Rates For Long Periods Research Articles

Dose-Effect Relationship of Chitosan and Danshen Combined Injection for Fallopian Tube Recanalization.

Objectives: This study examined the dose-effect relationship of chitosan and danshen combined injections on the long-term prevention of fallopian tube re-obstructions, with increased pregnancy rates in infertile women. Methods: High-performance liquid chromatography was used to determine the content changes of combined chitosan and danshen injection. Two hundred and eighty patients with fallopian tube obstructions were randomly assigned to four groups. Group A (control group, saline), Group B (2 ml chitosan, 4 ml danshen), Group C (2 ml chitosan, 10 ml danshen), and Group D (1 ml chitosan, 10 ml danshen). Injections were administered after tubal recanalization. Results: The effective constituent of chitosan and danshen injection was stable. Tubal patency rate was 94.2% and 87.3% in Group C after 1 and 3 years, respectively, which was significantly higher than Groups A (38.6%, 31.5%), B (73.5%, 64.1%), and D (68.5%, 50.7%). Intrauterine pregnancy rates were 61.8% and 79.4% in Group C after 1 and 3 years, respectively, and were significantly higher than Groups A (31.8%, 34.8%), B (40.1%, 62.5%), and D (38.5%, 58.5%) (p < 0.05). Conclusion: Combined Chitosan and danshen injections prevented tubal obstruction and increased pregnancy rates for long periods using an optimal ratio of 1 part chitosan and 5 parts danshen.

An Overview: Use of Polymer Microspheres in Controlled Drug Delivery

Polymer microspheres can be employed to deliver medication in a rate -controlled and sometimes targeted manner. Microspheres from which therapeutic agents may be released at controlled rates for long periods of time, ranging from days to months. Such systems offer numerous advantages over traditional methods of drug delivery, including tailoring of drug release rates, protection of fragile drugs and increased patient comfort and compliance. Polymeric microspheres are ideal vehicles for many controlled delivery applications due to their ability to encapsulate a variety of drugs, biocompatibility, high bioavailability and sustained drug release characteristics. This review describes methods of microsphere preparation and the major factors controlling the release rates of encapsulated drugs. Furthermore, pharmaceutical applications and recent advances in the use of polymer microsphere based systems for delivery of single shot vaccines, plasmid DNA and therapeutic proteins are discussed, as well as some future directions of microsphere research.

Brain and central nervous system cancer incidence in navarre (Spain), 1973-2008 and projections for 2014.

Different studies have pointed out Navarre as one of the regions of Spain with the highest incidence rates of brain and other central nervous system (CNS) cancer. Trend analysis for cancer incidence rates for long periods of time, might help determining risk factors as well as, assessing prevention actions involved in this disease. The objective of this study was to describe the incidence of brain and CNS cancer using data from the population-based cancer registry of Navarre, (Spain) during the period 1973-2008 and provide forecast figures up to-2014. Crude and age-standardized (world population) incidence rates of brain cancer per 100,000 person-years were calculated by the direct method separately by gender, area (Pamplona and others), and age-groups. Penalized splines for smoothing rates in the temporal dimensions were applied in order to estimate and forecast cancer incidence rates. Age-adjusted incidence rates showed an increase over the study and forecast periods in both sexes more marked in women than in men. Higher incidence rates were observed in men compared with women but the differences became smaller with time. The increase was due to the rise of rates in the oldest age groups since the rates for younger age groups remained stable or decreased over time. As the entire aetiology of brain and other CNS cancer is not still clear, keep promoting healthful lifestyles for cancer primary prevention among the whole population is necessary.

