Effects of MAC Approaches on Non-Monotonic Saturation with COPE - A Simple Case Study

We construct a simple network model to provide insight into network design strategies. We show that the model can be used to address various approaches to network coding, MAC, and multi-packet reception so that their effects on network throughput can be evaluated. We consider several topology components which exhibit the same non-monotonic saturation behavior found within the Katti et. al. COPE experiments. We further show that fairness allocation by the MAC can seriously impact performance and cause this non-monotonic saturation. Using our model, we develop a MAC that provides monotonic saturation, higher saturation throughput gains and fairness among flows rather than nodes. The proposed model provides an estimate of the achievable gains for the cross-layer design of network coding, multi-packet reception, and MAC showing that super-additive throughput gains on the order of six times that of routing are possible.United States. Dept. of Defense (Air Force Contract FA8721-05-C-0002)Irwin Mark Jacobs and Joan Klein Jacobs Presidential FellowshipInformation Systems of ASD(R&E

Characterizing the genetic basis of copper toxicity in Drosophila reveals a complex pattern of allelic, regulatory, and behavioral variation

A range of heavy metals are required for normal cell function and homeostasis. However, the anthropogenic release of metal compounds into soil and water sources presents a pervasive health threat. Copper is one of many heavy metals that negatively impacts diverse organisms at a global scale. Using a combination of quantitative trait locus (QTL) mapping and RNA sequencing in the Drosophila Synthetic Population Resource, we demonstrate that resistance to the toxic effects of ingested copper in D. melanogaster is genetically complex and influenced by allelic and expression variation at multiple loci. QTL mapping identified several QTL that account for a substantial fraction of heritability. Additionally, we find that copper resistance is impacted by variation in behavioral avoidance of copper and may be subject to life-stage specific regulation. Gene expression analysis further demonstrated that resistant and sensitive strains are characterized by unique expression patterns. Several of the candidate genes identified via QTL mapping and RNAseq have known copper-specific functions (e.g., Ccs, Sod3, CG11825), and others are involved in the regulation of other heavy metals (e.g., Catsup, whd). We validated several of these candidate genes with RNAi suggesting they contribute to variation in adult copper resistance. Our study illuminates the interconnected roles that allelic and expression variation, organism life stage, and behavior play in copper resistance, allowing a deeper understanding of the diverse mechanisms through which metal pollution can negatively impact organisms

Nature with a Human Touch: Human-Induced Alteration Negatively Impacts Perceived Naturalness and Preferences for Natural Environments

Natural environments vary in the degree to which humans have altered them; some environments, like wilderness areas, are relatively untouched, while others, like urban green spaces, are heavily manicured. The current research examined the effect of human-induced alteration to natural environments on perceived naturalness and environmental preferences in a student sample (Study 1) and a sample of nonstudent adults (Study 2). It was predicted that a human-altered natural environment would be viewed as less natural than a non-altered natural environment. It was also predicted that a human-altered natural environment would be viewed more negatively than a non-altered natural environment. Results largely supported these predictions. Human-altered natural environments were viewed as less natural than non-altered natural environments, and across several indicators of environmental preference, participants responded more negatively to human-altered natural environments than non-altered natural environments. Perceived naturalness mediated the effect of human-induced alteration on each environmental preference variable, suggesting that non-altered environments are preferred because they are viewed as more natural than their human-altered counterparts. These findings are consistent with an evolutionary account of non-altered natural environments offering more benefits and entailing fewer costs than human-altered natural environments. (PsycINFO Database Record (c) 2016 APA, all rights reserved) (journal abstract

A Study of the Dynamic Relationships between Depression, Treatment, and Work Behavior

It has been shown in the literature that depression has a significant negative correlation with employment outcomes as measured by labor force participation, earnings, work attendance and job performance. I expand the understanding of this relationship by exploring the effect of depression on employment choices as well as treatment choices over time rather than simply examining correlations at a point in time. Other health related outcomes and the relationship between choices and mental health will be examined. My analysis follows initially depressed individuals for nine months and examines the dynamic relationship between health status and function, treatment decisions and employment outcomes. I consider a dynamic model of individual decisions over time where lagged endogenous behavior is allowed to influence current behavior or health outcomes. Results indicate that depression does have a significant effect on labor productivity. Individuals who were the most depressed at the baseline interview saw the largest improvements in productivity following treatment. However, the estimates imply that depression is not a significant determinant of the worker's attendance at work

Brief of Scholars of the History and Original Meaning of the Fourth Amendment as Amici Curiae in Support of Petitioner, Carpenter v. United States, No. 16-402 (U.S. Aug. 14, 2017)

