segments. In Type 1 diabetes, when noise and calibration error are minimized to reduce effects that confound delay measurement, subcutaneous glucose sensors demonstrate a shorter lag duration and greater accuracy when glucose is falling than when rising. © 2011 The Authors. Diabetic Medicine © 2011 Diabetes UK.

Testing Under Fire: Chicago's Problem.

ERIC Educational Resources Information Center

Byrd, Manford, Jr.

The history and development of city-wide testing programs in Chicago since 1936 are reviewed and placed in context with the impact on testing of Sputnik and the passage of the National Defense Education Act of 1958. Current testing problems include the time lag between events and curricular changes and new test construction, the time lag between…

Modeling Time-Dependent Association in Longitudinal Data: A Lag as Moderator Approach

ERIC Educational Resources Information Center

Selig, James P.; Preacher, Kristopher J.; Little, Todd D.

2012-01-01

We describe a straightforward, yet novel, approach to examine time-dependent association between variables. The approach relies on a measurement-lag research design in conjunction with statistical interaction models. We base arguments in favor of this approach on the potential for better understanding the associations between variables by…

Summer Travel: Plan Ahead To Stay Healthy

MedlinePlus

... Twery says. “It’s especially important before and during travel to consciously schedule time to sleep.” Too little sleep leads to poor ... and their ability to meet the challenges of travel.” Jet lag is another sleep concern for travelers crossing multiple time zones. Jet lag is often more severe for ...

Distributed lags time series analysis versus linear correlation analysis (Pearson's r) in identifying the relationship between antipseudomonal antibiotic consumption and the susceptibility of Pseudomonas aeruginosa isolates in a single Intensive Care Unit of a tertiary hospital.

PubMed

Erdeljić, Viktorija; Francetić, Igor; Bošnjak, Zrinka; Budimir, Ana; Kalenić, Smilja; Bielen, Luka; Makar-Aušperger, Ksenija; Likić, Robert

2011-05-01

The relationship between antibiotic consumption and selection of resistant strains has been studied mainly by employing conventional statistical methods. A time delay in effect must be anticipated and this has rarely been taken into account in previous studies. Therefore, distributed lags time series analysis and simple linear correlation were compared in their ability to evaluate this relationship. Data on monthly antibiotic consumption for ciprofloxacin, piperacillin/tazobactam, carbapenems and cefepime as well as Pseudomonas aeruginosa susceptibility were retrospectively collected for the period April 2006 to July 2007. Using distributed lags analysis, a significant temporal relationship was identified between ciprofloxacin, meropenem and cefepime consumption and the resistance rates of P. aeruginosa isolates to these antibiotics. This effect was lagged for ciprofloxacin and cefepime [1 month (R=0.827, P=0.039) and 2 months (R=0.962, P=0.001), respectively] and was simultaneous for meropenem (lag 0, R=0.876, P=0.002). Furthermore, a significant concomitant effect of meropenem consumption on the appearance of multidrug-resistant P. aeruginosa strains (resistant to three or more representatives of classes of antibiotics) was identified (lag 0, R=0.992, P<0.001). This effect was not delayed and it was therefore identified both by distributed lags analysis and the Pearson's correlation coefficient. Correlation coefficient analysis was not able to identify relationships between antibiotic consumption and bacterial resistance when the effect was delayed. These results indicate that the use of diverse statistical methods can yield significantly different results, thus leading to the introduction of possibly inappropriate infection control measures. Copyright © 2010 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

Chromatic induction in space and time.

PubMed

Coia, Andrew J; Shevell, Steven K

2018-04-01

The color appearance of a light depends on variation in the complete visual field over both space and time. In the spatial domain, a chromatic stimulus within a patterned chromatic surround can appear a different hue than the same stimulus within a uniform surround. In the temporal domain, a stimulus presented as an element of a continuously changing chromaticity can appear a different color compared to the identical stimulus, presented simultaneously but viewed alone. This is the flash-lag effect for color, which has an analog in the domain of motion: a pulsed object seen alone can appear to lag behind an identical pulsed object that is an element of a motion sequence. Studies of the flash-lag effect for motion have considered whether it is mediated by a neural representation for the moving physical stimulus or, alternatively, for the perceived motion. The current study addresses this question for the flash-lag effect for color by testing whether the color flash lag depends on a representation of only the changing chromatic stimulus or, alternatively, its color percept, which can be altered by chromatic induction. baseline measurements for spatial chromatic induction determined the chromaticity of a flashed ring within a uniform surround that matched a flashed ring within a patterned surround. Baseline measurements for the color flash-lag effect determined the chromaticity of a pulsed ring presented alone (within a uniform surround) that matched a pulsed ring presented in a sequence of changing chromaticity over time (also within a uniform surround). Finally, the main experiments combined chromatic induction from a patterned surround and the flash-lag effect, in three conditions: (1) both the changing and pulsed rings were within a patterned chromatic surround; (2) the changing ring was within a patterned surround and the pulsed ring within a uniform surround; and (3) the changing ring was within a uniform surround and the pulsed ring within a patterned surround. the flash-lag measurements for a changing chromaticity were affected by perceptual changes induced by the surrounding chromatic pattern. Thus, the color shifts induced by a chromatic surround are incorporated in the neural representation mediating the flash-lag effect for color.

