IST Austria Thesis

A search problem lies in the complexity class FNP if a solution to the given instance of the problem can be verified efficiently. The complexity class TFNP consists of all search problems in FNP that are total in the sense that a solution is guaranteed to exist. TFNP contains a host of interesting problems from fields such as algorithmic game theory, computational topology, number theory and combinatorics. Since TFNP is a semantic class, it is unlikely to have a complete problem. Instead, one studies its syntactic subclasses which are defined based on the combinatorial principle used to argue totality. Of particular interest is the subclass PPAD, which contains important problems like computing Nash equilibrium for bimatrix games and computational counterparts of several fixed-point theorems as complete. In the thesis, we undertake the study of averagecase hardness of TFNP, and in particular its subclass PPAD. Almost nothing was known about average-case hardness of PPAD before a series of recent results showed how to achieve it using a cryptographic primitive called program obfuscation. However, it is currently not known how to construct program obfuscation from standard cryptographic assumptions. Therefore, it is desirable to relax the assumption under which average-case hardness of PPAD can be shown. In the thesis we take a step in this direction. First, we show that assuming the (average-case) hardness of a numbertheoretic problem related to factoring of integers, which we call Iterated-Squaring, PPAD is hard-on-average in the random-oracle model. Then we strengthen this result to show that the average-case hardness of PPAD reduces to the (adaptive) soundness of the Fiat-Shamir Transform, a well-known technique used to compile a public-coin interactive protocol into a non-interactive one. As a corollary, we obtain average-case hardness for PPAD in the random-oracle model assuming the worst-case hardness of #SAT. Moreover, the above results can all be strengthened to obtain average-case hardness for the class CLS ⊆ PPAD. Our main technical contribution is constructing incrementally-verifiable procedures for computing Iterated-Squaring and #SAT. By incrementally-verifiable, we mean that every intermediate state of the computation includes a proof of its correctness, and the proof can be updated and verified in polynomial time. Previous constructions of such procedures relied on strong, non-standard assumptions. Instead, we introduce a technique called recursive proof-merging to obtain the same from weaker assumptions

COLISTIN RESISTANCE IN CARBAPENEM-RESISTANT KLEBSIELLA PNEUMONIAE STRAINS

Objective: There is an increasing use of colistin consequent to increase in the infections caused by carbapenem-resistant Klebsiella pneumoniae.The present study was conducted to determine the minimum inhibitory concentration (MIC) of colistin and the resistance pattern of colistin in carbapenem-resistant K. pneumoniae (CRKP) strains in our intensive care unit (ICU).Methods: Antibiotic susceptibility testing for other antimicrobial agents was done by Kirby-Bauer disk diffusion method. MIC of colistin was determined by agar dilution method. The results of antibiotic susceptibility testing were interpreted as per Clinical Laboratory Standard Institute guidelines 2016 and MIC of colistin were interpreted as per European Committee on Antimicrobial susceptibility testing. The carbapenem resistance was phenotypically detected by modified hodge test and imipenem/imipenem ethylenediaminetetraacetic acid disk method.Results: Out of 518 K. pneumoniae, 329 were resistant to carbapenems, and 91 isolates showed resistance to colistin. The MIC of colistin ranged between 4 and >512 ug/ml and MIC90 was 16 ug/L and MIC50 was 4 ug/ml. A majority of the colistin-resistant isolates were found in multidisciplinary ICU (85/91).Conclusion: The emergence of colistin-resistant strains is a major problem due to limited treatment options for infections caused by CRKP carbapenemase producing K. pneumoniae. Colistin should not be used alone, combination therapy should be preferred

OPTIMIZED USE OF LICENSED CARRIER PRIMARY CELL SPECTRUM WITH NEW RADIO UNLICENSED (NR-U) AND LICENSED-ASSISTED ACCESS (LAA) DEPLOYMENTS

