Wheat Productivity, Efficiency, and Sustainability: A Stochastic Production Frontier Analysis

The agriculture sector plays a crucial role in the overall development of the country. The sector shares about 24 percent of the GDP and employs about 44 percent of the workforce in the country. Crops sub-sector is the major contributor towards agriculture, sharing more than 53 percent of the value-added. Wheat, being the staple food of Pakistanis, carries immense importance: it contributes about 12 percent of sector value-added, is sown on about 37 percent of the total cropped area, and shares 80 percent in consumption of food grains, while its share in food grain production is around 70 percent. As primary diet, wheat alone shares about 50 percent of the total calories’ and proteins intake in Pakistan, and contributes about 8 percent of the total fat consumed [FAO (Various Issues]. Consequently, overall dietary well being of our people especially the urban and rural poor is largely dependent on the performance of wheat economy. Despite serious efforts made by the wheat breeders in developing new highyielding varieties during the past three decades, wheat production in Pakistan remained short of demand and thus import has been the only alternative to fill the gap. The present wheat requirement of the country is more than 20 million tonnes. It has been estimated that by the year 2020 wheat import would rise up to 15 million tones costing 2 billion US dollars [PARC (1996)]. The situation could worsen further if Pakistan fails to achieve a higher level of growth rate in wheat production and sustain it.

Transfer of Technology: Competition or Cooperation

Looking at an economy as consisting of several layers of techniques gives us a way to spell out the implications of macroeconomic situations to micro levels. For instance, if macroeconomic consideration point to reducing total employment, a map of the layers of techniques of the economy should be able to pinpoint the firms of different regions that are likely to be effected. In such cases, to be able to delineate the effects of extra final demand of the new investment on the production and employment in the economy, we require best input-output and labour coefficients instead of the average ones that are at present computed worldwide. Similarly, for capacities going out of production either because of the lack of demand, or obsolescence, we want to have the knowledge of the least efficient techniques of production for finding out their economic implications [Azid (2002)]

Network Coding in Distributed, Dynamic, and Wireless Environments: Algorithms and Applications

The network coding is a new paradigm that has been shown to improve throughput, fault tolerance, and other quality of service parameters in communication networks. The basic idea of the network coding techniques is to relish the "mixing" nature of the information flows, i.e., many algebraic operations (e.g., addition, subtraction etc.) can be performed over the data packets. Whereas traditionally information flows are treated as physical commodities (e.g., cars) over which algebraic operations can not be performed. In this dissertation we answer some of the important open questions related to the network coding. Our work can be divided into four major parts. Firstly, we focus on network code design for the dynamic networks, i.e., the networks with frequently changing topologies and frequently changing sets of users. Examples of such dynamic networks are content distribution networks, peer-to-peer networks, and mobile wireless networks. A change in the network might result in infeasibility of the previously assigned feasible network code, i.e., all the users might not be able to receive their demands. The central problem in the design of a feasible network code is to assign local encoding coefficients for each pair of links in a way that allows every user to decode the required packets. We analyze the problem of maintaining the feasibility of a network code, and provide bounds on the number of modifications required under dynamic settings. We also present distributed algorithms for the network code design, and propose a new path-based assignment of encoding coefficients to construct a feasible network code. Secondly, we investigate the network coding problems in wireless networks. It has been shown that network coding techniques can significantly increase the overall throughput of wireless networks by taking advantage of their broadcast nature. In wireless networks each packet transmitted by a device is broadcasted within a certain area and can be overheard by the neighboring devices. When a device needs to transmit packets, it employs the Index Coding that uses the knowledge of what the device's neighbors have heard in order to reduce the number of transmissions. With the Index Coding, each transmitted packet can be a linear combination of the original packets. The Index Coding problem has been proven to be NP-hard, and NP-hard to approximate. We propose an efficient exact, and several heuristic solutions for the Index Coding problem. Noting that the Index Coding problem is NP-hard to approximate, we look at it from a novel perspective and define the Complementary Index Coding problem, where the objective is to maximize the number of transmissions that are saved by employing coding compared to the solution that does not involve coding. We prove that the Complementary Index Coding problem can be approximated in several cases of practical importance. We investigate both the multiple unicast and multiple multicast scenarios for the Complementary Index Coding problem for computational complexity, and provide polynomial time approximation algorithms. Thirdly, we consider the problem of accessing large data files stored at multiple locations across a content distribution, peer-to-peer, or massive storage network. Parts of the data can be stored in either original form, or encoded form at multiple network locations. Clients access the parts of the data through simultaneous downloads from several servers across the network. For each link used client has to pay some cost. A client might not be able to access a subset of servers simultaneously due to network restrictions e.g., congestion etc. Furthermore, a subset of the servers might contain correlated data, and accessing such a subset might not increase amount of information at the client. We present a novel efficient polynomial-time solution for this problem that leverages the matroid theory. Fourthly, we explore applications of the network coding for congestion mitigation and over flow avoidance in the global routing stage of Very Large Scale Integration (VLSI) physical design. Smaller and smarter devices have resulted in a significant increase in the density of on-chip components, which has given rise to congestion and over flow as critical issues in on-chip networks. We present novel techniques and algorithms for reducing congestion and minimizing over flows

