414 research outputs found
Recommended from our members
The impact of social and relational contexts on innovation transfer in foreign subsidiaries
It is widely acknowledged that innovation is one of the pillars of multinational enterprises (MNEs) and that
technological knowledge from different host locations is a key factor to the MNEs’ competitive advantages
development. Concerning these assumptions, in this paper we aim to understand how the social and the
relational contexts affect the conventional and reverse transfer of innovation from MNEs’ subsidiaries
hosted in emerging markets. We analyzed the social context through the institutional profile (CIP) level
and the relational context through trust and integration levels utilizing a survey sent to 172 foreign
subsidiaries located in Brazil, as well as secondary data. Through an ordinary least squares regression
(OLS) analysis we found that the relational context affects the conventional and reverse innovation transfer
in subsidiaries hosted in emerging markets. We however did not find support for the social context effect
Fine morphological assessment of quality of human mature oocytes after slow freezing or vitrification with a closed device: a comparative analysis
BACKGROUND:
Human mature oocytes are very susceptible to cryodamage. Several reports demonstrated that vitrification might preserve oocyte better than slow freezing. However, this is still controversial. Thus, larger clinical, biological and experimental trials to confirm this concept are necessary. The aim of the study was to evaluate and compare fine morphological features in human mature oocytes cryopreserved with either slow freezing or vitrification.
METHODS:
We used 47 supernumerary human mature (metaphase II) oocytes donated by consenting patients, aged 27-32 years, enrolled in an IVF program. Thirtyfive oocytes were cryopreserved using slow freezing with 1.5 M propanediol +0.2 M sucrose concentration (20 oocytes) or a closed vitrification system (CryoTip Irvine Scientific CA) (15 oocytes). Twelve fresh oocytes were used as controls. All samples were prepared for light and transmission electron microscopy evaluation.
RESULTS:
Control, slow frozen/thawed and vitrified/warmed oocytes (CO, SFO and VO, respectively) were rounded, 90-100 mum in diameter, with normal ooplasm showing uniform distribution of organelles. Mitochondria-smooth endoplasmic reticulum (M-SER) aggregates and small mitochondria-vesicle (MV) complexes were the most numerous structures found in all CO, SFO and VO cultured for 3-4 hours. M-SER aggregates decreased, and large MV complexes increased in those SFO and VO maintained in culture for a prolonged period of time (8-9 hours). A slight to moderate vacuolization was present in the cytoplasm of SFO. Only a slight vacuolization was present in VO, whereas vacuoles were almost completely absent in CO. Amount and density of cortical granules (CG) appeared abnormally reduced in SFO and VO, irrespective of the protocol applied.
CONCLUSIONS:
Even though, both slow freezing and vitrification ensured a good overall preservation of the oocyte, we found that: 1) prolonged culture activates an intracellular membrane "recycling" that causes the abnormal transformation of the membranes of the small MV complexes and of SER into larger rounded vesicles; 2) vacuolization appears as a recurrent form of cell damage during slow freezing and, at a lesser extent, during vitrification using a closed device; 3) premature CG exocytosis was present in both SFO and VO and may cause zona pellucida hardenin
Freeze/thaw stress induces organelle remodeling and membrane recycling in cryopreserved human mature oocytes
Purpose: Our aim was to evaluate the ultrastructure of human metaphase II oocytes subjected to slow freezing and fixed after thawing at different intervals during post-thaw rehydration. Methods: Samples were studied by light and transmission electron microscopy. Results: We found that vacuolization was present in all cryopreserved oocytes, reaching a maximum in the intermediate stage of rehydration. Mitochondria-smooth endoplasmic reticulum (M-SER) aggregates decreased following thawing, particularly in the first and intermediate stages of rehydration, whereas mitochondria-vesicle (MV) complexes augmented in the same stages. At the end of rehydration, vacuoles and MV complexes both diminished and M-SER aggregates increased again. Cortical granules (CGs) were scarce in all cryopreserved oocytes, gradually diminishing as rehydration progressed. Conclusions: This study also shows that such a membrane remodeling is mainly represented by a dynamic process of transition between M-SER aggregates and MV complexes, both able of transforming into each other. Vacuoles and CG membranes may take part in the membrane recycling mechanism
Fine morphological assessment of quality of human mature oocytes after slow freezing or vitrification with a closed device: a comparative analysis
Alterações clÃnicas e laboratoriais anteriores ao desenvolvimento do delirium tremens
Pituitary block with gonadotrophin-releasing hormone antagonist during intrauterine insemination cycles: a systematic review and meta-analysis of randomised controlled trials
BACKGROUND:
Several randomised controlled trials (RCTs) have investigated the usefulness of pituitary block with gonadotrophin-releasing hormone (GnRH) antagonists during intrauterine insemination (IUI) cycles, with conflicting results.
