Abstract: The ability to tune the gaps of direct bandgap materials has tremendous potential for
applications in the fields of LEDs and solar cells. However, lack of reproducibility of bandgaps
due to quantum confinement observed in experiments on reduced dimensional materials, severely
affects tunability of their bandgaps. In this article, we report broad theoretical investigations of
direct bandgap one-dimensional functionalized isomeric system using their periodic potential profile,
where bandgap tunability is demonstrated simply by modifying the potential profile by changing the
position of the functional group in a periodic supercell.We found that bandgap in one-dimensional
isomeric systems having the same functional group depends upon the width and depth of the deepest
potential well at global minimum and derived correlations are verified for known synthetic as well as
natural polymers (biological and organic), and also for other one-dimensional direct bandgap systems.
This insight would greatly help experimentalists in designing new isomeric systems with different
bandgap values for polymers and one-dimensional inorganic systems for possible applications in
LEDs and solar cells.
Keywords: density functional theory; bandgap; polymers; nanoribbons; one-dimensional systems
1. Introduction
One-dimensional materials are in focus amongst the current research areas for their remarkable
physical properties arising as a consequence of the reduced dimensionality. However, lack of control
over reproducibility of bandgap values in one-dimensional materials 1–3 is one of the challenges for
its electronic applications like LEDs and LASER diodes, as it affects their bandgap tunability. Several
theoretical studies have been reported to tune the bandgap of one-dimensional materials using various
methods like strain, functionalization at the edges, doping, etc. 4–6, however, the methods lack in
control over the bandgap values. Since, bandgap is one of the most important factors while selecting a
material for an electronic application; therefore, different direct bandgap materials have been explored
for LEDs and LASER applications, e.g., Aluminium gallium nitride (AlGaN) for ultraviolet LEDs (below
400 nm), while Aluminium gallium arsenide (AlGaAs) for infrared LEDs (above 760 nm). Therefore,
it would be of great interest if bandgap of a given material can be tuned, and this quest has been
extended to polymers. Several experimental and theoretical studies on bandgap in polymers 7–13
have been reported aimed at their applications in organic LEDs 14–16 and solar cells 9,17–22.
However, different values of bandgap noticed in experiments on isomeric polymers 23–25 and also
in theoretical studies 12,25–27 suggest that bandgaps may be tuned in one-dimensional system, if the
Condens. Matter 2018, 3, 34; doi:10.3390/condmat3040034 www.mdpi.com/journal/condensedmatter
Condens. Matter 2018, 3, 34 2 of 10
underlying physics is understood. The fact that the work so far reported on bandgaps in isomeric
polymers having the same functional group is still inconclusive 25–27, motivated us to investigate and
define the driving elements of different bandgaps seen in the isomeric systems. Once we understand
the mechanism behind this, we may be in a position to tune the bandgaps of such materials as per
our requirements. In this work, investigations are carried out on one-dimensional isomeric polymers
(synthetic and natural), and nanoribbons having the same functional groups. Since polymers are large
chain of monomers, Therefore, they are considered as one-dimensional periodic systems for band
structure calculations 28–32.
2. Results and Discussions
For investigating and defining the driving element of different bandgaps in isomeric
systems, an example of low bandgap synthetic polymer, polydithienyl naphthodithiophenes
(DThNDT) (C20H8S4)n is considered. It exists in two isomeric forms, poly(anti-DThNDT) and
poly(syn-DThNDT) 25 having periodic unit cell of length 14.681 Å, and 13.113 Å, respectively
(see Figure 1a). Cut-off energy of 500 eV is used for band structure calculations. Ground state energy
calculated per atom for poly(anti-DThNDT) and poly(syn-DThNDT) are ?7.034 eV and ?7.003 eV,
respectively, which are in close proximity of being isomers.
Figure 1. (color online) (a) Unit cells for poly(anti-DThNDT) and poly(syn-DThNDT) are represented
in the dotted boxes. Blue, yellow, and white spheres represent carbon, sulfur, and hydrogen atoms,
respectively; (b) Band structure plots corresponding to poly(anti-DThNDTP) and poly(syn-DThNDTP).
Given the one-dimensional nature of polymers, their band structures are plotted from G
to X point (see Figure 1b). Direct bandgaps are observed at G point for both the polymers of
poly(anti-DThNDT) and poly(syn-DThNDT) with bandgaps of 0.518 eV and 1.681 eV, respectively.
Bandgap for poly(anti-DThNDT) is smaller than that of poly(syn-DThNDT), which is in agreement with
the experimental report 25. Band structures for these isomeric polymers are significantly different,
even though they have same chemical formula, and practically the same ground state energy.
The polymers are one-dimensional systems with a repeating unit cell (monomer), Therefore,
their bandgap may be related to their one-dimensional periodic potential profile similar to that of
Kronig–Penney model. Since, potential is a scalar quantity, Therefore, average of potentials in the
periodic direction of isomeric unit cell may be considered for comparative analysis of bandgap values.
Average potential profile for poly(anti-DThNDT) and poly(syn-DThNDT) are plotted in the periodic
direction as shown in Figure 2.
Condens. Matter 2018, 3, 34 3 of 10
Figure 2. Average potential profile corresponding to the unit cell in the periodic direction of poly(anti-
DThNDT) and poly(syn-DThNDT) are denoted in solid and dotted lines, respectively.
