Experimentation and Start-up Performance: Evidence from A/B Testing

Recent scholarship argues that experimentation should be the organizing principle for entrepreneurial strategy. Experimentation leads to organizational learning, which drives improvements in firm performance. We investigate this proposition by exploiting the time-varying adoption of A/B testing technology, which has drastically reduced the cost of testing business ideas. Our results provide the first evidence on how digital experimentation affects a large sample of high-technology start-ups using data that tracks their growth, technology use, and products. We find that, although relatively few firms adopt A/B testing, among those that do, performance improves by 30%–100% after a year of use. We then argue that this substantial effect and relatively low adoption rate arises because start-ups do not only test one-off incremental changes, but also use A/B testing as part of a broader strategy of experimentation. Qualitative insights and additional quantitative analyses show that experimentation improves organizational learning, which helps start-ups develop more new products, identify and scale promising ideas, and fail faster when they receive negative signals. These findings inform the literatures on entrepreneurial strategy, organizational learning, and data-driven decision making. This paper was accepted by Toby Stuart, entrepreneurship and innovation.

Investigating the effect of an open window vs. a closed window on the concentrations of suspended particulate matter in the indoors with respect to the outdoors

A study was conducted to see the effect of an opened window vs. a closed window in New Delhi in peak winters. This is the time when the PM 2.5 and PM 10 concentrations are the highest in the ambient air due to various external factors. A PM 2.5 and PM 10 air quality meter was used at a singular location near the window for 10 days with 9 readings taken during the daily working hours. Contrary to the possible conjectural belief, it was found that the window opened or closed did not have a substantial effect on the concentrations of the indoor levels of PM 2.5 and PM 10. The results showed that opening of the windows does not substantially affect the levels of the indoors with respect to the levels of PM 2.5 and PM 10 in the outdoors. Outdoors may provide the source of the particulate matter in the indoor, but due to diffusive effect, open windows play a key role in the reducing the indoor levels. This study was reconfirmed with options where the windows were opened and then closed and vice-versa. In all cases, the effect of the outdoor was not visible. To curb indoor particulate matter levels, isolation is not the solution. (200 words)

Effect of the Extended Rigid Flapping Trailing Edge Fringe on an S833 Airfoil

A 2D numerical simulation was conducted to investigate the effect of an extended rigid trailing edge fringe with a flapping motion on the S833 airfoil and its wake flow field, as an analogy of an owl’s wing. This study aims to characterize the influence of the extended flapping fringe on the aerodynamic performance and the wake flow characteristics downstream of the airfoil. The length (Le) and flapping frequencies (fe) of the fringe are the key parameters that dominate the impact on the airfoil and the flow field, given that the oscillation angular amplitude is fixed at 5°. The simulation results demonstrated that the airfoil with an extended fringe of 10% of the chord at a flapping frequency of fe = 110 Hz showed a substantial effect on the pressure distribution on the airfoil and the flow characteristics downstream of the airfoil. An irregular vortex street was predicted downstream, thus causing attenuations of the vorticities, and shorter streamwise gaps between each pair of vortices. The extended flapping fringe at a lower frequency than the natural shedding vortex frequency can effectively break the large vortex structure up into smaller scales, thus leading to an accelerated attenuation of vorticities in the wake.

Changes in Electroencephalographic Results and Heart Rate Variability after Exposure to Green Landscape Photographs Correlated with Color Temperature and Illumination Level

