Visual pathways from the perspective of cost functions and multi-task deep neural networks

Vision research has been shaped by the seminal insight that we can understand the higher-tier visual cortex from the perspective of multiple functional pathways with different goals. In this paper, we try to give a computational account of the functional organization of this system by reasoning from the perspective of multi-task deep neural networks. Machine learning has shown that tasks become easier to solve when they are decomposed into subtasks with their own cost function. We hypothesize that the visual system optimizes multiple cost functions of unrelated tasks and this causes the emergence of a ventral pathway dedicated to vision for perception, and a dorsal pathway dedicated to vision for action. To evaluate the functional organization in multi-task deep neural networks, we propose a method that measures the contribution of a unit towards each task, applying it to two networks that have been trained on either two related or two unrelated tasks, using an identical stimulus set. Results show that the network trained on the unrelated tasks shows a decreasing degree of feature representation sharing towards higher-tier layers while the network trained on related tasks uniformly shows high degree of sharing. We conjecture that the method we propose can be used to analyze the anatomical and functional organization of the visual system and beyond. We predict that the degree to which tasks are related is a good descriptor of the degree to which they share downstream cortical-units.Comment: 16 pages, 5 figure

Modification of spintronic terahertz emitter performance through defect engineering

Spintronic ferromagnetic/non-magnetic heterostructures are novel sources for the generation of THz radiation based on spin-to-charge conversion in the layers. The key technological and scientific challenge of THz spintronic emitters is to increase their intensity and frequency bandwidth. Our work reveals the factors to engineer spintronic Terahertz generation by introducing the scattering lifetime and the interface transmission for spin polarized, non-equilibrium electrons. We clarify the influence of the electron-defect scattering lifetime on the spectral shape and the interface transmission on the THz amplitude, and how this is linked to structural defects of bilayer emitters. The results of our study define a roadmap of the properties of emitted as well as detected THz-pulse shapes and spectra that is essential for future applications of metallic spintronic THz emitters.Comment: 33 pages, 13 figure

Magnetic resonance imaging analysis of the bioabsorbable Milagro™ interference screw for graft fixation in anterior cruciate ligament reconstruction

Ligament graft fixation with bioabsorbable interference screws is a standard procedure in cruciate ligament replacement. Previous screw designs may resorb incompletely, and can cause osteolysis and sterile cysts despite being implanted for several years. The aim of this study was to examine the in vivo degradation and biocompatibility of the new Milagro™ interference screw (Mitek, Norderstedt, Germany). The Milagro™ interference screw is made of 30% ß-TCP (TriCalcium phosphate) and 70% PLGA (Poly-lactic-co-glycolic acid). In the period between June 2005 and February 2006, 38 patients underwent graft fixation with Milagro™ screws in our hospital. Arthroscopic ACL reconstruction was performed using hamstring tendon grafts in all the patients. MR imaging was performed on 12 randomly selected patients out of the total of 38 at 3, 6 and 12 months after surgery. During the examination, the volume loss of the screw, tunnel enlargement, presence of osteolysis, fluid lines, edema and postoperative screw replacement by bone tissue were evaluated. There was no edema or signs of inflammation around the bone tunnels. At 3, 6 and 12 months, the tibial screws showed an average volume loss of 0, 8.1% (±7.9%) and 82.6% (±17.2%, P < 0.05), respectively. The femoral screws showed volume losses of 2.5% (±2.1%), 31.3% (±21.6%) and 92.02% (±6.3%, P < 0.05), respectively. The femoral tunnel enlargement was 47.4% (±43.8%) of the original bone tunnel volume after 12 months, and the mean tunnel volume of the tibial tunnel was −9.5% (±58.1%) compared to the original tunnel. Bone ingrowth was observed in all the patients. In conclusion, the resorption behaviour of the Milagro™ screw is closely linked to the graft healing process. The screws were rapidly resorbed after 6 months and, at 12 months, only the screw remnants were detectable. Moreover, the Milagro™ screw is biocompatible and osteoconductive, promoting bone ingrowth during resorption. Tunnel enlargement is not prevented in the first months but is reduced by bone ingrowth after 12 months