The periodic average potential profiles of poly(anti-DThNDT) and poly(syn-DThNDT) are quite
different to each other, and even to ideal rectangular potentials of the Kronig–Penney model 33.
Since a system prefers to stay in its ground state, the deepest potential well at global minimum in
the periodic potential profiles are considered for comparative analysis of bandgap values 34 for
isomeric systems. The global minimum for poly(anti-DThNDT) is located at 9.849 Å, enclosed between
two crests (barriers) located at 9.058 Å and 11.432 Å, while global minimum for poly(syn-DThNDT)
is located at 5.517 Å, enclosed between two crests (barriers) located at 4.466 Å and 6.480 Å. From
Figure 2, it can be seen that shape of the potential wells in the potential profile looks like inverse
Gaussians, consisting of both well and barrier width. Therefore, for simplifying the calculations,
potential well is considered as square well potential of equal width for well and barrier (half of the
distance between crests of the potential well). Since depth of the deepest potential well at global
minimum ‘V0’, and its corresponding width ‘a’ are finite and non-zero, distinct from the KP model
(where a ! 0 and V0 ! ¥ for finite value of V0.a) 33. Hence, Schrödinger equation needs to be solved
for the periodic square well potential of finite width and depth at global minimum to get first order
bandgap, which may be correlated with the bandgap calculated using DFT. The energy eigenvalues
corresponding to Schrödinger wave equation for an electron of mass ‘m’ and energy ‘E’ (where E 0 (2)
and,
¯h2b2
2m
= ?E < 0 (3)
Condens. Matter 2018, 3, 34 4 of 10
For isomeric polymers of polydithienyl naphthodithiophenes (DThNDT) (C20H8S4)n, width
and depth of the deepest potential well at global minimum for poly(anti-DThNDT) are 1.187 Å and
0.212 eV, respectively, while for poly(syn-DThNDT) are 1.007 Å and 0.299 eV, respectively (Figure 2).
Using these values in Equation (1), it is found that poly(syn-DThNDT) has larger bandgap than
that of poly(anti-DThNDT), which is in agreement with bandgap values calculated using DFT, and
experimental reports 25. Therefore, it is concluded that bandgap of one-dimensional isomeric systems
may be correlated with depth and width of the potential well at global minimum in the periodic
average potential profile.
In order to find out how bandgap of one-dimensional isomeric systems may be correlated with
their deepest potential well at global minimum in the periodic direction; a general correlation needs
to be formulated and establish its validity for other isomeric systems. Since isomeric systems usually
would have different dimensions (V0 and a) of the deepest potential well at global minimum, Therefore,
the transcendental Equation (1) needs to be solved for bound states of different ‘V0.a’ varying both
‘V0’ and ‘a’. In fact for bound states (E V2) then 4Eg1 > 4Eg2
Case III (a1 > a2,V1 = V2) then 4Eg2 > 4Eg1
Case IV (a1 > a2,V2 > V1) then 4Eg2 > 4Eg1
Case V (a1 > a2,V1 > V2)
In this case, sign of slopes for bandgap as a function of ‘V0.a’ may change on changing ‘V0’ and ‘a’
w.r.t. a reference point, Therefore, bandgap correlation can be predicted only on solving Equation (1)
for corresponding ‘V0’ and ‘a’.
Condens. Matter 2018, 3, 34 5 of 10
For isomeric polymers of polydithienyl naphthodithiophenes (DThNDT) (C20H8S4)n, the width
and depth of the deepest potential well at global minimum in the periodic potential profile
for poly(anti-DThNDT) are 1.187 Å (say ‘a1’) and 0.212 eV (say V1), respectively, while for
poly(syn-DThNDT) are 1.007 Å (say ‘a2’) and 0.299 eV (say V2), respectively (see Figure 2). Since
a1 > a2 and V2 > V1, Therefore, according to correlations of Case IV, poly(syn-DThNDT) should have
larger bandgap than poly(anti-DThNDT); which agrees with our band structure calculations using
DFT, and other experimental reports 25. The agreement of derived correlation with theoretical and
experimental results establishes its validity.
To verify it further, the investigation is extended to other isomeric synthetic polymer
polydialkylterthiophenes (C36H54S3)n (see Supplementary Material Figure S1) and natural polymers
(biopolymers and organic polymers) (see Supplementary Material Figure S2 and S3), bandgaps are
found to be correlated with the dimension of the potential well at a global minimum as per the derived
correlations. The investigations have been extended to natural polymers for extensive validity of the
correlations, even though they are insulating and of little importance to electronic applications.
On the basis of theoretical analyses, it is established that bandgaps of isomeric systems are
correlated with width and depth of the deepest potential well at global minimum in their periodic
potential profile. From derived correlations, it may be predicted that bandgap of one-dimensional
periodic system may be tuned, if width and depth of the deepest potential well in the periodic potential
profile is altered on changing the position of functional group in the periodic unit cell.
To establish the concept of bandgap tunability in one-dimensional systems, the investigation is
extended to theoretical GNRs (same molecular formula for the unit cells) having the same functional
group in the periodic unit cell but of different arrangements. Zigzag GNRs (ZGNRs) of the same
width functionalized at the edges with oxygen atoms in two typical ways (say Config. I and Config.
