Protecting obfuscation against arithmetic attacks

Obfuscation, the task of compiling circuits or programs to make the internal computation unintelligible while preserving input/output functionality, has become an object of central focus in the cryptographic community. A work of Garg et al. [FOCS 2013] gave the first candidate obfuscator for general polynomial-size circuits, and led to several other works constructing candidate obfuscators. Each of these constructions is built upon another cryptographic primitive called a multilinear map, or alternatively a graded encoding scheme. Several of these candidates have been shown to achieve the strongest notion of security (virtual black-box, or VBB) against purely algebraic attacks in a model that we call the fully-restricted graded encoding model. In this model, each operation performed by an adversary is required to obey the algebraic restrictions of the graded encoding scheme. These restrictions essentially impose strong forms of homogeneity and multilinearity on the allowed polynomials. While important, the scope of the security proofs is limited by the stringency of these restrictions. We propose and analyze another variant of the Garg et al. obfuscator in a setting that imposes fewer restrictions on the adversary, which we call the arithmetic setting. This setting captures a broader class of attacks than considered in previous works. We also explore connections between notions of obfuscation security and longstanding questions in arithmetic circuit complexity. Our results include the following. (1) In the arithmetic setting where the adversary is limited to creating multilinear, but not necessarily homogenous polynomials, we obtain an unconditional proof of VBB security. This requires a substantially different analysis than previous security proofs. (2) In the arithmetic setting where the adversary can create polynomials of arbitrary degree, we show that a proof of VBB security for any currently available candidate obfuscator would imply VP != VNP. To complement this, we show that a weaker notion of security (indistinguishability obfuscation) can be achieved unconditionally in this setting, and that VBB security can be achieved under a complexity-theoretic assumption related to the Exponential Time Hypothesis

Damping and decoherence of a nanomechanical resonator due to a few two level systems

We consider a quantum model of a nanomechanical flexing beam resonator interacting with a bath comprising a few damped tunneling two level systems (TLS's). In contrast with a resonator interacting bilinearly with an ohmic free oscillator bath (modeling clamping loss, for example), the mechanical resonator damping is amplitude dependent, while the decoherence of quantum superpositions of mechanical position states depends only weakly on their spatial separation

Modular Design of Artificial Tissue Homeostasis: Robust Control through Synthetic Cellular Heterogeneity

Synthetic biology efforts have largely focused on small engineered gene networks, yet understanding how to integrate multiple synthetic modules and interface them with endogenous pathways remains a challenge. Here we present the design, system integration, and analysis of several large scale synthetic gene circuits for artificial tissue homeostasis. Diabetes therapy represents a possible application for engineered homeostasis, where genetically programmed stem cells maintain a steady population of β-cells despite continuous turnover. We develop a new iterative process that incorporates modular design principles with hierarchical performance optimization targeted for environments with uncertainty and incomplete information. We employ theoretical analysis and computational simulations of multicellular reaction/diffusion models to design and understand system behavior, and find that certain features often associated with robustness (e.g., multicellular synchronization and noise attenuation) are actually detrimental for tissue homeostasis. We overcome these problems by engineering a new class of genetic modules for ‘synthetic cellular heterogeneity’ that function to generate beneficial population diversity. We design two such modules (an asynchronous genetic oscillator and a signaling throttle mechanism), demonstrate their capacity for enhancing robust control, and provide guidance for experimental implementation with various computational techniques. We found that designing modules for synthetic heterogeneity can be complex, and in general requires a framework for non-linear and multifactorial analysis. Consequently, we adapt a ‘phenotypic sensitivity analysis’ method to determine how functional module behaviors combine to achieve optimal system performance. We ultimately combine this analysis with Bayesian network inference to extract critical, causal relationships between a module's biochemical rate-constants, its high level functional behavior in isolation, and its impact on overall system performance once integrated.National Institutes of Health (U.S.) (NIH NIGMS grant R01GM086881)National Science Foundation (U.S.) (NSF Award #1001092)National Science Foundation (U.S.) (NSF Graduate Research Fellowship Program)Swiss National Science Foundation (SystemsX.ch grant

Dorsal Anterior Cingulate Cortices Differentially Lateralize Prediction Errors and Outcome Valence in a Decision-Making Task.

