Dry mass is the mass remaining after a specimen has been dried under a stated procedure. Removing water makes comparisons less sensitive to hydration, but the result remains operational: drying conditions can also remove volatile compounds or alter the material. A reproducible measurement specifies specimen preparation, drying conditions and the criterion for stopping.

For example, a rice-biomass protocol separates leaves, stems and reproductive structures, dries the components at $70{}^{\circ }\mathrm{C}$, and checks for constant mass. Its stopping criterion is no change in the measured mass over 24 hours.^[ref] This is a protocol for those samples, rather than a temperature prescribed for every biological material.

For a synthetic calculation, a specimen has fresh mass 12 g and dry mass 3 g. The loss on drying is 9 g, or $9/12=75\%$ of fresh mass. The same loss is $9/3=300\%$ of dry mass. Both ratios describe the stipulated measurements, but use different denominators. Interpreting the loss specifically as water requires the assumption that other losses are negligible. Dry mass also includes retained inorganic material; it is not synonymous with the mass of organic nutrients.

The Lotus effect is self-cleaning by water droplets on a strongly water-repellent, textured surface, exemplified by lotus leaves. The surface structure reduces the contact of both water and contaminating particles with the solid. Mobile droplets can collect the particles and carry them away, connecting wetting, particle adhesion and surface microstructure.^[ref]

The motivating experiment was more specific than simply noticing that leaves look clean. W. Barthlott and C. Neinhuis artificially contaminated smooth and rough water-repellent plant surfaces with particles, then rinsed them with a sprinkler or fog generator. Rolling droplets removed the particles from the water-repellent surfaces. Comparing surface types linked cleaning performance to the combination of roughness and water repellency.^[ref]

A Cassie–Baxter state provides an idealized picture of a droplet supported partly by solid asperities and partly over trapped air. This reduces the effective solid contact area. Real cleaning additionally requires the drop to move: contact-line pinning and contact-angle hysteresis can hold a droplet even when its static contact angle is large. Thus measuring a contact angle and observing particle removal are different tests.

A force estimate explains why a cleaning experiment should specify drop size and tilt. On a surface inclined by $\alpha$, a droplet of mass $m$ has a downslope component of gravitational weightFor a $10\mu \mathrm{L}$ water drop, taking density $1000\mathrm{kg}{\mathrm{m}}^{-3}$ gives $m=10^{-5}\mathrm{kg}$. At $\alpha =10^{\circ }$, the driving force is about $17\mu \mathrm{N}$. A surface that requires more force to overcome contact-line pinning can retain that drop. This is an illustrative force balance, not a measured lotus-leaf threshold; different drop volumes supply different driving forces.

For a biomimetics experiment, compare contaminated surfaces under the same droplet volume, inclination and rinsing protocol, and record both droplet motion and particles remaining. Wear or a change in surface chemistry can alter the result even if the surface still looks rough. The useful mechanism is the coupled behavior of surface texture, wetting, adhesion and droplet motion.

A biomedical engineer develops, investigates or evaluates systems at the intersection of engineering, biology and medicine. Work can include instrument design, biomechanics, biomaterials, data analysis and technical support for medical equipment. The role includes constructing models and experiments, not only assembling a finished device.^[ref]

An original load cell example makes the measurement work concrete. Suppose reference loads $F=2\mathrm{N}$ and $6\mathrm{N}$ produce outputs $V=0.30\mathrm{V}$ and $0.70\mathrm{V}$. Fitting the stipulated linear measurement model $V=kF+b$ givesA later output of $0.50\mathrm{V}$ then corresponds to $4\mathrm{N}$. Ignoring the offset would instead report $5\mathrm{N}$. With the calibration coefficients held fixed, an output uncertainty of $0.01\mathrm{V}$ contributes $0.10\mathrm{N}$ to force uncertainty; uncertainty in the reference loads and fitted coefficients adds further terms.

The engineer must also determine whether that model remains useful. A third reference load tests interpolation; repeated loading and unloading can reveal hysteresis; a temperature change can expose drift. Mounting the sensor on a biological specimen can alter the load path compared with the calibration fixture. Thus a satisfactory calibration curve is one part of demonstrating fitness for the intended measurement. Collaborating with users and reporting the conditions and limitations connects engineering performance to the biological question.