II as shown in Figure 4a) are considered for calculations. sp2 and sp3 hybridized carbon atoms are
considered at edges for visible distinction of isomeric change in the periodic unit cell (7.378 Å) of
zigzag GNRs. Typical edge configurations of ZGNRs (Nz = 7) are shown in Figure 4a. Periodic average
potential profiles corresponding to Config. I and Config. II are plotted in Figure 4b. Even though their
average potential profiles look different, their potential profiles superpose on each other on relative
shifting in the periodic direction. The width and depth of potential well at global minimum for Config.
I and Config. II are exactly same 0.614 Å (a1 = a2) and 0.648 eV (V1 = V2). Since a1 = a2 and V1 = V2,
Therefore, according to the derived correlations (Case I), bandgap of both the configurations of ZGNRs
should be equal.
Figure 4. (color online) (a) Unit cells corresponding to two configurations Config. I and Config. II of
7-ZGNRs, where blue and red spheres represent carbon and oxygen atoms, respectively. (b) Average
potential profile of the unit cell for Config. I and Config. II in the periodic direction of 7-ZGNRs are
denoted with solid and dotted curve, respectively. Inset shows the overlap of potential profiles on
relative shifting along the periodic direction.
Condens. Matter 2018, 3, 34 6 of 10
To check the validity of the correlations, band structure calculations for 7-ZGNRs are performed
with cut-off energy of 450 eV. Band structures are plotted from G to X point for Nz = 7 (Figure 5). Direct
bandgap of 0.393 eV is observed at G point for both the configurations. It is found that bandgap values
of ZGNRs for Config. I and Config. II are same, even ground state energy per atom of the unit cell
calculated for both the configurations are same, ?8.762 eV. On further analyses of potential profiles
of ZGNRs, the same correlations are found to be held for other odd ZGNRs (Nz = 3 to 17), which are
verified with the band structure calculations using DFT.
Figure 5. Band structure plots corresponding to Config. I and Config. II for Nz = 7.
Further, we have considered even Nz-ZGNRs (Nz=8). The unit cells corresponding to Config. I
and Config. II are shown in Figure 6a for NZ = 8. The lattice parameters in periodic direction for both
the configurations are equal to 7.378 Å. The ground state energy per atom for Config. I and Config. II
are ?8.818 eV and ?8.817 eV, respectively, which are practically the same.
Average potential profiles in the periodic direction of unit cell corresponding to Config. I and
Config. II are plotted in Figure 6b. The width and depth of potential well at global minimum for Config.
I are 0.614 Å(‘a1’) and 1.091 eV (V1), respectively, while for Config. II are 0.614 Å(‘a2’) and 0.721 eV (V2),
respectively. Since a1 = a2 and V1 > V2, Therefore, from the proposed theory, Config. I should have
higher bandgap than that of Config. II (Case II). From band structure calculations, direct bandgaps
of 0.792 eV and 0.342 eV are observed at G point for Config. I and Config. II, respectively (Figure 7).
Thus, bandgap of Config. I is significantly higher than that of Config. II, which is in agreement with
derived correlation using potential profiles (Figure 6). On further analyses of potential profiles of even
ZGNRs, the same correlations are found to be hold for other even ZGNRs (Nz = 10 to 18), which are
verified with the band structure calculations using DFT. However, potential profiles of even Nz-ZGNRs
for Nz < 6 are found to fall under Case V (see Supplementary Material Figure S4). Thus, it justifies
tunability of a bandgap value in direct bandgap one-dimensional systems.
Condens. Matter 2018, 3, 34 7 of 10
Figure 6. (color online) (a) Unit cells corresponding to two different configurations Config. I and Config.
II of even ZGNRs corresponding to Nz = 8, where blue and red spheres represent carbon and oxygen
atoms, respectively; (b) their corresponding potential profiles.
Figure 7. Band structure plots corresponding to Config. I and Config. II for Nz = 8
3. Computational Details
Band structure calculations are performed using Density Functional Theory (DFT) as implemented
in Vienna ab initio simulation package (VASP) 35. Generalized gradient approximation (GGA) 36 is
used for exchange-correlation of electron-electron interactions as implemented in projected augmented
wave (PAW) formalism 37. Further, a vacuum layer of at least 15 Å is used to avoid interlayer
interactions. The system is relaxed until a force on each atom in the unit cell is less than 0.001 eV.Å?1.
k-mesh of size 25 1 1 is used in Monkhorst–Pack formalism for momentum space sampling.
4. Conclusions
On the basis of theoretical analyses of one-dimensional systems having the same functional group
in the periodic unit cell, but of different arrangements, it is observed that:
Bandgaps of one-dimensional systems are correlated to the depth and width of potential well at
global minimum in the periodic potential profile.
The correlations derived between bandgap and dimension of periodic potential well at global
minimum is verified for known isomeric systems of synthetic as well as natural polymers
Condens. Matter 2018, 3, 34 8 of 10
(biological and organic), and bandgap tunability is also established for one-dimensional
nanoribbons.
Finally, it is concluded that bandgap of one-dimensional system can be tuned by changing the
position of functional group in the periodic unit cell of the same material, which may be used for
designing materials of different bandgap values for LEDs applications and effectively harvesting
energy in solar cells; and insight may be extended to understand the different physical properties of
isomers of biopolymers such as proteins.