Obtaining and examining cell site location records to find a person is a “search” in any normal sense of the word — a search of documents and a search for a person and her personal effects. It is therefore a “search” within the meaning of the Fourth Amendment in that it constitutes “examining,” “exploring,” “looking through,” “inquiring,” “seeking,” or “trying to find.” Nothing about the text of the Fourth Amendment, or the historical backdrop against which it was adopted, suggests that “search” should be construed more narrowly as, for example, intrusions upon subjectively manifested expectations of privacy that society is prepared to recognize as reasonable.Entrusting government agents with unfettered discretion to conduct searches using cell site location information undermines Fourth Amendment rights. The Amendment guarantees “[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches.” The Framers chose that language deliberately. It reflected the insecurity they suffered at the hands of “writs of assistance,” a form of general warrant that granted state agents broad discretion to search wherever they pleased. Such arbitrary power was “unreasonable” to the Framers, being “against the reason of the common law,” and it was intolerable because of its oppressive impact on “the people” as a whole. As emphasized in one of the seminal English cases that inspired the Amendment, this kind of general power to search was “totally subversive of the liberty of the subject.” James Otis’s famous speech denouncing a colonial writ of assistance similarly condemned those writs as “the worst instrument of arbitrary power,” placing “the liberty of every man in the hands of every petty officer.” Thus, although those who drafted and ratified the Fourth Amendment could not have anticipated cellphone technology, they would have recognized the dangers inherent in any state claim of unlimited authority to conduct searches for evidence of criminal activity. Cell site location information provides insight into where we go and what we do. Because this information is constantly generated and can be retrieved by the government long after the activities it memorializes have taken place, unfettered government access to cell site location information raises the specter of general searches and undermines the security of “the people.

Multi-Path TCP with Network Coding for Mobile Devices in Heterogeneous Networks

Existing mobile devices have the capability to use multiple network technologies simultaneously to help increase performance; but they rarely, if at all, effectively use these technologies in parallel. We first present empirical data to help understand the mobile environment when three heterogeneous networks are available to the mobile device (i.e., a WiFi network, WiMax network, and an Iridium satellite network). We then propose a reliable, multi-path protocol called Multi-Path TCP with Network Coding (MPTCP/NC) that utilizes each of these networks in parallel. An analytical model is developed and a mean-field approximation is derived that gives an estimate of the protocol's achievable throughput. Finally, a comparison between MPTCP and MPTCP/NC is presented using both the empirical data and mean-field approximation. Our results show that network coding can provide users in mobile environments a higher quality of service by enabling the use of multiple network technologies and the capability to overcome packet losses due to lossy, wireless network connections.United States. Dept. of Defense. Assistant Secretary of Defense for Research & Engineering (Air Force Contract FA8721-05-C-0002

Cross-layer design with multi-packet reception, MAC, and network coding in multi-hop networks

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 87-90).A cross-layer design approach is proposed that can be used to optimize the cooperative use of multi-packet reception (MPR) and network coding. A simple and intuitive model is constructed for the behavior of an opportunistic network coding scheme called COPE proposed by Katti et. al., MPR, the 802.11 MAC, and their combination. The model is then applied to key small canonical topology components and their larger counterparts. The results obtained from this model match the available experimental results with fidelity. Using this model, fairness allocation by the 802.11 MAC is shown to significantly impede performance and cause non-monotonic saturation behaviors; hence, a new MAC approach is devised that not only substantially improves throughput by providing monotonic saturation but provides fairness to flows of information rather than to nodes. Using this improved MAC, it is shown that cooperation between network coding and MPR achieves super-additive gains of up to 6.3 times that of routing alone with the standard 802.11 MAC. Furthermore, the model is extended to analyze the improved MAC's asymptotic, delay, and throughput behaviors. Finally, it is shown that although network performance is reduced under substantial asymmetry or limited implementation of MPR to a central/bottleneck node, there are some important practical cases, even under these conditions, where MPR, network coding, and their combination provide significant gains.by Jason M. Cloud.S.M

Congestion control for coded transport layers

The application of congestion control can have a significant detriment to the quality of service experienced at higher layers, especially under high packet loss rates. The effects of throughput loss due to the congestion control misinterpreting packet losses in poor channels is further compounded for applications such as HTTP and video leading to a significant decrease in the user's quality of service. Therefore, we consider the application of congestion control to transport layer packet streams that use error-correction coding in order to recover from packet losses. We introduce a modified AIMD approach, develop an approximate mathematic model suited to performance analysis, and present extensive experimental measurements in both the lab and the “wild” to evaluate performance. Our measurements highlight the potential for remarkable performance gains, in terms of throughput and upper layer quality of service, when using coded transports.United States. Dept. of Defense. Assistant Secretary of Defense for Research & Engineering (United States. Air Force Contract FA8721-05-C-0002

Identification of Histoplasma-Specific Peptides in Human Urine

Histoplasmosis is a severe dimorphic fungus infection, which is often difficult to diagnose due to similarity in symptoms to other diseases and lack of specific diagnostic tests. Urine samples from histoplasma-antigen-positive patients and appropriate controls were prepared using various sample preparation strategies including immunoenrichment, ultrafiltration, high-abundant protein depletion, deglycosylation, reverse-phase fractions, and digest using various enzymes. Samples were then analyzed by nanospray tandem mass spectrometry. Accurate mass TOF scans underwent molecular feature extraction and statistical analysis for unique disease makers, and acquired MS/MS data were searched against known human and histoplasma proteins. In human urine, some 52 peptides from 37 Histoplasma proteins were identified with high confidence. This is the first report of identification of a large number of Histoplasma-specific peptides from immunoassay-positive patient samples using tandem mass spectrometry and bioinformatics techniques. These findings may lead to novel diagnostic markers for histoplasmosis in human urine