scholarly journals Modifications of Polymers through the Addition of Ultraviolet Absorbers to Reduce the Aging Effect of Accelerated and Natural Irradiation

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 20
Author(s):  
Gamal A. El-Hiti ◽  
Dina S. Ahmed ◽  
Emad Yousif ◽  
Omar S. A. Al-Khazrajy ◽  
Mustafa Abdallh ◽  
...  
Keyword(s):  
Polymeric Materials ◽  
Aging Effect ◽  
Degradation Process ◽  
Organometallic Complexes ◽  
Harsh Environments ◽  
Toxic Substances ◽  
Negative Effect ◽  
Ultraviolet Absorbers ◽  
Living Organisms ◽  
High Degree

The photooxidative degradation process of plastics caused by ultraviolet irradiation leads to bond breaking, crosslinking, the elimination of volatiles, formation of free radicals, and decreases in weight and molecular weight. Photodegradation deteriorates both the mechanical and physical properties of plastics and affects their predicted life use, in particular for applications in harsh environments. Plastics have many benefits, while on the other hand, they have numerous disadvantages, such as photodegradation and photooxidation in harsh environments and the release of toxic substances due to the leaching of some components, which have a negative effect on living organisms. Therefore, attention is paid to the design and use of safe, plastic, ultraviolet stabilizers that do not pose a danger to the environment if released. Plastic ultraviolet photostabilizers act as efficient light screeners (absorbers or pigments), excited-state deactivators (quenchers), hydroperoxide decomposers, and radical scavengers. Ultraviolet absorbers are cheap to produce, can be used in low concentrations, mix well with polymers to produce a homogenous matrix, and do not alter the color of polymers. Recently, polyphosphates, Schiff bases, and organometallic complexes were synthesized and used as potential ultraviolet absorbers for polymeric materials. They reduced the damage caused by accelerated and natural ultraviolet aging, which was confirmed by inspecting the surface morphology of irradiated polymeric films. For example, atomic force microscopy revealed that the roughness factor of polymers’ irradiated surfaces was improved significantly in the presence of ultraviolet absorbers. In addition, the investigation of the surface of irradiated polymers using scanning electron microscopy showed a high degree of homogeneity and the appearance of pores that were different in size and shape. The current work surveys for the first time the use of newly synthesized, ultraviolet absorbers as additives to enhance the photostability of polymeric materials and, in particular, polyvinyl chloride and polystyrene, based mainly on our own recent work in the field.

scholarly journals Substituted Organotin Complexes of 4-Methoxybenzoic Acid for Reduction of Poly(vinyl Chloride) Photodegradation

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3946
Author(s):  
Angham G. Hadi ◽  
Sadiq J. Baqir ◽  
Dina S. Ahmed ◽  
Gamal A. El-Hiti ◽  
Hassan Hashim ◽  
...  
Keyword(s):  
Vinyl Chloride ◽  
Polymeric Materials ◽  
Polymeric Films ◽  
Harsh Environments ◽  
Spectroscopic Methods ◽  
Poly Vinyl Chloride ◽  
Tin Complexes ◽  
Ultraviolet Absorbers ◽  
The Stability ◽  
Methoxybenzoic Acid

Poly(vinyl chloride) suffers from degradation through oxidation and decomposition when exposed to radiation and high temperatures. Stabilizers are added to polymeric materials to inhibit their degradation and enable their use for a longer duration in harsh environments. The design of new additives to stabilize poly(vinyl chloride) is therefore desirable. The current study includes the synthesis of new tin complexes of 4-methoxybenzoic acid and investigates their potential as photostabilizers for poly(vinyl chloride). The reaction of 4-methoxybenzoic acid and substituted tin chlorides gave the corresponding substituted tin complexes in good yields. The structures of the complexes were confirmed using analytical and spectroscopic methods. Poly(vinyl chloride) was doped with a small quantity (0.5%) of the tin complexes and homogenous thin films were made. The effects of the additives on the stability of the polymeric material on irradiation with ultraviolet light were assessed using different methods. Weight loss, production of small polymeric fragments, and drops in molecular weight were lower in the presence of the additives. The surface of poly(vinyl chloride), after irradiation, showed less damage in the films containing additives. The additives, in particular those containing aromatic (phenyl groups) substitutes, inhibited the photodegradation of polymeric films significantly. Such additives act as efficient ultraviolet absorbers, peroxide quenchers, and hydrogen chloride scavengers.

scholarly journals Can One Promote a Delegation of the Bilateral Aid to Multilateral Donors to Improve Foreign Aid Effect on Economic Growth in ECOWAS (Note 1) Countries?