Landless Homeowners in Forgotten America: Identifying the Nexus Between Long-Term Poverty, Homeownership, and Land Tenure

Several predominately rural regions and communities in the United States have experienced high poverty rates for long periods of time. Often forgotten or hidden from mainstream America, these areas are almost exclusively rural, isolated geographically, lack economic opportunities, and suffer from decades of disinvestment and double-digit poverty rates. Persistent poverty regions have many shared indices of economic distress; yet they also differ in terms of demographic and cultural composition, geography, and underlying economies. Another “shared difference, “ is the prevalence of unique land tenure issues such as contract for deeds, absentee ownership, mineral rights, heirs’ property, and tribal trust lands. Such land-home arrangements often complicate homeownership, wealth accumulation, and the provision of affordable housing. This research note introduces the nexus between land tenure, low-income homeownership, and persistent poverty communities from a comprehensive perspective with the goal of beginning a discussion on how to inform policies and strategies that assist low- and poverty-income homeowners realize their full asset and wealth accumulation potential.

ESTIMATING ANNUAL RIVERBANK EROSION RATES—A DENDROGEOMORPHIC METHOD

ABSTRACTAn accurate estimation of riverbank erosion rates is critical for the evaluation of the past, present, and future sediment regime of river systems. Understanding these relationships allows watershed managers and regulators to prioritize river restoration and contaminated site remediation projects. In this dendrogeomorphic study, changes in the anatomy of tree roots exposed between 1 and 31 years were used to estimate the average annual erosion rates of riverbank sediments on a large river in Michigan, USA. Exposed root samples from diffuse and ring‐porous hardwoods, together with buried ones as controls, were analyzed. Differences in the arrangement, size and frequency of vessels, fiber diameter, cell wall thickness, growth ring width, and scarring between the exposed and the buried samples were used to identify the first year of root exposure. Results of the regression analysis between the average annual erosion rate and the Bank Erosion Hazard Index (BEHI) indicated that the more recently exposed roots (less than 7 years in this study) explained more of the variance (R2 = 0.67) than when all samples were included (R2 = 0.38). Although the average erosion rates for long periods can be accurately determined from the dating of exposed tree roots, attempts to relate these rates using the BEHI for longer periods are less successful, as BEHI values can vary considerably over time as the riverbank erodes. Consequently, when using exposed tree roots to develop regression equations and erosion rate curves for the estimation of erosion rates based on BEHI scores, it is necessary to use roots that were recently exposed. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Response properties from turtle auditory hair cell afferent fibers suggest spike generation is driven by synchronized release both between and within synapses

Inner ear hair cell afferent fiber synapses are capable of transferring information at high rates for long periods of time with extraordinary fidelity. As at other sensory synapses, hair cells rely on graded receptor potentials and unique vesicle trafficking and release properties of ribbon synapses to relay intensity information. Postsynaptic recordings from afferent fibers of the turtle auditory papilla identified excitatory postsynaptic currents (EPSCs) that were fast AMPA receptor-based responses with rapid onset and decay times. EPSCs varied in amplitude by ≈ 15× per fiber, with kinetics that showed a tendency to slow at larger amplitudes. Complex EPSCs were produced by temporal summation of single events, likely across synapses. Complex EPSCs were more efficient at generating action potentials than single EPSCs. Potassium-evoked release increased the frequency of EPSCs, in particular complex events, but did not increase EPSC amplitudes. Temporal summation of EPSCs across synapses may underlie action potential generation at these synapses. Broad amplitude histograms were probed for mechanisms of multivesicular release with reduced external Ca(2+) or the introduction of Cd(2+) or Sr(2+) to uncouple release. The results are consistent with broad amplitude histograms being generated by a combination of the variability in synaptic vesicle size and coordinated release of these vesicles. It is posited that multivesicular release plays less of a role in multisynaptic ribbon synapses than in single synaptic afferent fibers.