Long-Term Evolution (LTE) and 3rd Generation Partnership Project (3GPP) Fifth Generation (5G) private and public wireless networks are deployed using both licensed spectrum and shared or unlicensed spectrum. Shared or unlicensed spectrum is frequently used in a carrier aggregation (CA) mode where a licensed carrier is aggregated together with an unlicensed carrier. However, CA is commonly enabled only when a user equipment (UE) has a higher volume of download (DL) data that needs to be drained, hence current mechanisms result in the use of a licensed carrier to drain the DL data for the UE with the unlicensed carrier not being used. Furthermore, unlicensed spectrum carriers are often mandated to operate with lower EIRP and hence has limited coverage footprint compared to licensed carrier with higher EIRP, which can better serve the users further away from the cell compared to unlicensed or share spectrum carrier. To address such a challenge, techniques are presented herein that support flexible options for the optimal utilization of both licensed and unlicensed spectrum. Aspects of the presented techniques support the default activation of CA for DL data draining for Licensed-Assisted Access (LAA) or any unlicensed or shared spectrum-capable UEs within a coverage footprint. Further aspects of the presented techniques support an operator configurable threshold for the distribution percentage of the DL data for LAA-capable UEs based on a UEs DL data. The need may be served by different modulation capabilities (such as, for example, 256 quadrature amplitude modulation (QAM)) for a primary cell (PCell) and a secondary cell (SCell) and may be driven by the number of LAA carriers that are configured on an evolved Node B (eNB) and the number of LAA-capable UEs that are under a cell. Further aspects of the presented techniques support the default automated activation of LAA CA for priority users such that any DL data packet, irrespective of burst size and volume, may be drained through an unlicensed carrier when the user device can be served by an LAA carrier

On treewidth, separators and Yao's garbling

We show that Yao’s garbling scheme is adaptively indistinguishable for the class of Boolean circuits of size S and treewidth w with only a S^O(w) loss in security. For instance, circuits with constant treewidth are as a result adaptively indistinguishable with only a polynomial loss. This (partially) complements a negative result of Applebaum et al. (Crypto 2013), which showed (assuming one-way functions) that Yao’s garbling scheme cannot be adaptively simulatable. As main technical contributions, we introduce a new pebble game that abstracts out our security reduction and then present a pebbling strategy for this game where the number of pebbles used is roughly O(d w log(S)), d being the fan-out of the circuit. The design of the strategy relies on separators, a graph-theoretic notion with connections to circuit complexity

Tuberculosis cutis orificialis with underlying pulmonary tuberculosis in an immunocompetent man

Tuberculosis cutis orificialis (TCO) is a rare form of tuberculosis more often secondary to pulmonary tuberculosis. TCO has varied differential diagnoses and thus results in delayed diagnosis and treatment leading to serious consequences. The diagnosis of TCO is confirmed by biopsy and nucleic acid amplification tests in majority of cases. We report a case of TCO with underlying pulmonary tuberculosis in a 50-year-old male, who presented with a painful nonhealing ulcer of the right buccal mucosa. Biopsy and real-time polymerase chain reaction helped in confirming the diagnosis. The patient was treated with antitubercular therapy

MUPIROCIN RESISTANCE IN STAPHYLOCOCCUS AUREUS IN A TERTIARY CARE HOSPITAL OF SOUTH INDIA – A PROSPECTIVE STUDY

Objective: Mupirocin is a topical antibiotic used for the treatment of skin and soft tissue infections caused by Staphylococcus aureus and for the nasal decolonization of methicillin-resistant S. aureus (MRSA). The increasing reports of resistance to mupirocin are a matter of concern. We undertook this study to detect and differentiate the mupirocin resistance pattern and to analyze the susceptibility pattern among S. aureus isolates of our hospital.Methods: This is a prospective laboratory-based study conducted during the period May–September 2014. Clinical samples that grew S. aureus during the study period were tested for mupirocin resistance using the 5 μg and 200 μg discs. Minimum inhibitory concentration (MIC) detection of resistant strains was performed using the E-test.Results: Mupirocin resistance was seen in 4.81% of our S. aureus isolates; all of which exhibited high-level resistance with MIC ≥1024 μg/ml.Conclusions: The resistance is bound to rise with the increased usage of mupirocin; regular testing will help in tackling this upcoming problem and in preserving this important antibiotic against MRSA