Combination of MALDI-TOf mass spectrometry and machine learning for rapid antimicrobial resistance screening: the CASE of Campylobacter spp

While MALDI-TOF mass spectrometry (MS) is widely considered as the reference method for the rapid and inexpensive identification of microorganisms in routine laboratories, less attention has been addressed to its ability for detection of antimicrobial resistance (AMR). Recently, some studies assessed its potential application together with machine learning for the detection of AMR in clinical pathogens. The scope of this study was to investigate MALDI-TOF MS protein mass spectra combined with a prediction approach as an AMR screening tool for relevant foodborne pathogens, such as Campylobacter coli and Campylobacter jejuni. A One-Health panel of 224 C. jejuni and 116 C. coli strains was phenotypically tested for seven antimicrobial resistances, i.e., ciprofloxacin, erythromycin, tetracycline, gentamycin, kanamycin, streptomycin, and ampicillin, independently, and were submitted, after an on- and off-plate protein extraction, to MALDI Biotyper analysis, which yielded one average spectra per isolate and type of extraction. Overall, high performance was observed for classifiers detecting susceptible as well as ciprofloxacin- and tetracycline-resistant isolates. A maximum sensitivity and a precision of 92.3 and 81.2%, respectively, were reached. No significant prediction performance differences were observed between on- and off-plate types of protein extractions. Finally, three putative AMR biomarkers for fluoroquinolones, tetracyclines, and aminoglycosides were identified during the current study. Combination of MALDI-TOF MS and machine learning could be an efficient and inexpensive tool to swiftly screen certain AMR in foodborne pathogens, which may enable a rapid initiation of a precise, targeted antibiotic treatment

Mining the Deep Seabed: A Range of Perspectives

Introduction to the symposium entitled: Mining the Deep Seabed: A Range of Perspectives. The introduction is written by Roger H. Hull, who introduces the panel, people in attendance, and core issues involving the system of exploration and exploitation for the the deep seabed resource policy, financial arrangements, and the structure of the Authority, which all parties agree will play a major role in the development of the deep seabed

Letting the cat out of the bag: The impact of respondent multitasking on disclosure of socially undesirable information and answers to knowledge questions

Previous research shows that a high proportion of respondents engage in other activities while answering surveys. In this study, we examine the effect of multitasking in reporting sensitive information and socially undesirable behavior (e.g., substance use, mental health, gambling) along with reporting of knowledge/awareness of publicly funded programs. The dataset comes from a dual-frame random digit dial telephone survey of adults in a Midwestern state (N = 1,761) who were asked about their attitudes and behaviors toward gambling and health-related behaviors. The results of the study reveal that nearly half of the respondents engaged in multitasking activities (46.9%). In addition, it was found that multitaskers disclosed more socially undesirable information and reported lower levels of knowledge than non-multitaskers. The implications of these findings and how they fit in with previous work are discussed

Investigating Respondent Multitasking and Distraction Using Self-reports and Interviewers’ Observations in a Dual-frame Telephone Survey

Previous research has shown that people often engage in other activities while responding to surveys and that respondents’ multitasking generally has no effect on indicators of data quality (e.g., item nonresponse, non-differentiation). One of the limitations of these studies is that they have mostly used selfreported measures of respondents’ multitasking. We build on prior research by combining self-reported measures of multitasking with interviewers' observations of respondents' distractions recorded after each interview. The dataset comes from a statewide dual-frame random digit dial telephone survey of adults in a Midwestern state (n = 1,006) who were queried on topics related to awareness of and attitudes toward STEM education. We found that multitasking was frequent (45.6%) and that respondents who reported engaging in other activities were described as distracted twice as often as those who did not report multitasking (38.3% versus 19.0%). In terms of data quality, respondents who were multitasking provided less accurate responses to a knowledge question. However, we found no evidence that distractions, assessed by interviewers, compromised data quality. The implications of the results for survey practices are discussed