Abstract: Sensation is the process that enables people’s brains to interpret information received through the five senses. People have normally five senses, and each sense plays a particular role in the organism. In everyday life, individuals use all senses to complete certain tasks; so living with the lack of one sense could make life more challenging. One may ask, how could a person born with the disability of deafness or blindness be independent and what kind of jobs could they do? Firstly, deafness is the loss of the sense of hearing, and blindness is the loss of the sense of sight; however there considerable reasons that might cause these disabilities. One might be born with deafness or blindness; others are born without the disability of deafness or blindness but become deaf or blind suddenly deaf or blind due to certain dysfunctions of some organs, also some chemicals could be responsible to these disabilities. However, the modern society is characterized by a continuous development of technologies, so these developments have a positive impact in the quality of blind or deaf people; the living conditions of those people has really changed and improved compare to past years. And these remarkable developments make them independent, autonomous and free. This paper is a study of deafness and blindness.

Humans were created with physical abilities to perceive the world around them. Through senses, people perceives external stimulus that is then interpret by the brain. Individuals normally have five senses, the five traditionally recognized senses are: sight, taste, hearing, touch and hearing. People feel pains, pressure, tension, temperature, and weight trough the sense of touch; so the organ for the sense of touch is the skin. The skin has receptors that receive signals from the outside and send those signals to the brain to interpret. The sense of smell allows humans to differentiate odors through the nose; the nose has the ability to smell tiny particles in the air, then receptors inside the nose send the information to the master of all senses, the brain. So that people are able to know whether it is a bad odor or good odor; some studies affirmed that the organ of smell influence the way people perceive the taste of food. One may be influence to eat because the food smells good. The second sense is the sense of taste, when it comes to eat; the organ that helps to appreciate tastes is the tongue. Through the tongue, one can say that the food is salty or bitter.
The sense of hearing allows people to hear sounds, appreciate melodies, and communicate with people around. People use their ears to hear; however it is a complex process it is not only about the external part of ears. Ears have several parts, including the external, middle and inner portions; so in order to hear, sound enter the ears then travel to the auditory canal and the tympanic membrane, which then go deeper in the inner part, so that the auditory nerve sends signals to the brain. When the vibrations are interpreted, people easily differentiate music from thunder. So when one of these parts is affected, people may end up being deaf.
So for the sense of sight, the major organ is the eye; the eye works in collaboration with the brain. Eyes help people to perceive the height, colors, width, and depth or things; to perceive things eyes need the light to be present, in the light environment, the vision is more controlled by cones which are inside the retina; so when the light penetrate eyes, eyes’ lens focus the light and then the image is focused on a region of retina.; Then the image will be sent to the brain for interpretation. However, rods work well in low light conditions, there are inside the retina; so when people transit form light from darkness to light, they experience a delay to see things around them; this happen because rods need to take control so the transition between rods and cones cause the delay when moving in the darkness. When some parts eyes do not function properly, it might cause defects on our ability to perceive our environment.
Actually people need their eyes and ears to know more about their surroundings and be involved in communities around the world; so blindness and deafness could limit people and hinders them to have a normal life or be involved in communities. One may say that having these two disabilities (deafness or blindness) would make life more miserable, people that do not have these disabilities could not imagine life without the five senses; as they rely on them to complete certain tasks. So people who are completely blind face many challenges in their life; they have a difficult time when they try to move or walk around, especially when they are not familiar with the area. In fact, even walking outside familiar spaces could still be challenging; so that is why blind people usually take with them sighted friends when they are moving around. Moreover, living with blind people is not easy as well; when living with a blind person, people should not move items in their home. The design of the house should remain the same for years, because blind people do their best to memorize the location of everything in the house to avoid accidents; each member should always care about walkways for their safety.
Besides having challenges with the environment, blind people could face social challenges as well. Blindness may hinder people to have access to certain activities and to perform some jobs; therefore, blind people do not easily choose a career. This may have a negative impact on their finances, because some blind people think that they are not able to perform any work, so blindness could make life worse for some. Furthermore, blind people cannot use internet and mobile devices such as cellphones.
Deaf people also face hard challenges. First of all, deaf people do not hear anything at all; so those people have lost their sense of hearing, it is just hard to imagine life without hearing any sounds, any music or noise. A study showed that when people are born with this disability (deafness) lack attention to sounds, they do not respond when someone calls them, they show delays in speech and language development, also they have difficulty achieving academically especially in reading and math. (SITE) So hearing loss might have negative impacts on speech and language acquisition, also on academic achievements and on social and emotional development; most people with hearing loss do have hearing parents and no history of hearing loss in their families. Majority of parents that have children born deaf are unable to effectively communicate and engage in deep communication with their deaf children. Therefore, a child born with deafness may be unable to participate adequately in family conversation. It is evident that deafness affects language skill, as said by Skinner: ” language is learned through reinforcements.”; meaning that the environment influence our way of learning languages. Language is learned from hearing our surroundings, so as deaf people cannot hear; they should definitely struggle to speak as well. It is surprising that there are not good at school; because every subject requires knowledge of language to understand, that is why deaf people need to go to specific school in order to overcome these challenges.