Sustained effect of glucagon on body weight and blood glucose: Assessed by continuous glucose monitoring in diabetic rats

PubMed Central

Thomsen, Maria; Rosenkilde, Mette Marie

2018-01-01

Insulin is a vital part of diabetes treatment, whereas glucagon is primarily used to treat insulin-induced hypoglycemia. However, glucagon is suggested to have a central role in the regulation of body weight, which would be beneficial for diabetic patients. Since the glucagon effect on blood glucose is known to be transient, it is relevant to investigate the pharmacodynamics of glucagon after repeated dosing. In the present study, we used telemetry to continuously measure blood glucose in streptozotocin induced diabetic Sprague-Dawley rats. This allowed for a more detailed analysis of glucose regulation compared to intermittent blood sampling. In particular, we evaluated the blood glucose-lowering effect of different insulin doses alone, and in combination with a long acting glucagon analog (LAG). We showed how the effect of the LAG accumulated and persisted over time. Furthermore, we found that addition of the LAG decreased body weight without affecting food intake. In a subsequent study, we focused on the glucagon effect on body weight and food intake during equal glycemic control. In order to obtain comparable maximum blood glucose lowering effect to insulin alone, the insulin dose had to be increased four times in combination with 1 nmol/kg of the LAG. In this set-up the LAG prevented further increase in body weight despite the four times higher insulin-dose. However, the body composition was changed. The insulin group increased both lean and fat mass, whereas the group receiving four times insulin in combination with the LAG only significantly increased the fat mass. No differences were observed in food intake, suggesting a direct effect on energy expenditure by glucagon. Surprisingly, we observed decreased levels of FGF21 in plasma compared to insulin treatment alone. With the combination of insulin and the LAG the blood glucose-lowering effect of insulin was prolonged, which could potentially be beneficial in diabetes treatment. PMID:29558502

The annual cycle of nitrate and net community production in surface waters of the Southern Ocean observed with SOCCOM profiling floats

NASA Astrophysics Data System (ADS)

Johnson, K. S.; Plant, J. N.; Sakamoto, C.; Coletti, L. J.; Sarmiento, J. L.; Riser, S.; Talley, L. D.

2016-12-01

Sixty profiling floats with ISUS and SUNA nitrate sensors have been deployed in the Southern Ocean (south of 30 degrees S) as part of the SOCCOM (Southern Ocean Carbon and Climate Observations and Modeling) program and earlier efforts. These floats have produced detailed records of the annual cycle of nitrate concentration throughout the region from the surface to depths near 2000 m. In surface waters, there are clear cycles in nitrate concentration that result from uptake of nitrate during austral spring and summer. These changes in nitrate concentration were used to compute the annual net community production over this region. NCP was computed using a simplified version of the approach detailed by Plant et al. (2016, Global Biogeochemical Cycles, 30, 859-879, DOI: 10.1002/2015GB005349). At the time the abstract was written 41 complete annual cycles were available from floats deployed before the austral summer of 2015/2016. After filtering the data to remove floats that crossed distinct frontal boundaries, floats with other anomalies, and floats in sub-tropical waters, 23 cycles were available. A preliminary assessment of the data yields an NCP of 2.8 +/- 0.95 (1 SD) mol C/m2/y after integrating to 100 m depth and converting nitrate uptake to carbon using the Redfield ratio. This preliminary assessment ignores vertical transport across the nitracline and is, therefore, a minimum estimate. The number of cycles available for analysis will increase rapidly, as 32 of the floats were deployed in the austral summer of 2015/2016 and have not yet been analyzed.

Spatial distributions of floating seaweeds in the East China Sea from late winter to early spring.

PubMed

Mizuno, S; Ajisaka, T; Lahbib, S; Kokubu, Y; Alabsi, M N; Komatsu, T

2014-01-01

Floating seaweeds play an important role as a habitat for many animals accompanying or attaching to them in offshore waters. It was in 2000 that the first report described abundant distributions of floating seaweeds in offshore waters in the East China Sea in spring. Young individuals of the yellowtail Seriola quinqueradiata are captured for aquaculture purposes from floating seaweeds in the East China Sea. Therefore, a sound understanding of the distributions of floating seaweeds in the East China Sea is needed. Detailed information is especially important during the late winter to early spring, which corresponds to the juvenile period of the yellowtail. Thus, field surveys using R/V Tansei-Maru were conducted in the Japanese Exclusive Economic Zone in the East China Sea from late winter to early spring in 2010 and 2011. We obtained positions of the vessel by GPS and transversal distances from the vessel to a raft by visual observation. Distance sampling method (Thomas et al. 2010) was applied to estimation of floating seaweed densities (rafts km -2 ). Seaweed rafts were also randomly sampled using nets during the research cruises. In the East China Sea, seaweed rafts were distributed mainly on the continental shelf west of the Kuroshio, especially in waters between 26° N and 30° N. Collected rafts consisted of only one species, Sargassum horneri (Turner) C. Agardh. Taking into account surface currents and geographical distribution of S . horneri , it is estimated that these floating seaweeds originated from natural beds along the coast between mid and south China. Considering the approximate travel times, it is suggested that floating patches are colonized by yellowtails early on during their trips, i.e., close to the Chinese coast.

Sleep and Alertness Management during Military Operations: Review and Plan of Action.

DTIC Science & Technology

1999-11-01

1996 Suhneretal. 1998b 17 pax across 8 time zones eastwards 52 pax across 9 time zones west- and eastwards 20 aircrew across 11 time zones west...and eastwards 30 pax across 6 time zones eastwards 52 aircrew across 11 time zones west- and eastwards 29 Army personnel across 7- 9 time...Jet Lag De missie-effectiviteit heeft in de eerste dagen na verplaatsing over meerdere tijdzones te lijden onder de gevolgen van jet lag, zoals

Time-Lag Bias in Trials of Pediatric Antidepressants: A Systematic Review and Meta-Analysis

PubMed Central

Reyes, Magdalena M.; Panza, Kaitlyn E.; Martin, Andrés; Bloch, Michael H.