2019 ◽  
Vol 2 (1) ◽  
pp. 51
Author(s):  
W. Jean Marie Kébré
Keyword(s):  
Economic Growth ◽  
Panel Data ◽  
Least Squares ◽  
Foreign Aid ◽  
Bilateral Aid ◽  
Multilateral Aid ◽  
Multilateral Institutions ◽  
Negative Effect ◽  
High Degree ◽  
The Relationship

<p><em>This article analyzes the relationship between external aid and economic growth in the ECOWAS region, with a focus on bilateral and multilateral aid effects. The key idea behind this analysis is an argument of Svensson</em><em> </em><em>(2000)</em><em> that multilateral aid is more effective than bilateral aid because of the high degree of altruism of bilateral donors. He therefore suggested a delegation of bilateral aid to multilateral institutions. To appreciate his suggestion, this analysis used panel data from the 16 ECOWAS countries from the period 1984 to 2014. The results of the estimates, based on the dynamic least squares estimator (DOLS), show a negative effect of foreign aid on economic growth. This negative effect on economic growth persists when the components of aid are introduced into the model. In addition, results highlight that governance is a channel through which foreign aid affect positively economic growth. In these conditions, bilateral aid is more effective on economic growth than multilateral aid. These results about foreign aid received by ECOWAS countries invalidates</em><em> </em><em>Svensson’s</em><em> </em><em>(</em><a title="Svensson, 2000 #5" href="#_ENREF_1"><em>2000</em></a><em>)</em><em> theory. Therefore, a delegation of bilateral aid to multilateral institutions is not relevant because bilateral aid contributes more to economic growth if governance is taken into account.</em></p>

scholarly journals Immigration, Wages and Employment under Informal Labor Markets

2021 ◽  
Author(s):  
Lukas Delgado-Prieto
Keyword(s):  
Labor Markets ◽  
Formal Sector ◽  
Informal Workers ◽  
Informal Labor ◽  
Wage Effect ◽  
Wage Effects ◽  
Market Impacts ◽  
Negative Effect ◽  
Informal Labor Markets ◽  
High Degree

This paper studies the labor market impacts of a massive inflow of Venezuelans in Colombia. By comparing areas that received different shares of migrants, I find a negative effect on wages and on local employment for natives. The negative wage effect is driven by a large drop of wages in the informal sector, where migrants are mostly employed, while the negative employment effect is driven by a reduction of employment in the formal sector, where the minimum wage is binding. To explain these results, I develop a model in which firms hire formal and informal workers with different costs. If these workers have a high degree of substitutability, and wages for formal workers are rigid, firms reallocate formal to informal employment as a response to lower informal wages. In settings with informal labor markets migration can therefore lead to asymmetric employment and wage effects across the informal and formal sectors.

scholarly journals Quantitative Assessment of Organic And Inorganic Contaminants In Charcoal Applied for Food Processing

2021 ◽  
Author(s):  
Zbigniew Jelonek ◽  
Monika Fabiańska ◽  
Iwona Jelonek
Keyword(s):  
Toxic Elements ◽  
Prolonged Exposure ◽  
Gas Chromatography Mass Spectrometry ◽  
Moderate Degree ◽  
Inorganic Contaminants ◽  
Low Degree ◽  
Wide Range ◽  
Polycyclic Aromatic ◽  
Living Organisms ◽  
High Degree