The dorsal anterior cingulate cortex (dACC) is proposed to facilitate learning by signaling mismatches between the expected outcome of decisions and the actual outcomes in the form of prediction errors. The dACC is also proposed to discriminate outcome valence—whether a result has positive (either expected or desirable) or negative (either unexpected or undesirable) value. However, direct electrophysiological recordings from human dACC to validate these separate, but integrated, dimensions have not been previously performed. We hypothesized that local field potentials (LFPs) would reveal changes in the dACC related to prediction error and valence and used the unique opportunity offered by deep brain stimulation (DBS) surgery in the dACC of three human subjects to test this hypothesis. We used a cognitive task that involved the presentation of object pairs, a motor response, and audiovisual feedback to guide future object selection choices. The dACC displayed distinctly lateralized theta frequency (3–8 Hz) event-related potential responses—the left hemisphere dACC signaled outcome valence and prediction errors while the right hemisphere dACC was involved in prediction formation. Multivariate analyses provided evidence that the human dACC response to decision outcomes reflects two spatiotemporally distinct early and late systems that are consistent with both our lateralized electrophysiological results and the involvement of the theta frequency oscillatory activity in dACC cognitive processing. Further findings suggested that dACC does not respond to other phases of action-outcome-feedback tasks such as the motor response which supports the notion that dACC primarily signals information that is crucial for behavioral monitoring and not for motor control

Tumor and circulating biomarkers in patients with second-line hepatocellular carcinoma from the randomized phase II study with tivantinib

ARQ 197-215 was a randomized placebo-controlled phase II study testing the MET inhibitor tivantinib in second-line hepatocellular carcinoma (HCC) patients. It identified tumor MET as a key biomarker in HCC. Aim of this research was to study the prognostic and predictive value of tumor (MET, the receptor tyrosine kinase encoded by the homonymous MNNG-HOS transforming gene) and circulating (MET, hepatocyte growth factor [HGF], alpha-fetoprotein [AFP], vascular endothelial growth factor [VEGF]) biomarkers in second-line HCC. Tumor MET-High status was centrally assessed by immunohistochemistry. Circulating biomarkers were centrally analyzed on serum samples collected at baseline and every 4-8 weeks, using medians as cut-off to determine High/Low status. Tumor MET, tested in 77 patients, was more frequently High after (82%) versus before (40%) sorafenib. A significant interaction (p = 0.04) between tivantinib and baseline tumor MET in terms of survival was observed. Baseline circulating MET and HGF (102 patients) High status correlated with shorter survival (HR 0.61, p = 0.03, and HR 0.60, p = 0.02, respectively), while the association between AFP (104 patients) or VEGF (103 patients) status and survival was non-significant. Conclusions: Tumor MET levels were higher in patients treated with sorafenib. Circulating biomarkers such as MET and HGF may be prognostic in second-line HCC. These results need to be confirmed in larger randomized clinical trials

Impacts of the global economic crisis on cyprus tourism and policy responses

This study examines the impacts of the global economic crisis on Cyprus tourism and the pertinent policy responses. A qualitative approach was adopted by conducting eight semi-structured interviews with tourism authorities and suppliers/professionals. Findings indicated the main impacts of the crisis on Cypriot tourism: lack of competitiveness, decreased visitation/revenues, inadequate quality and escalated pricing. Furthermore, findings identify three types of policy measures: (i) immediate response measures; (ii) foreign investment in tourism; and (iii) diversification of the tourism product and quality improvement. The study highlights the need for Cyprus to develop a comprehensive tourism planning framework. It is suggested that crisis plans of small island states should be developed upon a holistic framework that leverages their destination capitals