2013-01-01

Objective To determine if there is evidence of a time-lag bias in the publication of pediatric antidepressant trials. Method We conducted a meta-analysis of published and unpublished randomized, placebo-controlled trials of serotonin reuptake inhibitors (SRIs) in subjects less than 18 years old with major depressive disorder. Our main outcomes were (1) time to publication of positive versus negative trials, and (2) proportion of treatment responders in trials with standard (< 3 years after study completion) versus delayed publication. Results We identified 15 randomized, placebo-controlled trials of SRIs for pediatric depression. Trials with negative findings had a significantly longer time to publication (median years ± standard deviation = 4.2 ±1.9) than trials with positive findings (2.2 ±0.9; log-rank χ2 = 4.35, p = 0.037). The estimated efficacy in trials with standard publication time (number needed to treat = 7, 95% CI: 5 – 11) was significantly greater than those with delayed publication (17, 95% CI: 9 – ∞; χ2 = 4.98, p = 0.025). The inflation-adjusted impact factor of journals for published trials with positive (15.33 ±11.01) and negative results (7.54 ±7.90) did not statistically differ (t = 1.4, df = 10, p = 0.17). Conclusions Despite a small number of trials of SRIs for pediatric antidepressants we found a significant evidence of time-lag bias in the publication of findings. This time-lag bias altered the perceived efficacy of pediatric antidepressants in the medical literature. Time-lag bias is not unique to child psychiatry and reflects a larger problem in scientific publishing. PMID:21156271

Modeling of Engine Parameters for Condition-Based Maintenance of the MTU Series 2000 Diesel Engine

DTIC Science & Technology

2016-09-01

are suitable. To model the behavior of the engine, an autoregressive distributed lag (ARDL) time series model of engine speed and exhaust gas... time series model of engine speed and exhaust gas temperature is derived. The lag length for ARDL is determined by whitening of residuals using the...15 B. REGRESSION ANALYSIS ....................................................................15 1. Time Series Analysis

Using the Convergent Cross Mapping method to test causality between Arctic Oscillation / North Atlantic Oscillation and Atlantic Multidecadal Oscillation

NASA Astrophysics Data System (ADS)

Gutowska, Dorota; Piskozub, Jacek

2017-04-01

There is a vast literature body on the climate indices and processes they represent. A large part of it deals with "teleconnections" or causal relations between them. However until recently time lagged correlations was the best tool of studying causation. However no correlation (even lagged) proves causation. We use a recently developed method of studying casual relations between short time series, Convergent Cross Mapping (CCM), to search for causation between the atmospheric (AO and NAO) and oceanic (AMO) indices. The version we have chosen (available as an R language package rEDM) allows for comparing time series with time lags. This work builds on previous one, showing with time-lagged correlations that AO/NAO precedes AMO by about 15 years and at the same time is preceded by AMO (but with an inverted sign) also by the same amount of time. This behaviour is identical to the relationship of a sine and cosine with the same period. This may suggest that the multidecadal oscillatory parts of the atmospheric and oceanic indices represent the same global-scale set of processes. In other words they may be symptoms of the same oscillation. The aim of present study is to test this hypothesis with a tool created specially for discovering causal relationships in dynamic systems.

Time-lagged intraspecific competition in temporally separated cohorts of a generalist insect.

PubMed

Barnes, Elizabeth E; Murphy, Shannon M

2018-03-01

Competition can have far-reaching consequences for insect fitness and dispersion. Time-lagged interspecific competition is known to negatively affect fitness, yet time-lagged intraspecific competition is rarely studied outside of outbreak conditions. We tested the impact of competition between larval cohorts of the western tent caterpillar (Malacosoma californicum) feeding on chokecherry (Prunus virginiana). We reared larvae on host plants that either had or did not have feeding damage from tent caterpillars the previous season to test the bottom-up fitness effects of intraspecific competition. We measured host-plant quality to test potential mechanisms for bottom-up effects and conducted field oviposition surveys to determine if female adult tent caterpillars avoided host plants with evidence of prior tent caterpillar presence. We found that time-lagged intraspecific competition impacted tent caterpillar fitness by reducing female pupal mass, which is a predictor of lifetime fitness. We found that plants that had been fed upon by tent caterpillars the previous season had leaves that were significantly tougher than plants that had not been fed upon by tent caterpillars, which may explain why female tent caterpillars suffered reduced fitness on these plants. Finally, we found that there were fewer tent caterpillar egg masses on plants that had tent caterpillars earlier in the season than plants without tent caterpillars, which suggests that adult females avoid these plants for oviposition. Our results confirm that intraspecific competition occurs among tent caterpillars and suggests that time-lagged intraspecific competition has been overlooked as an important component of insect fitness.

Selection and optimization of mooring cables on floating platform for special purposes

NASA Astrophysics Data System (ADS)

Ma, Guang-ying; Yao, Yun-long; Zhao, Chen-yao

2017-08-01

This paper studied a new type of assembled marine floating platform for special purposes. The selection and optimization of mooring cables on the floating platform are studied. By using ANSYS AQWA software, the hydrodynamic model of the platform was established to calculate the time history response of the platform motion under complex water environments, such as wind, wave, current and mooring. On this basis, motion response and cable tension were calculated with different cable mooring states under the designed environmental load. Finally, the best mooring scheme to meet the cable strength requirements was proposed, which can lower the motion amplitude of the platform effectively.

Staying Healthy While You Travel (For Parents)

MedlinePlus

... ear discomfort , travel (or motion) sickness, and diarrhea . Jet Lag When you fly across time zones, it ... for longer than usual. In addition to tiredness, jet lag can also cause an upset stomach and ...

Aggregation of model amyloid insulin protein in crowding environments and under ac-electric fields

NASA Astrophysics Data System (ADS)

Zheng, Zhongli; Jing, Benxin; Murray, Brian; Sorci, Mirco; Belfort, Georges; Zhu, Y.

2013-03-01

In vitro experiments have been widely used to characterize the misfolding/unfolding pathway characteristic of amylodogenic proteins. Conversion from natively folded amyloidogenic proteins to oligomers via nucleation is the accepted path to fibril formation upon heating over a certain lag time period. In this work, we investigate the effect of crowing environment and external electric fields on the pathway and kinetics of insulin, a well-established amyloid model protein by single fluorescence spectroscopy and imaging. With added co-solutes, such as glycerol and polyvinylpyrrolidone (PVP), to mimic the cellular crowding environments, we have observed that the lag time can be significantly prolonged. The lag time increases with increasing co-solute concentration, yet showing little dependence on solution viscosity. Conversely, applied ac-electric fields can considerably shorten the lag timewhen a critical ac-voltage is exceeded. The strong dependence of lag time on ac-frequency over a narrow range of 500 Hz-5 kHz indicates the effect of ac-electroosmosis on the diffusion controlled process of insulin nucleation. Yet, no conformational structure is detected with insulin under applied ac-fields, suggesting the equivalence of ac-polarization to the conventional thermal activation process for insulin aggregation. These finding suggest that at least the aggregation kinetics of insulin can be altered by local solution condition or external stimuli, which gives new insight to the treatment of amyloid related diseases.