Formulation, evaluation and optimization of sustained release matrix tablets of captopril

Sustained release matrix tablet is a delivery system by which the drug can be delivered at a controlled rate for long period of time. The present study aims at formulation, evaluation and optimization of captopril matrix tablets. A 32 full factorial design was adopted and all 9 batches were prepared by wet granulation method. Prepared granules and tablets were evaluated for precompression and postcompression characteristics respectively. Check point analysis was applied to the observations and the formula of the tablet was optimized. Optimized formula, F6 showed zero order drug release kinetics for the time period of 24 hours i.e. 17.55% release at the end of 2 hours, 53.4% release at the end of 12 hours and 100.24% release at the end of 24 hours. The results revealed that concentration of matrix forming agent and solution of granulating agent significantly affected in vitro drug release profile.

An Advanced Single Particle Model for C3S and Alite Hydration

The hydration behavior of portland cement phases continues to be debated with new insights fueling the controversy. What causes the induction period? What initiates acceleration? What causes the onset and rapid decrease in reaction rate post peak? Does diffusion play a role and what causes low, but sustained reaction rates for long periods of time? Recent modeling efforts suggest that boundary nucleation and growth can explain at least some of the observations and that such occurs in a “limited reaction volume” accounting for about 30% of the initial cement mass. Yet, other efforts offer an alternative theory that would suggest that densification occurs in two steps. In an effort to resolve these and other questions, a single particle model for alite/Ca3SiO5 hydration has been developed using a mass continuity‐based continuum approach as an alternative to the Avramian basis used in most recent studies. Such single particle models are relevant starting points for fast model‐based experimentation, more elaborate single particle models, and simulation platforms that act on ensembles of particles. The present model includes transport effects, solution phase chemistry, and incorporates intraparticle nucleation.

Groundwater recharge in irrigated semi-arid areas: quantitative hydrological modelling and sensitivity analysis

For semi-arid regions, methods of assessing aquifer recharge usually consider the potential evapotranspiration. Actual evapotranspiration rates can be below potential rates for long periods of time, even in irrigated systems. Accurate estimations of aquifer recharge in semi-arid areas under irrigated agriculture are essential for sustainable water-resources management. A method to estimate aquifer recharge from irrigated farmland has been tested. The water-balance-modelling approach was based on VisualBALAN v. 2.0, a computer code that simulates water balance in the soil, vadose zone and aquifer. The study was carried out in the Campo de Cartagena (SE Spain) in the period 1999–2008 for three different groups of crops: annual row crops (lettuce and melon), perennial vegetables (artichoke) and fruit trees (citrus). Computed mean-annual-recharge values (from irrigation+precipitation) during the study period were 397 mm for annual row crops, 201 mm for perennial vegetables and 194 mm for fruit trees: 31.4, 20.7 and 20.5% of the total applied water, respectively. The effects of rainfall events on the final recharge were clearly observed, due to the continuously high water content in soil which facilitated the infiltration process. A sensitivity analysis to assess the reliability and uncertainty of recharge estimations was carried out.