Seasonal, Diurnal and Species Variation in Forage Moisture Content in Relation to Site on Mountain Summer Range of Northern Utah

Practical assessments of range production and utilization are based on forage weight estimates. In preparing these estimates moisture content in green vegetation offers some problems. The moisture component is not likely to be constant for a given species. Diurnal, seasonal and site variability have been well illustrated for agronomic and tree species (Salisbury, 1848; Jenkins, 1879; Miller, 1917; Pearson, 1924; Watkins, 1940; Parker, 1951; Ackley, 1954; Werner, 1954; Zohary and Orshan, 1956; Slatyer, 1959; Kozlowaki, 1965 and Jame son, 1966). Since variability is also likely for range plants, computations made on green weights are apt to be fallacious. It is a common practice, therefore, to express production on water free or dry weight basis. But the estimates of dry weight are made difficult by variations in herbage moisture. A variety of factors, relevant both to the vegetation and the site it occupies, would seem to account for variable moisture content. The prevalent methods for estimating moisture, however, seem to be more of a legacy from the past than an appreciation of ecological influences. Earlier investigators of pastures and fodder crops were largely agronomists interested in comparing yields. They were concerned primarily with irrigated crops where soil moisture is not a limiting factor and the ecological influences, such as humidity, rain, cloudy weather, dew, shade, exposure etc. are far from dominant (Atwater, 1869; Collier, 1881; Richardson , 1884; Ladd, 1888; Richardson, 1889; Morse, 1891 and Widstoe, 1897). The variations in water content and other components were accordingly related to stage of growth. Taking a cue from these studies agencies such as the United States Forest Service and Soil Conservation Service came to use certain reducing factors to convert green weight of range forage into dry weight. In developing these factors the type of vegetation and growth phases have been considered but ecological features and context have been neglected. The methodology adopted from pasture conditions became the accepted basis for making range management decisions (Range Memo, SCS-8, Soil Conservation Service, 1963; Range Analysis, Region IV, Forest Service, 1964). The influence of features of environment, particularly aspect, on growth differential, has long been recognized by foresters (Schlich, 1905; Champion, 1928 and Tourney, 1928). Plant physiologists have been aware of the significance of time-of-day on plant water for some time (Shreve, 1914; Miller, 1917). It is very probable that these influences express themselves in moisture content of herbage also. The investigations reported herein were conducted to define and assess the scope and intensity of some of these ecological features in modification of the moisture component of herbage. The objective is to determine whether differences in ecological context influence range herbage moisture to a sufficient extent to warrant consideration in developing conversion factors for deriving dry weights from green weights of vegetation samples. The appraisal should reaffirm present assumptions applied or yield more accurate adjustments for estimating forage production. In either circumstance the results should enhance the scientific basis of range management decisions

Knowledge of patients\u27 visual experience during cataract surgery: a survey of eye doctors in Karachi, Pakistan

Abstract BACKGROUND: Several recent studies have recommended that ophthalmologists must be aware of the visual sensations (and their associated anxiety/fear) experienced by patients undergoing cataract surgery. We assessed the knowledge of a group of eye doctors in Pakistan regarding these phenomena. METHODS: This was a cross-sectional survey. Eye doctors (ophthalmologists, residents and medical officers) attending the Ophthalmological Society of Pakistan Annual Conference 2011, in Karachi were invited to participate in the study. A self-administered structured questionnaire was used to examine their knowledge of visual sensations and their associated anxiety/fear experienced by patients during cataract surgery. Simple frequencies and proportions were calculated to describe the data. RESULTS: A total of 150 ophthalmologists, residents and medical officers were invited to participate in the study. Of these, 68 (45.3%) responded. The mean age (±SD) of the participants was 42.9 (13.2) years. The proportion of participants who thought that patients could experience visual sensations during cataract surgery under regional anaesthesia was 89.7% and that under topical anaesthesia was 73.5%. The most frequently cited sensations included: light perception, changes in light brightness, movements, instruments and surgeon\u27s hands or fingers.The eye doctors estimated that 38.9% and 64.3% patients would see at least something during cataractsurgery under regional anaesthesia and topical anaesthesia, respectively. They also believed that 24.2%-36.9% of patients may experience anxiety/fear as a result of visual sensations during such surgery. Approximately half of the eye doctors did not think that retained vision was a source of fear or anxiety for the patients. While most of them acknowledged the importance of preoperative counselling in helping to alleviate such fear/anxiety, the majority of them did not regularly counsel their patients on what to expect during the surgery. CONCLUSION: Our study reveals that a significant proportion of eye doctors do not have adequate knowledge of the visual phenomenon and their associated anxiety or fear, that patients can experience during cataract surgery. Targeted educational interventions are needed to increase awareness of this phenomenon among eye care professionals