A Correlated Optical and Gamma Emission from GRB 081126A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gendre, B.; Klotz, A.; CESR, Observatoire Midi-Pyrenees, CNRS, Universite de Toulouse, BP 4346, F-31028-Toulouse Cedex 04

2010-10-15

We present an analysis of time-resolved optical emissions observed from the gamma-ray burst GRB 081126 during the prompt phase. The analysis employed time-resolved photometry using optical data obtained by the TAROT telescope, BAT data from the Swift spacecraft and time-resolved spectroscopy at high energies from the GBM instrument onboard the Fermi spacecraft. The optical emission of GRB 081126 is found to be compatible with the second gamma emission pulse shifted by a positive time-lag of 8.4{+-}3.9 sec. This is the first well resolved observation of a time lag between optical and gamma emissions during a gamma-ray burst. Our observations couldmore » potentially provide new constraints on the fireball model for gamma ray burst early emissions. Furthermore, observations of time-lags between optical and gamma ray photons provides an exciting opportunity to constrain quantum gravity theories.« less

Designing seaplane hulls and floats

NASA Technical Reports Server (NTRS)

Benoit,

1926-01-01

Experimental data, such as the results of tank tests of models, render it possible to predict, at least in principle, as to how a hull or float of a given shape will comport itself. We will see further along, however, how uncertain these methods are and how they leave room for empiricism, which will reign for a long time yet in seaplane research bureaus.

The Impact of Onboard Maintenance Training on Surface Ship Readiness.

DTIC Science & Technology

1987-12-01

receives the majority of formal shipboard training time and resources. Watchstander training is managed through the t theory , systems, and watch...ASS :F(LSHIP.EQ .1.OR.LGE(CSHIP(NCASRP+1),CLASS(N4CLASS41)))THEN DO 795 J=1,NEIC IF(ITOTTM1(1 ,J) UGT 0)THEN FAILI’FLOAT(ITOTAL(1,J))/FLOAT(ITOTTM(1,J

33 CFR 207.480 - Lake Huron, Mich.; Harbor of refuge, Harbor Beach; use and navigation.

Code of Federal Regulations, 2011 CFR

2011-07-01

... at the time. (c) The use of chains in making fast to the breakwater will not be permitted. Lines must... floating property making fast to the breakwater must at once place such fenders between themselves and the... piece of floating property made fast to the breakwater, or anchored in the harbor, must keep outboard...

33 CFR 207.480 - Lake Huron, Mich.; Harbor of refuge, Harbor Beach; use and navigation.

Code of Federal Regulations, 2012 CFR

2012-07-01

... at the time. (c) The use of chains in making fast to the breakwater will not be permitted. Lines must... floating property making fast to the breakwater must at once place such fenders between themselves and the... piece of floating property made fast to the breakwater, or anchored in the harbor, must keep outboard...

33 CFR 207.480 - Lake Huron, Mich.; Harbor of refuge, Harbor Beach; use and navigation.

Code of Federal Regulations, 2013 CFR

2013-07-01

... at the time. (c) The use of chains in making fast to the breakwater will not be permitted. Lines must... floating property making fast to the breakwater must at once place such fenders between themselves and the... piece of floating property made fast to the breakwater, or anchored in the harbor, must keep outboard...

33 CFR 207.480 - Lake Huron, Mich.; Harbor of refuge, Harbor Beach; use and navigation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... at the time. (c) The use of chains in making fast to the breakwater will not be permitted. Lines must... floating property making fast to the breakwater must at once place such fenders between themselves and the... piece of floating property made fast to the breakwater, or anchored in the harbor, must keep outboard...

33 CFR 207.480 - Lake Huron, Mich.; Harbor of refuge, Harbor Beach; use and navigation.

Code of Federal Regulations, 2014 CFR

2014-07-01

... at the time. (c) The use of chains in making fast to the breakwater will not be permitted. Lines must... floating property making fast to the breakwater must at once place such fenders between themselves and the... piece of floating property made fast to the breakwater, or anchored in the harbor, must keep outboard...

33 CFR 146.104 - Safety and Security notice of arrival for foreign floating facilities.

Code of Federal Regulations, 2011 CFR

2011-07-01

... the NVMC's Web site at http://www.nvmc.uscg.gov/. (c) Updates to a submitted NOA. Unless otherwise... owner or operator of the foreign floating facility must revise and re-submit the NOA within the times required in paragraph (e) of this section. An owner or operator does not need to revise or re-submit an NOA...

33 CFR 146.104 - Safety and Security notice of arrival for foreign floating facilities.

Code of Federal Regulations, 2012 CFR

2012-07-01

... the NVMC's Web site at http://www.nvmc.uscg.gov/. (c) Updates to a submitted NOA. Unless otherwise... owner or operator of the foreign floating facility must revise and re-submit the NOA within the times required in paragraph (e) of this section. An owner or operator does not need to revise or re-submit an NOA...

33 CFR 146.104 - Safety and Security notice of arrival for foreign floating facilities.

Code of Federal Regulations, 2014 CFR

2014-07-01

... the NVMC's Web site at http://www.nvmc.uscg.gov/. (c) Updates to a submitted NOA. Unless otherwise... owner or operator of the foreign floating facility must revise and re-submit the NOA within the times required in paragraph (e) of this section. An owner or operator does not need to revise or re-submit an NOA...