As deaf people could not communicate by speaking, they use appropriate strategies to communicate with their surroundings, and they have a range of ways to communicate; there is no a specific way for every deaf people to communicate. Some of them use sign language to communicate, others use lip-reading. Lip-reading is not commonly used among people born deaf, because they do not know about words; as born deaf, they have heard about words in their life. But those who suddenly become deaf might use this strategy. Actually this is a technique of interpreting the lips movement to understand people, so they also pay attention on facial expressions as well; facial expression is a key when deaf people try to communicate, they rely more on it. Compare to under languages, this technique is hard to use for English people; because many words have the same lip pattern so it hard to differentiate similar words. By using this strategy, people could easily misunderstand. Sign language in contrast, is popular among those born deaf. This method rely on eyes, it is visual; people use their hands to be understand and to understand others. This technique has its own rules; others use a combination of lip- reading and sign language. So some deaf people change their way of communication depending on situations or context in which they are communicating; the most important thing to do is to ask them how they want to communicate and help them. (SITE)
So in order to facilitate the communication with deaf people, people should try to get their attention, then face them when discussing, also speak clearly and naturally, never cover the mouth, reduce background noise, and lastly never give up or say ” I will tell you later”. (Site) It is more complicated for deaf people to communicate than blind people, blindness does not have an impact on language acquisition; blind people hear normally. The interesting fact about deafness is that some deaf people, especially those born deaf, are normally born with the ability to talk but as they have never about sounds, they are not able to control their voices; some might try to talk but the sound is weird.
However, scientists invented a cochlear implant in order to improve the quality of their life. It is a treatment for people with a profound hearing loss; it is surgically implanted. A cochlear implant helps to listen and to communicate as well. This method is more convenient because it replace the function of the damaged parts of ears, so people could then hear sounds and this will improve speaking as well. But the cochlear implant does not restore complete the sense of hearing; people are still dissatisfied. Scientists tested this device, the results showed that a considerable amount of people were satisfied using a cochlear implant in a calm environment, but in a noisy environment this device was not efficient.
Blind people could speak but still face other challenges. However, there is a considerable increase in the living conditions of blind people compare to past years. People with blindness could do anything; however today, blindness does not hinder people to be independent, scientists invented some devices such as a white cane and the electromagnetic torch to help them to walk around alone. Some studies showed that his device is not completely efficient. Despite it is a passive technology with a limited range of work; it is completely sufficient for a safe mobility since it requires intensive training by instructors, also this devise is easy to use and does costs that much. (site)
Blind people also use guide dogs to travel, this technique seems to be impossible to those who rely on vision; actually a guide dog is a dog trained to guide blind individuals, and also blind people are assisted by sighted (humans) guide. Many blind persons use this method of sighted guide; a blind person is assisted by someone else who does not have this disability. All these methods are making life easier for blind people and allow them to be more independent, there are many others devices to help them read and write, but it was proved that these devices still have some limited functionalities; and others are expensive.
A common question is that what kinds of jobs are suitable for them? One may say, having these disabilities limit career options for blind and deaf people. However with today’s technology and the evolution of the world today has changed everything today. In the past it was impossible for blind people to be chefs, Architect, or doctors. With the technology, blind people are able to perform unbelievable tasks; a blind person could be a doctor, a chef, or a politician. So it is important for everyone to realize that they are normal persons, statistics showed that people born blind are better at work than people that suddenly become blind. It is because those born with the disability of blindness grow up learning everyday non visual strategies to compensate to the lack of vision. So some people today under estimate blind people, but the truth is that they might be more talented in some field than those who do not have the disability. Tim Cordes for instance was blind but he was a well reputed physician, and he was the second blind person to go to a medical school; this is unbelievable but it is a reality. Many think that blind people are supposed to be poor or miserable their all life; this is false. There are many famous musicians that are blind; it is true that they face many challenges in their life, but blindness should not be considered the principal factor that could make a person’s life miserable. Blind individuals are forced to rely on other senses, and they do have enhanced abilities in others senses, such as touch, or hearing. Having a good control on others senses might enable them to be doctors and good singers.
Although these disabilities cannot stop people to work normally because of technology, technology does not make does not make their life perfect, One may use his cochlear implant to communicate, but this device loses its efficiency when there is noise; so deaf people might be able to be a teacher or a doctor. But researches have demonstrated that a deaf teacher has difficulties teaching in a noisy classroom, and some physicians have difficulties listen to heart rates. There are considerable imperfections with this device. It can be conclude that blind or deaf people may today be independent, and be able to work as well no matter their disabilities.
It could be possible to imagine or to believe that in twenty years or thirty years, so probably in 2040 or 2050, these disabilities could disappear, especially deafness; in some country such as Australia, the cochlear implant is implanted to six months old children, knowing functions of cochlear implants, this seems to be a genius idea. Because the child will grow up knowing sounds and he will certainly speak correctly. Retina prosthesis also, devices for artificial vision, is being processing. This device was tested is someone and the person was able to see outlines of objects. As technology improves every day, scientists might end up finding solutions.
In my point of view, yes, technologies, scientists help to restore vision and hearing, people tend to rely more on technologies and doctors but they ignore the considerable job of psychologists as well. In fact, deaf or blind people also have emotional, psychological and social issues; some of them experience depression, anxiety as well. Some other deaf or blind people may develop very bad behaviors; so psychologists have a considerable impact on their life, they usually have to help them accept their conditions and live with that. When someone accepts his physical handicap, he will try to be confident, which is the key to success. Being able to see does not guarantee a successful life, life is all about confidence. Also in some countries, blind and deaf people are neglected and useless to the society. They are normal people, they deserve to be treat with respect and dignity, however when it comes to job, I think they should have limited career options for their safety. And I will suggest blind people to get for jobs that are more about speaking and or deaf people it is better to get a job that require sight than hearing or speaking. Or they may launch their own business.
