Non-line-of-sight ultraviolet transmission coverage in non-precipitating, foggy, and rainy weather.

Sensitivity to weather conditions is the principal limitation of free-space optical communication. However, for the scattering based ultraviolet (UV) non-line-of-sight (NLOS) communication, the atmospheric scattering effect functions as an attenuation factor and potentially as a performance enhancer. To investigate the UV NLOS transmission coverage under different weather conditions, we employ the Mie Theory in conjunction with classical aerosol and hydrometeor particle models to estimate the absorption coefficient, the scattering coefficient, and the scattering phase function. We then use these atmospheric parameters combined with a range estimation model to determine the coverage of the UV NLOS communication for specified path loss. Simulation results reveal that in non-precipitating weather, poorer visibility correlates with broader coverage. In foggy conditions, the coverage range in light fog exceeds that in fog-free environments; however, as fog intensity increases, the coverage range decreases. Rain enhances the coverage range; and heavier precipitation results in a larger coverage area.

Experimental demonstration of twin-single-sideband signal detection system based on a single photodetector and without optical bandpass filter.

A twin-single-sideband (twin-SSB) signal single-photodiode (PD) detection system without optical bandpass filter is experimentally demonstrated for the first time. After direct detection by a single-ended PD at the receiver side, we can directly separate the optical left sideband (LSB) and right sideband (RSB) using a simple one-path digital signal processing algorithm without separating the two sideband signals using an optical bandpass filter (OBPF), thus achieving lower complexity and low cost while doubling the spectral efficiency. Using our proposed twin-SSB scheme, we demonstrate 1-, 2-, and 4-Gbaud LSB geometric shaping 4-quadrature amplitude modulation and RSB quadrature phase shift keying signal transmission over 10 km of single-mode fiber (SMF). Our experimental results demonstrate that the bit-error rate (BER) of the 4-Gbaud LSB geometric shaping 4-quadrature amplitude modulation (GS-4QAM) and RSB quadrature phase shift keying (QPSK) transmission system is below the 7% hard decision forward error correction threshold.

Dataset for cognition processes, motivations, spatial presence experience, and customer engagement in retail mobile apps.

This article presents data for the estimation of a theory-driven dynamic and contingent model of customer engagement in the context of retail mobile apps. The data were collected from 558 participants who have installed at least one retail mobile app for a minimum of six months and have made relatively frequent purchases using the app. Customer-related data include participants' interactivity and vividness cognitions, spatial presence experience, and engagement behaviors (i.e., customer purchases, referrals, influences, and feedbacks/suggestions) toward retail mobile apps. The data additionally include individuals' tendency/motivation-related variables, such as need for cognition and domain-specific interest, which modulate customers' cognitions as well as affective evaluations that are then followed by their actions. The authors collected the data from early May through mid-July 2020 in three major cities (i.e., Hanoi, Danang, and Ho-Chi-Minh) with leading positions in the Vietnamese eBusiness index. The presented data can be used to investigate the contingency model of driving factors of customer engagement in the context of retail mobile apps and improve the design and functionalities of mobile apps that foster embodied and embedded cognitions, facilitate the feeling of a "real" shopping experience, and ultimately encourage customers to actively engage and effectively contribute to participating retailers. For findings, discussions and further information, please refer to our recent research article: "Customer engagement in the context of retail mobile apps: A contingency model integrating spatial presence experience and its drivers" [1].

Error rate analysis of few-mode fiber based free-space optical communication.

Few-mode fiber (FMF) based receiver emerges as a promising solution for free-space optical (FSO) communication due to its excellent performance in the presence of turbulence. We propose a theoretical model that uses the coupling efficiency of FMF to evaluate the performance of FMF-based FSO system in the presence of turbulence. The series solutions and asymptotic solutions to bit-error rate (BER) of such system are derived for maximal-ratio combining (MRC) scheme and equal gain combining (EGC) scheme over the Gamma-Gamma turbulence channels. Simulation results show that for the FMF-based FSO system, the asymptotic BER of MRC and EGC are highly accurate in the large transmitted optical power regimes.

A CD22-Shp1 phosphatase axis controls integrin ß7 display and B cell function in mucosal immunity.

The integrin α4ß7 selectively regulates lymphocyte trafficking and adhesion in the gut and gut-associated lymphoid tissue (GALT). Here, we describe unexpected involvement of the tyrosine phosphatase Shp1 and the B cell lectin CD22 (Siglec-2) in the regulation of α4ß7 surface expression and gut immunity. Shp1 selectively inhibited ß7 endocytosis, enhancing surface α4ß7 display and lymphocyte homing to GALT. In B cells, CD22 associated in a sialic acid-dependent manner with integrin ß7 on the cell surface to target intracellular Shp1 to ß7. Shp1 restrained plasma membrane ß7 phosphorylation and inhibited ß7 endocytosis without affecting ß1 integrin. B cells with reduced Shp1 activity, lacking CD22 or expressing CD22 with mutated Shp1-binding or carbohydrate-binding domains displayed parallel reductions in surface α4ß7 and in homing to GALT. Consistent with the specialized role of α4ß7 in intestinal immunity, CD22 deficiency selectively inhibited intestinal antibody and pathogen responses.