33 CFR 146.104 - Safety and Security notice of arrival for foreign floating facilities.

Code of Federal Regulations, 2013 CFR

2013-07-01

... the NVMC's Web site at http://www.nvmc.uscg.gov/. (c) Updates to a submitted NOA. Unless otherwise... owner or operator of the foreign floating facility must revise and re-submit the NOA within the times required in paragraph (e) of this section. An owner or operator does not need to revise or re-submit an NOA...

Aeroelastic impact of above-rated wave-induced structural motions on the near-wake stability of a floating offshore wind turbine rotor

NASA Astrophysics Data System (ADS)

Rodriguez, Steven; Jaworski, Justin

2017-11-01

The impact of above-rated wave-induced motions on the stability of floating offshore wind turbine near-wakes is studied numerically. The rotor near-wake is generated using a lifting-line free vortex wake method, which is strongly coupled to a finite element solver for kinematically nonlinear blade deformations. A synthetic time series of relatively high-amplitude/high-frequency representative of above-rated conditions of the NREL 5MW referece wind turbine is imposed on the rotor structure. To evaluate the impact of these above-rated conditions, a linear stability analysis is first performed on the near wake generated by a fixed-tower wind turbine configuration at above-rated inflow conditions. The platform motion is then introduced via synthetic time series, and a stability analysis is performed on the wake generated by the floating offshore wind turbine at the same above-rated inflow conditions. The stability trends (disturbance modes versus the divergence rate of vortex structures) of the two analyses are compared to identify the impact that above-rated wave-induced structural motions have on the stability of the floating offshore wind turbine wake.

Modelling large floating bodies in urban area flash-floods via a Smoothed Particle Hydrodynamics model

NASA Astrophysics Data System (ADS)

Albano, Raffaele; Sole, Aurelia; Mirauda, Domenica; Adamowski, Jan

2016-10-01

Large debris, including vehicles parked along floodplains, can cause severe damage and significant loss of life during urban area flash-floods. In this study, the authors validated and applied the Smoothed Particle Hydrodynamics (SPH) model, developed in Amicarelli et al. (2015), which reproduces in 3D the dynamics of rigid bodies driven by free surface flows, to the design of flood mitigation measures. To validate the model, the authors compared the model's predictions to the results of an experimental setup, involving a dam breach that strikes two fixed obstacles and three transportable floating bodies. Given the accuracy of the results, in terms of water depth over time and the time history of the bodies' movements, the SPH model explored in this study was used to analyse the mitigation efficiency of a proposed structural intervention - the use of small barriers (groynes) to prevent the transport of floating bodies. Different groynes configurations were examined to identify the most appropriate design and layout for urban area flash-flood damage mitigation. The authors found that groynes positioned upstream and downstream of each floating body can be effective as a risk mitigation measure for damage resulting from their movement.

[Controlled observation of the efficacy between floating acupuncture at Tianying point and warm-needling therapy for supraspinous ligament injury].

PubMed

Li, Xin-Wei; Shao, Xiao-Mei; Tan, Ke-Ping; Fang, Jian-Qiao

2013-04-01

To compare the efficacy difference in the treatment of supraspinous ligament injury between floating acupuncture at Tianying point and the conventional warm needling therapy. Ninety patients were randomized into a floating acupuncture group and a warm needling group, 45 cases in each one. In the floating acupuncture group, the floating needling technique was adopted at Tianying point. In the warm needling group, the conventional warm needling therapy was applied at Tianying point as the chief point in the prescription. The treatment was given 3 times a week and 6 treatments made one session. The visual analogue scale (VAS) was adopted for pain comparison before and after treatment of the patients in two groups and the efficacy in two groups were assessed. The curative and remarkably effective rate was 81.8% (36/44) in the floating acupuncture group and the total effective rate was 95.5% (42/44), which were superior to 44.2% (19/43) and 79.1% (34/43) in the warm needling group separately (P < 0.01, P < 0.05). VAS score was lower as compared with that before treatment of the patients in two groups (both P < 0.01) and the score in the floating acupuncture group was lower than that in the warm needling group after treatment (P < 0.01). Thirty-six cases were cured and remarkably effective in the floating acupuncture group after treatment, in which 28 cases were cured and remarkably effective in 3 treatments, accounting for 77.8 (28/36), which was apparently higher than 26.3 (5/19) in the warm-needling group (P < 0.01). The floating acupuncture at Tianying point achieves the quick and definite efficacy on supraspinous ligament injury and presents the apparent analgesic effect. The efficacy is superior to the conventional warm-needling therapy.

The generation time, lag time, and minimum temperature of growth of coliform organisms on meat, and the implications for codes of practice in abattoirs.

PubMed Central

Smith, M. G.

1985-01-01

The growth of coliform organisms on meat tissue from sheep carcasses processed in a commercial abattoir was investigated. The results indicated that for practical purposes the minimum temperature of growth of these organisms on meat may be taken as 8 degrees C. Equations were derived relating the generation time and the lag time of coliform organisms in raw blended mutton to the temperature at which the meat is held. Estimates of growth obtained with these equations were found to agree closely with the experimental results, especially at temperatures above 10 degrees C, and allowed the generation times and the lag times for all temperatures up to 40 degrees C to be calculated. These times were also found to agree closely with the times determined using a strain of Escherichia coli inoculated into blended mutton tissue. A strain of Salmonella typhimurium inoculated in the same way into blended mutton tissue gave longer generation and lag times at temperatures below 15 degrees C. Therefore, it is believed that the calculated tables of lag and generation times included in this paper can be used to determine the length of time raw chilled meat may be held afterwards at temperatures above the minimum temperature of growth without an increase in the number of any salmonella organisms present, and these times include a safety margin at each temperature. The study indicates that the mandatory codes of practice presently applied in commercial abattoirs are too stringent. Maintaining the temperature of boning rooms at 10 degrees C or less does not appear to be necessary providing the meat is processed within the calculated time limits. A relaxation of the restrictions on boning room temperatures would decrease costs, increase worker comfort and safety and would not compromise the bacteriological safety of the meat produced. PMID:3891847

A Disposable Tear Glucose Biosensor—Part 4

PubMed Central

Engelschall, Erica; Lan, Kenneth; Shah, Pankti; Saez, Neil; Maxwell, Stephanie; Adamson, Teagan; Abou-Eid, Michelle; McAferty, Kenyon; Patel, Dharmendra R.; Cook, Curtiss B.