In conclusion, Blindness or deafness has negative effects in all aspects of life. Recent studies showed that blind or deaf people rely on other senses; those people face challenges everyday of their life, it may be hard for them to get but even after hiring they still have challenges; they might be discriminated because of their disabilities, so life could be more difficult for them. But evidences has shown that these disabilities could make life challenging, but do not stop people to be independent or successful. Humans are born with a remarkable capacity to adapt to changes that may occur in their life, so they just need a support everyone, encouragement as well. However, there are many others questions related to this subject, one may ask how blind and deaf people perceive the world? How do they think about themselves or their surroundings? Do they live in an imaginary world? So, additional investigations should be done in order to respond to these questions.

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

Abstract:
The aim of this paper is that the exact solutions of Non-Newtonian fluid namely micropolar fluid with MHD in porous medium by traveling wave solution. The governing equations PEDs for incompressible micropolar fluid with MHD in porous medium are reduced to ODEs through wave parameter. Finally we represent the result in 2D or 3D graphs.
Introduction:
In the present, every researcher is working on the non-Newtonian fluid from the both essential and sensible point of view. These fluids are immediate effects on the processing of polymer, animal blood, liquid crystal, geological flows in the earth mantle. Non-Newtonian fluids were defined by ISSA.
The general equations of Non-Newtonian fluid are highly non-linear and higher- order than the Navier-stokes equations. Therefore many analytical and numerical solutions are available of Non-Newtonian fluid on the topic.

Micropolar fluid model is kind of Non-Newtonian fluid which is depended upon a microstructure and belongs to non-symmetrical stress tensor. Micropolar fluid theory was introduced by Eriggen.
Physically, Micropolar fluid may be rigid particles, at random oriented (spherical) elements suspended in a viscous medium where the change of fluid elements is disregarded. Micropolar fluid can perform a better model for animal blood.

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

Abstract:
Alternaria black spot of cruciferous vegetables, encouraged by different species of Alternaria, remains an increasing threat to Brassicaceae crops throughout the world, including Poland. Brassica plants are attacked by conidia of A. brassicae (Berk.) Sacc., A. brassicicola (Schw.) Wiltsh. The pathogens have a wide spectrum of hosts, such as head cabbage, Chinese cabbage, cauliflower, broccoli, and other crucifers including cultivated and wild grown plants. Alternaria pathogens usually cause damping-off of seedlings, spotting of leaves of cabbages, blackleg of heads of cabbages, and spotting of cauliflower curds and broccoli florets. In oilseed rape, A. brassicae is the dominant invasive species, while in the cruciferous vegetables, both species, A. brassicae, and A. brassicicola are encountered. Infected seeds with spores on the seed coat or mycelium under the seed coat are the main means of distribution for these pathogens. The fungus can overwinter on susceptible weeds or crop debris and on seed plants, as well as on stecklings.
Methods for disease prevention and control are based on combining agricultural management practices with chemical control. Using disease-free seeds or seeds treated with fungicides can greatly reduce disease incidence. After appearance of the first symptoms of disease, stringent fungicide spray program is an effective way to reduce losses. Many authors seem to agree, that the most economically feasible method of disease control is the development of resistant Brassicaceae crops varieties, as transgenic approach proved unsuccessful. Due to our increasing understanding of pathogen-host plant interactions, identification of resistance sources, and assessment of the resistance trait inheritance mode, breeding programs of Brassica crops for Alternaria resistance can be enhanced. This is of particular importance since recent years experience dynamic development of ecological and integrated plant production with an emphasis on plant biotic stress resistance. Highly resistant genetic resources have not been reported in Brassica cultivated species, although some varieties differ in their resistance/susceptibility level.
Introduction:
In the world the second largest oil seed crop is brassica after soybean (FAO, 2010; Raymer, 2002). Out of 37 species of brassica genus only 4 are highly cultivated species for oil and vegetables are for Brassica rapa L., B. juncea (L.) Czern. & Cosson, B. napus L., and B. carinata A. Braun. (Raymer, 2002; Rakow, 2004; Sovero, 1993). Two species derived from Oleiferous brassica that is B. napus L. and B. campestris L. (syn. B. rapa L.) B. campestris is also mentioned to by such local names in specific countries as toria, sarson, summer turnip rape, and Polish rape. All rapeseed-contributing cultivated Brassica spp. are highly polymorphic including oilseed crops, root crops, and vegetables such as Chinese cabbage, broccoli, and Brussels sprouts. B. compestris are also grown under European and Canadian conditions, both in summer and winter.
Production technology:
Rapeseed is cultivated over an area of 28.23 million hectares with production of about 58.21 Mt, by this production rapeseed ranks on third number in oil seed production after palm oil and soybean (FAO, 2010). Canada is the largest producer of and contributes about 22% of the total world production of oil (FAO, 2010). In Pakistan after cotton, rapeseed-mustard is the second most important source of oil in Pakistan. It is cultivated over an area of 307,000 hectares with annual production of 233,000 tones and contribute about 17% to the domestic production of edible oil (PASC). As we know that everything has some aspects in this case the aspect is the attack of pathogen on brassica plant.
