Validation and application of a standardized procedure for evaluating freshness of Citrus juices based on pectin methylesterase activity quantitation

A method developed for freshness authentication of freshly squeezed Citrus juices (FSCJ) was evaluated for routine application. It involved titrimetric assessment of pectin methylesterase (PE) activity after enzyme extraction from pulp-standardized juice samples. Standard test conditions enabled reliable discrimination between FSCJ and chilled Citrus juices that had comparative advantages due to extended shelf life. Unlike the latter, FSCJ always displayed PE activities in the linear range between the limit of identification (LOI, 0.42 units g-1 of juice) and the maximum activity found for FSCJ (1.94 units -1), equivalent to 0.0035-0.016 units during titration. However, for model samples having activities < LOI due to production by respective dilution of FSCJ, the responses abruptly fell to unspecific levels below the limit of detection (LOD, 0.21 units g-1). Accuracy was substantiated by 100 -106 % recovery for model juices with PE activities of 0.87 -1.22 units g-1 resulting from FSCJ dilution or PE standard addition, but it was lower (76 - 80 %) near LOI. The average of the mean activities, which were detected by 3 analysts with intraassay precision ≤ 8.4 %, varied with relative standard deviations of 8.2 % for FSCJ and 3.9 % for a sample of the same juice diluted to 60 % (w/w), thus proving reproducibility. FSCJ batches were unambiguously distinguished from four commercial chilled juices, because the activities detected for the latter were by far ≤ LOD and thus confirmed labeled mild preservation

LPWAN Technologies: Emerging Application Characteristics, Requirements, and Design Considerations

Low power wide area network (LPWAN) is a promising solution for long range and low power Internet of Things (IoT) and machine to machine (M2M) communication applications. This paper focuses on defining a systematic and powerful approach of identifying the key characteristics of such applications, translating them into explicit requirements, and then deriving the associated design considerations. LPWANs are resource-constrained networks and are primarily characterized by long battery life operation, extended coverage, high capacity, and low device and deployment costs. These characteristics translate into a key set of requirements including M2M traffic management, massive capacity, energy efficiency, low power operations, extended coverage, security, and interworking. The set of corresponding design considerations is identified in terms of two categories, desired or expected ones and enhanced ones, which reflect the wide range of characteristics associated with LPWAN-based applications. Prominent design constructs include admission and user traffic management, interference management, energy saving modes of operation, lightweight media access control (MAC) protocols, accurate location identification, security coverage techniques, and flexible software re-configurability. Topological and architectural options for interconnecting LPWAN entities are discussed. The major proprietary and standards-based LPWAN technology solutions available in the marketplace are presented. These include Sigfox, LoRaWAN, Narrowband IoT (NB-IoT), and long term evolution (LTE)-M, among others. The relevance of upcoming cellular 5G technology and its complementary relationship with LPWAN technology are also discussed

UAS Detection and Negation

Unauthorized operation of a UAV may present privacy or security risks. A software-defined radio (SDR) or other receiver can be used to monitor a specified range of frequencies to provide detection of wireless communication signals suspected of relating to UAV operation. A protocol detector corresponding to a trained classifier can be applied to data packets demodulated by the SDR. A transmitter can then be triggered to provide warnings by injecting warning data into a video channel in response to the detected protocol. Control of the UAV can be established by transmitting simulated control commands that overwhelm the signals received from the UAVs normal remote control. If transmission of warnings or simulated control signals fail to suppress unwanted UAV operation, other actions can be triggered such as jamming or dispatch of an interceptor such as a surveillance UAV

Transceivers as a Resource: Scheduling Time and Bandwidth in Software-Defined Radio