2014-01-01

Objective: A prototype tear glucose (TG) sensor was tested in New Zealand white rabbits to assess eye irritation, blood glucose (BG) and TG lag time, and correlation with BG. Methods: A total of 4 animals were used. Eye irritation was monitored by Lissamine green dye and analyzed using image analysis software. Lag time was correlated with an oral glucose load while recording TG and BG readings. Correlation between TG and BG were plotted against one another to form a correlation diagram, using a Yellow Springs Instrument (YSI) and self-monitoring of blood glucose as the reference measurements. Finally, TG levels were calculated using analytically derived expressions. Results: From repeated testing carried over the course of 12 months, little to no eye irritation was detected. TG fluctuations over time visually appeared to trace the same pattern as BG with an average lag times of 13 minutes. TG levels calculated from the device current measurements ranged from 4 to 20 mg/dL and correlated linearly with BG levels of 75-160 mg/dL (TG = 0.1723 BG = 7.9448 mg/dL; R2 = .7544). Conclusion: The first steps were taken toward preliminary development of a sensor for self-monitoring of tear glucose (SMTG). No conjunctival irritation in any of the animals was noted. Lag time between TG and BG was found to be noticeable, but a quantitative modeling to correlate lag time in this study is unnecessary. Measured currents from the sensors and the calculated TG showed promising correlation to BG levels. Previous analytical bench marking showed BG and TG levels consistent with other literature. PMID:24876546

Influenza newspaper reports and the influenza epidemic: an observational study in Fukuoka City, Japan.

PubMed

Hagihara, Akihito; Onozuka, Daisuke; Miyazaki, Shougo; Abe, Takeru

2015-12-30

We examined whether the weekly number of newspaper articles reporting on influenza was related to the incidence of influenza in a large city. Prospective, non-randomised, observational study. Registry data of influenza cases in Fukuoka City, Japan. A total of 83,613 cases of influenza cases that occurred between October 1999 and March 2007 in Fukuoka City, Japan. A linear model with autoregressive time series errors was fitted to time series data on the incidence of influenza and the accumulated number of influenza-related newspaper articles with different time lags in Fukuoka City, Japan. In order to obtain further evidence that the number of newspaper articles a week with specific time lags is related to the incidence of influenza, Granger causality was also tested. Of the 16 models including 'number of newspaper articles' with different time lags between 2 and 17 weeks (xt-2 to t-17), the β coefficients of 'number of newspaper articles' at time lags between t-5 and t-13 were significant. However, the β coefficients of 'number of newspaper articles' that are significant with respect to the Granger causality tests (p<0.05) were the weekly number of newspaper articles at time lags between t-6 and t-10 (time shift of 10 weeks, β=-0.301, p<0.01; time shift of 9 weeks, β=-0.200, p<0.01; time shift of 8 weeks, β=-0.156, p<0.01; time shift of 7 weeks, β=-0.122, p<0.05; time shift of 6 weeks, β=-0.113, p<0.05). We found that the number of newspaper articles reporting on influenza in a week was related to the incidence of influenza 6-10 weeks after media coverage in a large city in Japan. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Influenza newspaper reports and the influenza epidemic: an observational study in Fukuoka City, Japan

PubMed Central

Hagihara, Akihito; Onozuka, Daisuke; Miyazaki, Shougo; Abe, Takeru

2015-01-01

Objectives We examined whether the weekly number of newspaper articles reporting on influenza was related to the incidence of influenza in a large city. Design Prospective, non-randomised, observational study. Setting Registry data of influenza cases in Fukuoka City, Japan. Participants A total of 83 613 cases of influenza cases that occurred between October 1999 and March 2007 in Fukuoka City, Japan. Main outcome measure A linear model with autoregressive time series errors was fitted to time series data on the incidence of influenza and the accumulated number of influenza-related newspaper articles with different time lags in Fukuoka City, Japan. In order to obtain further evidence that the number of newspaper articles a week with specific time lags is related to the incidence of influenza, Granger causality was also tested. Results Of the 16 models including ‘number of newspaper articles’ with different time lags between 2 and 17 weeks (xt-2 to t-17), the β coefficients of ‘number of newspaper articles’ at time lags between t-5 and t-13 were significant. However, the β coefficients of ‘number of newspaper articles’ that are significant with respect to the Granger causality tests (p<0.05) were the weekly number of newspaper articles at time lags between t-6 and t-10 (time shift of 10 weeks, β=−0.301, p<0.01; time shift of 9 weeks, β=−0.200, p<0.01; time shift of 8 weeks, β=−0.156, p<0.01; time shift of 7 weeks, β=−0.122, p<0.05; time shift of 6 weeks, β=−0.113, p<0.05). Conclusions We found that the number of newspaper articles reporting on influenza in a week was related to the incidence of influenza 6–10 weeks after media coverage in a large city in Japan. PMID:26719323

Free-floating magnetic microstructures by mask photolithography

NASA Astrophysics Data System (ADS)

Huong Au, Thi; Thien Trinh, Duc; Bich Do, Danh; Phu Nguyen, Dang; Cong Tong, Quang; Diep Lai, Ngoc

2018-03-01

This work explores the fabrication of free-floating magnetic structures on a photocurable nanocomposite consisting of superparamagnetic magnetite nanoparticles (Fe3O4) and a commercial SU-8 negative tone photoresist. The nanocomposite was synthesized by mixing magnetic nanoparticles with different kinds of SU-8 resin. We demonstrated that the dispersion of Fe3O4 nanoparticles in nanocomposite solution strongly depended on the particles concentration, the viscosity of SU-8 polymer, and the mixing time. The influence of these factors was demonstrated by examining the structures fabricated by mask photolithography technique. We obtained the best quality of structures at a low concentration, below 5 wt%, of Fe3O4 nanoparticles in SU-8 2005 photoresist for a mixing time of about 20 days. The manipulation of free-floating magnetic microstructures by an external magnetic field was also demonstrated showing promising applications of this magnetic nanocomposite.