Major diseases of brassica:
Fungus and fungus-like diseases
• Blackleg (Leptosphaeria maculans)
• Clubroot (Plasmodiophora brassicae)
• Damping off (Fusarium or Pythium species)
• Downy mildew (Hyaloperonospora parasitica)
• Leaf spot/target spot (Alternaria species)
• Powdery mildew (Erysiphe cruciferarum)
• Ring spot (Mycosphaerella brassicicola)
• White blister (Albugo candida)
(https://www.agric.wa.gov.au)
Pathogen:
• Alternaria brassicae (Berk.) Sacc.,
• Alternaria brassicicola (Schw.) Wiltsh.,
• Alternaria raphani Groves & Skolko.
Pathogen biology:
The primary source of infection of dark leaf spot in UK is A. brassicae and A. brassicicola. The four species or alternaria can cause major negative influence on the Cruciferous plants (Brassicaceae) these species are A. brassicae (Berk.) Sacc., A. brassicicola (Schw.) Wiltsh., A. raphani Groves and Skolko, and A. alternata (Fr.) Kreissler. The most common alternaria species are A. brassicicola and A. brassicae that can cause disease on oleiferous and vegetable (oleraceous) Brassicas, the A. brassicicola is the dominant invasive species of the vegetable Brassicas, while the oleiferous crucifers are primary hosts for the A. brassicae fungus (Maude & Humpherson-Jones 1980, Humpherson-Jones 1989). These both species cause infection on leaves. The most common disease in the crucifer’s plant is dark spot that is located in tropical and sub-tropical regions.
Taxonomy:
• Kingdom Fungi
• Phylum Ascomycota
• Subdivision Pezizomycotina;
• Class Dothideomycetes;
• Order Pleosporales;
• Family Pleosporaceae;
• Subfamily mi-tosporic Pleosporaceae;
• Genus Al-ternaria
(http://www.uniprot.org/taxonomy/5598).
Distribution:
Both species are cosmopolitan in nature but occur sporadically. A. brassicicola is the predominant species on cabbage grown in New York (King, S. R. 1994). A. raphani is wide spread in Northern hemisphere.
Crops Affected:
Cruciferous vegetables, including cabbage, broccoli, cauliflower, Brussels sprouts, Chinese cabbage, kale, kohlrabi, rutabaga, turnip and cruciferous weeds.
Losses:
Severe economic losses cause by A. brassicicola and A. brassicae (HumphersonJones ; Maude 1982, HumphersonJones 1989). In Europe, only the seed losses due to both pathogens were expected to be 86% in B. oleracea in several years (Maude ; Hampherson-Jones 1980, Humpherson-Jones 1989).
Epidemiology factors:
Infected seeds are the primary source of infection or non-decomposed plant debris in the upper soil layers with over-wintering hyphae or spores. Second important source of the pathogen are the weeds of brassica, which increase infestations as pathogen host plants (Humpherson-Jones 1989). During the vegetation period, the rain and wind-transported fungal conidial spores are also an important source of infection. The conidial majority are released during harvest and in the cleaning of infected leaves; such released spores are then spread approximately within 1,800 m (Humpherson-Jones ; Maude 1982). Under Sophisticated climate, highest Alternaria spore presence are detected in the air mainly in June and July (Nowakowska et al. 2011).
Infection mechanism:
Three ways of Alternaria infection have been reported: Through epidermis penetration, through stomata, and through insects- or agro-technique-derived host plants wounding. Regardless of their means of entry, A. brassicicola and A. brassicae exhibit distinct differences in the host plant tissue penetration. A. brassicae invades host plants solely through their stomata, while for A. brassicicola, direct plant tissue penetration prevails over stomatal infections. Hyphae of both pathogens develop well on the epidermis, directly beneath the leaf waxes, and exhibit low cell penetration ratio.
During plant infection, both Alternaria fungi produce and exude phytotoxins that belong to HST clade (host-specific toxins or host-selective toxins; Parada et al. 2008, Wight et al. 2009). These compounds play a major role in the pathogenesis by determining the host plant spectrum, as well as the isolates’ virulence and pathogenicity levels (Nishimura & Kohmoto 1983). To date, two HSTs have been In addition to the above, A. brassicae produces a number of phytotoxins (destruxin B and derivatives, such as homodestruxin B, desmethyldestruxin B, and destruxin B2) responsible for typical black spot symptoms, such as necrotic and chlocharacterized in detail: AB toxin of A. brassicicola (Otani et al. 1998) and ABR of A. brassicae (Parada et al. 2008). Both phytotoxins are proteins with a suggested role in evoking disease symptoms on the infected cruciferous plants.