In the future, software-defined radio may enable a mobile device to support multiple wireless protocols implemented as software applications. These applications, often referred to as waveform applications, could be added, updated, or removed from a software-radio device to meet changing demands. Current software-defined radio solutions grant an active waveform exclusive ownership of a specific transceiver or analog front-end. Since a wireless device has a limited number of front-ends, this approach puts a hard constraint on the number of concurrent waveform applications a device can support. A growing trend in software-defined radio research is to virtualize front-ends to allow sharing and reuse among active waveform applications. This poses a difficult scheduling challenge. This article proposes a new approach in which shared access to front-ends is managed by a mixed-integer linear programming model. This model ties together the technique of time-division sharing and front-end bandwidth channelization. This scheduling model is evaluated in simulation under several different scenarios and workloads. Simulation results show that the proposed approach reduces hardware contention and missed radio accesses compared to existing techniques

Physical Layer Approach for Securing RFID Systems

Radio Frequency IDentification (RFID) is a contactless, automatic identification wireless technology primarily used for identifying and tracking of objects, goods and humans. RFID is not only limited to identification and tracking applications. This proliferating wireless technology has been deployed in numerous securities sensitive applications e.g. access control, e-passports, contactless payments, driver license, transport ticking and health cards. RFID inherits all the security and privacy problems that are related to wireless technology and in addition to those that are specific to RFID systems. The security and privacy protection schemes proposed in literature for wireless devices are mostly secured through symmetric/asymmetric keys encryption/decryption and hash functions. The security of all these cryptographic algorithms depends on computationally complex problems that are hard to compute using available resources. However, these algorithms require cryptographic operations on RFID tags which contradict the low cost demand of RFID tags. Due to limited number of logic gates in tags, i.e., 5K-10K, these methods are not practical. Much research effort has done in attempt to solve consumer's privacy and security problem. Solutions that prevent clandestine inventory are mostly application layer techniques. To solve this problem, a new RFID physical layer scheme has been proposed namely Direct Sequence Backscatter Encryption (DSB Enc). The proposed scheme uses level generator to produce different levels before transmitting the signal to the tag. The tag response to the signal sent by the reader using backscatter communications on the same signal which looks random to the eavesdropper. Therefore eavesdropper cannot extract the information from reader to tag and tag to reader communication using passive eavesdropping. As reader knows the different generated levels added to the carrier signal, it can remove the levels and retrieve the tag's messages. We proposed a lightweight, low-cost and practically secure physical layer security to the RFID system, for a supply chain processing application, without increasing the computational power and tag's cost. The proposed scheme was validated by simulations on GNU Radio and experimentation using SDR and a WISP tag. Our implementation and experimental results validate that DSB Enc is secure against passive eavesdropping, replay and relay attacks. It provides better results in the presence of AWGN channel.1 yea

Greening and Optimizing Energy Consumption of Sensor Nodes in the Internet of Things through Energy Harvesting: Challenges and Approaches

This paper presents a survey of current energy efficient technologies that could drive the IoT revolution while examining critical areas for energy improvements in IoT sensor nodes. The paper reviews improvements in emerging energy techniques which promise to revolutionize the IoT landscape. Moreover, the current work also studies the sources of energy consumption by the IoT sensor nodes in a network and the metrics adopted by various researchers in optimizing the energy consumption of these nodes. Increasingly, researchers are exploring better ways of sourcing sufficient energy along with optimizing the energy consumption of IoT sensor nodes and making these energy sources green. Energy harvesting is the basis of this new energy source. The harvested energy could serve both as the principal and alternative energy source of power and thus increase the energy constancy of the IoT systems by providing a green, sufficient and optimal power source among IoT devices. Communication of IoT nodes in a heterogeneous IoT network consumes a lot of energy and the energy level in the nodes depletes with time. There is the need to optimize the energy consumption of such nodes and the current study discusses this as well

Revealing the Secrets of Radio-Enabled Embedded Systems: on extraction of raw information from any on-board signal through RF