International Money and Common Currencies in Historical Perspective

Abstract: The authors review the history of international monies and the theory related to their adoption and use. There are four key characteristics of these currencies: high unitary value; relatively low inflation rates for long periods; issuance by major economic and trading powers; and spontaneous, as opposed to planned, adoption internationally. The economic theory of the demand for money provides support for the importance of these characteristics. The value of a unit is arbitrary for a fiat money, but the other characteristics are likely to be important for determining any fiat money that will be the international money in the future. If the euro continues to exist for the next half century or so and has a relatively stable value, the authors conclude that the euro is likely to be serious competition for the dollar as the international money. JEL classification: E42, F33, N10 Key words: euro, international money, fiat money, dollar, search theory 1. Introduction Is the euro likely to supplant the dollar as an international money? Such a question might seem premature, especially since the euro physically has been in existence only for a few months. We are inclined to think that it is not too early to start to think about this issue seriously since the implications are large for the world's monetary landscape. The move to a circulating euro on January 1, 2002 has been followed by little or no difficulty in the twelve countries involved. By most prognostications, moreover, the future for the new currency looks very good. That was not the case at all a decade ago, as devaluations and widened currency bands shook the Exchange Rate Mechanism (ERM). Skepticism with regard to the future of a single currency abounded among both economists and financial professionals. A major reason for this shift in opinion has doubtless been the change in the underlying economic environment in the countries involved, in particular the greater convergence in monetary policies that took place during the intervening period. The purpose of this paper is to review the historical evidence on the question of international monies. In contrast to other studies, we adopt a very broad temporal perspective, beginning with a discussion of the Byzantine gold solidus or bezant that was introduced by the Emperor Constantine and that served as a world currency for the next seven centuries. We continue with a review of medieval monetary history and the international currencies of the Italian city states. (1) We then turn to a discussion of the various international monies that have existed from the early modern period to the present. Using this review of the historical evidence as a background, we go on to discuss the theory surrounding this issue. The underlying questions of interest are with the factors affecting the establishment of common currencies and, more important, their longevity. Here we return to the earlier analyses of Carl Menger (1892) and a century later Friedrich A. Hayek (1978). In both analyses, the key distinction using some terminology borrowed from Hayek (1967) is between monetary institutions that are the result of human action but not human design and institutions that are planned and orchestrated from on high. 2. Historical Overview 2.1. The Early Middle Ages International monies, monies that circulate for use in transactions across national boundaries, begin with the silver drachma first coined in ancient Athens in the fifth century B.C. (Chown, 1994). Judged on the basis of the hoards that have been uncovered, not just within the Mediterranean region but throughout Europe and well into Asia, the coinage of Rome--first the gold aureus and the silver denarius after the currency reforms of Augustus--became the drachma's successor. (2) Beginning with Nero (A.D. 54-68) and continuing into the early fourth century, currency debasement and inflation became the rule. …

The Economics of International Monies

The purpose of this paper is to examine the history of international monies and the theory related to their adoption and use. We summarize the history of international monies, beginning with a discussion of the gold solidus introduced in the fourth century by the Emperor Constantine, continuing with the currencies of the Italian city states and ending with the currencies that have functioned as international monies from the early modern period to the present. We identify four key characteristics of these currencies: high unitary value; relatively low inflation rates for long periods; issuance by major economic and trading powers; and spontaneous, as opposed to planned, adoption internationally. We conclude with a theoretical discussion of these common characteristics that explains much of this history.

Microspheres for controlled release drug delivery

Controlled release drug delivery employs drug-encapsulating devices from which therapeutic agents may be released at controlled rates for long periods of time, ranging from days to months. Such systems offer numerous advantages over traditional methods of drug delivery, including tailoring of drug release rates, protection of fragile drugs and increased patient comfort and compliance. Polymeric microspheres are ideal vehicles for many controlled delivery applications due to their ability to encapsulate a variety of drugs, biocompatibility, high bioavailability and sustained drug release characteristics. Research discussed in this review is focused on improving large-scale manufacturing, maintaining drug stability and enhancing control of drug release rates. This paper describes methods of microparticle fabrication and the major factors controlling the release rates of encapsulated drugs. Furthermore, recent advances in the use of polymer microsphere-based systems for delivery of single-shot vaccines, plasmid DNA and therapeutic proteins are discussed, as well as some future directions of microsphere research.

Rheological behavior ofN,N-dimethyl acrylamide-acrylamido methylpropane sulphonate copolymer