Patients’ visual experience during phacoemulsification cataract surgery and associated fear

Abstract Background: Data from several published studies indicate that patients undergoing phacoemulsification cataract surgery can experience a variety of visual sensations which can result in fear. This phenomenon has not been studied in Pakistan to-date. We examined the visual experience and its associated fear among patients undergoing phacoemulsification cataract surgery under topical anaesthesia. Methods: This cross-sectional study was carried out in Aga Khan University Hospital, a tertiary care hospital, in Karachi, Pakistan from August 2010 to July 2011. Adults \u3e18 years of age scheduled to undergo cataract surgery (phacoemulsification with intraocular lens implantation) under topical anaesthesia by a single surgeon were included. A structured questionnaire was used to collect data on socio-demographics, intraoperative visual experiences and subsequent reaction to these sensations. Participants were asked if they experienced visual sensations such as colours, shapes and movements during surgery. Moreover, they were asked if they developed fear due to these sensations. Results: Fifty three patients (mean age: 60.4 ± 12.4 years) were enrolled. Thirty (56.6%) of them were men and 23 (43.4%) were women. All of them reported having experienced visual sensations during surgery, the most common being light perception (100%), different colours (77.4%), movements of instruments or surgeon’s hands (37.7%) and different shapes (7.5%) such as circles, clouds and patches. The most common colours perceived included white (46.2%), blue (35.8%), red (30.2%) and yellow (30.2%). One out of every four (26.4%) participants reported having developed fear due to these visual sensations. Only 4 (7.5%) reported having received preoperative counselling regarding such sensations. Conclusion: Patients in our study experienced a variety of visual sensations during cataract surgery under topical anaesthesia. The prevalence of frightening visual sensations is higher than that reported in all previous published studies on the subject and needs to be addressed through targeted interventions

Percutaneous management of biliary enteric anastomotic strictures: an institutional review

Purpose Stricture formation at the biliary enteric anastomotic site is a common complication due to fibrotic healing. Few therapeutic options are available for biliary-enteric anastomotic site stricture (BES) including new surgical reconstruction or percutaneous transhepatic biliary drainage followed by balloon dilation of BES or stent placement. The purpose of this study is to assess the technical success, complications and reintervention rate of percutaneous transhepatic balloon dilatation (PTBD) of BES after iatrogenic bile duct injuries (BDI). Methods A retrospective review of patients who underwent PTBD for benign resistant BES, previously treated for iatrogenic BDI, from December 2004 to January 2016 was performed. Diagnostic transhepatic cholangiogram was performed to assess the level of obstruction. BES was dilated using 8-12 mm diameter balloons followed by placement of eight to ten Fr internal-external drainage catheters, which were removed after three to six weeks post-PTBD cholangiogram. Follow-up by clinical assessment, liver function tests, and ultrasound was done. Fischer exact test was used to determine if there was a significant association between PTBD sessions and recurrent strictures. Results In total, 37 patients underwent 66 sessions of PTBD, including 10 (27%) males and 27 (73%) females. The mean age was 41.3 years (range 23-70 years). Out of these, 29 (78%) were treated with choledochojejunostomy and eight (22%) with hepaticojejunostomy. 100% technical success was achieved in all the PTBD sessions. Nineteen (51.3%) patients were treated with a single PTBD session. Mean follow-up time was 36 months (range 1-75 months). Eighteen (48.7%) patients needed reintervention, out of these, 11 (29.7%) were symptom-free after second session on three-year follow-up, three (8%) were symptom-free after the third session of PTBD. No significant difference was observed in risk of recurrent strictures after first and second PTBD sessions [18 (48%) vs. 7 (39%); p-value 0.495]. In four (11%) patients, the symptoms persisted and BES recurred even after third session and those were treated by placing metallic stent. In total, three (8.1%) patients got complicated with the stone formation; in two (5%) patients stone was successfully removed percutaneously and in one (3%) patient percutaneous attempt failed so it was followed by surgical removal. Conclusion PTBD is a safe and useful treatment option for benign BES for long-term symptom-free time-period. However, there is no significant difference in developing recurrent BES after PTBD sessions. Few patients with resistant strictures might require stent placement