Tissue engineering uses biological cells, engineered environments and material structures to build or restore tissue-like function. A construct must do more than resemble the shape of a tissue: its cells need suitable surroundings, and the resulting structure must perform the intended biological or mechanical task. The field lies within biomedical engineering, whose scope includes engineering methods applied to biological materials and systems.^[ref]

One approach seeds cells onto a tissue-engineering scaffold that provides an initial geometry and attachment environment. The cells can deposit extracellular matrix while the construct is maintained under controlled culture conditions. A bioreactor can supply nutrients and impose a defined mechanical environment. These roles should be distinguished: a scaffold’s initial strength, the matrix produced by the cells and the mature construct’s function need not be identical.

A motivating primary experiment is the 1999 report of arteries grown from vascular smooth muscle cells and endothelial cells. Bovine vessels were cultured under pulsatile conditions, then assessed for rupture strength, suture retention, contraction and cellular differentiation. The study also reported implantation in miniature swine, with a finite follow-up observation. The combination of mechanical and biological measurements illustrates why a tissue-like shape alone is insufficient evidence of function.^[ref]

A simple design calculation shows how size affects cell support. For diffusion with characteristic diffusivity $D$, the diffusion time over distance $L$ scales asFor illustrative $D=10^{-9}{\mathrm{m}}^2{\mathrm{s}}^{-1}$, a $0.1\mathrm{mm}$ distance gives $t_D\sim 10\mathrm{s}$, whereas $1\mathrm{mm}$ gives $t_D\sim 1000\mathrm{s}$. The tenfold increase in distance produces a hundredfold time scale. These chosen values do not establish a survival limit: consumption, binding, boundary concentrations and fluid transport also matter. They explain why scaling up a dense construct introduces a transport problem, rather than merely requiring more cells.

The engineering task is to coordinate transport, cell adhesion, matrix formation, biocompatibility and mechanical demands. An experiment can measure each separately: nutrient conditions, viable-cell distribution, matrix organization and force response. Together those observations test whether the designed environment has produced the intended tissue function.

Drug delivery concerns how a therapeutic substance is presented to a biological system: where it becomes available, over what time and in what form. Formulation, a carrier material and the route of administration can change the resulting transport. Drug release kinetics describes escape from a formulation or reservoir; pharmacokinetics additionally concerns what happens as the substance moves through and is removed from the body. These are related stages rather than interchangeable measurements.

A motivating historical development was the use of polymers for sustained release of proteins and other macromolecules, reported by Robert S. Langer and Judah Folkman in 1976.^[ref] The engineering question includes whether a carrier can retain a substance initially and then make it available over time while preserving the intended activity.

An elementary reservoir model separates remaining material from cumulative release. If the remaining amount $M(t)$ obeysthen $M(t)=M_0{e}^{-kt}$ and the released fraction is $1-e^{-kt}$. For an illustrative reservoir-release half-time of six hours, $k=\ln 2/(6\mathrm{h})$. Half has been released at six hours and three quarters at twelve hours. The second six-hour interval releases one quarter of the initial amount, even though the first interval released one half. These are model fractions, not a drug regimen; the reservoir-release half-time is not an elimination half-life measured in a person.

An in vitro drug release test can place a formulation in a controlled medium, separate released material from retained material and measure amount against time. The apparatus can influence the answer. The FDA’s technical account explains that passive transport through a dialysis membrane can limit the measured response; its adaptive-perfusion prototype instead uses pressure-driven separation to investigate release from complex formulations.^[ref]

A useful experimental record therefore states the medium, temperature, separation method, sampling schedule and material balance. A slowly changing measured concentration could reflect slow carrier release, slow transport through the apparatus or both. Comparing apparatus conditions and accounting for material remaining in the carrier helps distinguish these mechanisms. Evidence about release under those conditions must then be related to the biological environment before making claims about tissue exposure or therapeutic effect.

Primary maintained mammal catalogue, record1001207: Patagonian Mara, genus Dolichotis, family Caviidae, order Rodentia. Used for rank, name and common-name facts; no conservation status, disputed genus-wide species count or Chilean distribution inferred.

