In this thesis, we have studied the propagation of nonlinear electrostatic waves in a nonMaxwellian plasma in which electrons follow the generalized (??,??) distribution function which has the advantage that it mimics most of the distribution functions observed in space plasmas. Generally spectral index ?? corresponds to the flatness and ?? corresponds to the high energy tail in the profile of the distribution. The generalized (??,??) distribution function is the generalized form of kappa and Maxwellian distribution function and can be reduced to these in the limits ??=0,??=(??+1) and ??=0,??→∞, respectively. First we studied the propagation of nonlinear ion acoustic waves in a (??,??) distributed plasma and derived the Korteweg-de Vries (KdV) equation. In the past, KdV equation has been derived for ion acoustic waves with Boltzmannian or kappa distributed electrons and only compressive solitary structures were obtained. We have shown that when electrons are modelled by (??,??) distribution, the nonlinear ion acoustic waves admit both humps and dips in the perturbed potential. We found that for positive values of ??, which correspond to flat-topped distribution, the nonlinear ion acoustic waves admit compressive solitary structures or density humps. And for negative values of ??, which correspond to a spiky distribution, the nonlinear ion acoustic waves admit rarefactive solitary structures or density depletions. It has also been shown that the generalized (??,??) distribution function provides another way to explicate the density depletions observed by Freja and Viking satellites previously explained by proposing Cairns distribution function. In the third chapter, we have studied the propagation of nonlinear electron acoustic waves (EAWs) by deriving the KdV equation in a plasma comprising of cold and hot electron populations in which the ions form the neutralizing background. The hot electrons have been assumed to follow the generalized (??,??) distribution. Interestingly, it has been found that unlike Maxwellian and kappa distributions, the electron acoustic waves admit not only rarefactive structures but also allow the formation of compressive solitary structures for generalized (??,??) distribution. Using the plasma parameters, typically found in the Saturn’s magnetosphere and the Earth’s auroral region, where two x populations of electrons and electron acoustic solitary waves have been observed, we have given an estimate of the scale lengths over which these nonlinear waves are expected to form and how the size of these structures would vary with the change in the shape of the distribution function and with the change of the plasma parameters. In chapter-4, we then derived the modified Korteweg-de Vries (mKdV) equation to study nonlinear ion acoustic waves in a plasma in which electrons follow generalized (??,??) distribution. The spectral index ?? in the distribution corresponds to the flat top at low energy and by increasing its value flat top in the distribution increases. The spectral index ?? can also have negative values due to which distribution becomes spiky at low energies. Such flat topped or spiky distributions have been frequently observed in space plasmas. By employing (??,??) distribution, it has been shown that solitary structures are much influenced by the spectral index ??. This study highlighted the effect of low energy particles on the propagation characteristics of the solitary structures which could not be done by employing Maxwellian or kappa distributions and be helpful in explaining the underline physics in those regions where such flat top distributions are observed. In the chapter 5, we have studied the propagation of nonlinear ion acoustic shock waves in unmagnetized and collisionless plasma in the presence of electrons that follow the generalized (??,??) distribution. The Burger and Korteweg-de Vries–Burger (KdV-Burger) equations have been derived through reductive perturbation technique and via tangent hyperbolic method shock like solutions have been presented analytically for both Burger and KdV-Burger equations. It has been found that the strength and steepness of shock waves are affected by the flatness parameter ??, tail parameter ?? and the nonlinear propagation velocity ??. It is found that the shock strength of KdV–Burger is less than simple Burger equation’s shock. We concluded that propagation of nonlinear electrostatic waves strongly dependent on the profile of the distribution function and the results obtained are of great importance as they interpret those observations which could not be predicted on the basis of Maxwellian or kappa distribution functions.