Effectiveness of Home Health Care in Reducing Return to Hospital: Evidence from a Multi-hospital Study in the US

Background Home health care, a commonly used bridge strategy for transitioning from hospital to home-based care, is expected to contribute to readmission avoidance efforts. However, in studies using disease-specific samples, evidence about the effectiveness of home health care in reducing readmissions is mixed. Objective To examine the effectiveness of home health care in reducing return to hospital across a diverse sample of patients discharged home following acute care hospitalization. Research design Secondary analysis of a multi-site dataset from a study of discharge readiness assessment and post-discharge return to hospital, comparing matched samples of patients referred and not referred for home health care at the time of hospital discharge. Setting Acute care, Magnet-designated hospitals in the United States Participants The available sample (n = 18,555) included hospitalized patients discharged from medical-surgical units who were referred (n = 3,579) and not referred (n = 14,976) to home health care. The matched sample included 2767 pairs of home health care and non- home health care patients matched on patient and hospitalization characteristics using exact and Mahalanobis distance matching. Methods Unadjusted t-tests and adjusted multinomial logit regression analyses to compare the occurrence of readmissions and Emergency Department/Observation visits within 30 and 60-days post-discharge. Results No statistically significant differences in readmissions or Emergency Department /Observation visits between home health care and non-home health care patients were observed. Conclusions Home health care referral was not associated with lower rates of return to hospital within 30 and 60 days in this US sample matched on patient and clinical condition characteristics. This result raises the question of why home health care services did not produce evidence of lower post-discharge return to hospital rates. Focused attention by home health care programs on strategies to reduce readmissions is needed

Perceived diagnostic delay and cancer-related distress: a cross sectional study of patients with colorectal cancer.

Objective: This study aimed to examine the effect of perceived diagnostic delay on cancer-related distress, and determine whether fear of cancer-recurrence and quality of life mediate this relationship. Methods: Cross-sectional study in which 311 colorectal cancer (CRC) survivors in Scotland completed a survey which included questions on cancer-related distress (IES-R), perceived diagnostic delay, quality of life (trial outcome index of the FACT-C: FACT-C TOI) and fear of cancer recurrence. 15 patients withheld consent to data matching with medical records, leaving a sample size of 296. Participants were an average of 69 years old (range 56 to 81) and between 3.5 to 12 years post-diagnosis. Multiple regressions were used to test predictors of distress, and regression and bootstrapping to test for mediation. Results: Perceived diagnostic delay was correlated with higher cancer-related distress, while objective markers of diagnostic delay (disease stage at diagnosis and treatment received) were not. Some of the relationship between perceived diagnostic delay and cancer-related distress was mediated by quality of life, but not by fear of cancer recurrence. Conclusions: Perceived diagnostic delay was associated with higher cancer-related distress among CRC survivors. While poorer quality of life partly explained such associations, fear of cancer recurrence, stage at diagnosis and treatment did not. The exact features of diagnostic delay that are associated with cancer-related distress remain unclear. Future research should examine the experiences patients go through prior to diagnosis that may increase distress, in an effort to improve our understanding of the factors affecting emotional wellbeing among CRC survivors

Positive Youth Development: Developing, Implementing, and Sustaining Music-Based Services for Emerging Adults Experiencing Homelessness

Research suggests that comprehensive services that consider the complex and interconnected needs of emerging adults experiencing homelessness may be more effective than interventions with a singular focus. There is little research that demonstrates how agencies that implement programs for individuals experiencing homelessness develop and sustain meaningful services for emerging adults, especially under conditions of increasing austerity. This study targets this gap in the literature by investigating how one transitional living program for emerging adults experiencing homelessness developed a music studio. Specifically, this study examines the factors and processes that were involved in developing, implementing, and sustaining the music studio. Findings suggest an ongoing organizational commitment to Positive Youth Development plays an important role