LaTeX forum ⇒ Fonts & Character Sets ⇒ How to create upright Greek lowercase letters

[Rayan]

I am using the template of the Proceedings of the Royal Society A. In this template, I cannot produce upright Greek lowercase letters. For example, I use the command "\deltaup" to produce an upright delta, but the result is still the italic delta rather than the upright one. For the uppercase Greek characters, I used the command "\let\Deltaup\Delta" before \begin{document}, and it worked, however, it did not work for the lowercase delta. Could you please let me know how I can resolve this problem? (I copied the packages used in my document down below).
Thank you!

\documentclass[openacc]{rsproca_new}
\usepackage{upgreek}
\newcommand{\upDeltaup}{\upDelta}
\newcommand{\updeltaup}{\updelta}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{dblfloatfix} 
\usepackage{fixltx2e} 
\usepackage{float}
\usepackage{wrapfig}
\usepackage{rotating}
\usepackage{graphicx}
\usepackage{subcaption}
\usepackage[normalem]{ulem}
\usepackage[font=small,labelfont=bf,labelsep=endash,margin=20pt]{caption}
\usepackage[title,header]{appendix}

\usepackage{relsize} 
\usepackage{amsmath}
\usepackage{marvosym}
\usepackage{wasysym}
\usepackage{amssymb}
\usepackage{latexsym}
\usepackage{physics}
\newcommand\bmmax{0} 
\usepackage{bm}
\usepackage{mathtools}

%%%%%%%%%%% Defining Enunciations  %%%%%%%%%%%
\newtheorem{theorem}{\bf Theorem}[section]
\newtheorem{condition}{\bf Condition}[section]
\newtheorem{corollary}{\bf Corollary}[section]
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\titlehead{Research}

\let\Deltaup\Delta
\let\deltaup\delta
\begin{document}

[rais]

For the uppercase Greek characters, I used the command "\let\Deltaup\Delta" before \begin{document}, and it worked, however, it did not work for the lowercase delta.

Well, with this method you're ignoring whatever upgreek provides...it only seems to `work' for uppercase greek because uppercase greek is set upright by default, anyway.
I don't have the class you're using, for demo I just used one of the standard classes:

\documentclass{article}
\usepackage{upgreek}
\usepackage[T1]{fontenc}

\begin{document}
\[
\upalpha \upbeta \upgamma \updelta
\]
\end{document}

KR
Rainer