Abstract Thirty-one batches of commercial charcoal from various regions of Poland and Germany were tested for the presence of twenty toxic elements and polycyclic aromatic hydrocarbons (PAHs) using gas chromatography - mass spectrometry (GC-MS). Elements that are toxic to living organisms were determined using atomic absorption spectroscopy (AAS). They were classified as elements representing a very high degree of hazard (As, Cd, Cu, Hg, and Pb), high degree of hazard (Zn, Ba, Cr, Mn, and Mo), moderate degree of hazard (Co, Ni, Sn, and Te), and a low degree of hazard for living organisms and the environment (Ag, Bi, Ce, Se, Sr, and Zr). When it comes to the most toxic elements, the highest concentration in the whole tested material was recorded for Cu. In addition, considerable amounts of Ba, Mn, and Sr, i.e., elements representing high or moderate degree of hazard, were found in the tested charcoals. Moreover, all charcoals contained a wide range of PAHs, from naphthalene to benzo(ghi)perylene, with concentrations in the range between 12.55 and 3554.11 ng/g of charcoal. In total, 25 unsubstituted PAHs were identified in the charcoal extracts. PAHs distributions were dominated by 5-ring PAHs. The results indicate the high carcinogenicity with ∑PAHcarc/∑PAHtot close to 1, as well as high TEQ and MEQ values. Thus, prolonged exposure to charcoal and charcoal dust might cause serious health problems. This applies to employees actively involved in the production and transport of charcoal, and, to a lesser extent, also to users of this fuel.

scholarly journals Fermentative Utilization of Glycerol by Escherichia coli and Its Implications for the Production of Fuels and Chemicals

2007 ◽  
Vol 74 (4) ◽  
pp. 1124-1135 ◽  
Author(s):  
Abhishek Murarka ◽  
Yandi Dharmadi ◽  
Syed Shams Yazdani ◽  
Ramon Gonzalez
Keyword(s):  
Escherichia Coli ◽  
Anaerobic Fermentation ◽  
Glycerol Metabolism ◽  
Nuclear Magnetic Resonance Analysis ◽  
Glycerol Fermentation ◽  
Glycerol Utilization ◽  
Negative Effect ◽  
Balance Analysis ◽  
Fuels And Chemicals ◽  
High Degree

ABSTRACT Availability, low prices, and a high degree of reduction make glycerol an ideal feedstock to produce reduced chemicals and fuels via anaerobic fermentation. Although glycerol metabolism in Escherichia coli had been thought to be restricted to respiratory conditions, we report here the utilization of this carbon source in the absence of electron acceptors. Cells grew fermentatively on glycerol and exhibited exponential growth at a maximum specific growth rate of 0.040 ± 0.003 h−1. The fermentative nature of glycerol metabolism was demonstrated through studies in which cell growth and glycerol utilization were observed despite blocking several respiratory processes. The incorporation of glycerol in cellular biomass was also investigated via nuclear magnetic resonance analysis of cultures in which either 50% U-13C-labeled or 100% unlabeled glycerol was used. These studies demonstrated that about 20% of the carbon incorporated into the protein fraction of biomass originated from glycerol. The use of U-13C-labeled glycerol also allowed the unambiguous identification of ethanol and succinic, acetic, and formic acids as the products of glycerol fermentation. The synthesis of ethanol was identified as a metabolic determinant of glycerol fermentation; this pathway fulfills energy requirements by generating, in a redox-balanced manner, 1 mol of ATP per mol of glycerol converted to ethanol. A fermentation balance analysis revealed an excellent closure of both carbon (∼95%) and redox (∼96%) balances. On the other hand, cultivation conditions that prevent H2 accumulation were shown to be an environmental determinant of glycerol fermentation. The negative effect of H2 is related to its metabolic recycling, which in turn generates an unfavorable internal redox state. The implications of our findings for the production of reduced chemicals and fuels were illustrated by coproducing ethanol plus formic acid and ethanol plus hydrogen from glycerol at yields approaching their theoretical maximum.

