Lattice sum for a hexagonal close-packed structure and its dependence on the c/a ratio of the hexagonal cell parameters.

We continue the work by Lennard-Jones and Ingham, and later by Kane and Goeppert-Mayer, and present a general lattice sum formula for the hexagonal close packed (hcp) structure with different c/a ratios for the two lattice parameters a and c of the hexagonal unit cell. The lattice sum is expressed in terms of fast converging series of Bessel functions. This allows us to analytically examine the behavior of a Lennard-Jones potential as a function of the c/a ratio. In contrast to the hard-sphere model, where we have the ideal ratio of c/a=sqrt[8/3] with 12 kissing spheres around a central atom, we observe the occurrence of a slight symmetry-breaking effect and the appearance of a second metastable minimum for the (12,6) Lennard-Jones potential around the ratio c/a=2/3. We also show that the analytical continuation of the (n,m) Lennard-Jones potential to the domain n,m<3 such as the Kratzer potential (n=2,m=1) gives unphysical results.

Evaluation of vitamin D protocol in the neonatal intensive care unit at Rush University Medical Center.

BACKGROUND: In 2017, the neonatal intensive care unit (NICU) at Rush University Medical Center (RUMC) implemented a protocol to provide individualized vitamin D supplementation dosing for very low-birth-weight (VLBW) and very preterm infants. This study evaluated the association of demographic and socioeconomic factors, vitamin D dose, and health indicators, including bone mineral status, measured by alkaline phosphatase and phosphorus levels; linear growth velocity; and occurrence of fractures. METHOD: This retrospective cross-sectional study included 227 VLBW or very preterm infants (34 VLBW, 12 very preterm, and 181 VLBW and very preterm) born in and discharged from the RUMC NICU between February 1, 2017, and October 31, 2019. Vitamin D dose was classified as adjusted (supplemental dose of 800 IU/day, n = 169) or standard (recommended dose of 400 IU/day, n = 58), per the protocol. Binary logistic and linear regression models were constructed to test the associations between infant and maternal characteristics and vitamin D dose group and between vitamin D dose group and health indicators. RESULTS: The analysis found a statistically significant association between maternal age, gestational age, infant birth weight, and race/ethnicity and receipt of an adjusted vitamin D dose. No significant associations were found between health indicators and vitamin D dose. CONCLUSION: Sociodemographic factors may influence vitamin D deficiency in VLBW and very preterm infants in the NICU. At this time, there is insufficient evidence to support a tailored approach, but further research in this area is warranted.

Instability of the body-centered cubic lattice within the sticky hard sphere and Lennard-Jones model obtained from exact lattice summations.

A smooth path of rearrangement from the body-centered cubic (bcc) to the face-centered cubic (fcc) lattice is obtained by introducing a single parameter to lattice vectors of a cuboidal unit cell. As a result, we obtain analytical expressions in terms of lattice sums for the cohesive energy where the interaction is described by a Lennard-Jones (LJ) interaction potential or a sticky hard-sphere (SHS) model with a r^{-n} long-range attractive term. These lattice sums are evaluated to computer precision by expansions in terms of a fast converging Bessel function series. Applying the whole range of lattice parameters for the SHS and LJ potentials we prove that the bcc phase is unstable (or, at best, metastable) toward distortion into the fcc phase in the low temperature and pressure limit. Even if more accurate potentials are used, such as the extended LJ potential for argon or chromium, the bcc phase remains unstable. This strongly indicates that the appearance of a low temperature bcc phase for several elements in the periodic table is due to higher than two-body forces in atomic interactions.

Defining the root cause of reduced H1N1 live attenuated influenza vaccine effectiveness: low viral fitness leads to inter-strain competition.

In the 2013-14 and 2015-16 influenza seasons, reduced vaccine effectiveness (VE) was observed for the H1N1 component of the FluMist quadrivalent live attenuated influenza vaccine (QLAIV) in the USA, leading to loss of Advisory Committee on Immunization Practices recommendation. Here we demonstrate in ferrets that 2015-16A/H1N1pdm09 vaccine strain A/Bolivia/559/2013 (A/BOL13) is outcompeted in trivalent (TLAIV) and QLAIV formulations, leading to reduced protection from wild-type challenge. While monovalent (MLAIV) A/BOL13 provided significant protection from wild-type virus shedding and fever at doses as low as 3.0 log10 fluorescent focus units (FFU), it failed to provide a similar level of protection in TLAIV or QLAIV formulation, even at a 6.0 log10 FFU dose. Conversely, clinically effective H1N1 strain A/New Caledonia/20/1999 provided significant protection in MLAIV, TLAIV, and QLAIV formulations. In conclusion, reduced A/BOL13 replicative fitness rendered it susceptible to inter-strain competition in QLAIV, contributing to its reduced VE in the 2015-16 season.

