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Microphotoluminescence spectroscopy of single CdTe/ZnTe quantum dots grown on Si(001) substrates
Lee, H S,Rastelli, A,Benyoucef, M,Ding, F,Kim, T W,Park, H L,Schmidt, O G IOP Pub 2009 Nanotechnology Vol.20 No.7
<P>We have studied the emission properties of single CdTe/ZnTe quantum dots (QDs) grown on Si(001) substrates by using molecular beam epitaxy and atomic layer epitaxy. The good quality of the QDs is attested by the resolution-limited emission, negligible background and absence of measurable spectral jitter or blinking. Power-dependent, polarization-dependent, and temperature-dependent microphotoluminescence spectroscopy measurements were performed to identify the exciton, the biexciton, and two oppositely charged excitons in the emission spectra of single QDs.</P>
Insights into the Early Growth of Homogeneous Single-Layer Graphene over Ni–Mo Binary Substrates
Rü,mmeli, Mark H.,Zeng, Mengqi,Melkhanova, Svetlana,Gorantla, Sandeep,Bachmatiuk, Alicja,Fu, Lei,Yan, Chenglin,Oswald, Steffen,Mendes, Rafael G.,Makarov, Denys,Schmidt, Oliver,Eckert, Jü,r American Chemical Society 2013 Chemistry of materials Vol.25 No.19
<P>The employment of Ni–Mo films has recently been shown to yield strictly homogeneous single-layer graphene. In this study, we systematically investigate the different stages of nucleation and growth of graphene over Ni–Mo layers. The studies reveal that the Ni film breaks up and diffuses into the underlying Mo foil, forming a Ni–Mo intermetallic. Nucleation only occurs from Ni sites, and thus, the nucleation density can be controlled by the Ni film thickness. Both nucleation and growth of the graphene are shown to be susceptible to very efficient self-termination processes to the formation of molybdenum carbide, and this guarantees the formation of large area graphene that consists <I>entirely</I> of monolayer graphene.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2013/cmatex.2013.25.issue-19/cm4020783/production/images/medium/cm-2013-020783_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm4020783'>ACS Electronic Supporting Info</A></P>
Cho, W. B.,Yim, J. H.,Choi, S. Y.,Lee, S.,Schmidt, A.,Steinmeyer, G.,Griebner, U.,Petrov, V.,Yeom, D.-I.,Kim, K.,Rotermund, F. WILEY-VCH Verlag 2010 Advanced Functional Materials Vol.20 No.12
<P>Single-walled carbon-nanotube absorbers are experimentally demonstrated for laser mode-locking. A saturable absorber device is used to mode-lock three different bulk solid-state lasers in a 500 nm-wide wavelength interval. The devices exhibit a low saturation fluence of <10 mu J cm(-2), low scattering losses, and an exceptionally rapid relaxation, with time constants reaching <100 fs. The latter two properties are explained by a decreased curling tendency and increased tube-to-tube interactions of the nanotubes, respectively. These properties are the result of an optimized manufacturing procedure in combination with the use of a starting material with a higher microscopic order. The decreased scattering enables universal use of these devices in bulk solid-state lasers, which tend to be highly sensitive against non-saturable device losses as caused by scattering. The favorable saturable absorption properties are experimentally verified by mode-locking the three lasers, which all exhibit near transform-limited performance with about 100 fs pulse duration. The complete and unconditional absence of Q-switching side bands verifies the small saturation fluence of these devices.</P>
Lee, Y.-A.,Kim, Y.-H.,Ha, S.-J.,Kim, K.-J.,Kim, B.-J.,Kim, B.-G.,Choi, S.-H.,Kim, I.-C.,Schmidt, J. A.,Ryu, B.-Y. American Society of Animal Science 2014 Journal of Animal Science Vol.92 No.3
<P>Spermatogonial stem cells provide the foundation for continued adult spermatogenesis and their manipulation can facilitate assisted reproductive technologies or the development of transgenic animals. Because the pig is an important agricultural and biomedical research animal, the development of practical application techniques to manipulate the pig Spermatogonial stem cell is needed. The ability to preserve porcine Spermatogonial stem cell or testis tissue long term is one of these fundamental techniques. The objective of this study was to optimize methods to cryopreserve porcine Spermatogonial stem cell when freezing testis cells or testis tissue. To identify the most efficient cryopreservation technique, porcine testis cells (cell freezing) or testis tissue (tissue freezing) were frozen in medium containing dimethyl sulfoxide (DMSO) and fetal bovine serum (FBS) or DMSO, FBS, and various concentrations of trehalose (50, 100, or 200 m<I>M</I>). After thawing, undifferentiated germ cells were enriched and treatments were evaluated for cryopreservation efficiency. The tissue freezing method resulted in significantly greater germ cell recovery (<I>P</I> = 0.041) and proliferation capacity (<I>P</I> < 0.001) compared to the cell freezing treatment. Regardless of freezing method (cell vs. tissue), addition of 200 m<I>M</I> trehalose