Predictors of Multitasking and its Impact on Data Quality: Lessons from a Statewide Dual-frame Telephone Survey

Previous research shows that people often multitask while talking on the phone. This raises concerns about the quality of data yielded by telephone surveys as multitasking might distract respondents, inducing satisficing behaviors. Although respondents’ multitasking behavior has aroused great interest in the literature, most studies are based on online surveys. In this study, we expand on prior research by analyzing data from a random dual-frame telephone survey of adults in a Midwestern state regarding their perceptions and experiences with healthcare (N = 2,132; of which 245 are from landlines and 1,887 from cellphones). We found that multitasking was frequent (53.3%), especially among older respondents, parents with children in the household, less educated individuals, and those interviewed at night. Despite having over half of respondents report multitasking, we found no evidence that self-reported multitasking reduced the quality of the responses. The implications of the results for survey practices are discussed

The Impact of Advance Letters on Cellphone Response in a Statewide Dual-Frame Survey

Many studies have illustrated the effectiveness of prenotification letters to increase response rates for telephone surveys. However, most studies assessing the impact of advance letters have been carried out using landlines, so the evidence of the effectiveness of prenotification letters on cellphones is scarce. This is important because the proportion of cellphone numbers used in survey research continues to rise. In this study, we assess the impact of advance letters on response rates from a cellphone sample of a statewide dual-frame survey about perceptions of and experiences with healthcare. In a dual-frame telephone survey of a Midwestern state’s residents, half of cellphones with addresses were randomly assigned to receive advance letters (n = 600) and the other half (n = 600) did not receive prenotices. Cellphone results are similar to previous studies using landlines, showing a positive effect of advance letters on cellphone response and cooperation rates (9.1 and 10.3 percentage point gain, respectively). Despite this positive effect on responses, the letters seemed to affect the sample composition by increasing the presence of respondents who were white, with higher education and income. The impact of advance letters on calling effort varied; it reduced the number of call attempts needed to reach completions while increasing the attempts required that ultimately resulted in refusals. Implications of the results for the use of advance letters prior to calling cellphones in dual-frame telephone surveys are discussed

Recombination dynamics of a human Y-chromosomal palindrome:rapid GC-biased gene conversion, multi-kilobase conversion tracts, and rare inversions

The male-specific region of the human Y chromosome (MSY) includes eight large inverted repeats (palindromes) in which arm-to-arm similarity exceeds 99.9%, due to gene conversion activity. Here, we studied one of these palindromes, P6, in order to illuminate the dynamics of the gene conversion process. We genotyped ten paralogous sequence variants (PSVs) within the arms of P6 in 378 Y chromosomes whose evolutionary relationships within the SNP-defined Y phylogeny are known. This allowed the identification of 146 historical gene conversion events involving individual PSVs, occurring at a rate of 2.9-8.4×10(-4) events per generation. A consideration of the nature of nucleotide change and the ancestral state of each PSV showed that the conversion process was significantly biased towards the fixation of G or C nucleotides (GC-biased), and also towards the ancestral state. Determination of haplotypes by long-PCR allowed likely co-conversion of PSVs to be identified, and suggested that conversion tract lengths are large, with a mean of 2068 bp, and a maximum in excess of 9 kb. Despite the frequent formation of recombination intermediates implied by the rapid observed gene conversion activity, resolution via crossover is rare: only three inversions within P6 were detected in the sample. An analysis of chimpanzee and gorilla P6 orthologs showed that the ancestral state bias has existed in all three species, and comparison of human and chimpanzee sequences with the gorilla outgroup confirmed that GC bias of the conversion process has apparently been active in both the human and chimpanzee lineages