Background and objective: Various images from visual display terminals (VDTs) as well as living lighting are important parts of our daily life; thus, properly controlling the lighting environment – that is, illuminance, color temperature and good images from VDTs – can have a substantial effect on improving the mental health and work efficiency in everyday life. We examined electroencephalography (EEG) and heart rate variability (HRV) responses to various lighting conditions in 25 university students as they viewed images of a green landscape or traffic congestion.Methods: EEG was performed in darkness and when the room was illuminated with 10 different light-emitting diode (LED) color temperatures, while the EEG and HRV responses to green landscape or traffic congestion image stimuli were measured in darkness and during room illumination with three different LED color temperatures.Results: We found a significant difference between darkness and high LED illumination (400 lx) at 7 (CZ, F4, FZ, O1, O2, OZ, and T6) of 30 channels, while the alpha wave activity increased during darkness. In the second experiment, the green landscape image stimuli in the 30 lx–2600 K lighting condition elicited theta wave activity on the EEG, whereas the traffic congestion image stimuli under high LED illumination elicited high beta and gamma wave activities. Moreover, the subjects exhibited better stress coping ability and heart rate stability in response to green landscape image stimuli under illuminated conditions, according to their HRV.Conclusion: These results suggest that lower color temperatures and illumination levels alleviate tension, and that viewing green landscape image stimuli at low illumination, or in darkness, is effective for reducing stress. Conversely, high illumination levels and color temperatures are likely to increase tension and stress in response to traffic congestion image stimuli.

Effects of maternal exposure to acute stress on birth outcomes: a quasi-experiment study

Numerous studies have shown associations between maternal stress and poor birth outcomes, but evidence is unclear for causal inference. Natural disasters provide an opportunity to study effects of quasi-randomized hardship with an accurate measure of onset and duration. In a population-based quasi-experimental study, we examined the effect of maternal exposure to the January 1998 Québec ice storm on birth outcomes by comparing pregnant mothers who lived in an area hard hit by the ice storm with those in two unaffected regions. In a total of 147,349 singleton births between 1995 and 2001, we used a difference-in-differences method to estimate the effects of the ice storm on gestational age at delivery (GA), preterm birth (PTB), weight-for-gestational-age z-scores (BWZ), large for gestational age (LGA), and small for gestational age (SGA). After adjusting for maternal and sociodemographic characteristics, there were no differences between the exposed and the unexposed mothers for birth outcomes. The estimated differences (exposed vs. unexposed) were 0.01 SDs (95% CI: −0.02, 0.05) for BWZ; 0.10% point (95% CI: −0.95%, 1.16%) for SGA; 0.25% point (95% CI: −0.78%, 1.28%) for LGA; −0.01 week (95% CI: −0.07, 0.05) for GA; and 0.16% point (95% CI: −0.66%, 0.97%) for PTB. Neither trimester-specific nor dose–response associations were observed. Overall, exposure to the 1998 Québec ice storm as a proxy for acute maternal stress in pregnancy was not associated with poor birth outcomes. Our results suggest that acute maternal hardship may not have a substantial effect on adverse birth outcomes.

Delayed-Onset Neuropathic Pain after Septoplasty

Postoperative pain following a septoplasty is expected to be mild and limited to a few days after the operation. Chronic pain following the procedure is rare. No cases of delayed-onset neuropathic pain or allodynia have been described in the literature. This paper presents a case of delayed-onset neuropathic pain after septoplasty in a previously pain-free asthmatic patient that was successfully managed by administration of intranasal local anaesthesia. Physical examination and imaging excluded any other cause of neuralgia. A literature review revealed reports of chronic pain in patients following septoplasty if there were nasal contact or compression points or nasal tumours. Separately, acute postseptoplasty allodynia is documented in iatrogenic maxillary nerve damage. However, delayed-onset neuralgic pain, exacerbated by certain environmental triggers, has not been previously described. Facial pain can be debilitating; successfully managing this neuralgic pain with administration of intranasal local anaesthetic had a substantial effect on the patient’s quality of life.

Agronomic responses of diverse bread wheat genotypes to phosphorus levels and nitrogen forms in a semiarid environment