In addition to the above, A. brassicae produces a number of phytotoxins (destruxin B and derivatives, such as homodestruxin B, desmethyldestruxin B, and destruxin B2) responsible for typical black spot symptoms, such as necrotic and chlorotic lesions. Destruxin B was shown to be a major one responsible for inducing necrotic lesions on plant leaves and eliciting the phytoalexins brassilexin and sinalbin A (Sodelade et al. 2012). Majority of researchers classify destruxin B as an HST (Sodelade et al. 2012), while others have demonstrated its unspecific character and questioned its role in the initial host plant colonization (Buchwaldt & Green 1992, Parada et al. 2008). While some isolates of A. brassicae produce destruxin B as their sole toxin, others are capable of production of their derivatives (homodestruxin B, desmethyldestruxin B, and destruxin B2; Parada et al. 2008). Depudecin, an eleven-carbon linear polyketide and histone deacetylase (HDAC) inhibitor made by A. brassicicola, proved a minor virulence factor.
• Life cycle:Since both pathogens survive on crop debris, seeds, and in association with weed hosts (Humpherson-Jones & Maude 1982, Humpherson-Jones 1989), crop debris management Alternaria fungi proliferation is vegetative in character, and takes place by means of conidial spores, airborne and found in the soil and water, as well as indoors and on objects. Sexual recombination (teleomorphy) occurs very rarely.
• Spore size: dark-brown spots of different sizes (0.5 cm to several cm in diameter) appear on the leaves.
• Factors on which growth depends: Development of the pathogen’s infection structures and of the disease symptoms on the oleraceous Brassicas depends primarily on the incubation temperature (Bassey ; Gabrielson 1983), and relative air humidity. pores of both Alternaria species germinate in a rather broad temperature range, germination effectiveness is correlated with the temperature (Degenhardt et al. 1982).
Optimal hyphae growth temperature for A. brassicae is 18-24?, and for A. brassicicola 20- 30?. According to the in vitro studies, sporulation of A. brassicae is temperature-dependent: At 8-24ºC, fullydeveloped spores are detectable at 24 or 14 h, respectively. Temperature spectrum of A. brassicicola sporulation is broader (8-30ºC), with fully developed spores detectable after 43 or 14 h, respectively. High air humidity (95-100% RH) lasting at least 9-18 h is a crucial requirement displayed by both pathogen species during plant infection (Humperson-Jones ; Phelps 1989). Reports of massive infestations under air temperatures of 20-27ºC and constant plant moisture of at least 5 h, or RH exceeding 95% lasting at least 12-20 h are commonplace (reviewed in Bart ; Thomma 2003). Sporulation can occur over a wide range of temperatures and is optimal at 20 to 30°C. Spore dispersal occurs during the warmest and driest part of the day, and night dispersal is rare. In England, the highest spore catches of A. brassicicola occurred after a period of rain or prolonged leaf wetness (lasting more than 3 h) with a mean temperature above 13°C.
Symptoms:
Alternaria black spot symptoms appear on all host plant parts and at every developmental stage. A. brassicicola and A. brassicae cause the damping off of the crucifer’s seedlings. Elongated brownings develop on the sub-cotyledonous part of the stem and on the cotyledons, often leading to narrowing and breaking of the stems, and thus, to seedlings’ decease. Most often infected are the lower, older leaves of head cabbage. Chinese cabbage, cauliflower, broccoli, and of other crucifers. Infected cauliflower curds or broccoli florets develop slight dents with brownish spots covered with black bloom of spores. In these plants, infection usually remains on the surface and does not reach deep in the curd or the floret; however, symptomatic cauliflower or broccoli florets lose their commercial value. In case of radish, turnip, or rutabaga, the disease affects the root thickenings as well; the disease symptoms manifest themselves as brown rots only during their storage. Under favorable conditions, lesions become covered with brown-black downy-like bloom of sporulating hyphae. A. brasicicola-derived spots are darker and less regular in shape compared with those of A. brassicae origin.
Both most common Alternaria pathogens usually cause black spot disease, manifested by damping-off of seedlings, spotting of leaves of cabbages, blackleg of heads of cabbages (head cabbage and Chinese), and spotting/browning of cauliflower curds and broccoli florets.
Control and management:
Alternaria prevention and control methods include combining the proper agro-technique with chemical protection. An essential disease prevention method is production of healthy seeds, obtained from plantations with heavy fungicide protection. In the 2-year lasting crucifers seed production periods, good effects of protection against Alternaria infections during the 1st year of growth were expedited by fungicides containing iprodione as an active ingredient (Maude et al. 1984, Survilien? et al. 2010). In Poland, the only product containing it is Seed Protector T 75DS WS (Zaprawa Nasienna). Since both pathogens survive on crop debris, seeds, and in association with weed hosts (Humpherson-Jones ; Maude 1982, Humpherson-Jones 1989), crop debris management (for example through crop rotation and deep tillage) and use of clean seed and proper weed control should alleviate the disease. After appearance of disease symptoms, one may achieve limitation of the infection by repeated spray with fungicides containing strobilurines as active ingredients (Amistar 250 SC, Signum 33 WG, Zato 50 WG) and fungicides based on iprodione (Rovral FLO 255 SC) (Maude et al. 1984, Survilien? et al. 2010). This method, however, carries an economic disadvantage and may prove ineffective under pathogen infection-conducive weather conditions, particularly among the seed crops. An alternative protection method to be employed is use of antagonistic fungi; deployment of Aureobasidium pullulans and Epicoccum nigrum on the crucifers leaves reduced the infection level under controlled conditions (Pace ; Campbell 1974). Field studies concerning the biological control efficacy are yet to be carried out.

x

Hi!
I'm Piter!

Would you like to get a custom essay? How about receiving a customized one?

Check it out