Energy-band engineering for tunable memory characteristics through controlled doping of reduced graphene oxide.

PubMed

Han, Su-Ting; Zhou, Ye; Yang, Qing Dan; Zhou, Li; Huang, Long-Biao; Yan, Yan; Lee, Chun-Sing; Roy, Vellaisamy A L

2014-02-25

Tunable memory characteristics are used in multioperational mode circuits where memory cells with various functionalities are needed in one combined device. It is always a challenge to obtain control over threshold voltage for multimode operation. On this regard, we use a strategy of shifting the work function of reduced graphene oxide (rGO) in a controlled manner through doping gold chloride (AuCl3) and obtained a gradient increase of rGO work function. By inserting doped rGO as floating gate, a controlled threshold voltage (Vth) shift has been achieved in both p- and n-type low voltage flexible memory devices with large memory window (up to 4 times for p-type and 8 times for n-type memory devices) in comparison with pristine rGO floating gate memory devices. By proper energy band engineering, we demonstrated a flexible floating gate memory device with larger memory window and controlled threshold voltage shifts.

Work-Family Conflict and Psychological Well-Being: Stability and Cross-Lagged Relations within One- and Six-Year Follow-Ups

ERIC Educational Resources Information Center

Rantanen, Johanna; Kinnunen, Ulla; Feldt, Taru; Pulkkinen, Lea

2008-01-01

The rank-order stability and cross-lagged relations between work-to-family conflict (WFC), family-to-work conflict (FWC), and psychological well-being were examined in two longitudinal studies with full two-wave panel designs. In Study 1 (n = 365), the time lag was one year, and in Study 2 (n = 153), six years. The Structural Equation Modeling…

A New Measurement of the Spectral Lag of Gamma-Ray Bursts and its Implications for Spectral Evolution Behaviors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao, Lang; Wang, Fu-Ri; Cheng, Ye-Hao

We carry out a systematical study of the spectral lag properties of 50 single-pulsed gamma-ray bursts (GRBs) detected by the Fermi Gamma-Ray Burst Monitor. By dividing the light curves into multiple consecutive energy channels, we provide a new measurement of the spectral lag that is independent of energy channel selections. We perform a detailed statistical study of our new measurements. We find two similar power-law energy dependencies of both the pulse arrival time and pulse width. Our new results on the power-law indices would favor the relativistic geometric effects for the origin of spectral lag. However, a complete theoretical frameworkmore » that can fully account for the diverse energy dependencies of both arrival time and pulse width revealed in this work is still lacking. We also study the spectral evolution behaviors of the GRB pulses. We find that a GRB pulse with negligible spectral lag would usually have a shorter pulse duration and would appear to have a “hardness-intensity tracking” behavior, and a GRB pulse with a significant spectral lag would usually have a longer pulse duration and would appear to have a “hard-to-soft” behavior.« less

Nutrient pressures and legacies in a small agricultural karst catchment

NASA Astrophysics Data System (ADS)

Fenton, Owen; Mellander, Per-Erik; Daly, Karen; Wall, David P.; Jahangir, Mohammad M.; Jordan, Phil; Hennessey, Deirdre; Huebsch, Manuela; Blum, Philipp; Vero, Sara; Richards, Karl G.

2017-04-01

Catchments with short subsurface hydrologic time lags are commonly at risk for leached losses of nitrogen (N) and phosphorus (P). Such catchments are suitable for testing the efficacy of mitigation measures as management changes. In some sites, however, N and P may be retained in the soil and subsoil layers, and then leached, mobilised or attenuated over time. This biogeochemical time lag may therefore have enduring effects on the water quality. The aim of this study was to improve the understanding of N and P retention, attenuation and distribution of subsurface pathway in an intensively managed agricultural karst catchment with an oxidised aquifer setting, and also to inform how similar sites can be managed in the future. Results showed that in the years pre-2000 slurry from an on-site integrated pig production unit had been applied at rates of 33 t/ha annually, which supplied approximately 136 kg/ha total N and approximately 26 kg/ha total P annually. This practice contributed to large quantities of N (total N and NH4-N) and elevated soil test P (Morgan extractable P), present to a depth of 1 m. This store was augmented by recent surpluses of 263 kg N/ha, with leached N to groundwater of 82.5 kg N/ha and only 2.5 kg N/ha denitrified in the aquifer thereafter. Sub hourly spring data showed the largest proportion of N loss from small (54-88%) and medium fissure pathways (7- 21%) with longer hydrologic time lags, with smallest loads from either large fissure (1-13%) or conduit (1-10%) pathways with short hydrologic time lags (reaction time at the spring from onset of a rainfall event is within hours). Although soils were saturated in P and in mobile forms to 0.5 m, dissolved reactive P concentrations in groundwater remained low due to Ca and Mg limestone chemistry. Under these conditions a depletion of the legacy store, with no further inputs, would take approximately 50 years and with NO3-N concentrations in the source area dropping to levels that could sustain groundwater NO3-N concentrations below admissible levels within 9 years. Biogeochemical time lags (decades) are longer than hydrologic time lags on this site (months to years). Future management should target farm surpluses that maintain a legacy store at or below a soil organic N mass of ca. 20 kg N/ha. Incorporation of biogeochemical and hydrologic time lag principles into future water quality regulations will provide regulators with realistic expectations when implementing policies.

Lag and seasonality considerations in evaluating AVHRR NDVI response to precipitation

USGS Publications Warehouse

Ji, Lei; Peters, Albert J.