Absolute humidity of atmospheric air and COVID-19

2021 ◽  
pp. 8-24
Author(s):  
Vladimir Vasilievich Krivosheev ◽  
Artem Igorevich Stolyarov ◽  
Aleksandr Aleksandrovich Semenov
Keyword(s):  
Relative Humidity ◽  
Absolute Humidity ◽  
Atmospheric Parameter ◽  
Natural Factor ◽  
Incidence And Mortality ◽  
Optimal Value ◽  
Negative Effect ◽  
Northern Territories ◽  
High Degree ◽  
The Impact

Today COVID-19 is number one global point of focus. Therefore, study of the effects of environmental conditions, in which exist pandemic subjects — people and viruses, on pandemic dynamics and results is extremely important. The authors made a correlation analysis of dependence between incidence/mortality of population and absolute and relative humidity in 73 countries and regions on different continents of the Earth. The methodology developed defines how and in what periods of time the environmental factors effect on human incidence and mortality, how strongly particular atmospheric parameter affects the process of infection and disease flow. The undertaken calculations allowed to prove that the absolute humidity is one of the dominant natural factor which influences on pandemic COVID-19 and other infectious diseases dynamics. The growth of absolute air humidity can have both positive and negative effect on incidence and mortality of population while the effect’s character depends on absolute humidity’s own level and other atmospheric parameters. Correlation of absolute and relative humidity with incidence/mortality at the same time can be different in value or sign. Existing regulations at the federal level in Russian Federation are established without taking into account the minimum allowable and physiologically optimal value of absolute humidity, and need corrections. The question of the impact of absolute humidity is of great importance for northern territories, where most of the year the value of absolute humidity is less than the minimum allowed. The achieved results show high degree of the impact of absolute humidity on incidence and mortality of population due to COVID-19 and contribute to better understanding of pandemic peaks cyclicality and conscious forecasting of start of periods of the most dangerous epidemiological reality.

Modifiable Silicones for Harsh Environments

2011 ◽  
Vol 2011 (1) ◽  
pp. 000090-000098 ◽  
Author(s):  
Michelle Velderrain ◽  
Matthew Lindberg
Keyword(s):  
Elevated Temperatures ◽  
Electronic Devices ◽  
Polymeric Materials ◽  
Harsh Environments ◽  
Electrically Conductive ◽  
Polymeric Systems ◽  
Low Modulus ◽  
Conductive Fillers ◽  
Processing Techniques

Silicones have been used for decades in aerospace and other harsh environments where temperature extremes are common. As the level of sophistication increases for electronic devices to serve these industries where failure is not an option, the material supplier has to also be able to meet these needs. Silicones are polymeric materials composed primarily of repeating silicon and oxygen bonds, known as siloxanes, which can be optimized for various chemical and physical properties by incorporating different organic groups onto the silicon atom. Employing advanced processing techniques to the siloxane system can also greatly reduce mobile siloxane molecules to reduce contamination that can cause electronic failures during assembly or operation. Siloxane based polymeric systems are also unique polymers compared to standard organic based materials in that they have a large free volume that imparts a low modulus which absorbs stresses during thermal cycling as well as not degrading at continuous operating temperatures up to 250 C. They are also slightly polar which allows the incorporation of fillers to impart a variety of unique properties. Filler technology is also a rapidly growing enterprise where fillers with various particle sizes and shapes can be added to silicones to impart key properties such as maintaining electric conductivity at elevated temperatures. This paper will explain fundamentals of silicone chemistry and processing related to getting the optimal performance in harsh environments. A case study comparing two different electrically conductive fillers and how they can influence the electrical conductivity at elevated temperatures will be presented.

scholarly journals Electronic Health Record's Effects on the Outpatient Office Visit and Clinical Education

2017 ◽  
Vol 23 (4) ◽  
pp. 765 ◽  
Author(s):  
Marie B Sandoval ◽  
Mary Val Palumbo ◽  
Vicki Hart
Keyword(s):  
Cognitive Processing ◽  
Clinical Education ◽  
Cognitive Task ◽  
Office Visit ◽  
Chi Square ◽  
Negative Effect ◽  
Prior Literature ◽  
Electronic Health ◽  
High Degree ◽  
Positive Effect