Increasing wheat production has become an urgent requirement to cope with rapid population growth and abrupt climate change. The management of phosphorus (P) and nitrogen (N) is one of the most important factors for sustaining and increasing wheat production, particularly in semiarid environments. This 2-year field study, which aimed to investigate the effect of P levels (0, 35, and 70 kg P2O5 ha−1) and N forms (urea, ammonium sulfate, and ammonium nitrate) on the yield attributes of three diverse high-yielding commercial wheat cultivars (‘Shandawel-1’, ‘Sids-14’, and ‘Sakha-95’), was carried out at Om-Elzain Village, Zagazig, Egypt. The results indicated that increasing P levels was accompanied by a substantial increase in all evaluated traits, except spike length, and that high P level (70 kg P2O5 ha−1) was superior. Considerable genetic variation was detected among the evaluated cultivars for all studied traits. Cultivar ‘Sakha-95’, followed by ‘Sids-14’, presented the most vigorous growth and enhancements in most yield components, grain yield, and biological yield. Furthermore, ‘Sakha-95’ recorded the highest agronomic P use efficiency, followed by cultivar ‘Sids-14’. N forms did not significantly affect all of the tested traits except plant height, spike number m−2, and 1000-grain weight, during both seasons. Ammonium-containing fertilizer (ammonium sulfate and ammonium nitrate) resulted in the highest values for these traits when compared with urea. Accordingly, ‘Sakha-95’ and ‘Sids-14’ are recommended for commercial use under high P levels. N forms had a marginally substantial effect on grain yield and its attributes.

Digital psychiatry: implications for patients and services

The COVID-19 pandemic has resulted in an increased burden on all medical services and healthcare professionals are applying new strategies to cope with the added demands. During the pandemic mental healthcare services in many parts of the world have been reorganised to incorporate modern technology and maintain efficient service delivery. Mental health professionals are playing a major role in alleviating the suffering resulting from this pandemic. A selective survey of the literature, including narrative reviews, was carried out to study the implications of digital psychiatry. Historically, epidemics have had a substantial effect on mental health and general health services. Telehealth appears to be the right solution to the present mental health crisis, but technology cannot substitute for human presence and proximity in mental health services, so the newer interventions have advantages and disadvantages. Remote methods of therapy are likely to continue to be used and proper assessment of these new ways of working in psychiatry is required. In the post-pandemic period, the challenge will be to combine digital and in-person therapies. Discussions about digital revolution in the field of psychiatry should be modified to digital evolution.

Response Surface Approach to Optimize the Conditions of Foam Mat Drying of Plum in relation to the Physical-Chemical and Antioxidant Properties of Plum Powder

This research was done to optimize the influence of various egg albumin (EA) concentrations of 2, 4, and 6% as a foaming agent and whipping times of 5, 10, and 15 minutes, on physicochemical and antioxidant properties of plum powder produced using response surface methodology (RSM). Physical properties of the foam such as density, porosity, and expansion were determined. After drying and powder manufacturing, physical properties, namely, the water absorption index (WAI) and water solubility index (WSI), as well as chemical characteristics such as pH, titratable acidity, and browning index, were assessed. Finally, antioxidant capabilities such as the total phenol content (TPC), DPPH scavenging activity, beta carotene, and total flavonoid content (TFC) were measured. According to the findings, both whipping duration and EA concentration had a substantial effect on the foam forming characteristics. Foam expansion increased significantly with EA concentration and whipping time increase, but foam density exhibited an inverse relationship as expected. Increases in EA concentration and whipping duration both raised pH values whereas titratable acidity exhibited an inverse tendency as variable quantity rose. The browning index dropped as EA concentration increased. Antioxidant qualities were retained in dried sample powder as compared with the fresh sample, and they were also altered by variable changes. Overall, a 4% EA concentration for 10 to 15 minutes produced the best dehydration effects with the most antioxidant retention.

Elastic electron scattering with CH2Br2 and CCl2Br2: The role of the polarization effects

We present elastic electron scattering cross sections with holmethane molecules CH2Br2 and CCl2Br2 in the low energy region ranging from 0.01 to 20 eV. The calculations are performed with R-matrix method in static-exchange plus polarization (SEP) and close-coupling (CC) approximations. The integral, differential, and momentum transfer cross sections are calculated. The convergence of the obtained cross sections is checked at four different levels of SEP approximation. The predicted positions of the resonances agree well with available results. The precise resonance parameters are found to be sensitive to the treatment of polarization effects employed. We found that the polarization has a substantial effect on the cross sections, and this effect becomes even more important for lower impact energies.