Transfer of methylprednisolone into breast milk in a mother with multiple sclerosis.

High-dose intravenous methylprednisolone, a glucocorticoid with powerful anti-inflammatory activities, has become increasingly important in treating acute relapses of multiple sclerosis (MS). This is a case report of a 36-year-old lactating female who was receiving a 3-day course of high-dose methylprednisolone (1000 mg IV) to treat MS. Breast milk samples were obtained at 1, 2, 4, 8, and 12 hours following a 2-hour intravenous infusion on days 1, 2, and 3. The relative infant dose was found to be 1.45%, 1.35%, and 1.15% for days 1, 2, and 3, respectively. Using the average measured concentrations (C(avg)) for days 1, 2, and 3, the estimated infant exposure was 0.207, 0.194, and 0.164 mg/kg/day, respectively, which is below the recommended dose given to neonates requiring methylprednisolone drug therapy. Infant exposure is low and mothers could continue to breastfeed if treatment with IV methylprednisolone is very brief. However, if the mother wishes to limit infant exposure further, she could wait 2 to 4 hours after IV methylprednisolone administration, thus significantly limiting the amount of drug in the breast milk.

Transfer of natalizumab into breast milk in a mother with multiple sclerosis.

Natalizumab (Tysabri) is a recombinant humanized antibody to α4-integrin that is approved by the Food and Drug Administration for the treatment of multiple sclerosis (MS) and Crohn disease. This is a case report of a 28-year-old woman with MS who was taking natalizumab (300 mg intravenously infused over 1 hour every 4 weeks) while breastfeeding her 11.5-month-old daughter 3 times a day. Breast milk samples were collected over a 50-day period after the patient's first drug infusion. The average concentration of natalizumab was 0.93 µg/mL/d, and the relative infant dose was 1.74% of the weight-adjusted maternal dose. Transfer of natalizumab into human milk increased over time and with subsequent injections, with the highest concentration of 2.83 µg/mL at day 50 with a relative infant dose of 5.3%. Because these data suggest continued accumulation of natalizumab in milk, and because we cannot provide an accurate assessment of levels of this drug at 24 weeks (steady state), we are unable to determine safety at this time.

Transfer of linezolid into breast milk.

Linezolid, a broad-spectrum antibiotic used primarily for treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections, is the first oxazolidinone approved for clinical use. This is a case report of a 30-year-old woman who was exclusively breastfeeding her infant prior to taking linezolid 600 mg orally every 12 hours to treat a MRSA mastitis. Breast milk samples were obtained over a 12-hour dosing interval on day 1 (after a single dose of therapy) and again on day 14 (at steady state). The relative infant dose at steady state was found to be 15.61% on day 14 of therapy. Using the average concentration at steady state, the estimated infant dose would have been 1.84 mg/kg/day, which is well below the recommended dose given to neonates requiring linezolid drug therapy. The infant did not breastfeed during maternal treatment with linezolid.

Coordination complexes as molecular glue for immobilization of antibodies on cyclic olefin copolymer surfaces.

A novel metal-based chelating method has been used to provide an order of magnitude increase in immunoassay performance on cyclic olefin copolymer (COC) plastics compared with passive binding. COCs are hydrophobic, and without surface modification they are often unsuitable for applications where protein adhesion is desired. When interacting with the bare plastic, the majority of the bound proteins will be denatured and become nonfunctional. Many of the surface modification techniques reported to date require costly equipment setup or the use of harsh reaction conditions. Here, we have successfully demonstrated the use of a simple and quick metal chelation method to increase the sensitivity, activity, and efficiency of protein binding to COC surfaces. A detailed analysis of the COC surfaces after activation with the metal complexes is presented, and the immunoassay performance was studied using three different antibody pairs.