In this work we are interested in evaluating the possibility of extracting information from radio-enabled embedded-systems from a long distance. That is, our focus is capturing information from sources in the micrometer to tens of centimeters scale, such as intra- or inter- device busses, board-level routing traces etc. Moreover, we focus on distances in the range of millimeters to tens of centimeters from the (on-chip or on-board) embedded-system Tx Antenna to the signal source. Side-channels denotes presence of information in illegitimate channels. Side-channel analysis (SCA) attacks typically require statistical analysis and many leakage traces, focusing on micrometer level signals (sources) which emanate direct Near-Field information up to centimeters-level distances. In the same context (Near-Field and micrometer-level) simple power analysis (SPA) like attacks typically extract either direct raw information from one or few leakages or utilize statistical analysis on various samples from the same trace, similarly to horizontal attacks. Lately, radio-enabled systems were shown to emanate to a large distance (Far-Field), information from micrometer level sources, such as CPU processing, through the RF Tx Antenna: so far, SCA-like statistical analysis were shown. On the other hand, various reports exist on direct information eavesdropping/ sniffing or data exfiltration, emanated from centimeter to tens of centimeters scale sources, e.g., SATA, USB, Power-lines, Serial interface, Air-Gap systems, Screens and even optical fibers. All these elements are typically being used as a source and a direct Tx Antenna (huge, several to tens of centimeters) of the sensitive information. These antennas typically transmit information to short distances and the decay is very steep (proportional to $r^{-2}$-$r^{-3}$ depending on various factors and models). To the best of our knowledge, we report here for the first time an alarming security challenge: any signal in the embedded system, from serial ports, DMA-controlled memory-access, JTAG and SPI interfaces, on-board signals with galvanic connection to the Tx Antenna-chip and \emph{on-board signals without galvanic connection to the Tx Antenna-chip itself, all leak direct information up to tens of centimeters from source to the Tx Antenna}. This alarming situation induce signal-integrity implications within the embedded system, and significant implications relating to device-isolation and user-isolation, it may also affect standards and specifications for e.g., electromagnetic compatibility (EMC), on-board signal shielding, electromagnetic and RF interference (EMI, RFI), cross-talk, and generally design-for-manufacturing (DFM) guidelines for both intra-IC and PCB board. We demonstrate such direct readout of signals with commercial and low-cost equipment indicating how problematic the situation is. The existence of such leakage is demonstrated both over an ultra-low-cost platform such as the nRF52832(nRF) embedded-system and on a more advanced ESP32-c3-devkitc-02 board which is far more widespread in ISM radio applications and meets certification like FCC and CE (as compared to the nRF device). We have constructed an experiment to demonstrate leakage scenarios from (1) on- and (2) off-chip, on-board or (3) signals without galvanic connection to the RF front-end chip, showing the severity of the leakage, repetitively and systematic nature of the phenomena over various devices. We further demonstrate how sophisticated adversaries can build a code-injection Gadget which can carry sensitive-data and modulate it to be best extracted by the RF-channel. The main observation we push forward is that unless concrete interference and isolation standards appear with security metrics in mind, which are significantly different than ones needed for communication, it would be hard to prevent such leakages

Immigration in High-Skill Labor Markets: The Impact of Foreign Students on the Earnings of Doctorates

The rapid growth in the number of foreign students enrolled in American universities has transformed the higher education system, particularly at the graduate level. Many of these newly minted doctorates remain in the United States after receiving their doctoral degrees, so that the foreign student influx can have a significant impact in the labor market for high-skill workers. Using data drawn from the Survey of Earned Doctorates and the Survey of Doctoral Recipients, the study shows that a foreign student influx into a particular doctoral field at a particular time had a significant and adverse effect on the earnings of doctorates in that field who graduated at roughly the same time. A 10 percent immigration-induced increase in the supply of doctorates lowers the wage of competing workers by about 3 to 4 percent. About half of this adverse wage effect can be attributed to the increased prevalence of low-pay postdoctoral appointments in fields that have softer labor market conditions because of large-scale immigration.