Direct genus tree inspected. TaxID10140 under Caviidae; displayed Cavia porcellus and Cavia aperea among children. No claim that the displayed children all have the same nomenclatural status or constitute an immutable species count.

Direct family tree inspected. TaxID10139; lineage Rodentia/Hystricomorpha; displayed children include Cavia and Dolichotis. Provider-specific classification recorded; no assertion of an exhaustive or universally agreed modern circumscription, and no capybara placement inferred from this record.

TaxID10141, species Cavia porcellus, guinea pig; lineage Rodentia, Caviidae, Cavia. Direct primary taxonomy record inspected. No breed, domestication-date, wild-range or conservation-status claim inferred.

Reviewed human entry P01375 (TNFA_HUMAN); directly inspected machine-readable primary record rest.uniprot.org/uniprotkb/P01375.txt . Locators: protein names, FUNCTION, SUBUNIT and processed membrane/soluble forms. No clinical treatment claims inferred.

Primary full-text record pmc.ncbi.nlm.nih.gov/articles/PMC433057/ . PNAS72(9),3666–3670(1975). Verified Abstract: serum from BCG-infected mice treated with endotoxin caused tumor necrosis; tests distinguished a host-derived factor from residual endotoxin; two neoplastic cell lines and mouse embryo cultures differed in toxicity. Macrophage origin is the authors' proposed interpretation, not direct identification by this experiment. Initial-only E. A. Carswell identity preserved.

By Mark A. Knepper.

Verified locator: PNAS119(30),e2209749119(2022); primary colleague-authored remembrance by MarkA.Knepper, published15July2022. Opening:1931–2022, death24April2022, isolated-perfused-nephron method and physiological importance. Indexed primary article text inspected; direct fetch may show a browser challenge.

Verified locator: Fellow profile: recombination intermediate, epigenetics/DNA methylation, elected2005, died2014. Labelled RobinHolliday portrait science.org.au/sites/default/files/styles/profile_image/public/Fellow/image/Profile%20image/holliday_0.jpg?h=78b7a964&itok=igSNB5at . Birth year1932 corroborated by Royal Society catalogue record catalogues.royalsociety.org/CalmView/Record.aspx?id=IM%2F007182&src=CalmView.Catalog .

Verified locator: Institutional faculty page explicitly gives English name ChunyingKang; research summary describes strawberry organ development and genetics, Maryland postdoctoral research and HZAU appointment. ORCID0000-0001-9269-5185 and linked publications establish identity. No unverified portrait URL used.

Verified locator: Faculty/emeritus list, Laudano,AndrewP entry: associate professor emeritus, molecular/cellular/biomedical sciences; UC San Diego PhD1981. Historical catalog supports a dated appointment rather than a current employment claim.

Verified locator: University memorial: dates1931–2019; UCSD appointment history; fibrinopeptide sequences, comparative evolution, fibrinogen sequences and structures. Avoid conflicting doctoral-year metadata found in other sources; no doctoral year used.

By Maurice B. Burg.

Verified locator: Biographical Memoirs77(1999), chapter Carl W. Gottschalk, opening p123: dates28April1922–15October1997 and byline MauriceB.Burg. Early research/micropuncture sections pp126–130: collaboration with Margaret Mylle, local fluid sampling, osmolality, dye/microdissection site verification. DOI10.17226/9681. Colleague-authored institutional memoir; original experimental observations separately cited to1959 paper.

Verified locator: Overview: transcription/DNA damage research; Stanford structural-biology postdoctoral training. Publications identify the2006 trigger-loop paper. ORCID0000-0002-2829-1546. Labelled photo link researcherprofiles.org/profile/Modules/CustomViewPersonGeneralInfo/PhotoHandler.ashx?NodeID=198795&cachekey=74193dda-7673-4135-b933-1affe0ac0b27 .

Verified locator: Biographical Details: cytokine receptors, growth hormone receptor and JAK2 research; listed publications use Brooks,A.J.; ORCID0000-0002-2691-1668. Labelled portrait researchers.une.edu.au/files-asset/86313573/Head.jpg?f=jpg&w=160 .

Verified locator: Research summary: epithelial polarity, polarized virus budding discovered1978, retinal pigment epithelium. Publication listing links the1978 Sabatini paper; institutional full name Enrique Rodriguez-Boulan.