2005-01-01

Assessment of the relationship between the normalized difference vegetation index (NDVI) and precipitation is important in understanding vegetation and climate interaction at a large scale. NDVI response to precipitation, however, is difficult to quantify due to the lag and seasonality effects, which will vary due to vegetation cover type, soils and climate. A time series analysis was performed on biweekly NDVI and precipitation around weather stations in the northern and central U.S. Great Plains. Regression models that incorporate lag and seasonality effects were used to quantify the relationship between NDVI and lagged precipitation in grasslands and croplands. It was found that the time lag was shorter in the early growing season, but longer in the mid- to late-growing season for most locations. The regression models with seasonal adjustment indicate that the relationship between NDVI and precipitation over the entire growing season was strong, with R2 values of 0.69 and 0.72 for grasslands and croplands, respectively. We conclude that vegetation greenness can be predicted using current and antecedent precipitation, if seasonal effects are taken into account.

The growth of Listeria monocytogenes in cheese packed under a modified atmosphere.

PubMed

Whitley, E; Muir, D; Waites, W M

2000-01-01

The effect of modified atmosphere Packaging (MAP) on the growth of Listeria monocytogenes in mould ripened cheeses was studied at refrigeration temperatures (2-8.3 degrees C) over a storage period of 6 weeks. Control experiments in cling film with no atmospheric modification produced a lag time before growth of up to 1 week and rapid subsequent growth. MAP with a CO2 concentration of less than 20% allowed growth to occur but when O2 was incorporated; the lag time was reduced from 3 to 2 weeks and subsequent growth was also faster, producing an increase in cell numbers of 1.4 log cycles over the incubation period. N2-MAP in the absence of O2 increased the lag time to 3 weeks and slowed growth, while the inclusion of CO2 extended the lag to 3 weeks and slowed subsequent growth even more. In MAP with 80:10:10 (v/v/v) N2:CO2:O2, there was a lag period of 2-3 weeks before growth of L. monocytogenes occurred, while the total viable aerobic count (TVAC) decreased by 2-3 log cycles and the total Lactobacillus count showed little change. It was concluded that MAP was not suitable for preventing the growth of L. monocytogenes in such cheeses.

Time-Lag Bias in Trials of Pediatric Antidepressants: A Systematic Review and Meta-Analysis

ERIC Educational Resources Information Center

Reyes, Magdalena M.; Panza, Kaitlyn E.; Martin, Andres; Bloch, Michael H.

2011-01-01

Objective: To determine whether there is evidence of a time-lag bias in the publication of pediatric antidepressant trials. Method: We conducted a meta-analysis of published and unpublished randomized placebo-controlled trials of serotonin reuptake inhibitors (SRIs) in subjects less than 18 years of age with major depressive disorder. Our main…

Heat conduction errors and time lag in cryogenic thermometer installations

NASA Technical Reports Server (NTRS)

Warshawsky, I.

1973-01-01

Installation practices are recommended that will increase rate of heat exchange between the thermometric sensing element and the cryogenic fluid and that will reduce the rate of undesired heat transfer to higher-temperature objects. Formulas and numerical data are given that help to estimate the magnitude of heat-conduction errors and of time lag in response.

A Voice Onset Time Analysis of Apical Stop Production in 3-Year-Olds

ERIC Educational Resources Information Center

Gilbert, John H. V.

1977-01-01

This paper reports data for voice onset time (VOT) for /d/ and /t/, from six children at average age 3;0. Values for /d/ clearly achieve the short voicing lag category of adults, reported previously. Values for /t/, however, are much more varied, although falling within the category long voicing lag. (CHK)

Individual Differences in Working-Memory Capacity and Task Resumption Following Interruptions

ERIC Educational Resources Information Center

Foroughi, Cyrus K.; Werner, Nicole E.; McKendrick, Ryan; Cades, David M.; Boehm-Davis, Deborah A.

2016-01-01

Previous research has shown that there is a time cost (i.e., a resumption lag) associated with resuming a task following an interruption and that the longer the duration of the interruption, the greater the time cost (i.e., resumption lag increases as interruption duration increases). The memory-for-goals model (Altmann & Trafton, 2002)…

Biogeochemical sensor performance in the SOCCOM profiling float array

NASA Astrophysics Data System (ADS)

Johnson, Kenneth S.; Plant, Joshua N.; Coletti, Luke J.; Jannasch, Hans W.; Sakamoto, Carole M.; Riser, Stephen C.; Swift, Dana D.; Williams, Nancy L.; Boss, Emmanuel; Haëntjens, Nils; Talley, Lynne D.; Sarmiento, Jorge L.

2017-08-01

The Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) program has begun deploying a large array of biogeochemical sensors on profiling floats in the Southern Ocean. As of February 2016, 86 floats have been deployed. Here the focus is on 56 floats with quality-controlled and adjusted data that have been in the water at least 6 months. The floats carry oxygen, nitrate, pH, chlorophyll fluorescence, and optical backscatter sensors. The raw data generated by these sensors can suffer from inaccurate initial calibrations and from sensor drift over time. Procedures to correct the data are defined. The initial accuracy of the adjusted concentrations is assessed by comparing the corrected data to laboratory measurements made on samples collected by a hydrographic cast with a rosette sampler at the float deployment station. The long-term accuracy of the corrected data is compared to the GLODAPv2 data set whenever a float made a profile within 20 km of a GLODAPv2 station. Based on these assessments, the fleet average oxygen data are accurate to 1 ± 1%, nitrate to within 0.5 ± 0.5 µmol kg-1, and pH to 0.005 ± 0.007, where the error limit is 1 standard deviation of the fleet data. The bio-optical measurements of chlorophyll fluorescence and optical backscatter are used to estimate chlorophyll a and particulate organic carbon concentration. The particulate organic carbon concentrations inferred from optical backscatter appear accurate to with 35 mg C m-3 or 20%, whichever is larger. Factors affecting the accuracy of the estimated chlorophyll a concentrations are evaluated.