Quantitative Group

Fremantle, Australia

Quantitative Group

Fremantle, Australia
Time filter
Source Type

Ye F.,Quantitative Group | Zhang C.-H.,Rutgers University
Journal of Machine Learning Research | Year: 2010

We consider the estimation of regression coefficients in a high-dimensional linear model. For regression coefficients in ℓ r balls, we provide lower bounds for the minimax ℓ q risk and minimax quantiles of the ℓ q loss for all design matrices. Under an ℓ 0 sparsity condition on a target coefficient vector, we sharpen and unify existing oracle inequalities for the Lasso and Dantzig selector. We derive oracle inequalities for target coefficient vectors with many small elements and smaller threshold levels than the universal threshold. These oracle inequalities provide sufficient conditions on the design matrix for the rate minimaxity of the Lasso and Dantzig selector for the ℓ q risk and loss in ℓ r balls, 0 ≤ r ≤ 1 ≤ q ≤ ∞. By allowing q = ∞, our risk bounds imply the variable selection consistency of threshold Lasso and Dantzig selectors. © 2010 Fei Ye and Cun-Hui Zhang.

Fried E.I.,Quantitative Group | Nesse R.M.,Arizona State University
Journal of Affective Disorders | Year: 2015

Background: The DSM-5 encompasses a wide range of symptoms for Major Depressive Disorder (MDD). Symptoms are commonly added up to sum-scores, and thresholds differentiate between healthy and depressed individuals. The underlying assumption is that all patients diagnosed with MDD have a similar condition, and that sum-scores accurately reflect the severity of this condition. To test this assumption, we examined the number of DSM-5 depression symptom patterns in the "Sequenced Treatment Alternatives to Relieve Depression" (STAR∗D) study. Methods: We investigated the number of unique symptom profiles reported by 3703 depressed outpatients at the beginning of the first treatment stage of STAR∗D. Results: Overall, we identified 1030 unique symptom profiles. Of these profiles, 864 profiles (83.9%) were endorsed by five or fewer subjects, and 501 profiles (48.6%) were endorsed by only one individual. The most common symptom profile exhibited a frequency of only 1.8%. Controlling for overall depression severity did not reduce the amount of observed heterogeneity. Limitations: Symptoms were dichotomized to construct symptom profiles. Many subjects enrolled in STAR∗D reported medical conditions for which prescribed medications may have affected symptom presentation. Conclusions: The substantial symptom variation among individuals who all qualify for one diagnosis calls into question the status of MDD as a specific consistent syndrome and offers a potential explanation for the difficulty in documenting treatment efficacy. We suggest that the analysis of individual symptoms, their patterns, and their causal associations will provide insights that could not be discovered in studies relying on only sum-scores. © 2014 Elsevier B.V. All rights reserved.

Nilakantan K.,Quantitative Group
International Journal of Systems Science | Year: 2010

This article takes up the study of the dynamics of a single product in a prototype three-stage supply chain system, at the downstream warehouse end of the chain, under a responsive chain strategy. The dynamics under various ordering policies and the parameters which will yield desired responses are systematically analysed, both for deterministic and stochastic systems. Higher-order control policies are then proposed and analysed. The considered key performance criteria are the permanent inventory deviations from the desired levels, or the offset, the maximum dip in inventory, the 'undershoot', the damping effect and decay rates, and the duration of time in the negative region, for deterministic systems; and additionally, the inventory variance for stochastic systems. It is shown that the disadvantages of the conventional (proportional-integral-derivative) control policies, like large negative deviations, low decay rates, and high inventory variance, can be overcome by the use of higher-order control policies proposed herein. © 2010 Taylor & Francis.