Copolymer of N,N-dimethylacrylamide (NNDAM) and sodium 2-acrylamido-2-methylpropanesulfonate (NaAMPS) have been prepared by free-radical copolymerization and characterized with the help of molecular weight, molecular weight distribution, intrinsic viscosity, and monomer ratio in the copolymer. The solution behavior of a copolymer containing 26.62 wt % NaAMPS is studied in different solvents, namely, water (W), dimethyl sulfoxide (DMSO), ethylene glycol (EG), and ethanol (EtOH). The reduced viscosity of the copolymer is highly dependent on the ionic strength of the copolymer solution. The reduced viscosity decreases as a function of solvent selection in the order W > DMSO > EtOH > EG. The shapes of the η sp / C vs. C plots indicate the polyelectrolyte behavior of the copolymer, except for the case of EG solutions, where nonpolyelectrolyte behavior is observed. However, at a certain degree of ionization attained by adding W as cosolvent, the copolymer begins to demonstrate polyelectrolyte behavior. For this copolymer, there exists a minimum concentration of brine (NaCl, CaCl 2 , etc.) above which solution viscosity is not further reduced. The copolymer solution behaves as a power law fluid, and exhibits time-dependent thixotropic behavior. The copolymer cannot regain its solution viscosity when allowed to shear at a constant rate for long period of time. The reduced viscosities of copolymer solutions increase with increasing temperature in W and DMSO, yet decreases with increasing temperature in EG.

Economic Crisis and Its Impact:Chemical industry in Thailand

The economic crisisthat started in Thailand since July 2, 1997 has escalated into a contagious global recession in 1998. ASEAN including Korea were probably among the hardest hit economies under the crisis. [t was generally believed that the crisis was caused by lack of discipline among the private sector and outdated financial infrastructure in view of rapid and accelerated market liberalization. From the chemical industry viewpoint, the industry plays a critical role in propelling industrialization effort in Thailand. The industry, along with steel and cement industries,serves as the three main pillarsfor furtherdevelopments of other downstream manufacturing industries such as auto. electronics, home appliances, etc. Chemical industry in precrisis era used to enjoy a good GDP annualiz!;!d average growth rate of around 20 percent. With an aggressive growth rate for long period. the industry, along with Thai economy, face, peril in the 1997 crisis. The crisis effectively sets-back local demand by 3 years and forces the industry to reexamine its position and strategy for a more stable and sustainable growth in next millennium. The crisisrenders a costly check and balance tools for developing economies in ASEAN to strictly maintaining fine balance and harmony in all facets of developments, industrial,human, legaland moral framework, etc. From various macroeconomic indicies announced recently, Thai economy is on the path of recovery. Local demands along with the export of chemical products have improved in the firsthalf of 1999 and the tendency for the second half is rather promising.

Economics of increasing the persistence of sown pastures: costs, stocking rate and cash flow

Poor persistence of sown pastures, trends of low pasture resowing rates and a substantial decline in carrying capacity of non-crop areas bring into question the basis of the philosophy of pasture improvement by sowing pasture species. If graziers are to adopt grazing strategies or stocking rates that are more ecologically sustainable, then clearly they must also be cost-effective in either increasing income or reducing costs so that they are economically sustainable. This paper describes the use of an interactive spreadsheet model developed to assist graziers and their advisers with assessing the long-term profitability of pasture management and/or improvement (and therefore pasture persistence). The model provides a comparative cash flow for different levels of inputs (fertiliser, herbicides and feed supplements) over a 15-year period. Results clearly show that at the same stocking rate, different animal enterprises have markedly different profitabilities over a 15-year period. Further, for native, improved and sown pastures, the most profitable pastures are those that can sustain increased stocking rates for long periods of time, without the need for resowing.

Modifiers of lung cancer risk in uranium miners from the Colorado Plateau.

Given the scientific consensus that exposure to radon decay products causes lung cancer, most recent studies have focused on the nature of the exposure-response relationship. Since residential radon exposure is now a primary public health issue, a better understanding of the effects of low levels of radon as well as factors modifying risk estimates has become very important. Several factors are shown to affect risk estimates in the latest update of the vital status follow-up (through 1990) and smoking history for the cohort of underground uranium miners in the Colorado Plateau. This analysis confirms earlier results indicating a strong dependence of relative risk estimates upon attained age. Quantitative estimates of relative risk as a function of cumulative exposure to radon decay products (WLM) are provided for three age strata. The non-linearity often reported in the Colorado Plateau data is shown to be at least partially due to an inverse exposure-rate effect, i.e., low exposure rates for long periods are more hazardous than equivalent cumulative exposure received at higher rates for shorter periods of time. However, this effect is shown to diminish at lower exposure rates and cumulative exposures. In addition, use of the new smoking data indicates that the radon/smoking interaction is submultiplicative and may depend upon attained age.