The influence of vector-borne disease on human history: socio-ecological mechanisms.

Vector-borne diseases (VBDs) are embedded within complex socio-ecological systems. While research has traditionally focused on the direct effects of VBDs on human morbidity and mortality, it is increasingly clear that their impacts are much more pervasive. VBDs are dynamically linked to feedbacks between environmental conditions, vector ecology, disease burden, and societal responses that drive transmission. As a result, VBDs have had profound influence on human history. Mechanisms include: (1) killing or debilitating large numbers of people, with demographic and population-level impacts; (2) differentially affecting populations based on prior history of disease exposure, immunity, and resistance; (3) being weaponised to promote or justify hierarchies of power, colonialism, racism, classism and sexism; (4) catalysing changes in ideas, institutions, infrastructure, technologies and social practices in efforts to control disease outbreaks; and (5) changing human relationships with the land and environment. We use historical and archaeological evidence interpreted through an ecological lens to illustrate how VBDs have shaped society and culture, focusing on case studies from four pertinent VBDs: plague, malaria, yellow fever and trypanosomiasis. By comparing across diseases, time periods and geographies, we highlight the enormous scope and variety of mechanisms by which VBDs have influenced human history.

Privacy preserving with adaptive link selection for hybrid radio-frequency and free space optical networks.

In order to improve the secrecy performance, we propose a secure hybrid radio frequency/free space optical (RF/FSO) transmission scheme that takes advantage of both the RF and FSO channels to protect the privacy messages. In the proposed scheme, Alice adaptively selects RF link or FSO link for information transmission according to the secrecy performance of each link. Considering the priority of the FSO link, we propose two secure transmission policies: the FSO dominant secure (FDS) policy and the secrecy rate optimal (SRO) policy. In the FDS policy, we assign high priority to the FSO link due to its high secrecy performance. Therefore, in this policy, Alice transmits the privacy information through the FSO link when the FSO link is reliable. When the FSO link cannot provide successful transmission, Alice will consider the RF secure transmission. In the SRO policy, Alice optimally selects FSO link or RF link according to the secrecy rates of both the FSO and RF links in each time slot. For both FDS and SRO policies, we analyze the secrecy performances and derive closed-form expressions for the average secrecy rate. Numerical results demonstrate the performance improvement of the proposed policies when compared with the current RF or FSO secure schemes in terms of the average secrecy rate.

Cooperative Micromanipulation Using the Independent Actuation of Fifty Microrobots in Parallel.

Micromanipulation for applications in areas such as tissue engineering can require mesoscale structures to be assembled with microscale resolution. One method for achieving such manipulation is the parallel actuation of many microrobots in parallel. However, current microrobot systems lack the independent actuation of many entities in parallel. Here, the independent actuation of fifty opto-thermocapillary flow-addressed bubble (OFB) microrobots in parallel is demonstrated. Individual microrobots and groups of microrobots were moved along linear, circular, and arbitrary 2D trajectories. The independent addressing of many microrobots enables higher-throughput microassembly of micro-objects, and cooperative manipulation using multiple microrobots. Demonstrations of manipulation with multiple OFB microrobots include the transportation of microstructures using a pair or team of microrobots, and the cooperative manipulation of multiple micro-objects. The results presented here represent an order of magnitude increase in the number of independently actuated microrobots in parallel as compared to other magnetically or electrostatically actuated microrobots, and a factor of two increase as compared to previous demonstrations of OFB microrobots.

Secure transmission for mixed FSO-RF relay networks with physical-layer key encryption and wiretap coding.

In this paper, we propose a secure transmission scheme to protect the confidential messages in a mixed free space optical-radio frequency (FSO-RF) relay network against malicious eavesdroppers. In the proposed scheme, the physical-layer key generation, encryption method and physical-layer wiretap coding are exploited to protect the FSO and RF links. Specifically, the overall transmission is divided into two time slots. In the first time slot, the transmitter and relay of the FSO link utilize the channel reciprocity of the FSO link to generate key packets. In the second time slot, the confidential messages will be securely transmitted from the transmitter to the receiver assisted by the relay over two phases. In the first phase, the transmitter sends the confidential messages to the relay through the FSO link encrypted by the generated key packets. In the second phase, the relay will forward these confidential messages to the receiver through the RF link protected by the physical-layer wiretap coding. For the proposed scheme, the key generation rate can be obtained. In addition, we analyze the performance of the connection outage probability and the secrecy outage probability, and optimally design the target transmission rate and secrecy rate such that the average secrecy rate is maximized. Numerical results are presented to demonstrate the performance superiority of the proposed scheme in terms of the average secrecy rate.