Fried E.I.,Quantitative Group | Nesse R.M.,Arizona State University
BMC Medicine | Year: 2015

Most measures of depression severity are based on the number of reported symptoms, and threshold scores are often used to classify individuals as healthy or depressed. This method - and research results based on it - are valid if depression is a single condition, and all symptoms are equally good severity indicators. Here, we review a host of studies documenting that specific depressive symptoms like sad mood, insomnia, concentration problems, and suicidal ideation are distinct phenomena that differ from each other in important dimensions such as underlying biology, impact on impairment, and risk factors. Furthermore, specific life events predict increases in particular depression symptoms, and there is evidence for direct causal links among symptoms. We suggest that the pervasive use of sum-scores to estimate depression severity has obfuscated crucial insights and contributed to the lack of progress in key research areas such as identifying biomarkers and more efficacious antidepressants. The analysis of individual symptoms and their causal associations offers a way forward. We offer specific suggestions with practical implications for future research. © Fried and Nesse.

A mathematical model is proposed that describes the colonization of host tissues by a contagious pathogen and the early nonspecific immune response, the impact of the infection on the performances of the host, and the spread of the infection in the population. The model obeys specific biological characteristics: Susceptible hosts are infected after contact with an infected one. The number of pathogenic units that invade a susceptible host is dependent on the infectious dose provided by the infected host and on the ability of the susceptible host to resist the invasion. After entry in host, pathogenic changes over time are expressed as the difference between the intrinsic logistic growth rate and the Holling type II kill rate provided by the immune response cells. Hosts have different ability to restrict reproduction of the pathogen units. The number of response cells actively recruited to the site of infection depends on the number of the pathogenic units. Response cells are removed after having killed a fixed number of pathogenic units. The effects of the number of pathogenic units on the performances of the host depend upon its levels of tolerance to the deleterious effects of both pathogenic and response cells. Pre-infection costs are associated to tolerance and resistance levels. Estimates of most biological parameters of the model are based on published experimental studies while resistance/tolerance parameters are varied across their allowable ranges. The model reproduces qualitatively realistic outcomes in response to infection: healthy response, recurrent infection, persistent infectious and non-infectious inflammation, and severe immunodeficiency. Evolution across time at the animal and population levels is presented. Effects on animal performances are discussed with respect to changes in resistance/tolerance parameters and selection strategies are suggested. © 2012 Detilleux.

Javad F.,Quantitative Group
Archives of dermatological research | Year: 2012

Clinically, keloids are defined as scars that invade adjacent healthy tissue and are caused by tissue injury; however, the clear distinction relating keloids to wound healing or to cancer remains elusive. This study profiled protein extracts from the regions of keloid tissues to determine the activities within these different zones, and to help underpin the activities apparent within different regions of the disease. Two-dimensional gel electrophoresis, liquid chromatography mass spectrometer (LCMS) and a Mascot online database search were employed for comparative proteomic analysis between four sites in keloidal scars (KS). Out of 400 spots identified in all gels, 21 were unique to given KS sites. These were identified using LCMS and the results showed the presence of mitochondrial and structural proteins in the margin, while the top contained keratin II. Heat shock protein was the only protein present in the internal normal control and margin, while the external normal contain keratin II and the voltage-dependent anion-selective channel protein, annexin A6, plus glial fibrillary acidic protein. This work is novel since it has identified differentially expressed proteins across the tested keloidal scar sites. The presence of mitochondrial-associated proteins at the margins suggests that this is the most active part of the scar.

Detilleux J.C.,Quantitative Group
Genetics Selection Evolution | Year: 2011

Background: Tolerance and resistance provide animals with two distinct strategies to fight infectious pathogens and may exhibit different evolutionary dynamics. However, few studies have investigated these mechanisms in the case of animal diseases under commercial constraints. Methods. The paper proposes a method to simultaneously describe (1) the dynamics of transmission of a contagious pathogen between animals, (2) the growth and death of the pathogen within infected hosts and (3) the effects on their performances. The effectiveness of increasing individual levels of tolerance and resistance is evaluated by the number of infected animals and the performance at the population level. Results: The model is applied to a particular set of parameters and different combinations of values. Given these imputed values, it is shown that higher levels of individual tolerance should be more effective than increased levels of resistance in commercial populations. As a practical example, a method is proposed to measure levels of animal tolerance to bovine mastitis. Conclusions: The model provides a general framework and some tools to maximize health and performances of a population under infection. Limits and assumptions of the model are clearly identified so it can be improved for different epidemiological settings. © 2011 Detilleux; licensee BioMed Central Ltd.

