Role of processing parameters in CVD grown crystalline monolayer MoSe2

The quality of as-synthesized monolayers plays a significant role in atomically thin semiconducting transition metal dichalcogenides (TMDCs) to determine the electronic and optical properties. For designing optoelectronic devices, exploring the effect of processing parameters on optical properties is a prerequisite. In this view, we present the influence of processing parameters on the lattice and quasiparticle dynamics of monolayer MoSe₂. The lab-built chemical vapour deposition (CVD) setup is used to synthesize monolayer MoSe₂ flakes with varying shapes, including sharp triangle (ST), truncated triangle (TT), hexagon, and rough edge circle (REC). In particular, the features of as-synthesized monolayer MoSe₂ flakes are examined using Raman and photoluminescence (PL) spectroscopy. Raman spectra reveal that the frequency difference between the A_1g and E¹_2g peaks is >45 cm⁻¹ in all the monolayer samples. PL spectroscopy also shows that the synthesized MoSe₂ flakes are monolayer in nature with a direct band gap in the range of 1.50–1.58 eV. Furthermore, the variation in the direct band gap is analyzed using the spectral weight of quasiparticles in PL emission, where the intensity ratio {I(A⁰)/I(A⁻)} and trion binding energy are found to be ∼1.1–5.0 and ∼23.1–47.5 meV in different monolayer MoSe₂ samples. Hence, these observations manifest that the processing parameters make a substantial contribution in tuning the vibrational and excitonic properties.

Monolayer MoSe₂ flakes with varying shapes, including sharp triangle, truncated triangle, hexagon, and rough edge circle are synthesized using APCVD method. The lattice and quasiparticle dynamics are examined under different growth conditions.     

Defining negative margins in DCIS patients treated with breast conservation therapy: The University of Chicago experience

Management of ductal carcinoma in situ (DCIS) has been evolving and the majority of women are now being treated with breast-conserving surgery and radiation therapy (i.e. breast conservation therapy [BCT]). Controversies still exist regarding the histologic features and margin status that are associated with local recurrence. The goal of this study was to review our institution's experience in patients diagnosed with DCIS and treated with BCT to determine pathologic features that can predict local recurrence, with particular emphasis on the final surgical margin status. We analyzed 103 consecutive patients with DCIS who were treated with BCT between 1986 and 2000. The slides were reviewed to determine the final margin status, type of DCIS, size of DCIS, nuclear grade, presence of necrosis and calcification, and volume of excised specimen. Margins were considered positive when DCIS touched or was transected at an inked margin. Negative margins were further categorized as close (less than 1 mm), 1--5 mm, and more than 5 mm. The size of the DCIS was determined based on either the maximal dimension on a slide or from the number of consecutive slides containing DCIS. Morphology and immunohistochemical profiles of the recurrent DCIS cases were compared with original DCIS. All patients were treated uniformly with external beam radiation therapy to the entire breast (median dose 46 Gy) with a boost to the tumor bed (median dose 14 Gy). The median follow-up was 63 months (range 7--191 months). The actuarial 5-year local control rate was 89%. The median time to local recurrence was 55 months. There were 13 local recurrences, of which 9 recurred as pure DCIS and 4 as invasive ductal carcinomas. Univariate analysis showed a significant association with local recurrence for positive margin (p=0.008), high nuclear grade (p=0.02), and young age at diagnosis (p=0.03). If margins were negative, the 5-year local control was 93%, as compared to 69% if margins were positive. A multivariate analysis showed that early age at diagnosis, positive margin status, and high nuclear grade were independently associated with local recurrence. The morphology and immunohistochemical stains of all nine recurrent DCIS were similar to those of the original DCIS. Breast conservation can be achieved with excellent local control by obtaining microscopically negative margins as strictly defined by DCIS not touching the inked surgical margins, and postoperative radiation that includes boost therapy to the tumor bed.     

Carcinoma of the rectum in children

Two cases of carcinoma of the rectum in children (10 and 11 years old) are presented. Both cases presented as acute intestinal obstruction with the history of bleeding per rectum, constipation, abdominal distention, and loss of weight and appetite. Carcinoma of the colon and rectum in children is rare. Its clinical, pathologic, and biological characteristics are different than those of adults. The prognosis is poorer in children, the reason for which is explained, and its management is briefly discussed.     

The 87-kD A gamma-globin enhancer-binding protein is a product of the HOXB2(HOX2H) locus

Developmental regulation of globin gene expression may be controlled by developmental stage-specific nuclear proteins that influence interactions between the locus control region and local regulatory sequences near individual globin genes. We previously isolated an 87-kD nuclear protein from K562 cells that bound to DNA sequences in the beta- globin locus control region, gamma-globin promoter, and A gamma-globin enhancer. The presence of this protein in fetal globin-expressing cells and its absence in adult globin-expressing cells suggested that it may be a developmental stage-specific factor. A lambda gt11 K562 cDNA clone encoding a portion of the HOXB2 (formerly HOX2H) homeobox gene was isolated on the basis of the ability of its beta-galactosidase fusion protein to bind to the same DNA sequences as the 87-kD K562 protein. Because no other relationship had been established between the 87-kD K562 protein and the HOXB2 protein other than their ability to bind ot the same DNA sequences, we have investigated whether the two proteins are related antigenically. Our data show that antisera produced against the HOXB2-beta-gal fusion protein and a synthetic HOXB2 decapeptide react specifically with an 87-kD protein from K562 nuclear extract, showing that the 87-kD K562 nuclear protein is a product of the HOXB2 locus, and is the first demonstration of cellular HOXB2 protein.