OBJECTIVE:
The aim of the present systematic review and meta-analysis of RCTs was to evaluate the effectiveness of GnRH antagonist administration as an intervention to improve the success of IUI cycles.
SEARCH STRATEGY:
Electronic databases (MEDLINE, Scopus, EMBASE, Sciencedirect) and clinical registers were searched from their inception until October 2017.
SELECTION CRITERIA:
Randomised controlled trials of infertile women undergoing one or more IUI stimulated cycles with GnRH antagonists compared with a control group.
DATA COLLECTION AND ANALYSIS:
The primary outcomes were ongoing pregnancy/live birth rate (OPR/LBR) and clinical pregnancy rate (CPR). Pooled results were expressed as odds ratio (OR) or mean differences with 95% confidence interval (95% CI). Sources of heterogeneity were investigated through sensitivity and subgroups analysis. The body of evidence was rated using GRADE methodology. Publication bias was assessed with funnel plot, Begg's and Egger's tests.
MAIN RESULTS:
Fifteen RCTs were included (3253 IUI cycles, 2345 participants). No differences in OPR/LBR (OR 1.14, 95% CI 0.82-1.57, P = 0.44) and CPR (OR 1.28, 95% CI 0.97-1.69, P = 0.08) were found. Sensitivity and subgroup analyses did not provide statistical changes in pooled results. The body of evidence was rated as low (GRADE 2/4). No publication bias was detected.
CONCLUSION:
Pituitary block with GnRH antagonists does not improve OPR/LBR and CPR in women undergoing IUI cycles.
TWEETABLE ABSTRACT:
Pituitary block with GnRH antagonists does not improve the success of IUI cycles
Temperature Dependence of Electric Transport in Few-layer Graphene under Large Charge Doping Induced by Electrochemical Gating
The temperature dependence of electric transport properties of single-layer and few-layer graphene at large charge doping is of great interest both for the study of the scattering processes dominating the conductivity at different temperatures and in view of the theoretically predicted possibility to reach the superconducting state in such extreme conditions. Here we present the results obtained in 3-, 4- and 5-layer graphene devices down to 3.5 K, where a large surface charge density up to about 6.8·1014 cm-2 has been reached by employing a novel polymer electrolyte solution for the electrochemical gating. In contrast with recent results obtained in single-layer graphene, the temperature dependence of the sheet resistance between 20 K and 280 K shows a low-temperature dominance of a T2 component - that can be associated with electron-electron scattering - and, at about 100 K, a crossover to the classic electron-phonon regime. Unexpectedly, this crossover does not show any dependence on the induced charge density, i.e. on the large tuning of the Fermi energy
Graphene-based mid-infrared room-temperature pyroelectric bolometers with ultrahigh temperature coefficient of resistance.
There is a growing number of applications demanding highly sensitive photodetectors in the mid-infrared. Thermal photodetectors, such as bolometers, have emerged as the technology of choice, because they do not need cooling. The performance of a bolometer is linked to its temperature coefficient of resistance (TCR, ∼2-4% K-1 for state-of-the-art materials). Graphene is ideally suited for optoelectronic applications, with a variety of reported photodetectors ranging from visible to THz frequencies. For the mid-infrared, graphene-based detectors with TCRs ∼4-11% K-1 have been demonstrated. Here we present an uncooled, mid-infrared photodetector, where the pyroelectric response of a LiNbO3 crystal is transduced with high gain (up to 200) into resistivity modulation for graphene. This is achieved by fabricating a floating metallic structure that concentrates the pyroelectric charge on the top-gate capacitor of the graphene channel, leading to TCRs up to 900% K-1, and the ability to resolve temperature variations down to 15 μK
Temperature Dependence of Electric Transport in Few-layer Graphene under Large Charge Doping Induced by Electrochemical Gating
The temperature dependence of electric transport properties of single-layer
and few-layer graphene at large charge doping is of great interest both for the
study of the scattering processes dominating the conductivity at different
temperatures and in view of the theoretically predicted possibility to reach
the superconducting state in such extreme conditions. Here we present the
results obtained in 3-, 4- and 5-layer graphene devices down to 3.5 K, where a
large surface charge density up to about 6.8x10^14 cm^(-2) has been reached by
employing a novel polymer electrolyte solution for the electrochemical gating.
In contrast with recent results obtained in single-layer graphene, the
temperature dependence of the sheet resistance between 20 K and 280 K shows a
low-temperature dominance of a T^2 component - that can be associated with
electron-electron scattering - and, at about 100 K, a crossover to the classic
electron-phonon regime. Unexpectedly this crossover does not show any
dependence on the induced charge density, i.e. on the large tuning of the Fermi
energy.Comment: 13 pages, 6 color figure
- …