Cook C.N.,Quantitative Group | Cook C.N.,University of Queensland | Possingham H.P.,University of Queensland | Fuller R.A.,University of Queensland
Conservation Biology | Year: 2013

Systematic reviews comprehensively summarize evidence about the effectiveness of conservation interventions. We investigated the contribution to management decisions made by this growing body of literature. We identified 43 systematic reviews of conservation evidence, 23 of which drew some concrete conclusions relevant to management. Most reviews addressed conservation interventions relevant to policy decisions; only 35% considered practical on-the-ground management interventions. The majority of reviews covered only a small fraction of the geographic and taxonomic breadth they aimed to address (median = 13% of relevant countries and 16% of relevant taxa). The likelihood that reviews contained at least some implications for management tended to increase as geographic coverage increased and to decline as taxonomic breadth increased. These results suggest the breadth of a systematic review requires careful consideration. Reviews identified a mean of 312 relevant primary studies but excluded 88% of these because of deficiencies in design or a failure to meet other inclusion criteria. Reviews summarized on average 284 data sets and 112 years of research activity, yet the likelihood that their results had at least some implications for management did not increase as the amount of primary research summarized increased. In some cases, conclusions were elusive despite the inclusion of hundreds of data sets and years of cumulative research activity. Systematic reviews are an important part of the conservation decision making tool kit, although we believe the benefits of systematic reviews could be significantly enhanced by increasing the number of reviews focused on questions of direct relevance to on-the-ground managers; defining a more focused geographic and taxonomic breadth that better reflects available data; including a broader range of evidence types; and appraising the cost-effectiveness of interventions. © 2013 The Authors. Conservation Biology published by Wiley Periodicals, Inc., on behalf of the Society for Conservation Biology.

Bahinipati B.K.,Quantitative Group | Deshmukh S.G.,Indian Institute of Technology Delhi
Computers and Industrial Engineering | Year: 2012

Vertical collaboration problem focuses on integrating and modeling the decision problems of the suppliers and buyers together with the market intermediary by identifying the inefficiencies in the traditional marketplace and aligning the incentives of members in the e-marketplace. The present work develops and solves real life e-marketplace models for complex buyers-suppliers procurement problems by estimating the order quantities in the collaborated supply chain. The newsvendor framework considers demand to be independent of the selling price as is generally the case in the semiconductor industry supply chain dealing with techno-savvy customers. The vertical collaboration process would be more effective if the length of the planning horizon and order size is considered as a negotiation parameter between the buyer and supplier. It is observed that the supplier's expected profit function increases with the buyers' ordering quantity, which is important in characterizing the general structure of the collaboration scheme of the supply chain. © 2011 Elsevier Ltd. All rights reserved.