Spatial dimming scheme for optical OFDM based visible light communication.

A new dimming control scheme termed spatial dimming orthogonal frequency division multiplexing (SD-OFDM) is proposed for multiple-input and multiple output OFDM based visible light communication. The basic idea of SD-OFDM is that the illumination can be represented by the number of glared light emitting diodes (LEDs) in an LED lamp. As the biasing level of LEDs does not adjust to represent the required illumination level, the proposed scheme can significantly mitigate the clipping noise compared to analogue dimming schemes. Furthermore, unlike digital dimming schemes that control illumination levels by setting different duty cycles of pulse width modulation, the proposed scheme is always in the "on-state" for varied illumination levels. Both analytical and simulation results indicate that the proposed scheme is an efficient and feasible dimmable scheme.

Effects of haze particles and fog droplets on NLOS ultraviolet communication channels.

The performance of non-line-of-sight ultraviolet (UV) scattering communication depends largely on atmospheric parameters. In this paper, we consider haze, fog, two common types of aerosols, and introduce the density and size of aerosols as variables to study the channel path loss for the UV scattering communications. We modify a Monte-Carlo based multiple-scattering model and provide fitting functions to replace the complex calculations of Mie theory, which can be used to obtain the atmospheric coefficients and phase functions for the aerosols. Simulation results reveal that, given fixed elevation angles, the channel path loss is related to both communication range, the aerosol density, and size of aerosols. For a short communication range, an increase of aerosol density can reduce the path loss, which improves the performance of UV scattering communication. However, when the communication range is extended, the path loss will fall first and then rise with density of aerosols. This phenomenon also occurs for an increase of fog drop size. The density or size of aerosols that has the lowest path loss is inversely proportional to the communication range.

Clinical impact of sample interference on intensive insulin therapy in severely burned patients: a pilot study.

Severely burned patients benefit from intensive insulin therapy (IIT) for tight glycemic control (TGC). The authors evaluated the clinical impact of automatic correction of hematocrit and ascorbic acid interference for bedside glucose monitoring performance in critically ill burn patients. The performance of two point-of-care glucose monitoring systems (GMSs): 1) GMS1, an autocorrecting device, and 2) GMS2, a noncorrecting device were compared. Sixty remnant arterial blood samples were collected in a prospective observational study to evaluate hematocrit and ascorbic acid effects on GMS1 vs GMS2 accuracy paired against a plasma glucose reference. Next, we enrolled 12 patients in a pilot randomized controlled trial. Patients were randomized 1:1 to receive IIT targeting a TGC interval of 111 to 151 mg/dl and guided by either GMS1 or GMS2. GMS bias, mean insulin rate, and glycemic variability were calculated. In the prospective study, GMS1 results were similar to plasma glucose results (mean bias, -0.75 [4.0] mg/dl; n = 60; P = .214). GMS2 results significantly differed from paired plasma glucose results (mean bias, -5.66 [18.7] mg/dl; n = 60; P = .048). Ascorbic acid therapy elicited significant GMS2 performance bias (29.2 [27.2]; P < .001). Randomized controlled trial results reported lower mean bias (P < .001), glycemic variability (P < .05), mean insulin rate (P < .001), and frequency of hypoglycemia (P < .001) in the GMS1 group than in the GMS2 group. Anemia and high-dose ascorbic acid therapy negatively impact GMS accuracy and TGC in burn patients. Automatic correction of confounding factors improves glycemic control. Further studies are warranted to determine outcomes associated with accurate glucose monitoring during IIT.

A laterally-coupled distributed feedback laser with equivalent quarter-wave phase shift.

We report the first laterally-coupled distributed feedback (LC-DFB) laser with a quarter-wave equivalent phase shift (EPS) realized by interference lithography (IL) and conventional photolithography. A specially designed sampled grating is fabricated on both sidewalls of a ridge waveguide to provide a quarter-wave EPS at the center of the cavity. The resulting laser exhibits stable single-mode lasing operation over a wide range of injection currents, with a side mode suppression ratio (SMSR) of 41.1 dB. This provides a practical, low-cost method to fabricate quarter-wave phase shifted DFB lasers with high performance without any epitaxial regrowth or the use of electron-beam lithography, thereby simplifying the fabrication of DFB lasers with stable and precise wavelengths, as single devices or as arrays in photonic integrated circuits.