‘‘اگر آپ خودکوشش نہیں کریں گے تو اِس مصیبت سے آپ کو کوئی اور نہیں نکالے گا۔’’
بزرگ کافی دیر سے اُسے سمجھانے کی کوشش کر رہے تھے۔
‘‘آخر آپ سمجھتے کیو ں نہیں؟ مانا کہ بہت مشکل ہے لیکن آپ پڑھے لکھے ہیں۔یہ جانتے ہیں کہ اِس کا علاج تو حکیم لقمان کے پاس بھی نہیں تھا۔ ’’
وہ ہمہ تن گوش تھا۔ ‘‘ بجا فرمایا حضرت آپ نے۔ ’’ بڑی دیر کے بعد بالآخر اُس نے زبان کھولی۔ ‘‘ پھر بھی آپ اللہ والے ہیں۔ دعا بھی تو تقدیر بدلتی ہے۔’’بزرگ مسکرائے، اُن کا دلآویز تبسم مایوس اور نا امید لوگوں کے لیے زندگی کی علامت تھا تاہم وہ اِس وقت بہت بکھرا ہوا ، بے حدتھکا ہوا لگ رہا تھا اُس کی نظر اُن پر تو تھی مگر ذہن کہیں اور تھا۔ ‘‘ میاں تم ٹھیک کہتے ہو ، لیکن یہ بھی جانتے ہو کہ اللہ اُس وقت تک کسی قوم یا فرد کی حالت نہیں بدلتا جب تک وہ خود اپنی حالت نہ بدلے۔ ’’
اُس کی نگاہوں میں دنیا جہاں کا کرب تھا۔ ‘‘ اِس کا مطلب ہے۔۔۔۔۔۔۔۔ ’’
ً ‘‘ہاں۔ ’’ اُ نہوں نے اُس کی بات کاٹتے ہوئے کہا۔ ‘‘ اب یہ صرف آپ پر منحصر ہے۔ آپ کوشش تو کریں، مالک کرم کرے گا۔’’
شام کا اندھیرا چھا چکاتھا۔جب وہ بزرگ سے اِجازت لے کر نکلا۔سڑک پر چلتے ہوئے وہ اپنے خیالوں میں گم تھا ، جب اچانک ہی کسی گاڑی کے زور سے بریک لگانے کی آواز نے اُسے چونکا دیا:
‘‘او بھائی ! اگر خودکشی کا اِتنا ہی شوق ہے تو کہیں اور جا کر مرو۔’’
The inclusion of women in the workforce is imperative for the advancement of every country in the world. In Pakistan the role of women is undergoing dynamic transformation which can have considerable influence on the mother-child relationship and child development. This research attempts to understand the influence of out-of-home maternal employment on the development of child, as perceived by mothers. The study is qualitative in nature using snowball sampling. A total of six working mothers were interviewed from Lahore, Pakistan. Thematic analysis technique has been used to analyze the data. The following themes were identified: (i) Child Neglect; (ii) Strained Child-Parent Relationship; (iii) Child Aggression; (iv) Low Academic Achievement; and (v) Independence and Sense of Responsibility. The study concludes that working mothers need family and employer support to ensure child development in Pakistan. Some of the key reforms that are needed include respect for women’s triple role in society and employment benefits for working mothers.
Fusarium wilt of potato caused by Fusarium oxysporum f.sp. tuberosi is an important disease that causes losses to potato growers in Pakistan. Limited information is available about the management of this disease. Therefore different control measures were investigated under lab. and green house conditions and then the best treatments were applied collectively in integrated management trial. To fulfill first objective, pathogenicity test was performed to check the virulence of the pathogen on susceptible variety “Desiree”. Isolate Okara-1 (O1) proved to be highly virulent and was used in all management trials. In screening of germplasm,. two varieties and eight lines were used for screening purpose.Cardinal and Karoda showed least mean disease severity index (MDSI) i.e. 22.67 and 16.00 % with the yield reduction of 23.2 and 25.5 % respectively. After varietal screening, chemical management was done by using 5 fungicides namely Topsin-M, Carbendazim, Score, Copper oxychloride and Ridomil under lab and green house conditions.In vitroresults showed that Carbendazim and Topsin-Mcontrolled maximumradial growth of fungus (100 %) as compared to rest of the fungicides. Green house results showed that Carbendazim followed by Topsin-M gave less MDSI (17.67% and19.00 %) as compared to Copper oxychloride (55.00 %). The yield reduction by Carbendazim and Topsin-M was 21.59% and 25.91 % as compared to copper oxychloride i.e. 60.91%. Efficacy of biological control agents Trichoderma hazianum and T. virens were checked under lab. condition. T. virens showed higher percent inhibition as compared to T. harzianum in dual culture assay on PDA. Green house results showed that application of T. virens at the time of sowing, 20 and 40 days after sowing (DAS) gave less MDSI (30.76 %) as compared to T. xv harzianum (34.14 %) with yield reduction of28.283 % and 32.56 % respectively. Efficacy of Brassica spp.was checked under lab. conditions, the macerated leaves of B. juncea significantly reduced the radial growth of pathogen i.e. 91.75 % as compared to B. napus(85.67 %). The roots of both brassica spp were less effective in controlling the disease. Under green house conditions, B. juncea leaf extracts reduced the MDSI by 42.95 % as compared to B. napus i.e. 45.61 %with no significant results by roots of both spp.As the management of the disease is difficult by single control measure therefore the best treatments from above mentioned experiments were applied together in integrated management trial. The integration of soil treatment with T. virens at the time of sowing, 20 and 40 DAS, green manuring with B. juncea and seed treatment with carbendazim exhibited significant results in reducing Fusariumwilt as compared to single or dual application of these in green house. The results of this study showed importance of integrating selective fungicide, microbial antagonists and biofumigant crop to achieve appropriate management of Fusarium wilt to increase yield of the crop.