Cupric Canyon Capital ("Cupric") is pleased to announce that its wholly owned subsidiary, Khoemacau Copper Mining Pty. Limited ("KCM"), has entered into a $50 million, term loan facility agreement with Red Kite Mine Finance to provide funding for KCM's Khoemacau copper-silver project in Botswana. Proceeds from the loan will be used to fund project development costs and front end engineering in advance of commencing full scale construction in the second half of 2017. KCM will construct an underground mine at its high-grade Zone 5 deposit. The Zone 5 resource contains 100 million tonnes of ore grading 2% copper and 20 g/t silver as reported in November 2015. The Zone 5 mine will initially feed the near-by Boseto copper concentrator, which was acquired as part of Cupric's purchase of Discovery Copper Botswana ("DCB") announced in July 2015. The Zone 5 underground mine will be accessed with three declines and will utilize a highly-mechanized, low-cost sub-level open stoping mining method. The Boseto concentrator will be upgraded from its current 3.0 million tonnes per annum nameplate capacity to 3.6 million tonnes per annum. Metal production from the Starter Project will average 50,000 tonnes of copper and 1.4 million ounces of silver per annum. The Zone 5 mine is expected to have a minimum life of 25 years and average C1 cash costs of c. $1.00 per pound. The total cost to develop KCM's Starter Project is c. US$350 million, with underground mine development being the largest single cost component. Efforts are underway to optimize both ore grade and capital expenditures. Within the next few months, the Botswana Environmental Ministry is expected to approve modifications to KCM's environmental permits to facilitate processing Zone 5 ore at the upgraded Boseto plant. The Botswana Power Company is also progressing development of the high-tension power line that will provide commercial power to the northwest region of Botswana. This power-line project includes a spur line to Boseto and Zone 5, providing low-cost commercial power when KCM starts production in 2019. Dennis Bartlett, Cupric's Chief Executive Officer, said: "Proceeds from the term loan will enable us to continue development work at Khoemacau as we prepare to begin full scale construction of the Starter Project in the second half of 2017. All design, engineering and permitting work is progressing well and on schedule, bolstering our confidence that production will commence in 2019. In addition, the most recent drilling results including the discovery of Zone 5 North and mineral resource updates for the deposits acquired last year are very exciting. We continue to believe that Zone 5, combined with the expansion potential offered by the other deposits within our license areas, represents perhaps the most attractive new copper project in the world today, with the potential to ultimately achieve copper production in excess of 120,000 tonnes per annum." Following Cupric's 2015 acquisition of the adjacent Boseto property, KCM began drilling the high-grade Zeta NE deposit and started exploration on the acquired prospecting licenses. Deep drilling at Zeta NE included eight diamond core holes totaling approximately 5,561 meters. The results from this drilling confirmed high-grade copper and silver mineralization over thick intervals to a depth of 900 meters below surface with a strike length of three kilometers. The Zeta NE deposit remains open at depth and along strike. Exploration on the Boseto licenses also resulted in the discovery of the Zone 5 North deposit. Eighteen diamond core holes totaling 7,085 meters and 10 reverse circulation holes totaling 1,594 meters intersected mineralization over a strike length of five kilometers and to a depth of 700 meters below surface. This deposit is still open at depth and along strike. The results from KCM's recent drilling and DCB's previous drilling at Zeta NE were used to develop the following inferred mineral resource estimates for Zeta NE and Zone 5 North. The Zeta NE and Zone 5 North estimates were prepared by RungePincockMinarco (RPM) in 2016. The estimate for Zeta Underground, which represents the resource beneath the Zeta pit that can be mined underground, was prepared by Quantitative Group in 2014. All estimates are classified using JORC Code (2012). In the second half of 2016, four additional diamond core holes totaling 4,063 meters were drilled at depth at Zone 5 North and two additional diamond core holes totaling 1,669 meters were drilled deep at Zeta NE. All of these holes intersected mineralization below the current Inferred Mineral Resources and confirm continuous high-grade copper mineralization to depths greater than 1,000 meters below surface at both Zeta NE and Zone 5 North. The results from these holes are in addition to the mineral resource estimates reported above and have the potential to increase both the tonnage and grade of the mineral resource estimates at both Zeta NE and Zone 5 North. The mineral resource estimates will be updated in the second quarter of 2017 to include these latest drill results. Future expansions are expected to increase production at Khoemacau up to at least 120,000 tonnes per annum of copper. A prefeasibility study with very positive results has been completed for a future concentrator to be built at Zone 5 that will process 6.0 million tonnes and produce an average 80,000 tonnes of copper per annum. Once this new concentrator is built, the Boseto concentrator will process ore mined underground from the nearby Zeta and Zone 5 North deposits. The feasibility study for the new concentrator and definition drilling of the Zeta, Zeta NE and Zone 5 North deposits is expected to commence in 2018. Cupric was formed in 2010 with a goal to acquire undeveloped copper assets with a known resource. The management of Cupric consists of former executive, technical, financial, and operational leadership of major mining companies, including Phelps Dodge Corporation and its successor, Freeport McMoRan Copper & Gold Inc. (which acquired Phelps Dodge in 2007). The Cupric team has decades of experience in the exploration, development, construction and operation of world-class open pit and underground mines, processing facilities, and infrastructure.

Loading Quantitative Group collaborators
Loading Quantitative Group collaborators