Ergodic capacity comparison of optical wireless communications using adaptive transmissions.

Ergodic capacity is investigated for the optical wireless communications employing subcarrier intensity modulation with direct detection, and coherent systems with and without polarization multiplexing over the Gamma-Gamma turbulence channels. We consider three different adaptive transmission schemes: (i) variable-power, variable-rate adaptive transmission, (ii) complete channel inversion with fixed rate, and (iii) truncated channel inversion with fixed rate. For the considered systems, highly accurate series expressions for ergodic capacity are derived using a series expansion of the modified Bessel function and the Mellin transformation of the Gamma-Gamma random variable. Our asymptotic analysis reveals that the high SNR ergodic capacities of coherent, subcarrier intensity modulated, and polarization multiplexing systems gain 0.33 bits/s/Hz, 0.66 bits/s/Hz, and 0.66 bits/s/Hz respectively with 1 dB increase of average transmitted optical power. Numerical results indicate that a polarization control error less than 10° has little influence on the capacity performance of polarization multiplexing systems.

Bladder dysfunction changes from underactive to overactive after experimental traumatic brain injury.

Although bladder dysfunction is common after traumatic brain injury (TBI), few studies have investigated resultant bladder changes and the detailed relationship between TBI and bladder dysfunction. The goal of this study was to characterize the effects of TBI on bladder function in an animal model. Fluid-percussion injury was used to create an animal model with moderate TBI. Female Sprague-Dawley rats underwent TBI, sham TBI or were not manipulated (naïve). All rats underwent filling cystometry while bladder pressure and external urethral sphincter electromyograms were simultaneously recorded 1 day, 1 week, 2 weeks, and 1 month after injury. One day after injury, 70% of the animals in the TBI group and 29% of the animals in the sham TBI group showed no bursting activity during urination. Compared to naïve rats, bladder function was mainly altered 1 day and 1 week after sham TBI, suggesting the craniotomy procedure affected bladder function mostly in a temporary manner. Compared to either naïve or sham TBI, bladder weight was significantly increased 1 month after TBI and collagen in the bladder wall was increased. Bladder function in the TBI group went from atonic 1 day post-TBI to overactive 1 month post-TBI, suggesting that TBI significantly affected bladder function.

Performance analysis of coherent wireless optical communications with atmospheric turbulence.

Coherent wireless optical communication systems with heterodyne detection are analyzed for binary phase-shift keying (BPSK), differential PSK (DPSK), and M-ary PSK over Gamma-Gamma turbulence channels. Closed-form error rate expressions are derived using a series expansion approach. It is shown that, in the special case of K-distributed turbulence channel, the DPSK incurs a 3 dB signal-to-noise ratio (SNR) penalty compared to BPSK in the large SNR regime. The outage probability is also obtained, and a detailed outage truncation error analysis is presented and used to assess the accuracy in system performance estimation. It is shown that our series error rate expressions are simple to use and highly accurate for practical system performance estimation.

Moment-based estimation for the shape parameters of the Gamma-Gamma atmospheric turbulence model.

We study the parameter estimation problem for the Gamma-Gamma turbulence model for free-space optical communication. An estimation scheme for the shape parameters of the Gamma-Gamma distribution is proposed based on the concept of fractional moments and convex optimization. To improve the estimation performance, we further propose a modified scheme which exploits the relationship between the Gamma-Gamma shape parameters in free-space optical communication. Simulation results reveal that the modified estimation scheme can achieve satisfactory performance for a wide range of turbulence conditions.

Exact error rate analysis of equal gain and selection diversity for coherent free-space optical systems on strong turbulence channels.

Exact error rate performances are studied for coherent free-space optical communication systems under strong turbulence with diversity reception. Equal gain and selection diversity are considered as practical schemes to mitigate turbulence. The exact bit-error rate for binary phase-shift keying and outage probability are developed for equal gain diversity. Analytical expressions are obtained for the bit-error rate of differential phase-shift keying and asynchronous frequency-shift keying, as well as for outage probability using selection diversity. Furthermore, we provide the closed-form expressions of diversity order and coding gain with both diversity receptions. The analytical results are verified by computer simulations and are suitable for rapid error rates calculation.

A study of the perceived recognition affecting the adoption of innovation with respect to the online game in Taiwan.

The potential of online games to become a major global business and the existence of limited related references led to the current study. In this study, Rogers's diffusion of innovation (DOI) theory is applied to investigate the principles for the adoption of online games in Taiwan. The findings suggest that relative advantages and compatibility both have a significant effect on the adoption of online games for purposes of amusement, with the former being more important for early gamers and the latter being regarded as more critical for later gamers. In addition, complexity is found to impede online game diffusion and is regarded as the most important facilitator.