to freezing medium increased germ cell recovery and proliferation capacity compared to cells frozen using the same freezing method without trehalose. Interestingly, addition of trehalose to the tissue freezing medium significantly increased germ cell recovery (<I>P</I> = 0.012) and proliferation capacity (<I>P</I> = 0.004) compared to the cell freezing treatment supplemented with trehalose. To confirm that cryopreservation in trehalose improves the survival of Spermatogonial stem cell, testis cells enriched for undifferentiated germ cells were xenotransplanted into recipient mouse testes. Germ cells recovered from tissue frozen with 200 m<I>M</I> trehalose generated significantly more (<I>P</I> < 0.001) donor derived colonies than tissue frozen without trehalose. Regardless of cryopreservation medium or freezing method, testis cell recovery, viability, and proliferation capacity of germ cells after thawing were significantly lower compared to those of untreated fresh control. Nevertheless, these data demonstrate that undifferentiated porcine germ cells can be efficiently cryopreserved in the presence of 200 m<I>M</I> trehalose.</P>
Lentiviral modification of enriched populations of bovine male gonocytes
Kim, K.-J.,Cho, C. M.,Kim, B.-G.,Lee, Y.-A.,Kim, B.-J.,Kim, Y.-H.,Kim, C. G.,Schmidt, J. A.,Ryu, B.-Y. American Society of Animal Science 2014 Journal of Animal Science Vol.92 No.1
<P>Undifferentiated germ cells have the capacity to develop into sperm capable of fertilizing oocytes and contributing genetic material to subsequent generations. The most primitive prepubertal undifferentiated germ cells include gonocytes and undifferentiated spermatogonia, including spermatogonial stem cells (SSC). Gonocytes, present in the testis at birth, differentiate into SSC, which maintain spermatogenesis for the remainder of the male’s life. Because of their capacity to contribute to lifelong spermatogenesis, undifferentiated germ cells are attractive targets for genetic modification to produce transgenic animals, including cattle. To maximize the efficiency of genetic modification of bovine gonocytes and SSC, effective enrichment techniques need to be developed. Selection of bovine gonocytes using differential plating was improved 8-fold (<I>P</I> < 0.001) when using a combination of extracellular matrix proteins, including laminin, fibronectin, collagen type IV, and gelatin, compared to using laminin and gelatin alone. Selected cells labeled with PKH26 formed colonies of donor-derived germ cells after transplantation into recipient mouse testes, indicating putative stem cell function. Significantly more colonies (<I>P</I> < 0.001) per 1 × 10<SUP>5</SUP> viable transplanted cells were formed from isolated nonadherent cells (203 ± 23.2) compared to adherent (20 ± 2.7) or Percoll (45.5 ± 4.5) selected cells. After selection, some gonocytes were transduced using a lentiviral vector containing the transgene for the enhanced green fluorescent protein. Transduction efficiency was 17%. Collectively, these data demonstrate effective methods for the selection and genetic modification of bovine undifferentiated germ cells.</P>
Matthew Conlon,Rachel Thommen,Syed Faraz Kazim,Alis J. Dicpinigaitis,Meic H. Schmidt,Rohini G. McKee,Christian A. Bowers 대한척추신경외과학회 2022 Neurospine Vol.19 No.4
Objective: To assess the discriminative ability of the Risk Analysis Index-administrative (RAI-A) and its recalibrated version (RAI-Rev), compared to the 5-factor modified frailty index (mFI-5), in predicting postoperative outcomes in patients undergoing surgical intervention for traumatic spine injuries (TSIs). Methods: The Current Procedural Terminology (CPT) and International Classification of Disease-9 (ICD-9) and ICD-10 codes were used to identify patients ≥ 18 years who underwent surgical intervention for TSI from National Surgical Quality Improvement Program (ACS-NSQIP) database 2015–2019 (n = 6,571). Multivariate analysis and receiver operating characteristic (ROC) curve analysis were conducted to evaluate the comparative discriminative ability of RAI-Rev, RAI-A, and mFI-5 for 30-day postoperative outcomes. Results: Multivariate regression analysis showed that with all 3 frailty scores, increasing frailty tiers resulted in worse postoperative outcomes, and patients identified as frail and severely frail using RAI-Rev and RAI-A had the highest odds of poor outcomes. In the ROC curve/ C-statistics analysis for prediction of 30-day mortality and morbidity, both RAI-Rev and RAI-A outperformed mFI-5, and for many outcomes, RAI-Rev showed better discriminative performance compared to RAI-A, including mortality (p = 0.0043, DeLong test), extended length of stay (p = 0.0042), readmission (p < 0.0001), reoperation (p = 0.0175), and nonhome discharge (p < 0.0001). Conclusion: Both RAI-Rev and RAI-A performed better than mFI-5, and RAI-Rev was superior to RAI-A in predicting postoperative mortality and morbidity in TSI patients. RAIbased frailty indices can be used in preoperative risk assessment of spinal trauma patients.