Background: During an office visit, the provider has the important cognitive task of attending to the patient while actively using the electronic health record (EHR).  Prior literature suggests that EHR may have a positive effect on simple tasks, but a negative effect on tasks that require complex cognitive processes.  No study has examined the provider’s perception of EHR on multiple distinct aspects of the office visit.Methods: We surveyed providers/preceptors regarding their perception of EHR on multiple aspects of the office visit.  We summarized their EHR utilization history and their perceptions of the EHR during the visit using descriptive statistics.  We tested for associations between time spent using the EHR and distinct aspects of the visit using Chi-square tests of association.Results: In total, 83 providers/preceptors reported use of EHR (response rate 52%). Provider/preceptors reported an overall negative effect of EHR on the patient-provider connection, but an overall positive effect on the review of medications/medical records, communication between providers, review of results with patients and review of follow-up to testing results with patients. The effect of EHR on history taking and teaching students was neutral.  We observed no correlation between the provider’s time spent using the EHR and their perception of its effectiveness.Conclusions:  Providers reported a positive perception of EHR on aspects of the office visit that involved a single cognitive task.  However, providers reported a negative perception of EHR on patient-provider connection, which involves a high degree of cognitive processing.

Natural disasters and MNC sub-national investments in China

2020 ◽  
Vol 28 (2) ◽  
pp. 245-274 ◽  
Author(s):  
Chang Hoon Oh ◽  
Jennifer Oetzel ◽  
Jorge Rivera ◽  
Donald Lien
Keyword(s):  
Natural Disasters ◽  
Fixed Effects ◽  
Event History Analysis ◽  
Foreign Firms ◽  
Geographic Proximity ◽  
Content Type ◽  
History Analysis ◽  
Negative Effect ◽  
Context Specific ◽  
High Degree

Purpose The purpose of this study is to examine how foreign firms consider natural disaster risk in subsequent investment decisions in a host country and whether different location portfolios can serve to mitigate investment risk. Design/methodology/approach The author sample includes data on 437 Fortune Global 500 firms and their initial entry into Chinese provinces between 1955 and 2008. Findings Using a fixed effects logit model of discrete time event history analysis, results show that geographic proximity to same multinational corporation (MNC) subsidiaries and different MNC subsidiaries from the same home country mitigates the negative effect of natural disasters on MNC entry into an affected province, while geographic proximity to other MNC subsidiaries from different home countries does not. Originality/value The knowledge needed to respond to severe disasters appears to be highly context-specific and shared only between firms with a high degree of commonality and trust.

A Planned Complex Suicide: Need for a High Index of Suspicion

2006 ◽  
Vol 72 (5) ◽  
pp. 454-455
Author(s):  
Michael W. Parra ◽  
Matthew W. Lube ◽  
Haitham Al-Khayat ◽  
Michael L. Cheatham
Keyword(s):  
Gunshot Wound ◽  
High Index ◽  
Toxic Substances ◽  
Degree Of Protection ◽  
Legal Literature ◽  
Suicidal Person ◽  
Complex Suicide ◽  
Single Method ◽  
High Index Of Suspicion ◽  
High Degree

Unusual ways of committing suicide are reported in the medico-legal literature, but few refer to the so-called “planned complex suicide” (PCS).1 PCS, also termed primary combined suicide, is defined as the combination of two or more methods of injury by the suicidal person to prevent failure of a single method of suicide alone. In contrast, in secondary or unplanned complex suicide, the victim uses the second method of suicide only after failure of the first method.2 Combinations of shooting, hanging, burning, and/or poisoning have been used as suicidal methods.3–6 Sometimes the double use of one method such as simultaneous gunshot wound from two firearms or ingestion of two different toxic substances has been reported. This gives the suicidal person a high degree of protection against failure of one of the methods, as both modes of injury are relatively certain.2 This case report demonstrates the importance of the treating physician maintaining a high index of suspicion for the possibility PCS with the aim of avoiding a misdiagnosis that may be fatal.

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