On the growth rates of human malignant tumors: Implications for medical decision making

Testicular carcinomas, pediatric tumors, and some mesenchymal tumors are examples of rapidly proliferating cell populations, for which the tumor volume doubling time (TVDT) can be counted in days. Cancers from the breast, prostate, and colon are frequently slow-growing, displaying a TVDT of months or years. Irrespective of their growth rates, most human tumors have been found: to start from one single cell, to have a long subclinical period, to grow at constant rates for long periods of time, to start to metastasize often even before the primary is detected, and to have metastases that often grow at approximately the same rate as the primary tumor. The recognition of basic facts in tumor cell kinetics is essential in the evaluation of important present-day strategies in oncology. Among the facts emphasized in this review are: (1) Screening programs. Most tumors are several years old when detectable by present-day diagnostic methods. This makes the term "early detection" questionable. (2) Legal trials. The importance of so-called doctor's delay is often discussed, but the prognostic value of "early" detection is overestimated. (3) Analyses of clinical trials. Such analysis may be differentiated depending on the growth rates of the type of tumor studied. Furthermore, uncritical analysis of survival data may be misleading if the TVDT is not taken into consideration. (4) Analyses of epidemiological data. If causes of malignant tumors in humans are searched for, the time of exposure must be extended far back in the subject's history. (5) Risk estimations by insurance companies. For the majority of human cancers, the 5-year survival rate is not a valid measurement for cure. Thus, basic knowledge of tumor kinetics may have important implications for political health programs, legal trials, medical science, and insurance policies.

Drug Evaluation Central &amp; Peripheral Nervous Systems: Remifentanil: an opioid metabolised by esterases

Remifentanil is a new opioid metabolised by circulating and tissue esterases. It is therefore extremely short-acting, and it does not depend on redistribution for terminating its effects as do the other ‘short-acting’ opioids. The kinetics of remifentanil have been examined in detail and these studies have revealed that remifentanil dosing does not need to be adjusted for the presence of hepatic or renal dysfunction. Although its pharmacokinetic profile is similar in elderly persons, the required doses are lower in the elderly due to an increase in pharmacodynamic response. The major metabolite of remifentanil is approximately three orders of magnitude less potent an opioid agonist and therefore does not produce clinically significant opioid effects even when remifentanil is given at high infusion rates for long periods of time. Many clinical trials employing remifentanil have now been completed. These demonstrate that remifentanil may be used as the opioid component in intravenous general anaesthesia for...

A Dynamic Model of Investment and Endogenous Growth

Models of endogenous growth assume that private investment in either physical or human capital yields positive externalities to production possibilities as a whole. But what is the structure of such externalities? We present a model of learning by watching which implies a nonlinear relationship between productivity growth and the investment rate. This results in multiple steady-state growth rates in a deterministic setting, and in a rich dynamic structure that generates both growth and cycles in a stochastic model (calibrated by reference to observable shocks to tax rates in the U.K.). Economies with identical structures can experience very different growth rates for long periods. The model exhibits pathdependence and history matters.

Analyses of 1-min Rain Rates Extracted from Weighing Raingage Recordings

Abstract A method for extracting 1-min rain rates from original weighing raingage recordings is described. The method allows the retrieval of rates for long periods at approximately 300 United States weather stations. The process combines magnification of original chart records with modern digitizing and filtering techniques to obtain the 1-min data that are ordinarily unreadable. Analyses are presented of the frequency and duration of 1-min rates for these seven locations and an eighth location, for which data were collected using a high speed recorder.